Analog Signal Acquisition for PC Printer Port

Electronic Component Template

#179

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Fri Jun 29, 2001 2:18 pm
Subject: Analog Signal Acquisition for PC Printer Port

nsfetcu@...

Analog Signal Acquisition for PC Printer Port

DIRT CHEAP ANALOG SIGNAL ACQUISITION, for PC Printer Port
Circuitry and Software by Allen Sullivan

Schematic

 +---> +(Voice > Accumulator)
|
+5Volts | 100UF bypass
o----------+-----------------------+----------------------|(-----GND
| | | diode
| | 4.7K +--|<-- 2.2K---Most Sig Bit
4.7K | | |
| e---- | -----+ (DAC) +--|<-- 4.3K---Next Most Sig
+----+----bQpnp | | |
| | c | | +----+--|<-- 9.1K-----
| 10K |___ | | | |
c | | | | +--+ +--|<-- 18K -----
npn Qb---+----+ 1K | | | | |
+-------e | | | | c | c +--|<-- 36K -----
| | | | c npnQb-*-bQnpn |
\----(+)------+ 2.2K 100UF +-bQnpn e e +--|<-- 75K -----
|Loudspeaker | | | | e | | |
|as Microphone| | | 10K | 100ohm 100ohm +--|<-- 150K ---
/----(-)------+ Ground | | | | |
| Ground Ground +--|<-- 300K--- Least Sig Bit
Ground

The point labeled (DAC) is a crude/cheap analog version of the digital value. You can use an emitter follower, with about 100ohm pulldown, to drive a 100uF capacitor to drive a speaker, for playback.

The diodes serve to make current contribution unidirectional, thus avoiding modulation of the sum-of-current by exactly how good a logic-0 is provided.

There are NO ANTIALIASING FILTERS, and no reconstruction filters. You can experiment with tones greater than one-half the sampling rate, and observe where they are placed in the sampled data spectrum. By the way, running without a 80287, my PC (12MHz AT) needs about 7 seconds to perform a 256-point FFT. On my PC, acceptable ports are: #1=0x0378, #2=0x0278, #3=0x03bc

Driver in C

/* This routine implements, in conjunction with an external
Digital-to-Analog converter and analog comparator, a TRACKING
ANALOG-TO-DIGITAL CONVERTER. This routine has in software an
accumulator that sums the input signal---a single bit. The bit
indicates whether the accumulator value, the current guess as
to the actual analog signal, is GREATER or LESS than the analog
signal.
Turns out that a "C" routine on a 12MHz PC-AT is more than
fast enough to sample a voice signal. The loop spins about
60,000 times per second. This allows 20 samples--of 1 bit
change per sample---for 3KHz signals, or 10 samples peak-peak
at 3KHz. The normal male voice at 500 Hz can be 60 samples
peak-peak, or 1/4 of full scale.
At one time, variable-size steps were used, but the benefit
was not observable since there are NO ANTI-ALIASING filters,
and the distortion of the voice as judged by playback quality
was not improved by dynamically varying the step size.
But the electronic parts cost is only $2.00 */
/* will bind global 'sample_rate' */
void grab_voice()
{
unsigned char tracking_value;
unsigned int vndx;
char interval;
unsigned char input_signal;
int control_port;
char slew_accum; /* will vary between +5 and -5 ? */
unsigned char delta; /* how much to step 'tracking_value' */
clock_t start_t, stop_t;
printf("\nStarting to grab voice\n");
control_port = active_port + 2;
outportb(control_port, 0x04); /* free up the 4 OpenCollector I/O pins */
/* We'll can read data from Pin 1 */
tracking_value = 0x80; /* Init voltage to half-scale */
interval = 0;
delta = 1;
slew_accum = 0;
start_t = clock();
for ( vndx = 0 ; vndx < VOICE_SIZE; ) /* until VOICE is full */
{
input_signal = 0x01 & inportb(control_port); /* PIN 1, by chance */
if ( !input_signal ) {
/* tracking_value = min(0xfb, tracking_value + delta); */
tracking_value++;
slew_accum++;
}
else {
/* tracking_value = max(4, tracking_value - delta); */
tracking_value--;
slew_accum--;
}
/* FASTER if port is constant */
outportb(active_port, tracking_value);
if ( interval++ EQUALS 4 ) /* 10 gives about 5 seconds in 0x02ff */
{
voice[vndx++] = tracking_value;
interval = 0;
if ((slew_accum > 3) || (slew_accum < -3)) /* Has this any use? */
delta++;
else if (delta > 2)
delta--;
slew_accum = 0;
}
} /* end FOR ( VNDX ; VNDX ; ) */
stop_t = clock();
sample_rate = /* bind global var */
(VOICE_SIZE * CLK_TCK) / ( stop_t - start_t) ;
printf("Grabbed voice. Took %f seconds. Rate is %d samples/sec\n",
((stop_t - start_t) / CLK_TCK), sample_rate );
}
/* ------------------------------------------------------------------- */
/* This function supports exploring the behavior of your printer port.
You specify an input pin of that port- 1, 14, 16 17.
Pin 2 will output a signal that alternates between low and high. The
rate is determined by how fast your computer can scroll. You are
shown the state of Pin 2 as output, and the state of the input pin.
This continues until you PRESS ANY KEY to EXIT.
Needs some HELP words, to explain what is good and bad display */
void input_diddle()
{
unsigned char diddle_out, diddle_in, bitmask;
int pinspec, which_io_port;
printf("\nWill alternately turn Pin 2 ON and OFF, as test output.\n");
printf("Select an input Pin that has pullup: 1 14 16 17, as 1 4 6 7 ? ");
printf("You must CONNECT a WIRE BETWEEN pin 2 AND your test input.\n");
pinspec = getche();
which_io_port = active_port + 2;
outportb(which_io_port, 0x04); /* 0100 frees the pullups */
/* of I/O bits 17, 16, 14, 1 */
switch( pinspec )
{
case '1': bitmask = 0x01; break;
case '4': bitmask = 0x02; break;
case '6': bitmask = 0x04; break;
case '7': bitmask = 0x08; break;
default: ;
}
diddle_out = 1;
for ( ; ; )
{
if ( kbhit() )
{
getch(); /* eat char so won't exit the outer loop */
break;
}
outportb(active_port, diddle_out);
diddle_in = inportb(which_io_port);
diddle_in = diddle_in & bitmask;
printf("Output > %x <, Input value > %x < Phase-%s Default-%s\n",
diddle_out, diddle_in,
((pinspec=='6') ? "NonInvert" : "Invert"),
((pinspec=='6') ? "High" : "Low")
);
diddle_out = ((diddle_out == 1) ? 0 : 1);
}
}
/* ------------------- end function INPUT_DIDDLE -------------------- */
/* This routine allows keyboard/cursor-key definition of the relative
output analog voltage. Thus you can test the threshold characteristics
of the comparator. Early on, the comparator had a non-voice-in
threshold of level 174; this was moved to about 135.
The size of the transition is 3 bits, so a continuous dither occurs.
*/
void define_level()
{
unsigned char level;
int action;
int which_io_port;
unsigned char diddle_in;
level = 128;
which_io_port = active_port + 2;
outportb(which_io_port, 0x04); /* 0100 frees the pullups */
/* of I/O bits 17, 16, 14, 1 */
printf("\nStarting at level of 128/midscale, move (u)p or (d)own.\n");
printf("The comparator digital output is reported. SPACE to abort.\n");
printf("\nHardware MUST be in DIGITIZE mode, not PLAYBACK.\n");
for ( ; ; )
{
action = getch();
if ( action EQUALS ' ')
break;
switch(action)
{
case 'u': level = level + 1; break;
case 'd': level = level - 1; break;
default: ;
}
outportb(active_port, level);
diddle_in = inportb(which_io_port);
diddle_in = diddle_in & 0x01;
printf("Level %d Comparator %d\n", level, diddle_in);
} /* end FOR */
}

#178

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Thu Jun 28, 2001 3:22 pm
Subject: Micr-Spy with FETs

nsfetcu@...

o T1 & T2 are BF245 N-channel FET's and can be replaced with a NTE133. The ECG312 could likely be used also. The varactor diode BA121 can be replaced with a ECG/NTE611. USW stands for 'Ultra-Short-Wave'.
o L1 = 7 turns of 0.8mm Silverwire on a 5mm round Ferrit-core (adjustable).
o This very stable oscillator has a frequency of approximately 100 Megaherz.
o Feedback via 16pF capacitor. No interference from antenna on resonance-loop.
o Distance is at *least* 300 meters!

#177

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Wed Jun 27, 2001 4:21 pm
Subject: Adjustable flashing LED

nsfetcu@...

Adjustable flashing LED

From: dwg@... (David Grieve)

Use a 555 timer IC as the (resistor controlled) frequency source, choose component values to run at 2 x desired flash rate - get the data sheet for this part, it's pretty comprehensive. Use the output to clock a flip flop (e.g. 74HC74). Feed flip-flop Q and /Q outputs to simple transistor stages, viz...

 ___+5V
|
_|_
_\_/_ LED
____ |
TTL ____|6k8 |__________|/
|____| | |\e
_|_ _|_
|4k7| |270|
|_ _| |_ _|
| |
_|_______|_GND

Drive transistor 1 from Q, drive transistor 2 from Q or /Q via a switch. Run the whole thing from +5V. If you want to run it from +9V, no problem, us a 4000 series CMOS flip-flop and change the emitter resistor to 560. If you don't want the hassle of transistors then the ULN2003 darlington driver array could replace the transistor stages.

From: NURDEN1@... (Dale Nurden)

Yes, you do get variable capacitors, but they are usually very low values so they probably won't be much good to you. The easiest way to do this IMO is just a pair of transistors plus 4 resistors and 2 capacitors. I threw one together the other day and it works perfectly. To change the flash rates, you just change two resistor values (one for each LED). To make both LEDs flash together, you would your switch to switch them in parallel.

The circuit is called a monostable multivibrator (should find one in a good elementary electronics book), and goes something like this (drawn from memory, so don't count on it being 100% error free):

 -----+--------+--------+--------+--> +9v (whatever)
| | | |
R1 R2 R3 R4
| | | |
+------+ | | +------+
| +---C1---+ +---C2---+ |
D1 c| | | | D2
| \ | | |c |
| Q1 |------|--------+ b / |
| / b +---------------| Q2 |
| e| \ |
| | |e |
-+------+--------------------------+------+--->GND
Q1, Q2 ... anything NPN : BC108, 2N2222, etc
R1, R4 ... 1k0
R2, R3 ... 10k0
C1, C2 ... 10uF
D1, D2 ... Your LEDs

I think it is R2 and R3 that you vary to change the frequency, but you can just fiddle a bit to figure it out. Also, the capacitor values will also affect the frequency. If this doesn't work this way round, then try swapping the values of R1 and R2, and R3 and R4. I can never remember which way round they go - I always do it by trial and error.

