An alternative approach would be to put a resistor between HV+ and the
base of the transistors and then four new transistors to pull down the
base to turn it off. That might be easier to add and maybe there are
already all the components at hand without ordering HV-PNP. A 1N4148
between base and emitter of the tube drivers would be a good idea to
avoid capacitive reverse currents from eventually degrading the
transistors.

On 1 Sep 2006, at 06:50, ductapemaster360 wrote:

> I am in the process of building a clock with some Burroughs 5870 tubes
> and I am having problems with the anode drivers.  I think I'm doing it
> wrong, but I'm not sure.  So far, I have a MPSA42 between the HV+ and
> the anode resistor for each nixie.

Dan, the 'normal' way is to have an MPSA42 switch an MPSA92 on the
anode side of the nixie, so a logic high from your controller
switches on the tube. There are examples of such arrangements in the
files section, such as:
http://snipurl.com/vroa

> I already have everythign soldered together, so add on's would be
> appreciated, no complete redesigns (I'm out of solder removal wick)!

You may need to add an MPSA92 and another 2 resistors per nixie, so a
solder sucker might be useful.

Best wishes,

John

--- In NEONIXIE-L@yahoogroups.com, "ductapemaster360"
<Ductapemaster@...> wrote:
>
> I am in the process of building a clock with some Burroughs 5870 tubes
> and I am having problems with the anode drivers.  I think I'm doing it
> wrong, but I'm not sure.  So far, I have a MPSA42 between the HV+ and
> the anode resistor for each nixie.  The MPSA42's are directly driven
> from my Basic Stamp 2 through 4 I/O lines.  So far, all I get from
> each anode resistor is 5 volts, but my multimeter says there is no
> connectivity between the emitter and collector of the
> transistors...what's going on here?
>
> Just a FYI, the other end of the nixies are driven by a 74141 chip
> directly driven by my BS2.
>
> I already have everythign soldered together, so add on's would be
> appreciated, no complete redesigns (I'm out of solder removal wick)!
>
> Any help is appreciated!
>
> Dan
>

Yep, that's what you're gonna get. What you have is an emitter
follower. That is the emitter voltage will track (follow) the base
voltage, which in your case is 5V max.

What you need to do is use two transistors, a NPN (MPSA42) and a PNP
(MPSA92) both tied as commom emitter. That is their emitters are tied
to 'hard' points like ground or a supply voltage. The MPSA42 (NPN) has
its emitter grounded, while the MPSA92 (PNP) has its emitter tied to
the +HV. Connect a 470K, or so, resistor from the collector of the NPN
to the Base of the PNP. Tie another 'bleeder' resistor (to ensure
proper, quick, shutoff) across the base and emitter of the PNP (10K
min). Connect the anode resistor to the collector of the PNP and the
other end to the nixie's anode. Also a base resistor should be
inserted between the uCs output and the base of the NPN. 10K to 47K is
fine.

This is the common way anodes are driven with mux'd designs, so there
should be drawings in the groups files section. I'll dig one out later
if you can't find it, or someone else will surely point it out to you.

At 5:50 AM +0000 9/1/06, ductapemaster360 wrote:
>I am in the process of building a clock with some Burroughs 5870 tubes
>and I am having problems with the anode drivers.  I think I'm doing it
>wrong, but I'm not sure.  So far, I have a MPSA42 between the HV+ and
>the anode resistor for each nixie.  The MPSA42's are directly driven
>from my Basic Stamp 2 through 4 I/O lines.  So far, all I get from
>each anode resistor is 5 volts, but my multimeter says there is no
>connectivity between the emitter and collector of the
>transistors...what's going on here?
>
>Just a FYI, the other end of the nixies are driven by a 74141 chip
>directly driven by my BS2.
>
>I already have everythign soldered together, so add on's would be
>appreciated, no complete redesigns (I'm out of solder removal wick)!
>
>Any help is appreciated!
>
>Dan
\
Dan,

Welcome to the group.

