Hi all,

I have a 0-5 volt signal into my ADC and was looking for a way to
change the input range before the ADC to get a little better
resolution.

A 10:1 is the maximum amplification I would be using and it is all in a
linear fashion.

That said, I can use a single channel of an op-amp to get
amplification, but in looking for the most appropriate op-amps, I keep
coming across instrumentation op-amps and they typically use 3 or 4
channels.

I have found stuff on how to use them, but not why to use one style
over another.   I guess that by using both the inverting and non-
inverting, that any temperature or power changes will be negated and
the output will remain accurate.

Can anyone offer better facts than my conjecture?

Dave

If your signal is single ended, I see no advantage in using a balanced
amplifier. Especially if it is all on the same PCB and you are careful
to avoid ground current loops.

A reason to go differential would be if the signal starts out 10 feet
or more away. Then you want it to send a differential signal from the
sensor.

Steve Greenfield aka Alien Steve

--- In Electronics_101@yahoogroups.com, "Dave Mucha" <dave_mucha@y...>
wrote:
> Hi all,
>
> I have a 0-5 volt signal into my ADC and was looking for a way to
> change the input range before the ADC to get a little better
> resolution.
>
> A 10:1 is the maximum amplification I would be using and it is all in a
> linear fashion.
>
> That said, I can use a single channel of an op-amp to get
> amplification, but in looking for the most appropriate op-amps, I keep
> coming across instrumentation op-amps and they typically use 3 or 4
> channels.
>
> I have found stuff on how to use them, but not why to use one style
> over another.   I guess that by using both the inverting and non-
> inverting, that any temperature or power changes will be negated and
> the output will remain accurate.
>
> Can anyone offer better facts than my conjecture?
>
> Dave

Once again, I have to recommend "Op Amps For Everyone", a free book
available at www.ti.com.  Particularly appropriate for single supply
rail-to-rail op amp circuits which will allow you to scale and
offset in one operation.

Chapter 4 is what you need.

--- In Electronics_101@yahoogroups.com, rgsparber@a... wrote:
> In a message dated 12/1/2003 9:34:02 AM Central Standard Time,
> dave_mucha@y... writes:
> I have a 0-5 volt signal into my ADC and was looking for a way to
change the
> input range before the ADC to get a little better resolution.
>
> A 10:1 is the maximum amplification I would be using and it is all
in a
> linear fashion.
>
> That said, I can use a single channel of an op-amp to get
amplification, but
> in looking for the most appropriate op-amps, I keep coming across
> instrumentation op-amps and they typically use 3 or 4 channels.
>
> I have found stuff on how to use them, but not why to use one
style over
> another.   I guess that by using both the inverting and non-
inverting, that any
> temperature or power changes will be negated and the output will
remain
> accurate.
>
> Can anyone offer better facts than my conjecture?
>
> Dave
> I'm a bit confused here. Your ADC has an input range of 0 to 5V.
What is the
> desired input range of your system? Are you saying that you want
it to be 0 to
> 0.5V with the x10 amp? What input resistance do you want and what
frequency
> range do you expect.
>
> Assuming you want a x10 amp with less than 10K input resistance,
any old
> cheap OP amp should work fine given proper external circuit.
>
> Rick Sparber
> rgsparber@A...

> Dave
> I'm a bit confused here. Your ADC has an input range of 0 to 5V. What is the
> desired input range of your system? Are you saying that you want it to be 0 to
> 0.5V with the x10 amp? What input resistance do you want and what frequency
> range do you expect.
>
> Assuming you want a x10 amp with less than 10K input resistance, any old
> cheap OP amp should work fine given proper external circuit.
>
> Rick Sparber
> rgsparber@A...

The off-board sensor has a 0-5 volt response and reports it's value
back to my ADC.

a 0 to 100 psi sensor would offer 0-100psi = 0-5VDC.  if I can double
the input value, that would make the sensor a 0 to 100 with a 0-10V
range, or a 0 to 50psi with 0-5V,  4x the input would simulate the
sensor as 0 to 25 psi @ 0-5V.  (ADC is 0-5VDC input)

I do understand that if the device accuracy is 1% of full span  ie:1%
of 100, it too is multiplied.  so a 0 to 25 psi range has a 4% error.
at some point, the error can be greater than the sensing range.