#176

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Tue Jun 26, 2001 6:07 pm
Subject: Alternating ON-OFF Control

nsfetcu@...

Alternating ON-OFF Control

Use this circuit instead of a standard on-off switch. Switching is very gentle. Connect unused input pins to an appropriate logic level. Unused output pins *MUST* be left open!. First 'push' switches ON, another 'push' switches OFF. You can use 1/4 watt resistors if they are metal-film type. Any proper substitute will work for Q1, including the european TUN's. For C2, if you find the relay acts not fast enough, leave it out or change to a ceramic cap between 10 and 100nF.

Alternating ON-OFF Control

Parts List
All resistors are 1/2 Watt and 5% tolerance.
R1 = 10K
R2 = 100K
R3 = 10K
C1 = 0.1uF, Ceramic
C2 = 1uF/16V, Electrolytic
D1= 1N4001
Q1 = 2N4401 (ECG123AP, NTE123AP, etc.)
IC1 = MC4069, CMOS, Hex Inverter (MC14069)
S1 = Momentary on-switch

#175

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Mon Jun 25, 2001 7:26 pm
Subject: 8 Watt Audio Amp

nsfetcu@...

8 Watt Audio Amp

Here is the schematic for an 8 watt audio amp. This amp can be used as a simple booster, the heart of a more complicated amplifier or used as a guitar amp.

Schematic

LM383 Pinout

Parts:

Part	Total Qty.	Description	Substitutions
C1	1	10uf Electrolytic Capacitor
C2	1	470uf Electrolytic Capacitor
C3	1	0.1uF Disc Capacitor
C4	1	2000uf Electrolytic Capacitor	2200uF
R1	1	2.2 Ohm Resistor	Anything Within 10%
R2	1	220 Ohm Resistor	Anything Within 10%
IC1	1	LM383 8 Watt Amp IC	ECG1232

Notes:

1. IC1 MUST be installed on a heat sink.

2. C3 is for filtering and to prevent oscillation and should not be omitted.

3. The circuit can be built on a perf board, universal solder board or PC board, the PC board is preferred. I built the circuit on a perf board and had to add extra inductors, capacitors and resistors to prevent oscillation.

4. The circuit draws about 880 ma at 12 V.

5. By swapping the values of R1 and R3, you can turn this amplifier into a guitar amp with no preamp required.

6. If you can't find 2000uF, then replace C4 with a 2200uF unit.

7. If you add a 0.2uF capaciitor in series with a 1 ohm resistor to the output you can prevent oscillation of the circuit under certain conditions.

#174

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Fri Jun 22, 2001 6:25 pm
Subject: Filtering PC bus POWER

nsfetcu@...

Filtering PC bus POWER

From: jkubicky@... (Joseph J. Kubicky)

Many years ago I tried to build a decent A/D circuit with a switching supply and I had a similar experience. While good grounding is important, it may not be enough. Particularly, be aware that many switching converters, even those spec'd for low-noise output, still pass any INPUT noise through (that is, the spec really speaks to the amount of additional switching noise introduced). Thus, you're really at the mercy of the power supplied by the PC's switcher (which is usually pretty ugly, particularlly on a loaded bus).

Analog Devices suggests a circuit in their 1992 Amplifier Application Guide for filtering a 5V (digital) supply for use in single-supply analog applications. Should work just as well for dual-supply (with appropriate modifications):

 -------/==\------*-------*------*------ +5 (filtered)
\__/ | | |
2 turns --- --- ---
around /-\ /-\ ---
Fair-Rite | | |
#2677006301 | | |
ferrite bead | | |
-------/==\------*-------*------*------ +5 return (filtered)
\__/ 100uF 10-22uF 0.1uF
elec. tant. cer.

In the book they show rather dramatic reduction of high-speed switching transients for loads up to 100mA. For much higher loads you'll have to be careful not to saturate the ferrites.

#173

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Thu Jun 21, 2001 3:02 pm
Subject: Operational Amplifiers - 741 (4)

nsfetcu@...

Electrical Ratings:
Electrical characteristics for op-amps are usually specified for a certain (given) supply voltage and ambient temperature. Also, other factors may play an important role such as certain load and/or source resistance. In general, all parameters have a typical minimum/maximum value in most cases.
741(C) Op-Amp - Lay Out

The two most common types are shown in the diagram on the right. I believe the 8-pin version is used the most, worldwide. Actually, there is a third type in the form of a metal-can but is obsolete and, by my knowledge, no longer used. I have two of these metal-can types and keep them as a gone-by-memory.

Dual volt with two 9V batteries

Experiments:
You are given the opportunity to play with and analyze experiments to demonstrate the principles, concepts, and applications of a couple of these basic configured op-amps.
If you have already a dual-voltage power supply (positive/negative), that would make things alot easier for you. If not, build a Dual Voltage Powersupply to get you started. This power supply has two variable voltages; +5 to +15volts and -5 to -15volts. However, in general, a very simple and cheap power supply can be rigged up with two 9volt alkaline batteries and does the job in most cases.

Bread Board Module:
A bread board module, or just 'breadboard', is a board manufactured of plastic with a couple 100 tiny holes with tiny sockets in them connected electrically together and in the center of the breadboard a grove to hold a plastic panel for leds, pots and switches. They measure about 6 by 2 inches and come in white and blue. The blue kind is called 'BimBoard' and made in the UK.

Radio Shack and the European Tandy are both selling their own version and they work fine too.
The Bread Board Design System is also available, if you can afford it, and would be preferred if you intend to do a lot more experimenting in the future. This system contains everything you need already build-in, like the powersupply, jacks, switches, leds, function generator and lots more goodies. Kindah nice to have everything in one place.

Planning Your Prototype or Experiment:
Planning the layout of your experiments could be important, especially with large circuits

Remove every component and all wires from previous experiments.
Important: Before starting to insert components into the breadboard, make sure all power and signal connections are removed and the power source disconnected. And if required, take the glue/dirt of the components' legs before inserting them into the sockets, it is very hard if not impossible to get it cleaned out.

Suggested Reading:

"Introductory Experiment in Digital Electronics" (Book 1&2) by Howard W. Sams & Co., Inc. Publisher SAMS.
"Logic & Memory Experiments using TTL Integrated Circuits" (Book 1&2) by Howard W. Sams & Co., Inc. Publisher SAMS.
"Operational Amplifiers" by Robert Seippel. Publ. Reston Publishing Co., Inc. ISBN: 0-8359-5242-8

#172

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Wed Jun 20, 2001 4:35 pm
Subject: Operational Amplifiers - 741 (3)

nsfetcu@...

Output Parameters:

Output Resistance (Zoi)
The resistance seen 'looking into' the op-amp's output.
Output Short-Circuit Current (Iosc)
This is the maximum output current that the op-amp can deliver to a load.
Output Voltage Swing (Vo max)
Depending on what the load resistance is, this is the maximum 'peak' output voltage that the op-amp can supply without saturation or clipping.

Dynamic Parameters:

Open-Loop Voltage Gain (Aol)
The output to input voltage ratio of the op-amp without external feedback.
Large-Signal Voltage Gain
This is the ratio of the maximum voltage swing to the cahge in the input voltage required to drive the ouput from zero to a specified voltage (e.g. 10 volts).
Slew Rate (SR)
The time rate of change of the ouput voltage with the op-amp circuit having a voltage gain of unity (1.0).

Other Parameters:

Supply Current
This is the current that the op-amp will draw from the power supply.
Common-Mode Rejection Ratio (CMRR)
A measure of the ability of the op-amp' to reject signals that are simultaneously present at both inputs. It is the ratio of the common-mode input voltage to the generated output voltage, usually expressed in decibels (dB).
Channel Seperation
Whenever there is more than one op-amp in a single package, like the 747 op-amp, a certain amount of "crosstalk" will be present. That is, a signal applied to the input of one section of a dual op-amp will produce a finite output signal in the remainin ssection, even though there is no input signal applied to the unused section.

#171

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Tue Jun 19, 2001 7:05 pm
Subject: Operational Amplifiers - 741 (2)

nsfetcu@...

Summed-up Features:

Internal Frequency Compensation

Short Circuit Protection

Offset voltage null capability

Excellent temperature stability

High input voltage range

NO latch-up

�A741 Equivalent Circuit

Input Parameters:

Input Offset Voltage (Voi)
This is the voltage that must be applied to one of the input pins to give a zero output voltage. Remember, for an ideal op-amp, output offset voltage is zero!
Input Bias Current (Ib)
This is the average of the currents flowing into both inputs. Ideally, the two input bias currents are equal.
Input Offset Current (Ios)
This is the difference of the two input bias currents when the output voltage is zero.
Input Voltage Range (Vcm)
The range of the common-mode input voltage (i.e. the voltage common to both inputs and ground).
Input Resistance (Zi)
The resistance 'looking-in' at either input withe the remaining input grounded.

#170

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Mon Jun 18, 2001 4:34 pm
Subject: Operational Amplifiers - 741 (1)

nsfetcu@...

What Exactly Is An Op-Amp?

What exactly is an OPerational AMPlifier? Let's define what that component is and look at the parameters of this amazing device.
The term 'op-amp' was originally used to describe a chain of high performance dc amplifiers that was used as a basis for the analog type computers of long ago. The very high gain op-amp IC's our days uses external feedback networks to control responses. The op-amp without any external devices is called 'open-loop' mode, refering actually to the so-called 'ideal' operational amplifier with infinite open-loop gain, input resistance, bandwidth and a zero output resistance.
However, in practice no op-amp can meet these ideal characteristics. And as you will see, a little later on, there is no such thing as an ideal op-amp. Since the LM741/NE741/�A741 Op-Amp is the most popular one, this tutorial is direct associated with this particular type. Nowadays the 741 is a frequency compensated device.

Let's go back in time a bit and see how this device was developed.
The term "operational amplifier" goes all the way back to about 1943 where this name was mentioned in a paper written by John R. Ragazzinni with the title "Analysis of Problems in Dynamics" and also covered the work of technical aid George A. Philbrick. The paper, which was defined to the work of the U.S. National Defense Research Council, was published by the IRE in May 1947 and is considered a classic in electronics.
The very first series of modular solid-state op-amps were introduced by Burr-Brown Research Corporation and G.A. Philbrick Researches Inc. in 1962. The op-amp has been a workhorse of linear systems ever since.
The first op-amp offered to the public in 1963 was the �A702 manufactured by Fairchild Semiconductors but it had very weird supply voltages such as +12 and -6volts.