To do multiplexing, you need to contro la votlage that's way up there
at 180V. A single transitro will not be able to convert the TTL
signal at0-5V to 180V, since its emitter-base junction is a
forward-biased diode that drops about 0.6V maximum.

You need to build a two-stage circuit with an MPSA42 driving a
high-valued resistorto make a control signal that is used to switch
another transistor at the high voltage.

I used such a circuit in several of my clocks, but wiith a PNP
transistor for the second stage. You can use either. Here's my
schematic:

http://www.cathodecorner.com/nc620a.gif

But you will need to do some more soldering. Oh, well.
--

--David Forbes, Tucson, AZ
http://www.cathodecorner.com/

I am in the process of building a clock with some Burroughs 5870 tubes
and I am having problems with the anode drivers.  I think I'm doing it
wrong, but I'm not sure.  So far, I have a MPSA42 between the HV+ and
the anode resistor for each nixie.  The MPSA42's are directly driven
from my Basic Stamp 2 through 4 I/O lines.  So far, all I get from
each anode resistor is 5 volts, but my multimeter says there is no
connectivity between the emitter and collector of the
transistors...what's going on here?

Just a FYI, the other end of the nixies are driven by a 74141 chip
directly driven by my BS2.

I already have everythign soldered together, so add on's would be
appreciated, no complete redesigns (I'm out of solder removal wick)!

Any help is appreciated!

Dan

that makes three of us...main focus is audio DIY stuff and then the nixie
bug bit. now i have too many nixies to mention and 3 clocks ;)

have fun!


>From: "copier_dude666" <briohill@...>
>Reply-To: NEONIXIE-L@yahoogroups.com
>To: NEONIXIE-L@yahoogroups.com
>Subject: [NEONIXIE-L] Re: New member
>Date: Thu, 31 Aug 2006 00:42:23 -0000
>
>Welcome Nick.  I caught the Nixie bug in the same way you did.  I have
>finished 2 clocks and have 2 more on the go!
>Cheers, Gordon.
>
>--- In NEONIXIE-L@yahoogroups.com, "Nick" <shieldjaguar2002@...> wrote:
> >
> > Just replied to a post and i haven't introduced myself!
> >
> > Hi all,
> > Got started in elec-diy only recently, mainly building audio stuff.
> > My interest in nixies started when i saw some ready built clocks on
>Ebay.
> > As i'm a novice i'm going to buy a kit+tubes, but i'll probably
>still have questions 8-)
> > Promise i'll read all the FAQs etc.
> >
> > regards
> > Nick
> >
>
>
>
>
>
>
>

--- In NEONIXIE-L@yahoogroups.com, "copier_dude666" <briohill@...> wrote:
>
> Welcome Nick.  I caught the Nixie bug in the same way you did.  I have
> finished 2 clocks and have 2 more on the go!
> Cheers, Gordon.

Thanks Gordon,
got some NOS tubes on Ebay, so just looking at the kits now.
Trouble is the hardest part will be casing-up the finished kit, my case/cabinet
skills suck!
8-)

atb
Nick

I was part of this group for about 6 months and was mysteriously
fropped from membership, but I respplied and I'm here again.

I never really introduced myself fromally, so here it goes...

My name is Dan and I'm 15.  I have had an interest in electronics
since I was very young, and hope to continue furthering my knowledge
by pursuing a degree in electrical engineering (maybe mechanical, not
sure yet) and work somewhere in the robotics field.

I discovered nixie tubes after reading an article in IEEE magazine and
I've been hooked ever since.  I searched and searched for a good
tutorial on how to build a clock (no kits for me!  I love DIY...) and
I found one on Mike's Electric Stuff.  I started buying parts and
eventually found some IN-14 nixies from Russia on eBay.  I bought
eight of them for $12; it was an absolute steal!  Soon, though, I
realized they had circular pins and I only had square grid boards from
radioshack.  I started to design a custom PCB to have made for it, but
school started and I kind of forgot about the project.