Since I have a common ground it may be that the single ended input
means I can use a single op-amp.  also since I cannot ampliphy the
input excessivly, it also seems that a 5x range is all I may be able to
use, but that should be enough.

As for the "Op-Amps for Everyone" I think I may need to review that to
get the theory why a single channel vs the Insturmentation style.

Dave
(ps: sorry for the spelling, I'm using my wife's MAC as my AXT power
supply went POP rather abruptly on Thanksgiving.)

--- In Electronics_101@yahoogroups.com, "Dave Mucha" <dave_mucha@y...>
wrote:

> The off-board sensor has a 0-5 volt response and reports it's value
> back to my ADC.

The advantage to differential would be in putting the single ended to
differential conversion at the sensor. Then it is more noise resistant.


> Dave
> (ps: sorry for the spelling, I'm using my wife's MAC as my AXT power
> supply went POP rather abruptly on Thanksgiving.)

Yeah, the keyboards different and the electrons have that Mac smell...
nice try, Dave. ;')

>
> > Dave
> > (ps: sorry for the spelling, I'm using my wife's MAC as my AXT power
> > supply went POP rather abruptly on Thanksgiving.)
>
> Yeah, the keyboards different and the electrons have that Mac smell...
> nice try, Dave. ;')

Nope, just teh way teh desks are situated.

seems I just cannot type with my hands and arms laying across the desk
as she has it.

but for the PC, it went POP in a big way !

blew 8 of the 10 caps on the motherboard.
and the Hard Disk will not spin up in another computer.

Can you say "____________" (insert your favorite profanity)

seems I will attempt a brain transplant on the hard drive.
swap not only the IDE board on the drive itself, but also the heads
inside.  Just to save a measly $1,500 from one of those recovery
houses.

(recommendations more than welcome)

I was thinking of just drilling a little hole on the side, but when all
the 1's an 0's come out, it gets real hard to tape and staple them onto
another drive.

Dave
(and as you might notice, I wern't a good speller to begin wit.)

Hi,

I would like to know if any of you have a schematic of a electronic cable
tester (for DB9, DB25, DB37,...).

I want something that I could built using simple logic (no microcontroler).


thanks to all,

David Levasseur

What is the difference between power dissipation at Ta=25C and power
dissipation at TC=25C? I understand that Ta is ambient temperature
and assume that TC is temperature of the casing.

TC is usually much higher than Ta and I was wondering if this is
because if the temperature of the air is 25C and there is no
heatsink, that the maximum allowable power will be much lower because
less heat can be transferred away from the casing, while if a
heatsink is used, it will dissipate the heat from the casing much
better, approaching 25C and allowing the power to be higher?

Thanks for any information,

Tom

----- Original Message -----

From: tom_bihn

To: Electronics_101@yahoogroups.com

Sent: 12/2/03 9:11:14 AM

Subject: [Electronics_101] Question on spec sheet parameter in BJT spec sheet

What is the difference between power dissipation at Ta=25C and power
dissipation at TC=25C? I understand that Ta is ambient temperature
and assume that TC is temperature of the casing.

TC is usually much higher than Ta and I was wondering if this is
because if the temperature of the air is 25C and there is no
heatsink, that the maximum allowable power will be much lower because
less heat can be transferred away from the casing, while if a
heatsink is used, it will dissipate the heat from the casing much
better, approaching 25C and allowing the power to be higher?

Thanks for any information,

Tom



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Electronics_101-unsubscribe@yahoogroups.com



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OK... The spec sheet gives:

Pc(@Ta=25C) = 1W
Pc(@TC=25C) = 10W
Tj = 150C

The derating curve shows Pc=10W at Tc=25C with a straight line to
Pc=0 at 150C. I'm not real clear yet how the two Pc terms work into
the equation. Is it simply saying that if an ideal heatsink were
chosen that could transfer all the heat away from the casing, making
it the same as ambient, that the transistor would be able to handle
10W?