Below in Fig.1 are op-amp symbols as used today. The one on the right is an older way of drawing it but still used in books like the ARRL (American Radio Relay Leaque) and older schematics. It is common practice to omit the power supply connections as they are implied.

Op-Amp Schematic Symbols

Absolute Maximum Parameters:
Maximum means that the op-amp can safely tolerate the maximum ratings as given in the data section of such op-amp without the possibility of destroying it. The �A741 is a high performance operational amplifier with high open loop gain, internal compensation, high common mode range and exceptional temperature stability. The �A741 is short-circuit protected and allows for nulling of the offset voltage. Manufactured by Signetics Corporation.

�A741 Maximum Ratings

Supply Voltage (- + Vs): The maximum voltage (positive and negative) that can be safely used to feed the op-amp.
Dissipation (Pd): The maximum power the op-amp is able to dissipate, by specified ambient temperature (500mW @ <80� C).
Differential Input Voltage (Vid): This is the maximum voltage that can be applied across the + and - inputs.
Input Voltage (Vicm): The maximum input voltage that can be simultaneously applied between both input and ground also referred to as the common-mode voltage. In general, the maximum voltage is equal to the supply voltage.
Operating Temperature (Ta): This is the ambient temperature range for which the op-amp will operate within the manufacutre's specifications. Note that the military grade version (�A741)has a wider temperature range than the commercial, or hobbyist, grade version (�A741C).
Output Short-Circuit Duration: This is the amount of time that an op-amp's ouput can be short-circuited to either supply voltage.

#169

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Fri Jun 15, 2001 3:35 pm
Subject: Colour (Sound) Organ

nsfetcu@...

Colour (Sound) Organ

Anyone who has been to a night club, concert or school dance has probobly seen a colour organ. Colour organs cause lights to blink and flash to music from your TV, stereo, guitar and even your own voice. The colour organ presented here needs no connection to the sound source, it picks up sound from its built in microphone.

Schematic

PC board layout

This is the printed circuit layout of the Colour Organ

Parts Placement

Parts:

Part	Total Qty.	Description	Substitutions
C1	1	22uf 250V Electrolytic Capacitor
C2	1	22uf 250V Electrolytic Capacitor
C3	1	0.1uf Disc Capacitor
C4	1	0.01uf Disc Capacitor
C5	1	0.0047uf Disc Capacitor
R1	1	47K 1/2 W Resistor
R2, R4	2	6.8K 1/2 W Resistor
R3, R5	2	1M 1/2 W Resistor
R6	1	3.3K 1/2 W Resistor
R7, R8, R9	3	1K 1/2 W Resistor
R10, R11, R12	3	10K Pot
D1	1	1N4004 Diode
Q1, Q2	2	2N3904 NPN Transistor	2N2222
Q3, Q4, Q5	3	106B1 SCR	Teccor S2003LS1
T1	1	10K:600 Ohm Audio Transformer
S1	1	SPDT Switch
J1, J2, J3	3	AC Socket
MISC	1	AC Line Cord, Crystal Microphone, Case, Wire

Notes:

1. R10, R11 and R12 control the response of the different lights.

2. The circuit can handle up to 300 watts per channel.

3. This circuit is NOT isolated from the 115 Volt line. If it is used with the case opened or not installed in a case, you could recieve a bad shock or be killed.

4. You can also use the Teccor S2003LS1 SCR for SCR1. These give better sensitivity and brightness than the 106B1 units.

#168

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Thu Jun 14, 2001 11:10 pm
Subject: Clock Generator

nsfetcu@...

o - Excellent clock generator to drive 4017 type cmos circuits.
o - R1 = 10K to 10M, C1 = 100pF to 47uF.
o - Fo is �1Kz when R1=100K and C1=10nF.
o - Input voltage can be from 5 to 15V.

#167

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Wed Jun 13, 2001 2:44 pm
Subject: Joysticks and other game controllers

nsfetcu@...

Joysticks and other game controllers

By Tomi Engdal 1996-1998

DISCLAIMER: This information and the circuits are provided as is without any express or implied warranties. I disclaim everything. The contents of the articles below might be totally inaccurate, inappropriate, or misguided. There is no guarantee as to the suitability of said circuits and information for any purpose whatsoever other than as a self-training aid. I.E. If it blows your equipments, trashes your hard disc, wipes your backup, burns your building down or just plain don't work, IT ISN'T MY FAULT. In the event of judicial ruling to the contrary, any liability shall be limited to the sum charged on you by us for the aforementioned document or nothing, whichever is the lower.

NOTE: If you do not find the information you are looking for from this document collection or from links I have provived then please DO NOT send me e-mail and ask where to find that information. I receive already too many questions on special joystick I know nothing about and I don't want to spend my days on replying those mails. If the information on some special joystick is here then I don't have information on it. If the information is not complete then I don't have more information than that.

Introduction to joysticks
- Different joystick types and other game controllers
- Comparision of analogue and digital joysticks features
PC analogue joystick interface
Special PC joysticks
Circuits for PC joystick interface
Strange PC joystick interfacing ideas
- Interfacing Atari style joysticks to serial and parallel port
- Parallel Gameport Adapter
- Digital JoyStick for the IBM-PC Parallel Printer Port
- Use game console joysticks with PC
Atari style digital joysticks
- Pinout and circuit diagram
Amiga curcuits
- PC Analogue Joystick to Amiga
- PC Gamepad to Amiga
- Adding four joystick to Commodore Amiga
Other computer joystick interfaces
- Apple Macintosh
Joystick used in TV games
Light guns
- Sega lightgun pinout
- How lightguns work
Information sources

If you have problems on finding components to the electronics project on this document collection then don't e-mail me how to find those components. I know where to buy the components in Helsinki in Finland. If you happen to live in some other country or city then I don't know what are good places for you toget those components. Please consult my list of electronics component dealers to find one which can supply you the components.

If you don't want to stay on-line all the time reading this, you can download an off-line readable version. It is a zip file with size of around 200 kilobytes. The off-line version contains also version information which you can use to see if the one you have is older than the one here in on-line (just compare the dated on your off-line versio and version information of this on-line version).

If you find something which is wrong in the documents then e-mail about the problem and I will try to correct possible errors or remove incorrect information. When you report about the problem then write a good description which states form what document you got the information, what is wrong in it and why you think the information is wrong. If you know what corrections should be done to the document then please specify it also. New information to be added to the documents is also wellcome, especially Windows programming examples because it is frequently asked but I have not found good information about it.

#166

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Tue Jun 12, 2001 7:54 pm
Subject: Automatic Device Locator

nsfetcu@...

Table 1

Part	Description	Radio Shack	Digi Key	Notes
IC1	LM555 timer/oscillator	276-1723		NE555, etc.
T1	2N3906 transistor			NPN, 50V150mA
R1*	3M3 resistor		3M3QBK-ND	orange orange blue gold
R2	1K resistor		1KQBK-ND	brown black red gold
C1*	220�F, 16V capacitor			electrolytic (see text)
C2	220�F, 16V capacitor			electrolytic

A Couple of Final Notes:

o All partnumbers are Radio Shack/Tandy or DigiKey unless otherwise indicated.

o All resistors are minimum 5%, 1/4 watt, regular carbon, unless otherwise indicated. 3M3 (R1) is the same as 3.3M

o With this circuit you can find your aircraft easily in high grass, corn fields, soybeans or whatever. As soon as you power on you receiver the timer will start to count down.

o If you power the unit via the receiver battery, make sure to purchase a 3 - 6 volt buzzer! Remember that in the case of a crash (heaven forbid!) the receiver may loose its power from the battery pack because of the force of impact. It would be safer to provide the ADL with a 9-volt Alkaline battery + on/off switch and wrap the whole thing in 1/4" SIG latex rubber.

o The timer, with the components shown above, goes off in about 18 minutes @ 9-volt. To increase the delay, increase the value of R1. Also, R1 could be made adjustable with a 5-Mega Ohm trimpot of the proper wattage.

o The ADL can be used for all forms of R/C equipment, the only thing needed may be to adjust the delay to tailor your needs.

o This device is tested for interference with JR, Futaba, HiTec, Airtronics, and ACE radio equipment. None were found and none are expected when used with other brands of Radio equipment.

#165

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Mon Jun 11, 2001 4:09 pm
Subject: Black Light

nsfetcu@...

Black Light

This circuit is a simple ultraviolate light that can be powered by a 6 volt battery or power that is capable of supplying 1 or more amps.

Schematic

PCB Layout and Parts Placement

Parts

Part	Total Qty.	Description	Substitutions
C1	1	0.0047uf Mono Capacitor
C2	1	0.1uf Disc Capacitor
D1, D2	2	1N4007 Diode
FTB	1	Filtered Blacklight Tube
IC1	1	555 Timer IC
P1	1	10k Trim Pot
Q1	1	TIP30 PNP Power Transistor
R1	1	470 Ohm Resistor
R2	1	270 Ohm Resistor
S1	1	Slide Switch
T1	1	Medium Yellow Inverter Transformer
MISC	1	IC Socket, Heat Sink For Q1, Screw, Nut, Wire and PC Board

Notes:

1. P1 changes brightness of the black light tube.

2. Transformer T1 and the blacklight tube are available from The Electronics Goldmine

#164

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Fri Jun 8, 2001 8:20 pm
Subject: 555 Timer Tester

nsfetcu@...

Parts List
R1 = 68K, 5%
R2 = 39K, 5%
C1 = 1uF, 16V
C2 = 10nF (0.01uF) ceramic
Two red led's
8-pin dip socket
On-off switch or push-on switch

1 - The ON-OFF Switch is optional, as is the Pulse output.
2 - When both led's are flashing your 555 is most likely in good shape; if one or both are not flashing, not lit, or are on solid, the 555 is defective. Throw it out!
3 - The flashrate can be adjusted by using a different value for C2.

#163

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Thu Jun 7, 2001 3:32 pm
Subject: 555 Timer Tutorial (6)

nsfetcu@...

The following circuits are examples of how a 555 timer IC assist in combination with another Integrated Circuit. Again, don't be afraid to experiment. Unless you circumvent the min and max parameters of the 555, it is very hard to destroy. Just have fun and learn something doing it.

555 Two-tone experiment

555 Recorder Beep Coin Toss

555 Logic Probe with Pulse

Circuits 11 to 14:
Play with different indicating devices such as bells, horns, lights, relays, or whatever (if possible). Try different types of LDR's. If for any reason you get false triggering, connect a ceramic 0.01uF (=10nF) capacitor between pin 5 (555) and ground. In all circuit diagrams below I used the LM555CN timer IC from National. The 555 timer will work with any voltage between 3.5 and 15volt. A 9-volt battery is usually a general choice. Keeping notes is an important aspect of the learning process.