Recently I went to a surplus show (TRW in Los Angeles, CA) and some
guy was selling an old fluke nixie multimeter.  He sold it to me for
$5...I couldn't believe it!  When I got home I immediately tore it
apart to find 4 Burroughs tubes (all the work!) and a single 74141
driver chip.  I started designing a new clock, as the tube bases were
in rextangular fashion, and are easy to fit on the available
protoboards.  I decided on a Basic Stamp 2 platform, with a
multiplexed display and timebase provided by a Pocket Watch B made by
Solutions Cubed.  I worked with the BS2 for a while and I know quite a
bit of programming, so it was the obviuos choice.  I ordered parts
from Neonixie.com; a powersupply  and some neon tubes for "colon"
indicators and the project went from there.  So far I have assembled
the PCB and I am point to point wiring it now.  I have some code
written and it seems to work pretty well in the debug terminal, so I
am hoping for the best.

I have picked up a ton of new knowledge since the discovery of these
tubes so if you have any question on either my current project or
anything else, I'd be happy to share my 2 cents...

--- In NEONIXIE-L@yahoogroups.com, Derryck Croker <derryck@...> wrote:
>
>
> On 30 Aug 2006, at 18:35, Philip Zucarelli wrote:
>
> > DigiKey has a "universal" (WWVB, DCF77, JJY40, JJY60, MSF) time
code
> > receiver in stock for $26.95 each. C-Max Model CME8000-BUS-LP-01,
> > DigiKey number 561-1005-ND. It has a serial output for time, date,
> > etc.
>
> If any kind soul in the US is putting in an order to DigiKey, then
I
> wonder if two of these could be included for me and sent to the
UK?
> Payment by PayPal.
>
> Shipping and handling charges for anything under 75UKP is 22UKP
plus
> VAT through the UK arm of DigiKey!
>
> --
>
> Cheers
>
> Derryck

I'll be placing an order soon to DigiKey if you have not had any
offers yet, I can add your order to the mix.  It'll take me over the
minimum. ):  Cover the paypal fees and of course shipping and you
have a deal.  Oh and it'll be a "gift" to you from me.  Let me know
g _ c w at m s n dot c o m


Charles
>

> <http://img135.imageshack.us/img135/5505/guideopux5.gif>
>
> --- In NEONIXIE-L@yahoogroups.com, "Mike Moorrees" <threeneurons@...>

Here's an animated gif showing the voltages on the cathodes as bars.
Taller bars are more postive, and shorter bars are more negative:

<http://img318.imageshack.us/img318/5240/dekxfraf2.gif>

The 'glow' is the orange ball. Like a real ball, it tends to roll
downhill, or more negative. Stepping the guides (G1 & G2) will move
the glow.

Its really that simple.

On 30 Aug 2006, at 18:35, Philip Zucarelli wrote:

> DigiKey has a "universal" (WWVB, DCF77, JJY40, JJY60, MSF) time code
> receiver in stock for $26.95 each. C-Max Model CME8000-BUS-LP-01,
> DigiKey number 561-1005-ND. It has a serial output for time, date,
> etc.

If any kind soul in the US is putting in an order to DigiKey, then I
wonder if two of these could be included for me and sent to the UK?
Payment by PayPal.

Shipping and handling charges for anything under 75UKP is 22UKP plus
VAT through the UK arm of DigiKey!

--

Cheers

Derryck

Welcome Nick.  I caught the Nixie bug in the same way you did.  I have
finished 2 clocks and have 2 more on the go!
Cheers, Gordon.

--- In NEONIXIE-L@yahoogroups.com, "Nick" <shieldjaguar2002@...> wrote:
>
> Just replied to a post and i haven't introduced myself!
>
> Hi all,
> Got started in elec-diy only recently, mainly building audio stuff.
> My interest in nixies started when i saw some ready built clocks on
Ebay.
> As i'm a novice i'm going to buy a kit+tubes, but i'll probably
still have questions 8-)
> Promise i'll read all the FAQs etc.
>
> regards
> Nick
>

Phil,

> I purchased the C-Max unit about a month ago, but I have not had time
> to play with it yet... so many projects, so little free time. The
> receiver has an onboard microprocessor and real time clock. It will
> output fully decoded time messages via its RS232 or RS485 serial
> port. C-Max has a huge user's manual and interface/operation software
> available for it on their website:

I was hoping someone had tried it out. I'm not too worried about talking to
it, but I was wondering how the reception was. I live in a crappy RF spot,
and my old unit could only get a lock at night.