Thanks for your patience,

Tom

--- In Electronics_101@yahoogroups.com, "Scott Thompson"
<electronguy@e...> wrote:
> You are correct that Tc is the temperature of the casing.  There
is a thermal resistance of Theta_cs which is the case-to-sink
thermal resistance and there is a thermal resistance of Theta_sa,
which is the sink-to-ambient thermal resistance.  These are in
series.
>
> If you think of power as a current source, then to get the
individual power drops across these thermal resistances, you
multiply the current times the resistance like Ohm's law.
>
> The differential temperature is the temperature from the junction
to the ambient air, or Tj-Ta.  There is a thermal resistance to get
from the die to the case of the transistor, which is Theta_jc for
junction-to-case.  Most datasheets show that the die must be <150°C
or <125°C.  You will notice Theta_jc on TO-220 devices somewhere in
the range of maybe 0.8 to 3 or more.  If you use a thermal washer,
it has a thermal resistance, too.
>
> A device rated for a Tc of 25°C will probably have a much lower
power handling capability than one similarly rated with a Ta of 25°
C, because there are a few thermal resistances that are eliminated
in the first case.  I would assume that they were not expecting the
devices to have the extra thermal resistances and would, indeed, be
without a heatsink.  You may get about 2W out of a TO-220 device
without a heatsink at 25°C.
>
> You can anticipate the power handling of the heatsink by:
>
> P=(Tj-Ta)/(Theta_jc+Theta_cs+Theta_sa).
>
> The heatsink gives the Theta_sa parameter.  You can rearrange the
equation to solve for the required heatsink given your power
requirements:
>
> Theta_sa=(Tj-Ta)/P-Theta_jc-Theta_cs.
>
> For example, assume Theta_jc is 1.2, Theta_cs is 1.8, and you want
to dissipate 25W).  Your heatsink should be rated at Theta_sa < 2°/W
(assuming Tj=150°C and Ta=25°C).
>
> Be sure to look at the derating curve for the device.  Usually it
will have a graph or a value.  The graph will start out at maximum
power dissipation at 25°C and drop to zero power at the maximum
temperature of the device.  Take (Pmax-Pmin)/Delta_T to get the
derating value.  If this value is, say, 2W/°C and you plan on
operating the device at 60°C and the device was rated for 125W to
begin with, you will only be able to use 5W at 60°C.
>
> I hope this helps.
>
> Best,
> Scotty
>
> ----- Original Message -----
> From: tom_bihn
> To: Electronics_101@yahoogroups.com
> Sent: 12/2/03 9:11:14 AM
> Subject: [Electronics_101] Question on spec sheet parameter in BJT
spec sheet
>
>
> What is the difference between power dissipation at Ta=25C and
power
> dissipation at TC=25C? I understand that Ta is ambient temperature
> and assume that TC is temperature of the casing.
>
> TC is usually much higher than Ta and I was wondering if this is
> because if the temperature of the air is 25C and there is no
> heatsink, that the maximum allowable power will be much lower
because
> less heat can be transferred away from the casing, while if a
> heatsink is used, it will dissipate the heat from the casing much
> better, approaching 25C and allowing the power to be higher?
>
> Thanks for any information,
>
> Tom
>
>
> Yahoo! Groups Sponsor
> ADVERTISEMENT
>
>
>
>
> To unsubscribe from this group, send an email to:
> Electronics_101-unsubscribe@yahoogroups.com
>
>
>
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Service.

From: tom_bihn

To: Electronics_101@yahoogroups.com

Sent: 12/2/03 8:40:36 PM

Subject: [Electronics_101] Re: Question on spec sheet parameter in BJT spec sheet

OK... The spec sheet gives:

Pc(@Ta=25C) = 1W
Pc(@TC=25C) = 10W
Tj = 150C

The derating curve shows Pc=10W at Tc=25C with a straight line to
Pc=0 at 150C. I'm not real clear yet how the two Pc terms work into
the equation. Is it simply saying that if an ideal heatsink were
chosen that could transfer all the heat away from the casing, making
it the same as ambient, that the transistor would be able to handle
10W?