Fig. 11, Two-Tones: The purpose of this experiment is to wire two 555 timers together to create a 2-note tone. If you wish, you can use the dual 556 timer ic.

Fig. 12, Recording Beep: This circuit is used to keep recording of telephone conversations legal. As you may know, doing otherwise without consent of the other party is illegal. The output of IC1 is fed to the 2nd 555's pin 3 and made audible via C2 and the speaker. Any 8-ohm speaker will do.

Fig. 13, Coin Toss: Electronic 'Heads-or-tails' coin toss circuit. Basically a Yes or No decision maker when you can't make up your mind yourself. The 555 is wired as a Astable Oscillator, driving in turn, via pin 3, the 7473 flip-flop. When you press S1 it randomly selects the 'Heads' or 'Tails' led. The leds flashrate is about 2Khz (kilo-Hertz), which is much faster than your eyes can follow, so initially it appears that both leds are 'ON'. As soon as the switch is released only one led will be lit.

Fig. 14, Logic Probe: Provides you with three visible indicators; "Logic 1" (+, red led), "Logic 0" (-, green led), and "Pulse" (yellow led). Good for TTL and CMOS. The yellow or 'pulse' led comes on for approximately 200 mSec to indicate a pulse without regards to its width. This feature enables one to observe a short-duration pulse that would otherwise not be seen on the logic 1 and 0 led's. A small switch (subminiature slide or momentary push) across the 20K resistor can be used to keep this "pulse" led on permanently after a pulse occurs.
In operation, for a logic 0 input signal, both the '0' led and the pulse led will come 'ON', but the 'pulse' led will go off after 200 mSec. The logic levels are detected via resistor R1 (1K), then amplified by T1 (NPN, Si-AF Preamplifier/Driver), and selected by the 7400 IC for what they are. Diode D1 is a small signal diode to protect the 7400 and the leds from excessive inverse voltages during capacitor discharge.
For a logic '1' input, only the logic '1' led (red) will be 'ON'. With the switch closed, the circuit will indicate whether a negative-going or positive-going pulse has occurred. If the pulse is positive-going, both the '0' and 'pulse' led's will be on. If the pulse is negative-going, the '1' and 'pulse' led's will be on.

Table 2, variations in manufacturer

Check the listing in Table 2. It shows some variations in the 555 manufacturing process by two different manufacturers, National Semiconductor and Signetics Corporation. Since there are other manufacturers then those two I suggest when you build a circuit to stick with the particular 555 model they specify in the schematic.
Unless you know what you're doing ofcourse... [grin].

The absolute maximum ratings (in free air) for NE/SA/SE types are:

 Vcc, supply voltage: 18V
Input voltage (CONT, RESET, THRES, TRIG): Vcc
Output current: 225mA (approx)
Operating free-air temp. range: NE555........... 0�C - 70�C
SA555........... -40�C - 85�C
SE555, SE555C... -55�C - 125�C
Storage temperature range: -65�C - 150�C
Case temperature for 60sec. (FK package): 260�C

Suggested Reading:

1. 555 Timer IC Circuits. Forrest M. Mims III, Engineer's Mini Notebook. Radio Shack Cat. No: 62-5010.
"Create & experiment with pulse generators, oscillators, and time delays."

2. IC Timer Cookbook. Walter G. Jung. Published by Howard W. Sams & Co., Inc. ISBN: 0-672-21932-8.
"A reference 'must' for hobby, technicians, and engineers."

3. The 555 Timer Applications Sourcebook. Howard M. Berlin. Published by Sams Inc. ISBN: 0-672-21538-1.
"Learn how to connect the 555, perform 17 simple experiments."

#162

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Wed Jun 6, 2001 3:12 pm
Subject: 555 Timer Tutorial (5)

nsfetcu@...

Example Circuits:

I have placed a couple of 555 circuit examples below for your convenience. Play with different component values and use the formulas mentioned earlier to calculate your results. Things to remember: For proper monostable operation with the 555 timer, the negative-going trigger pulse width should be kept short compared tot he desired output pulse width. Values for the external timeing resistor and capacitor can either be determined from the previous formulas. However, you should stay within the ranges of resistances shown earlier to avoid the use of large value electrolytic capacitors, since they tend to be leaky. Otherwise, tantalum or mylar types should be used. (For noise immunity on most timer circuits I recommend a 0.01uF (10nF) ceramic capacitor between pin 5 and ground.) In all circuit diagrams below I used the LM555CN timer IC from National, but the NE555 and others should not give you any problems

Dark Detector      Power Alarm

Tilt Switch      Elec-Eye Alarm

Metronome      CW Keyer

CW Monitor      10-Min. Timer

Schmitt Trig.      Better Timing

Circuits 1 to 10:
Play with different indicating devices such as bells, horns, lights, relays, or whatever (if possible). Try different types of LDR's. If for any reason you get false triggering, connect a ceramic 0.01uF (=10nF) capacitor between pin 5 (555) and ground. Keeping the basic rules of the 555 timer, try different values for Ct and Rt (or the C & R over pins 2, 6 & 7) Replace Rt with a 1 megohm potentiometer if you wish. Make notes of the values used and use the formulas to calculate timing. Verify your calculations with your timing.

Fig. 1, Dark Detector: It will sound an alarm if it gets too dark all over sudden. For example, this circuit could be used to notify when a lamp (or bulb) burns out. The detector used is a regular cadmium-sulphide Light Dependent Resistor or LDR, for short, to sense the absense of light and to operate a small speaker. The LDR enables the alarm when light falls below a certain level.

Fig. 2, Power Alarm: This circuit can be used as a audible 'Power-out Alarm'. It uses the 555 timer as an oscillator biased off by the presence of line-based DC voltage. When the line voltage fails, the bias is removed, and the tone will be heard in the speaker. R1 and C1 provide the DC bias that charges capacitor Ct to over 2/3 voltage, thereby holding the timer output low (as you learned previously). Diode D1 provides DC bias to the timer-supply pin and, optionally, charges a rechargeable 9-volt battery across D2. And when the line power fails, DC is furnished to the timer through D2.

Fig. 3 Tilt Switch: Actually really a alarm circuit, it shows how to use a 555 timer and a small glass-encapsulated mercury switch to indicate 'tilt'.
The switch is mounted in its normal 'open' position, which allows the timer output to stay low, as established by C1 on startup. When S1 is disturbed, causing its contacts to be bridged by the mercury blob, the 555 latch is set to a high output level where it will stay even if the switch is returned to its starting position. The high output can be used to enable an alarm of the visual or the audible type. Switch S2 will silent the alarm and reset the latch. C1 is a ceramic 0.1uF (=100 nano-Farad) capacitor.

Fig. 4, Electric Eye Alarm: The Electric-Eye Alarm is actually a simular circuit like the Dark Detector of Fig. 1. The same type of LDR is used. The pitch for the speaker can be set with the 500 kilo-ohm potentiometer. Watch for the orientation of the positive (+) of the 10uF capacitor. The '+' goes to pin 3.

Fig. 5, Metronome: A Metronome is a device used in the music industry. It indicates the ritme by a 'toc-toc' sound which speed can be adjusted with the 250K potentiometer. Very handy if you learning to play music and need to keep the correct ritme up.

Fig. 6, CW Practice Oscillator: CW stands for 'Contineous Wave' or Morse-Code. You can practice the morse-code with this circuit. The 100K potmeter is for the 'pitch' and the 10K for the speaker volume. The "Key" is a morse code key.

Fig. 7, CW Monitor: This circuit monitors the morse code 'on-air' via the tuning circuit hookup to pin 4 and the short wire antenna. The 100K potmeter controls the tone-pitch.

Fig. 8, Ten-Minute Timer: Can be used as a time-out warning for Ham Radio. The Federal Communications Commission (FCC) requires the ham radio operator to identify his station by giving his call-sign at least every 10 minutes. This can be a problem, especially during lengthy conversations when it is difficult to keep track of time. The 555 is used as a one-shot so that a visual warning indicator becomes active after 10-minutes. To begin the cycle, the reset switch is pressed which causes the 'Green' led to light up. After 10 minutes, set by the 500K potentiometer R1, the 'Red' led will light to warn the operator that he must indentify.

Fig. 9, Schmitt Trigger: A very simple, but effective circuit. It cleans up any noisy input signal in a nice, clean and square output signal. In radio control (R/C) it will clean up noisy servo signals caused by rf interference by long servo leads. As long as R1 equals R2, the 555 will automatically be biased for any supply voltage in the 5 to 16 volt range. (Advanced Electronics: It should be noted that there is a 180-degree phase shift.) This circuit also lends itself to condition 60-Hz sine-wave reference signal taken from a 6.3 volt AC transformer before driving a series of binary or divide-by-N counters. The major advantage is that, unlike a conventional multivibrator type of squarer which devides the input frequency by 2, this method simply squeares the 60-Hz sine wave reference signal without division.

Fig. 10, Better Timing: Better and more stable timing output is created with the addition of a transistor and a diode to the R-C timing network. The frequency can be varied over a wide range while maintaining a constant 50% duty-cycle. When the output is high, the transistor is biased into saturation by R2 so that the charging current passes through the transistor and R1 to C. When the output goes low, the discharge transistor (pin 7) cuts off the transistor and discharges the capacitor through R1 and the diode. The high & low periods are equal. The value of the capacitor (C) and the resistor (R1 or potmeter) is not given. It is a mere example of how to do it and the values are pending on the type of application, so choose your own values. The diode can be any small signal diode like the NTE519, 1N4148, 1N914 or 1N3063, but a high conductance Germanium or Schottky type for the diode will minimize the diode voltage drops in the transistor and diode. However, the transistor should have a high beta so that R2 can be large and still cause the transistor to saturate. The transistor can be a TUN (europe), NTE123, 2N3569 and most others.

#161

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Tue Jun 5, 2001 4:35 pm
Subject: 555 Timer Tutorial (4)

nsfetcu@...

Applications:
There are literally thousands of different ways that the 555 can be used in electronic circuits. In almost every case, however, the basic circuit is either a one-shot or an astable.
The application usually requires a specific pulse time duration, operation frequency, and duty-cycle. Additional components may have to be connected to the 555 to interface the device to external circuits or devices.
In the remainder of this experiment, you will build both the one-shot and astable circuits and learn about some of the different kinds of applications that can be implemented. Furthermore, the last page of this document contains 555 examples which you can build and experiment with.

Required Parts:
In addition to a breadboard and a DC powersupply with a voltage in the 5 to 12 volt range, you will need the following components: 555 timer, LED, 2-inch /8 ohm loudspeaker, 150-ohm 1/4 watt resistor, two 10K ohm 1/4 resistors, two 1-Mega ohm 1/2 watt resistors, 10 Mega ohm 1/4 watt resistor, 0.1 uF capacitor, and a 0.68uF capacitor. All parts are available from Radio Shack or Tandy.