> I just happen to have an Oncore User's manual (VP and XT models -
> also applicable to other Oncore model receivers) with all of the
> binary commands and responses spelled out in detail. Contact me at my
> email address and I will send you some scanned pages of the commands
> you are looking for. You can also try Synergy Systems at:

That would be great! Any and all info, especially on the binary commands and
responses. I don't see your email addy in this mail, but you can reach me
at:

jpeakall AT madlabs.info



>
> http://www.synergy-gps.com/
>
> They are the last company supporting the Motorola Oncore receiver
> line. Motorola got out of the GPS receiver business and sold their
> GPS operation to SiRF about a year ago. SiRF only kept the FC and FS
> Oncore lines, everything else bit the dust.

I'm going to go poke around there now. Thanks again!

Jonathan
www.madlabs.info

snip
>
> Philip, have you or anyone else on the list used one of the units
you
> mentioned?

I purchased the C-Max unit about a month ago, but I have not had time
to play with it yet... so many projects, so little free time. The
receiver has an onboard microprocessor and real time clock. It will
output fully decoded time messages via its RS232 or RS485 serial
port. C-Max has a huge user's manual and interface/operation software
available for it on their website:

(http://c-maxgroup.com/products/showProduct.php?id=34).

Basically interfacing to this receiver is like interfacing to a GPS
receiver.

>
> I actually got it up and running with the Motorola Oncore GPS unit.
I can
> get time and date using the Motorola binary data format, but I
can't seem to
> find information on getting detailed sat status or how to set UTC
> corrections. That isn't a big deal, I can do that easily, but it
would be
> nice to use the onboard correction feature. I think that will auto
correct
> the date, which would make implementing automatic DST correction
easier.
>
> Anyone have experience with these units? All  really need to know
is what
> data to expect and how it is interpreted. I have a listing of the
binary
> commands, just not the expected response.
snip

I just happen to have an Oncore User's manual (VP and XT models -
also applicable to other Oncore model receivers) with all of the
binary commands and responses spelled out in detail. Contact me at my
email address and I will send you some scanned pages of the commands
you are looking for. You can also try Synergy Systems at:

http://www.synergy-gps.com/

They are the last company supporting the Motorola Oncore receiver
line. Motorola got out of the GPS receiver business and sold their
GPS operation to SiRF about a year ago. SiRF only kept the FC and FS
Oncore lines, everything else bit the dust.

Phil

What an excellent post- thats why i joined.
I'm looking to build a nixie clock, but since i'm a complete novice i'm going to
buy a kit.
Meantime i'll keep reading all the posts.

Nick.

Just replied to a post and i haven't introduced myself!

Hi all,
Got started in elec-diy only recently, mainly building audio stuff.
My interest in nixies started when i saw some ready built clocks on Ebay.
As i'm a novice i'm going to buy a kit+tubes, but i'll probably still have
questions 8-)
Promise i'll read all the FAQs etc.

regards
Nick

----- Original Message -----
From: "Jonathan Peakall" <jpeakall@...>
To: <NEONIXIE-L@yahoogroups.com>
Sent: 30 August, 2006 9:20 PM
Subject: Re: [NEONIXIE-L] Re: WWVB Alternatives, again


> All,
>
>> Or this one, just the board and antenna:
>>
> http://www.franktechniek.nl/catalog/product_info.php?cPath=32_21_53&products
> _id=213&language=en
>>
> Frank, I'm guessing this is a 1PPS unit? So, I would use a RTC unit and
> correct that with the 1PPS signal?

No, that won't work. It spits out the WWVB signal, one pulse per second,
each having a different lenght representing a '0' or '1'. Then you need
to filter/decode that with a microcontroller, check for sanity etc. My
nixie kits already have the WWVB decoding in software.