Thanks for your patience,

Tom

--- In Electronics_101@yahoogroups.com, "Scott Thompson"
<electronguy@e...> wrote:
> You are correct that Tc is the temperature of the casing.  There
is a thermal resistance of Theta_cs which is the case-to-sink
thermal resistance and there is a thermal resistance of Theta_sa,
which is the sink-to-ambient thermal resistance.  These are in
series.
>
> If you think of power as a current source, then to get the
individual power drops across these thermal resistances, you
multiply the current times the resistance like Ohm's law.
>
> The differential temperature is the temperature from the junction
to the ambient air, or Tj-Ta.  There is a thermal resistance to get
from the die to the case of the transistor, which is Theta_jc for
junction-to-case.  Most datasheets show that the die must be <150°C
or <125°C.  You will notice Theta_jc on TO-220 devices somewhere in
the range of maybe 0.8 to 3 or more.  If you use a thermal washer,
it has a thermal resistance, too.
>
> A device rated for a Tc of 25°C will probably have a much lower
power handling capability than one similarly rated with a Ta of 25°
C, because there are a few thermal resistances that are eliminated
in the first case.  I would assume that they were not expecting the
devices to have the extra thermal resistances and would, indeed, be
without a heatsink.  You may get about 2W out of a TO-220 device
without a heatsink at 25°C.
>
> You can anticipate the power handling of the heatsink by:
>
> P=(Tj-Ta)/(Theta_jc+Theta_cs+Theta_sa).
>
> The heatsink gives the Theta_sa parameter.  You can rearrange the
equation to solve for the required heatsink given your power
requirements:
>
> Theta_sa=(Tj-Ta)/P-Theta_jc-Theta_cs.
>
> For example, assume Theta_jc is 1.2, Theta_cs is 1.8, and you want
to dissipate 25W).  Your heatsink should be rated at Theta_sa < 2°/W
(assuming Tj=150°C and Ta=25°C).
>
> Be sure to look at the derating curve for the device.  Usually it
will have a graph or a value.  The graph will start out at maximum
power dissipation at 25°C and drop to zero power at the maximum
temperature of the device.  Take (Pmax-Pmin)/Delta_T to get the
derating value.  If this value is, say, 2W/°C and you plan on
operating the device at 60°C and the device was rated for 125W to
begin with, you will only be able to use 5W at 60°C.
>
> I hope this helps.
>
> Best,
> Scotty
>
> ----- Original Message -----
> From: tom_bihn
> To: Electronics_101@yahoogroups.com
> Sent: 12/2/03 9:11:14 AM
> Subject: [Electronics_101] Question on spec sheet parameter in BJT
spec sheet
>
>
> What is the difference between power dissipation at Ta=25C and
power
> dissipation at TC=25C? I understand that Ta is ambient temperature
> and assume that TC is temperature of the casing.
>
> TC is usually much higher than Ta and I was wondering if this is
> because if the temperature of the air is 25C and there is no
> heatsink, that the maximum allowable power will be much lower
because
> less heat can be transferred away from the casing, while if a
> heatsink is used, it will dissipate the heat from the casing much
> better, approaching 25C and allowing the power to be higher?
>
> Thanks for any information,
>
> Tom
>
>
> Yahoo! Groups Sponsor
> ADVERTISEMENT
>
>
>
>
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>
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Service.



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-----Original Message-----
From: rgsparber@... [mailto:rgsparber@...]
Sent: Tuesday, December 02, 2003 4:27 PM
To: Electronics_101@yahoogroups.com
Subject: Re: [Electronics_101] simple cable tester

In a message dated 12/2/2003 10:33:20 AM Central Standard Time, dlevasse@... writes:

I would like to know if any of you have a schematic of a electronic cable tester (for DB9, DB25, DB37,...).

 

I want something that I could built using simple logic (no microcontroler).


thanks to all,

David Levasseur

David,

 

Are you just looking for a continuity tester? If so, what kinds of faults are you trying to detect? The simpliest tester would just verify that there is continuity where it should be but not catch extra connections like a short between wires inside the cable.