Experimental steps:

Fig. 11, one-shot

This circuit is resetable by grounding pin 4, so be sure to have an extra wire at pin 4 ready to test that feature.

1. On your breadboard, wire the one-shot circuit as shown in figure 11.
2. Apply power to the circuit. If you have a standard 5 volt logic supply, use it for convenience. You may use any voltage between 5 and 15 volts with a 555 timer. You can also run the circuit from battery power. A standard 9-volt battery will work perfectly.
With the power connected, note the status of the LED:
is it on or off? ________________
3. Connect a short piece of hook-up wire to the trigger input line on pin 2.
Momentarily, touch that wire to ground. Remove it quickly. That will create a pulse at the trigger input. Note and record the state of LED: _____________________
4. Continue to observe the LED and note any change in the output state
after a period of time. What is the state? ______________
5. When you trigger the one-shot, time the duration of the output pulse with
a stopwatch or the seconds hand on your watch. To do that, the instant
that you trigger the one-shot by touching the wire to ground, immediately start your stopwatch or make note of the seconds hand on your watch.
Trigger the one-shot and time the ouput pulse. Write in the approximate
value of the pulse-duration: ______________________
6. Using the values of external resistor and capacitor values in Fig. 11 and the time interval formula for a one-shot, calculate the output-pulse duration.
What is your value? _____________________
7. Compare your calculated and timed values of output pulses. Explain any discrepencies between your calculated and measured values.
Answer: _________________________________________________
8. Connect a short piece of hook-up wire to pin 4. You will use that as a reset.
9. Trigger the one-shot as indicated previously. Then immediately thouch the reset wire from pin 4 to ground. Note the LED result: _____________
10. With a DC voltmeter, measure the output voltage at pin 3 during the one
shot's off and on states. What are your values?
OFF: __________ volts ON: ___________ volts.
11. Replace the 10 MegOhm resistor with a 1 MegOhm resostor and repeat
steps 5 and 6. Record your timed and calculated results:
Timed: ________ seconds Calculated: _________seconds

Fig. 12, astable multivibrator

If you want to get fancy, after you've completed the experiment you can replace the resistors with potentiometers to build a variable function generator and play with that to learn more.


12. Next you will experiment with astable circuits. First, rewire the circuit so it appears as shown in Fig. 12.
13. Apply power to the circuit and observe the LED. What is happening?
Answer: ____________________________________________________
14. Replace the 10 MegOhm resistor with a 1 MegOhm resistor. Again observe the LED. Is the frequency higher or lower? _________________
15. Using the forumla given in the tutorial, calculate the oscillation frequency
using R1 as 10 MegOhm, and again with R1 as 1 MegOhm, and again with
R1 as 10 MegOhm. R2 is 1 MegOhm in both cases. Record your freq's:
f = _____________ Hz (R1 = 10 MegOhm)
f = _____________ Hz (R1 = 1 MegOhm)
16. Calculate the period, t1 and t2, and the duty-cycle for each resistor value:
10 MegOhm: t = ___________ t1 = ____________ t2 = ____________
1 MegOhm: t = ___________ t1 = ____________ t2= ____________

Fig. 13, with speaker

Monitoring the timer with a speaker can be amusing if you switch capacitors or resistors to make an organ.


17. Rewire the circuit making R1 and R2 10,000 ohms and C equal to 0.1uF.
Use the same circuit in Fig. 12. But, replace the LED and its resistor with a speaker and capacitor as shown in Fig. 13.
18. Apply power to the circuit and note the result: ______________________
19. Calculate the frequency of the circuit: f = ____________________ Hz
20. If you have an oscilloscope, monitor the output voltage on pin 3.
Disconnect the speaker and note the output. Also, observe the capacitor
charge and discharge at pin 6 or 2: _____________________________

Review of steps 1 through 20:
The circuit you built for those steps was a one-shot multi-vibrator. The circuit is similar to that described in the tutorial. The trigger input is held high with a 10,000 ohm resistor. When you bring pin 2 low, by touching the wire to ground, the one-shot is fired. The LED installed at the output of the 555 is used to monitor the output pulse. The LED goes on when the one-shot is triggered.
The component values selected for the circuit are large, so as to generate a long output pulse. That allows you to measure the pulse duration with a stop watch. Once the one-shot is triggered, the output LED stays on until the capacitor charges to 2/3 of the supply voltage. That triggers the upper comparator and causes the internal control flip-flop to reset, turning off the pulse and discharging the capacitor. The one-shot will remain in that state until it is triggered again.
Timing the pulse should have produced an output duration of approximately 7.5 seconds. Calculating the output time interval using the formula given previously, you found the pulse duration to be:

t = 1.1 x .68 x 10^-6 x 10⁷ = 7.48 seconds

You may have notice some difference between the calculated and actual measured values. The differences probably result from inaccuracies in your timing. Further more, component tolerances may be such that the actual values are different from the marked values.
In steps 8 and 9 you demonstrated the reset function. As you noticed, you could terminate the output pulse before the timing cycle is completed by touching pin 4 to ground. That instantly resets the flip-flop and shuts off the output pulse.
In step 10, you measured the output voltage. When off, the output is only a fraction of a volt. For all practical purposes it is zero. When triggered, the 555 generates a 3.5 volt pulse with a 5-volt supply. If you used another value of supply voltage, you would probably have discovered that the output during the pulse is about 1.5 volt less than the supply voltage.
In step11, you lowered the resistor value to 1 Megohm. As you noticed, that greatly shortens the output pulse duration. The LED only stayed on for a brief time; so brief in fact that you probably couldn't time it accurately. The calculated duration of the output pulse is 0.748 seconds.

The circuit you built for steps 12 - 20 was an astable multi-vibrator. The astable circuit is an oscillator whose frequency is dependent upon the R1, R2, and C values. In step 13, you should have found that the LED flashed off and on slowly.
The oscillation frequency is 0.176 Hz. That gives a period of:

t = 1/f = 1/.176 = 5.66 seconds

Since R1 is larger than R2, the LED will be on for a little over 5 seconds and it will stay off for only 0.5 seconds. That translates to a duty-cycle of:

D = t1/t = 5.18/5.66 = .915 or 91.5%

In step 14, you replaced the 10 MegOhm resistor with a 1 MegOhm resistor making both R1 and R2 equal. The new frequency is 0.706 Hz, much higher than in step 13. That translates to a period of 1.41 seconds. Calculating the t1 and t2 times, you see that the LED is on for 0.942 second and off for 0.467 second. That represents a duty-cycle of:

D = 0.942/1.41 = 0.67 or 67%

In step 17, you made R1 = R2 = 10,000 ohm (10K) and C = 0.1uF. That increased the frequency to 480Hz. The result should have been a loud tone in the speaker.
If you had used an oscilloscope, you saw the output to be a distorted rectangular wave of about 2 volts peak-to-peak. That distortion is caused by the speaker load. Removing it makes the waveform nice and square and the voltage rises to about 5 volts peak-to-peak. The capacitor waveform is a combination of the classical charge and discharge curves given earlier.
The time is useful in computer, function generators, clocks, music synthesizers, games, flashing lights, printers, scanners and the list goes on and on.

#160

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Mon Jun 4, 2001 7:49 pm
Subject: 555 Timer Tutorial (3)

nsfetcu@...

Monostable Mode:
The 555 in fig. 9a is shown here in it's utmost basic mode of operation; as a triggered monostable. One immediate observation is the extreme simplicity of this circuit. Only two components to make up a timer, a capacitor and a resistor. And for noise immunity maybe a capacitor on pin 5. Due to the internal latching mechanism of the 555, the timer will always time-out once triggered, regardless of any subsequent noise (such as bounce) on the input trigger (pin 2). This is a great asset in interfacing the 555 with noisy sources. Just in case you don't know what 'bounce' is: bounce is a type of fast, short term noise caused by a switch, relay, etc. and then picked up by the input pin.
The trigger input is initially high (about 1/3 of +V). When a negative-going trigger pulse is applied to the trigger input (see fig. 9a), the threshold on the lower comparator is exceeded. The lower comparator, therefore, sets the flip-flop. That causes T1 to cut off, acting as an open circuit. The setting of the flip-flop also causes a positive-going output level which is the beginning of the output timing pulse.

The capacitor now begins to charge through the external resistor. As soon as the charge on the capacitor equal 2/3 of the supply voltage, the upper comparator triggers and resets the control flip-flop. That terminates the output pulse which switches back to zero. At this time, T1 again conducts thereby discharging the capacitor. If a negative-going pulse is applied to the reset input while the output pulse is high, it will be terminated immediately as that pulse will reset the flip-flop.

Whenever a trigger pulse is applied to the input, the 555 will generate its single-duration output pulse. Depending upon the values of external resistance and capacitance used, the output timing pulse may be adjusted from approximately one millisecond to as high as on hundred seconds. For time intervals less than approximately 1-millisecond, it is recommended that standard logic one-shots designed for narrow pulses be used instead of a 555 timer. IC timers are normally used where long output pulses are required. In this applicaton, the duration of the output pulse in seconds is approximately equal to:

T = 1.1 x R x C (in seconds)

The output pulse width is defined by the above formula and with relatively few restrictions, timing components R(t) and C(t) can have a wide range of values. There is actually no theoretical upper limit on T (output pulse width), only practical ones. The lower limit is 10uS. You may consider the range of T to be 10uS to infinity, bounded only by R and C limits. Special R(t) and C(t) techniques allow for timing periods of days, weeks, and even months if so desired.
However, a reasonable lower limit for R(t) is in the order of about 10Kilo ohm, mainly from the standpoint of power economy. (Although R(t) can be lower that 10K without harm, there is no need for this from the standpoint of achieving a short pulse width.) A practical minimum for C(t) is about 95pF; below this the stray effects of capacitance become noticeable, limiting accuracy and predictability. Since it is obvious that the product of these two minimums yields a T that is less the 10uS, there is much flexibility in the selection of R(t) and C(t). Usually C(t) is selected first to minimize size (and expense); then R(t) is chosen.