It's impossible to use as a 1pps generator, because you get extra pulses,
miss pulses, all depending on how good or bad reception is.

Best regards,
Frank
www.franktechniek.nl

All,

> Or this one, just the board and antenna:
>
http://www.franktechniek.nl/catalog/product_info.php?cPath=32_21_53&products
_id=213&language=en
>
  Frank, I'm guessing this is a 1PPS unit? So, I would use a RTC unit and
correct that with the 1PPS signal?

Dave, I did poke around and called the maker. Don't look good for fixing it.

Phillip, have you or anyone else on the list used one of the units you
mentioned?

I actually got it up and running with the Motorola Oncore GPS unit. I can
get time and date using the Motorola binary data format, but I can't seem to
find information on getting detailed sat status or how to set UTC
corrections. That isn't a big deal, I can do that easily, but it would be
nice to use the onboard correction feature. I think that will auto correct
the date, which would make implementing automatic DST correction easier.

Anyone have experience with these units? All  really need to know is what
data to expect and how it is interpreted. I have a listing of the binary
commands, just not the expected response.

And by the way, the Oncore seems to update right on the beep! I guess my
garmin unit is busy doing other things, and updating the seconds is low
priority. After all, only clock geeks like us care about such precise time.
However, I just sleep better when I know the Atomic Nixie Clock is dead on!

Thanks all, as always!

----- Original Message -----
>Frank Bemelman from this forum sells cheap WWVB receivers in
>his webshop.
>http://www.franktechniek.nl/catalog/product_info.php?products_id=358

Or this one, just the board and antenna:
http://www.franktechniek.nl/catalog/product_info.php?cPath=32_21_53&products_id=\
213&language=en

I have 5 left.

Best regards,
Frank
www.franktechniek.nl

> Well, my Ultralink WWVB receiver is on the fritz. I called them,
and they no
> longer make any kind of WWVB unit, they don't even have an old one
laying
> around that I can buy. So, I need a new time source.
snip

DigiKey has a "universal" (WWVB, DCF77, JJY40, JJY60, MSF) time code
receiver in stock for $26.95 each. C-Max Model CME8000-BUS-LP-01,
DigiKey number 561-1005-ND. It has a serial output for time, date,
etc.


> I do have a Motorola Oncore II and a DS1302 RTC, so I could go that
route.
> On firing up my other GPS, I see that if I call the time, the GPS
doesn't
> update *quite* on the beep, it's about 250mS (by eye) off or so.
> Disapointing.
snip

OK, the serial time messages on most, if not all GPS receivers are
not synchronized to the exact UTC time. They are output sometime
after the time epoch, with the delay varying by receiver and the
number of other messages that you are outputing on the receiver's
serial port.

You can handle this one of two ways.
One way is to receive the serial time message and put it in a
temporary buffer. Add one second to the time in the buffer and then
delay updating the display by one second minus the message delay of
the receiver (in your case, the display update delay is approximately
750mS).
The other way is to again put the serial time message into a
temporary buffer and add one second to it. This time, the display is
updated on the active edge of the 1 pulse per second (1pps) output of
the GPS receiver. The active edge of 1pps (varies by receiver
manufacturer, but typically it is the rising edge) is synchronized to
UTC time to within 1microsecond or less (typically 100ns). The 1pps
signal is usually used as an interrupt by the microprocessor that
updates your display.
This second method is more preferable, as it eliminates having to
tune your delay time to the specific GPS receiver model that you are
using.

Hope this helps.

Phil

--- In NEONIXIE-L@yahoogroups.com, "Jonathan Peakall" <jpeakall@...>
wrote:

Frank Bemelman from this forum sells cheap WWVB receivers in
his webshop.
http://www.franktechniek.nl/catalog/product_info.php?products_id=358

Don't know if these are suitable to you.