 

Rick Sparber
rgsparber@...

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Hi All,

  Is anyone having new troubles with the dallas DS1621?

  We have been using it here for years, and have used 10k+ of them and all is
well in the same design. However, recently all new batches no longer seem to
operate the thermostat output pin. Which means our fan is on permanently. If I
put an old date code IC in, it works, and if I then put a new date code in, it
fails. :(

  Just wondered if anyone else is having any troubles, as Maxim have just said
that nothing has changed, and both chips I sent back work correctly.

  I would imagine if our timing was on the 'edge' then in the 10k we have used
already, we would have come across some that would not have worked, like this
batch.

  Any ideas? I am about to put the logic analyser on the SDA and SCL lines to see
whether there is an acknoldegement difference between the two.

  Also, does anyone know of any decent IIC testers? It might be useful to have
one here, even if it's just to solve this problem.

Best Regards,
Brian Sidebotham.

Please contact me if you have successfully built a tuning fork
resonator, either the old fashioned way or w/opamps..

I know it should be the easiest tank circuit to build however the
tolerances and capabilities of hand winding a coil (versus
preordering, I'm trying to go for the 'old look' of the antique
resonators, with cherry wood and all) makes it rather difficult to
make even a tunable ULF coil.

On the same subject it would be immensely useful to make a tunable
ULF capacitor for similar purposes, preferably not a plate-based..  I
can probably pull off a sliding cylinder design.  If you know of any
resources on the web..

Thanks,
LM

Ok, you know that replacing the fuse will not help; have you replaced
the fuse to find out? Remember that a PC supply must be connected to a
load to work correctly.

It is generally cheaper in the US to look through dumpsters for an old
computer case and then recover the supply rather than fix one that is
broken. They are very cheaply built and are not designed to be easily
repaired.

If you still need to repair it, there are a few things you can try. It
there any obvious damage like bubbled plastic on a capacitor or small
chips of plastic missing from the center of a transistor case? Look
carfully and replace obviously damaged parts.

You may want to build a dummy load for testing. Make sure that the
regulator is switching buy checking pins at the regulator or on the
switching device; you will need a scope for this. Be careful, there
can be up to 1000V at some points on the supply. Find out the part
number of the switching regulator that the supply uses and get the
datasheet.

Most of the time it is fairly obvious what is wrong and it can be
found by careful observation.

--- In Electronics_101@yahoogroups.com, ravi sumith
<mindover2003@y...> wrote:
> Hi,
>
> I have a compaq ATX -145W switch mode PC power supply which I have
salvaged from an old PC. It is not powering up due to a problem and I
want to fix it.The fuse has blown but I know replacing the fuse does
not help. I checked the switching transistor (power MOSFET), the
bridge rectifire,fast recovery diodes all of them are OK.
>
> Can any one help me to figure out the problem please.
>
> Ravi
> Colombo
> Sri Lanka
>
>
> ---------------------------------
> Download Yahoo! Messenger now for a chance to WIN Robbie Williams
"Live At Knebworth DVD"

This is interesting but I am not sure what you are building. What is a
tuning fork resonator and what is it used for? How do you go about
building one? Is it transmitting circuit of some kind?

--- In Electronics_101@yahoogroups.com, "larry_matthews3000"
<larry_matthews3000@y...> wrote:
> Please contact me if you have successfully built a tuning fork
> resonator, either the old fashioned way or w/opamps..
>
> I know it should be the easiest tank circuit to build however the
> tolerances and capabilities of hand winding a coil (versus
> preordering, I'm trying to go for the 'old look' of the antique
> resonators, with cherry wood and all) makes it rather difficult to
> make even a tunable ULF coil.
>
> On the same subject it would be immensely useful to make a tunable
> ULF capacitor for similar purposes, preferably not a plate-based..  I
> can probably pull off a sliding cylinder design.  If you know of any
> resources on the web..
>
> Thanks,
> LM

A long time ago I build a cable teste and it worked well. It used a
lot of S-R latches and a red and green led on the output of each
latch. It was designed to catch intermittant connections. One end of
the cable was connected to I think a 5V source and the other end was
connected to the latch input and a strong pull down resistor.