The upper limit for R(t) is in the order of about 15 Mega ohm but should be less than this if all the accuracy of which the 555 is capacle is to be achieved. The absolute upper limit of R(t) is determined by the threshold current plus the discharge leakage when the operating voltage is +5 volt. For example, with a threshold plus leakage current of 120nA, this gives a maximum value of 14M for R(t) (very optimistic value). Also, if the C(t) leakage current is such that the sum of the threshold current and the leakage current is in excess of 120 nA the circuit will never time-out because the upper threshold voltage will not be reached. Therefore, it is good practice to select a value for R(t) so that, with a voltage drop of 1/3 V+ across it, the value should be 100 times more, if practical.
So, it should be obvious that the real limit to be placed on C(t) is its leakage, not it's capacitance value, since larger-value capacitors have higher leakages as a fact of life. Low-leakage types, like tantalum or NPO, are available and preferred for long timing periods. Sometimes input trigger source conditions can exist that will necessitate some type of signal conditioning to ensure compatibility with the triggering requirements of the 555. This can be achieved by adding another capacitor, one or two resistors and a small signal diode to the input to form a pulse differentiator to shorten the input trigger pulse to a width less than 10uS (in general, less than T). Their values and criterion are not critical; the main one is that the width of the resulting differentiated pulse (after C) should be less than the desired output pulse for the period of time it is below the 1/3 V+ trigger level.

There are several different types of 555 timers. The LM555 from National is the most common one these days, in my opinion. The Exar XR-L555 timer is a micropower version of the standard 555 offering a direct, pin-for-pin (also called plug-compatible) substitute device with an advantage of a lower power operation. It is capable of operation of a wider range of possitive supply voltage from as low as 2.7volt minimum up to 18 volts maximum. At a supply voltage of +5V, the L555 will typically dissipate of about 900 microwatts, making it ideally suitable for battery operated circuits. The internal schematic of the L555 is very much similar to the standard 555 but with additional features like 'current spiking' filtering, lower output drive capability, higher nodal impedances, and better noise reduction system.

Intersil's ICM7555 model is a low-power, general purpose CMOS design version of the standard 555, also with a direct pin-for-pin compatibility with the regular 555. It's advantages are very low timing/bias currents, low power-dissipation operation and an even wider voltage supply range of as low as 2.0 volts to 18 volts. At 5 volts the 7555 will dissipate about 400 microwatts, making it also very suitable for battery operation. The internal schematic of the 7555 (not shown) is however totally different from the normal 555 version because of the different design process with cmos technology. It has much higher input impedances than the standard bipolar transistors used. The cmos version removes essentially any timing component restraints related to timer bias currents, allowing resistances as high as practical to be used.
This very versatile version should be considered where a wide range of timing is desired, as well as low power operation and low current sync'ing appears to be important in the particular design.
A couple years after Intersil, Texas Instruments came on the market with another cmos variation called the LINCMOS (LINear CMOS) or Turbo 555. In general, different manufacturers for the cmos 555's reduced the current from 10mA to 100�A while the supply voltage minimum was reduced to about 2 volts, making it an ideal type for 3v applications. The cmos version is the choice for battery powered circuits. However, the negative side for the cmos 555's is the reduced output current, both for sync and source, but this problem can be solved by adding a amplifier transistor on the output if so required. For comparison, the regular 555 can easily deliver a 200mA output versus 5 to 50mA for the 7555. On the workbench the regular 555 reached a limited output frequency of 180Khz while the 7555 easily surpassed the 1.1Mhz mark and the TLC555 stopped at about 2.4Mhz. Components used were 1% Resistors and low-leakage capacitors, supply voltage used was 10volt.

Fig. 9b, Astable example Astable operation: Figure 9b shows the 555 connected as an astable multivibrator. Both the trigger and threshold inputs (pins 2 and 6) to the two comparators are connected together and to the external capacitor. The capacitor charges toward the supply voltage through the two resistors, R1 and R2. The discharge pin (7) connected to the internal transistor is connected to the junction of those two resistors.

When power is first applied to the circuit, the capacitor will be uncharged, therefore, both the trigger and threshold inputs will be near zero volts (see Fig. 10). The lower comparator sets the control flip-flop causing the output to switch high. That also turns off transistor T1. That allows the capacitor to begin charging through R1 and R2. As soon as the charge on the capacitor reaches 2/3 of the supply voltage, the upper comparator will trigger causing the flip-flop to reset. That causes the output to switch low. Transistor T1 also conducts. The effect of T1 conducting causes resistor R2 to be connected across the external capacitor. Resistor R2 is effectively connected to ground through internal transistor T1. The result of that is that the capacitor now begins to discharge through R2.

The only difference between the single 555, dual 556, and quad 558 (both 14-pin types), is the common power rail. For the rest everything remains the same as the single version, 8-pin 555.

Fig. 10, initial charge-up As soon as the voltage across the capacitor reaches 1/3 of the supply voltage, the lower comparator is triggered. That again causes the control flip-flop to set and the output to go high. Transistor T1 cuts off and again the capacitor begins to charge. That cycle continues to repeat with the capacitor alternately charging and discharging, as the comparators cause the flip-flop to be repeatedly set and reset. The resulting output is a continuous stream of rectangular pulses.

The frequency of operation of the astable circuit is dependent upon the values of R1, R2, and C. The frequency can be calculated with the formula:

f = 1/(.693 x C x (R1 + 2 x R2))

The Frequency f is in Hz, R1 and R2 are in ohms, and C is in farads.
The time duration between pulses is known as the 'period', and usually designated with a 't'. The pulse is on for t1 seconds, then off for t2 seconds. The total period (t) is t1 + t2 (see fig. 10).
That time interval is related to the frequency by the familiar relationship:

f = 1/t

t = 1/f

The time intervals for the on and off portions of the ouput depend upon the values of R1 and R2. The ratio of the time duration when the ouput pulse is high to the total period is known as the duty-cycle. The duty-cycle can be calculated with the formula:

D = t1/t = (R1 + R2) / (R1 + 2R2)

You can calculate t1 and t2 times with the formulas below:

t1 = .693(R1+R2)C

t2 = .693 x R2 x C

The 555, when connected as shown in Fig. 9b, can produce duty-cycles in the range of approximately 55 to 95%. A duty-cycle of 80% means that the ouput pulse is on or high for 80% of the total period. The duty-cycle can be adjusted by varying the values of R1 and R2.

#159

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Fri Jun 1, 2001 8:45 pm
Subject: 555 Timer Tutorial (2)

nsfetcu@...

Definition of Pin Functions:

Refer to the internal 555 schematic of Fig. 4-2

Pin 1 (Ground):  The ground (or common) pin is the most-negative supply potential of the device, which is normally connected to circuit common when operated from positive supply voltages.

Pin 2 (Trigger):  This pin is the input to the lower comparator and is used to set the latch, which in turn causes the output to go high. This is the beginning of the timing sequence in monostable operation. Triggering is accomplished by taking the pin from above to below a voltage level of 1/3 V+ (or, in general, one-half the voltage appearing at pin 5). The action of the trigger input is level-sensitive, allowing slow rate-of-change waveforms, as well as pulses, to be used as trigger sources.
One precaution that should be observed with the trigger input signal is that it must not remain lower than 1/3 V+ for a period of time longer than the timing cycle. If this is allowed to happen, the timer will retrigger itself upon termination of the first output pulse. Thus, when the timer is driven in the monostable mode with input pulses longer than the desired output pulse width, the input trigger should effectively be shortened by differentiation.
The minimum-allowable pulse width for triggering is somewhat dependent upon pulse level, but in general if it is greater than the 1uS (micro-Second), triggering will be reliable.
A second precaution with respect to the trigger input concerns storage time in the lower comparator. This portion of the circuit can exhibit normal turn-off delays of several microseconds after triggering; that is, the latch can still have a trigger input for this period of time after the trigger pulse. In practice, this means the minimum monostable output pulse width should be in the order of 10uS to prevent possible double triggering due to this effect.
The voltage range that can safely be applied to the trigger pin is between V+ and ground. A dc current, termed the trigger current, must also flow from this terminal into the external circuit. This current is typically 500nA (nano-amp) and will define the upper limit of resistance allowable from pin 2 to ground. For an astable configuration operating at V+ = 5 volts, this resistance is 3 Mega-ohm; it can be greater for higher V+ levels.

Pin 3 (Output):  The output of the 555 comes from a high-current totem-pole stage made up of transistors Q20 - Q24. Transistors Q21 and Q22 provide drive for source-type loads, and their Darlington connection provides a high-state output voltage about 1.7 volts less than the V+ supply level used. Transistor Q24 provides current-sinking capability for low-state loads referred to V+ (such as typical TTL inputs). Transistor Q24 has a low saturation voltage, which allows it to interface directly, with good noise margin, when driving current-sinking logic. Exact output saturation levels vary markedly with supply voltage, however, for both high and low states. At a V+ of 5 volts, for instance, the low state Vce(sat) is typically 0.25 volts at 5 mA. Operating at 15 volts, however, it can sink 100mA if an output-low voltage level of 2 volts is allowable (power dissipation should be considered in such a case, of course). High-state level is typically 3.3 volts at V+ = 5 volts; 13.3 volts at V+ = 15 volts. Both the rise and fall times of the output waveform are quite fast, typical switching times being 100nS.
The state of the output pin will always reflect the inverse of the logic state of the latch, and this fact may be seen by examining Fig. 3. Since the latch itself is not directly accessible, this relationship may be best explained in terms of latch-input trigger conditions. To trigger the output to a high condition, the trigger input is momentarily taken from a higher to a lower level. [see "Pin 2 - Trigger"]. This causes the latch to be set and the output to go high. Actuation of the lower comparator is the only manner in which the output can be placed in the high state. The output can be returned to a low state by causing the threshold to go from a lower to a higher level [see "Pin 6 - Threshold"], which resets the latch. The output can also be made to go low by taking the reset to a low state near ground [see "Pin 4 - Reset"].

Pin 4 (Reset):  This pin is also used to reset the latch and return the ouput to a low state. The reset voltage threshold level is 0.7 volt, and a sink current of 0.1mA from this pin is required to reset the device. These levels are relatively independent of operating V+ level; thus the reset input is TTL compatible for any supply voltage.
The reset input is an overriding function; that is, it will force the output to a low state regardless of the state of either of the other inputs. It may thus be used to terminate an output pulse prematurely, to gate oscillations from "on" to "off", etc. Delay time from reset to output is typically on the order of 0.5 uS, and the minumum reset pulse width is 0.5 uS. Neither of these figures is guaranteed, however, and may vary from one manufacturer to another. When not used, it is recommended that the reset input be tied to V+ to avoid any possibility of false resetting.

Pin 5 (Control Voltage):  This pin allows direct access to the 2/3 V+ voltage-divider point, the reference level for the upper comparator. It also allows indirect access to the lower comparator, as there is a 2:1 divider (R8 - R9) from this point to the lower-comparator reference input, Q13. Use of this terminal is the option of the user, but it does allow extreme flexibility by permitting modification of the timing period, resetting of the comparator, etc.
When the 555 timer is used in a voltage-controlled mode, its voltage-controlled operation ranges from about 1 volt less than V+ down to within 2 volts of ground (although this is not guaranteed). Voltages can be safely applied outside these limits, but they should be confined within the limits of V+ and ground for reliability.
In the event the control-voltage pin is not used, it is recommended that it be bypassed with a capacitor of about 0.01uF (10nF) for immunity to noise, since it is a comparator input.

Pin 6 (Threshold):  Pin 6 is one input to the upper comparator (the other being pin 5) and is used to reset the latch, which causes the output to go low.
Resetting via this terminal is accomplished by taking the terminal from below to above a voltage level of 2/3 V+ (the normal voltage on pin 5). The action of the threshold pin is level sensitive, allowing slow rate-of-change waveforms.
The voltage range that can safely be applied to the threshold pin is between V+ and ground. A dc current, termed the threshold current, must also flow into this terminal from the external circuit. This current is typically 100nA, and will define the upper limit of total resistance allowable from pin 6 to V+. For either timing configuration operating at V+ = 5 volts, this resistance is 16 Mega-ohm.

Pin 7 (Discharge):  This pin is the open collector of an npn transistor (Q14), the emitter of which goes to ground. The conduction state of this transistor is identical in timing to that of the output stage. It is "on" (low resistance to ground) when the output is low and "off" (high resistance to ground) when the output is high.
In both the monostable and astable time modes, this transistor switch is used to clamp the appropriate nodes of the timing network to ground. Saturation voltage is typically below 100mV (milli-Volt) for currents of 5 mA or less, and off-state leakage is about 20nA (these parameters are not specified by all manufacturers, however).
Maximum collector current is internally limited by design, thereby removing restrictions on capacitor size due to peak pulse-current discharge. In certain applications, this open collector output can be used as an auxiliary output terminal, with current-sinking capability similar to the output (pin 3).

Pin 8 (V +):  The V+ pin (also referred to as Vcc) is the positive supply voltage terminal of the 555 timer IC. Supply-voltage operating range for the 555 is +4.5 volts (minimum) to +16 volts (maximum), and it is specified for operation between +5 volts and + 15 volts. The device will operate essentially the same over this range of voltages without change in timing period. Actually, the most significant operational difference is the output drive capability, which increases for both current and voltage range as the supply voltage is increased. Sensitivity of time interval to supply voltage change is low, typically 0.1% per volt.

Fig. 5, 555 Timer Tester

Try the simple 555 testing-circuit of Fig. 5. to get you going, and test all your 555 timer ic's. I build several for friends and family. I bring my own tester to ham-fests and what not to instantly do a check and see if they are oscillating. Or use as a trouble shooter in 555 based circuits. This tester will quickly tell you if the timer is functional or not. Although not foolproof, it will tell if the 555 is shorted or oscillating. If both Led's are flashing the timer is most likely in good working order. If one or both Led's are either off or on solid the timer is defective. Simple huh?

Fig. 6, capacitor charging

The capacitor slows down as it charges, and in actual fact never reaches the full supply voltage. That being the case, the maximum charge it receives in the timing circuit (66.6% of the supply voltage) is a little over the charge received after a time constant (63.2%).

Fig. 7, capacitor discharging

The capacitor slows down as it discharges, and never quite reaches the ground potential. That means the minimum voltage it operates at must be greater than zero. Timing circuit is 63.2% of the supply voltage.

Fig. 8, discharge of a capacitor

The discharge of a capacitor also takes time and we can shorten the amount of time by decreasing resistance (R) to the flow of current.

Operating Modes: The 555 timer has two basic operational modes: one shot and astable. In the one-shot mode, the 555 acts like a monostable multivibrator. A monostable is said to have a single stable state--that is the off state. Whenever it is triggered by an input pulse, the monostable switches to its temporary state. It remains in that state for a period of time determined by an RC network. It then returns to its stable state. In other words, the monostable circuit generates a single pulse of a fixed time duration each time it receives and input trigger pulse. Thus the name one-shot. One-shot multivibrators are used for turning some circuit or external component on or off for a specific length of time. It is also used to generate delays. When multiple one-shots are cascaded, a variety of sequential timing pulses can be generated. Those pulses will allow you to time and sequence a number of related operations.

The other basic operational mode of the 555 is as and astable multivibrator. An astable multivibrator is simply and oscillator. The astable multivibrator generates a continuous stream of rectangular off-on pulses that switch between two voltage levels. The frequency of the pulses and their duty cycle are dependent upon the RC network values.

One-Shot Operation: Fig. 4 shows the basic circuit of the 555 connected as a monostable multivibrator. An external RC network is connected between the supply voltage and ground. The junction of the resistor and capacitor is connected to the threshold input which is the input to the upper comparator. The internal discharge transistor is also connected to the junction of the resistor and the capacitor. An input trigger pulse is applied to the trigger input, which is the input to the lower comparator.

With that circuit configuration, the control flip-flop is initially reset. Therefore, the output voltage is near zero volts. The signal from the control flip-flop causes T1 to conduct and act as a short circuit across the external capacitor. For that reason, the capacitor cannot charge. During that time, the input to the upper comparator is near zero volts causing the comparator output to keep the control flip-flop reset.

Fig. 9a, monostable

Notice how the monostable continues to output its pulse regardless of the inputs swing back up. That is because the output is only triggered by the input pulse, the output actually depends on the capacitor charge.

#158

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Thu May 31, 2001 6:02 pm
Subject: 555 Timer Tutorial (1)

nsfetcu@...

555 Timer Tutorial

by Tony van Roon

     The 555 timer IC was first introduced arround 1971 by the Signetics Corporation as the SE555/NE555 and was called "The IC Time Machine" and was also the very first and only commercial timer ic available. It provided circuit designers and hobby tinkerers with a relatively cheap, stable, and user-friendly integrated circuit for both monostable and astable applications. Since this device was first made commercially available, a myrad of novel and unique circuits have been developed and presented in several trade, professional, and hobby publications. The past ten years some manufacturers stopped making these timers because of competition or other reasons. Yet other companies, like NTE (a subdivision of Philips) picked up where some left off.
     This primer is about this fantastic timer which is after 30 years still very popular and used in many schematics. Although these days the CMOS version of this IC, like the Motorola MC1455, is mostly used, the regular type is still available, however there have been many improvements and variations in the circuitry. But all types are pin-for-pin plug compatible. Myself, every time I see this 555 timer used in advanced and high-tech electronic circuits, I'm amazed. It is just incredible.
     In this tutorial I will show you what exactly the 555 timer is and how to properly use it by itself or in combination with other solid state devices without the requirement of an engineering degree. This timer uses a maze of transistors, diodes and resistors and for this complex reason I will use a more simplified (but accurate) block diagram to explain the internal organizations of the 555. So, lets start slowly and build it up from there.

Table 1, Manufacturers

The first type-number, in Table 1 on the left, represents the type which was/is preferred for military applications which have somewhat improved electrical and thermal characteristics over their commercial counterparts, but also a bit more expensive, and usually metal-can or ceramic casing. This is analogous to the 5400/7400 series convention for TTL integrated circuits.

Fig. 1&2, 555 pin-out

The 555, in fig. 1 and fig. 2 above, come in two packages, either the round metal-can called the 'T' package or the more familiar 8-pin DIP 'V' package. About 20-years ago the metal-can type was pretty much the standard (SE/NE types). The 556 timer is a dual 555 version and comes in a 14-pin DIP package, the 558 is a quad version with four 555's also in a 14 pin DIP case.

Fig. 3, 555 Block Diagram

Inside the 555 timer, at fig. 3, are the equivalent of over 20 transistors, 15 resistors, and 2 diodes, depending of the manufacturer. The equivalent circuit, in block diagram, providing the functions of control, triggering, level sensing or comparison, discharge, and power output. Some of the more attractive features of the 555 timer are: Supply voltage between 4.5 and 18 volt, supply current 3 to 6 mA, and a Rise/Fall time of 100 nSec. It can also withstand quite a bit of abuse.

The Threshold current determine the maximum value of Ra + Rb. For 15 volt operation the maximum total resistance for R (Ra +Rb) is 20 Mega-ohm.

The supply current, when the output is 'high', is typically 1 milli-amp (mA) or less. The initial monostable timing accuracy is typically within 1% of its calculated value, and exhibits negligble (0.1%/V) drift with supply voltage. Thus longterm supply variations can be ignored, and the temperature variation is only 50ppm/�C (0.005%/�C).

Fig. 4, 555 Timing All IC timers rely upon an external capacitor to determine the off-on time intervals of the output pulses. As you recall from your study of basic electronics, it takes a finite period of time for a capacitor (C) to charge or discharge through a resistor (R). Those times are clearly defined and can be calculated given the values of resistance and capacitance.
The basic RC charging circuit is shown in fig. 4. Assume that the capacitor is initially discharged. When the switch is closed, the capacitor begins to charge through the resistor. The voltage across the capacitor rises from zero up to the value of the applied DC voltage. The charge curve for the circuit is shown in fig. 6. The time that it takes for the capacitor to charge to 63.7% of the applied voltage is known as the time constant (t). That time can be calculated with the simple expression:

t = R X C

Assume a resistor value of 1 MegaOhm and a capacitor value of 1uF (micro-Farad). The time constant in that case is:

t = 1,000,000 X 0.000001 = 1 second

Assume further that the applied voltage is 6 volts. That means that it will take one time constant for the voltage across the capacitor to reach 63.2% of the applied voltage. Therefore, the capacitor charges to approximately 3.8 volts in one second.

Fig. 4-1, Pulse change

Fig. 4-1, Change in the input pulse frequency allows completion of the timing cycle. As a general rule, the monostable 'ON' time is set approximately 1/3 longer than the expected time between triggering pulses. Such a circuit is also known as a 'Missing Pulse Detector'.

Looking at the curve in fig. 6. you can see that it takes approximately 5 complete time constants for the capacitor to charge to amost the applied voltage. It would take about 5 seconds for the voltage on the capacitor to rise to approximately the full 6-volts.

Fig. 4-2, Equivalent Circuit

#157

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Wed May 30, 2001 4:33 pm
Subject: 40W Fluorescent Lamp Inverter

nsfetcu@...

40W Fluorescent Lamp Inverter

This 40W fluorescent lamp inverter allows you to run 40W fluorescent tubes from any 12V source capable of delivering 3A. This is basically a larger version of the 12VDC Fluorescent Lamp Driver and can be used to light regular or blacklight tubes.