Here's how it worked, After the cable is connected, the latches are
set and then the cable is checked for continuity by looking at the
leds. Moving the cable around will detect most intermittent opens in
the connections since the latch only needs the connection to fail for
an instant before changing state and lighting the red led. Our most
commom cable failure was intermittent connection and the test helped
in trouble shooting cables from returned units.

It had another mode where it would strobe through the lines to detect
shorted wires too but I forget how that was connected.

Think lots of wires and lots of parts. It was easy to design but a
pain to build.


--- In Electronics_101@yahoogroups.com, "David Levasseur"
<dlevasse@m...> wrote:
> Hi,
>
> I would like to know if any of you have a schematic of a electronic
cable
> tester (for DB9, DB25, DB37,...).
>
> I want something that I could built using simple logic (no
microcontroler).
>
>
> thanks to all,
>
> David Levasseur

Hey guys, anybody who might be interested, I am putting a Feedback
brand CNC932 robot milling machine on EBay. It will be listed under
industrial, gadgets. My Ebay handle is Technogeezer2000. I thought
someone might like to have this, I hate to get rid of it but, I am
running out of room....

David,

If I understand you correctly you want a device to determine the
pinout of the cable, is this correct?

Is this just something you want to build or is it for work or a
school project?

Chris

--- In Electronics_101@yahoogroups.com, "David Levasseur"
<dlevasse@m...> wrote:
> Yes, I'm looking for a continiuty tester. I want to read the pinout
of
> cables from 4 to 50 or maybe 64 pins. Both ends of the cable plug
into the
> device.
>
> David
>
>
>   -----Original Message-----
>   From: rgsparber@a... [mailto:rgsparber@a...]
>   Sent: Tuesday, December 02, 2003 4:27 PM
>   To: Electronics_101@yahoogroups.com
>   Subject: Re: [Electronics_101] simple cable tester
>
>
>   In a message dated 12/2/2003 10:33:20 AM Central Standard Time,
> dlevasse@m... writes:
>     I would like to know if any of you have a schematic of a
electronic
> cable tester (for DB9, DB25, DB37,...).
>
>     I want something that I could built using simple logic (no
> microcontroler).
>
>
>     thanks to all,
>
>     David Levasseur
>   David,
>
>   Are you just looking for a continuity tester? If so, what kinds
of faults
> are you trying to detect? The simpliest tester would just verify
that there
> is continuity where it should be but not catch extra connections
like a
> short between wires inside the cable.
>
>   Rick Sparber
>   rgsparber@A...
>
>         Yahoo! Groups Sponsor
>               ADVERTISEMENT
>
>
>
>
>   To unsubscribe from this group, send an email to:
>   Electronics_101-unsubscribe@yahoogroups.com
>
>
>
>   Your use of Yahoo! Groups is subject to the Yahoo! Terms of
Service.

It's simply a circuit to cause a tuning fork to resonate
continually.  For example say I have an 'A' fork which resonates at
440Hz, placing this fork in a position with a resonant coil/tank
(~440) between the two tines will cause it to 'ring' continuously.
Have a look at some of the older units:

<a href="

http://physics.kenyon.edu/EarlyApparatus/Acoustics/Tuning_Fork/Tuning_
Fork.html

">
Here
</a>

(sorry, dunno if html is on or not)

Sympathetic resonance is one of the major applications for these
devices..



--- In Electronics_101@yahoogroups.com, "manifold" <manifold_1@y...>
wrote:
> This is interesting but I am not sure what you are building. What
is a
> tuning fork resonator and what is it used for? How do you go about
> building one? Is it transmitting circuit of some kind?
>
> --- In Electronics_101@yahoogroups.com, "larry_matthews3000"
> <larry_matthews3000@y...> wrote:
> > Please contact me if you have successfully built a tuning fork
> > resonator, either the old fashioned way or w/opamps..