Schematic

Parts:

Part	Total Qty.	Description	Substitutions
R1	1	180 Ohm 1W Resistor
R2	1	47 Ohm 1/4W Resistor
R3	1	2.2 Ohm 1W Resistor (only needed once)
C1, C2	2	100uF 16V Electrolytic Capacitor
C3	1	100nF Ceramic Disc Capacitor
Q1	1	TIP 3055 or 2N3055 or equivalent
L1	1	See "Notes"
T1	1	See "Notes"
MISC	1	Wire, Case, Board, Heatsink For Q1, heatshrink, AM antenna rod for coil

Notes:

Wind L1/T1. You will need an AM antenna rod that is about 60mm (2.5 inches) long to wind T1/L1 on. T1/L1 are wound on the same core. Shrink a layer of heatshrink over the core to insulate it. Leave 50mm of wire at each end of the coils.
Primary: Wind 60 turns of 1mm diameter enamelled copper wire on the first layer and put a layer of heatshrink over it.
Feedback: Wind 13 turns of 0.4mm enamelled copper wire on the core and then heatshrink over that.
Secondary: This coil has 450 turns of 0.4mm enamelled copper wire in three layers. Wind one layer and then heatshrink over it. Do the same for the next two.
Transformer/Inductor Winding

Calibrate/test the circuit. To calibrate/set up the circuit connect the 2.2 Ohm 1W resistor (R3) in series with the positive supply. Connect a 40W fluorescent tube to the high voltage ends of the transformer. Momentarily connect power. If the tube doesn't light immediately reverse the connections of L1. If the tube still doesn't work, check all connections. When you get the tube to light remove the 2.2 ohm resistor and the circuit is ready for use. You will not need R3 again.

This circuit is designed for 220V lamps. It will work with 120V units just fine, but will shorten the life of the tube.

This page has been extensively rewritten by Bart Milne.

#156

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Tue May 29, 2001 8:24 pm
Subject: Frequency and Capacitance meter

nsfetcu@...

Frequency and Capacitance meter

From: kenny@...

An [...] idea is to use the 555 as a monostable, and trigger it with a fixed frequency clock. Duty cycle will be proportional to capacitance.

Circuit will look something like:

+5 ---+---------------+---+
| | |
R +----------+
|(see below) | 8 4 |
+---+------+-----|7 3|------/\/\/\---+------- Vout
: | | LMC555 | |
C to test +-----|6 | -----
: | | -----
ground +-----|2 5|----+ |
| | 1 | | ground
| +----------+ 0.1 uF
| | |
Clock ----+ ground ground
^
(see | next section - CMOS Oscillator)

The ON time for the monostable is about 1.1RC, so component values that should work would be a 50 Hz clock, say a 1 Hz low-pass filter on the output, and R = 9.09K, 1%. That combination will give an output of one volt per microfarad. Switch R in decades for smaller capacitors. Trim R for calibration.

#155

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Mon May 28, 2001 6:09 pm
Subject: Telephone Recorder

nsfetcu@...

Telephone Recorder

This nifty little circuit lets you record your phone conversations automatically. The device connects to the phone line, your tape recorder's microphone input, and the recorder's remote control jack. It senses the voltage in the phone line and begins recording when the line drops to 5 volts or less.

Schematic

Parts

Part	Total Qty.	Description	Substitutions
R1	1	270K 1/4 W Resistor
R2	1	1.5K 1/4 W Resistor
R3	1	68K 1/4 W Resistor
R4	1	33K 1/4 W Resistor
C1	1	0.22uF 150 Volt Capacitor
Q1, Q2	2	2N4954 NPN Transistor
D1	1	1N645 Diode
MISC	1	Wire, Plugs To Match Jacks On Recorder, Board, Phone Plug

Notes

1. The circuit can be placed anywhere on the phone line, even inside a phone.

2. Some countries or states require you to notify anyone you are talking to that the conversation is being recorded. Most recoders do this with a beep-beep. Also, you may have to get permission from the phone company before you connect anything to their lines.

#154

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Sun May 27, 2001 2:14 am
Subject: Third Brake Light

nsfetcu@...

( http://www.uoguelph.ca/~antoon/circ/circuits.htm )

Third Brake Light Schematic

Bench-test your circuit first and apply power to the circuit, with the brakelight connected, for at least a couple of minutes. If the two SCR's are getting hot (depending on the type of bulb in your 3rd brake light), mount coolribs on them. Here, it is used the NTE5483 which is a 8A, 200Vrm type.

#153

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Fri May 25, 2001 5:52 pm
Subject: Headlight Reminder Circuit

nsfetcu@...

Headlight Reminder Circuit

From: ps10@... (Paul Simmonds)

A [...] solution is to go from the +12 Switched sidelight feed, via a buzzer to the drivers door light switch, you then need to put a diode in the door circuit to stop the other doors operating the buzzer.

 +12v (sidelights)
|
+-+--+
| | Buzzer (12v)
+-+--+
|
+-------|<|-------- To existing drivers interior light switch
| Diode
|
O
----| Drivers door switch
O
|
Car Chassis

Thus when you leave your lights on AND open the drivers door, the buzzer sounds. If you mean to leave your lights on, just shut the door and the buzzer stops!

Connectors: D25 male
Resistors: 640k,320k,160k,80k,40k,20k,10k,5k,390 (+-1%)
(You can use different values of resistors, but the ratio of the values of the resistors must be same. 0.5, 1, 2, 4, 8, 16, 32, 64 etc.) 1, 2, 4, 8, 16, 32, 64, 128
Capacitor: Electrolytic or solid Tantalum 10 uF 10V

SCHEMATIC

 +---+
| 2 | ---<640k>---+
| 3 | ---<320k>---+
| 4 | ---<160k>---+
| 5 | ---<80k>----+
| 6 | ---<40k>----+
| 7 | ---<20k>----+-----+---- 10 uF -------> Out
| 8 | ---<10k>----+ |
| 9 | ---<5k>-----+ <390>
| | |
| 25| ------------------+------------------+
+---+ |
===
Ground

How to build

Solder all D25 male connector pins to corresponding D25 female connector pins (pin 1 to pin 1 etc) Connect the resistors according the chematic. It is maybe not possible to obtain exact resistor values. If you can't obtain them, try nearest values. <1% deviation is acceptable.

How to use

Connect this circuit to the centronics printer port of your IBM PC or compatible. Connect the printer cable to the D25 female connector of the circuit. Your printer should work correctly with this circuit and you can keed this circuit connected all the time. Connect the sound output to your stereo system. Line in and mic lines are suitable because the output level of this circuit is adjustable (about 0-2V PP). The sound quality is very good.

#152

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Thu May 24, 2001 11:19 pm
Subject: 'Nixie' display tubes

nsfetcu@...

'Nixie' display tubes

From: mkuhn@... (Martin W Kuhn)

Nixies are lots of fun. I just recently built a digital clock out of Nixies, so I think I can help you here. (BTW, if anyone is interested in details of the clock, let me know)

There is no heater connection; these are not like vaccuum tubes. There may be some unused pins, however, or perhaps they are for a decimal point or other symbol the old equipment didn't use.

Nixies have a cathode for each symbol, and one anode which is used for all the symbols (usually a grid-shaped element in the middle of or in front of the symbol elements.)

Here's a super-simple power supply to try experimenting with them:

 D R
<------>|-------/\/\/\/---
^
|---------------> To anode terminal
To |
120 VAC | C
----|(----
|
<--------------------------|----> To selected cathode
D : any rectifier diode of >= 250 PIV
R : 100 K or so variable resistor
C : 20 uf (or more) at at least 250 WVDC (observe polarity!)

CAUTION: Take care when using the above circuit! If you have an isolation transformer around, use it! Output of this supply can be over 150 VDC! Also, make sure you discharge C when you are done using it--- It is a good idea to wire a resistor across C when you use this circuit as a shunt. (something like 100K to 1M or so is fine) Make sure you connect it to the tube BEFORE plugging it into an outlet, in order to avoid a nasty shock by accidently touching the output leads! A .5 amp or so fuse might be a good idea too, to protect against short circuits.

NOTE: This might not be the best possile circuit, and others might want to suggest changes to it, but it works, and is simple enough.

After you wire it up, connect it to the anode and one of the cathodes. Make sure R is at its MAXIMUM resistance. After you plug it in, slowly adjust R until the selceted digit just manages to glow completely. If the wire lead connecting the number to the pin on the base of the tube also glows, then R is too low; turn it back! The exact voltage necessary to light the tube will depend on the particular tube you are using. Also, you may want to wire an ammeter in series with the tube when you first try this out. The tube should only draw a few mA. If it draws much more than 5mA or so, something is probably wrong!

BTW, the Nixies should glow a "pure" even amber-orange color. If they are sort of a lighter color with blueish fringes, then they are somewhat gassy, but still usable. If you see blue "clouds" in the tube and/or the symbols are fuzzy and indistinct, then the neon has gotten too contaminated, and the tube should not be used.

If you are planning to use Nixies in something like a logic circuit, you can easily drive them with any NPN transistor with a CEO of at least 200V and an Ic of at least 10mA or so. (actually, low-power high-voltage transistors of this type are not so easy to get these days)

If you have any specific problems/questions let me know; I am not sure what sort of info you are looking for. Hope this helps, anyway.

#151

From: "Nicolae Sfetcu" <nsfetcu@...>
Date: Wed May 23, 2001 4:54 pm
Subject: 'Rounding Off' a square wave

nsfetcu@...

'Rounding Off' a square wave

From: CXW14@... Christopher Webster

To "round" your square wave, you need to integrate it twice; once to produce a triangular wave, and a second time to produce a parabolic waveform. (A parabolic wave looks pretty much sinusoidal.) You can do this passively using a simple network such as the one shown below. Let R2 = 10*R1, and let R1*C1 = R2*C2 = 1/f, where 'f' is the frequency of the applied square wave. It's important that R2 be much (at least a factor of 5 or so) smaller than the input impedance of the amplifier; likewise, R1 should be a good bit larger than the microcontroller's output impedance.

 R1 R2
from u-controller >---/\/\/\----*----/\/\/\----*----> to amplifier
| |
| |
C1 ----- C2 -----
----- -----
| |
| |
----- -----
--- ---
- -

Note that this is nothing more than a two-pole low pass filter; however, the filter cutoff frequency is placed BELOW the square wave's fundamental, so the circuit isn't just filtering out the higher harmonics of the incoming waveform. To see that this is so, change the square wave's duty cycle--this will produce a similar change in the width of the "humps" in the output waveform.

From: apollo@... (Andrew P. Herdman)

Just create a low pass filter set a couple of khz above the frequency your square wave is running at. Seeing a squarewave is made up of an infinite amount (well supposed to be inifinite but we'll settle for a lot) of odd harmonics, cutting off all the harmonics after the first will usually result in a nice sinewave. Something like this will do:

 R
o------/\/\/\/\-----+-------------o Sine wave out.
|
Square Wave in | fc=1/(2piRC)
=C where fc= -3dB drop (half power
| point). There may be a slight
| shift. Live with it.
o-------------------+-------------o