Chris 'Turbokeu'

At 8:08 AM -0700 8/30/06, Jonathan Peakall wrote:
>Hi All,
>
>Well, my Ultralink WWVB receiver is on the fritz. I called them, and they no
>longer make any kind of WWVB unit, they don't even have an old one laying
>around that I can buy. So, I need a new time source. Bummer, as the unit I
>have is perfect and has been great for years.

Jpnathan,

Sorry to hear about your WWVB receiver dying. Separate WWVB receiver
chips seem to be unavailable these days, as the market went to
embedded WWVB receiver/clock chips for the $20 consumer grade clocks.

The problem might be something simple... have you looked at its power
supply with a voltmeter and a scope to see if it's still working
right? Are there any bad connections, etc? Is there any
troubleshooting info available in the manual?

Failing that, there's a nice, low-cost hockey-puck GPS receiver
called the Garmin GPS-18-LVC that puts out 1PPS and a serial data
stream to the NMEA standard. IT costs less than $100, and the antenna
is included. Or you could buy a used rubidium standard from ebay for
a couple hundred dollars and never have to set your clock again!

--

--David Forbes, Tucson, AZ
http://www.cathodecorner.com/

Hi All,

Well, my Ultralink WWVB receiver is on the fritz. I called them, and they no
longer make any kind of WWVB unit, they don't even have an old one laying
around that I can buy. So, I need a new time source. Bummer, as the unit I
have is perfect and has been great for years.

I do have a Motorola Oncore II and a DS1302 RTC, so I could go that route.
On firing up my other GPS, I see that if I call the time, the GPS doesn't
update *quite* on the beep, it's about 250mS (by eye) off or so.
Disapointing. I also use the time source for my seismometer, and so I do
want the most accurate time I can get.

As well, the Oncore, DS1302 and the antenna seem like a lot of dog for this
project. I mean, I could use the GPS in a robot some day, and I hate to make
it sit around and do nothing but read the time whe it is capable of more.
Plus it uses more power, so the battery backup system will have to be
bigger. I guess I could detect power out and shutdown the GPS, but more
programming, hardware and PITA.

So, anyone try any of the newer options out there? There has been some
discussion of possibilities, but I don't see any sucess stories with
particular units.

Jonathan
www.madlabs.info

> "Walter Jann" <walterjann@>
> wrote:
> <snip>
> > My Dad is coming in town and we need a project.  He's an old tube
> > theory guy (he helped me rebuild my predicta tube TV last year)
> > and I thought this would be a fun project.  ...
> <snip>
>
>...

For starters here are some 'neon basics'. All neon devices work like
neon bulbs (be it nixies, triggers, or dekatrons). They have a
'strike' or 'start' voltage in order for the ionization and for
electrical conduction to start. Once started, they have a 'sustain',
mantaining, or operating voltages, that's some what lower than the
start voltage. For a dekatron its usually 400V, or so to, to strike,
and ~200V once ionized. Your supply voltage should always be higher
than the 'worst case' maximum strike voltage. An anode, or ballast,
resistor is usually stuck between the supply and device anode, to take
up difference between supply and operating voltage.

In a dekatron, you have one anode, which is a disk in the middle, and
30 cathode rods circling it. These cathodes are arranged into 3 groups
of 10 as shown in the upper portion of the drawing in the link:

<http://img135.imageshack.us/img135/5505/guideopux5.gif>

Ignore the lower portion. Its for special types of dekatrons, less
frequently encountered, and discussed in message 32309:

<http://groups.yahoo.com/group/NEONIXIE-L/message/32309>

Two of the groups, called the 'guides', group G1 and group G2, are
usually biased slighty more positive than the third group, referred to
as the 'main cathodes'. In traditional hookup, the 'main cathodes' are
usually at ground potential (potential = voltage = electrical
pressure). When 1st powered up, conduction will occur, RANDOMLY,
between the anode, and any one of the cathodes. It will occur at
cathodes with the more negative voltage, so in this case it will be
one of the 10 mains. Remember the guides are usually biased slighty
positive. If a guide G1 or G2 has it voltage lowered below that of the
main cathodes, then the glow will switch (transfer) over to it. If
that same guide is raised back to its bias level, the the glow will
just flop back to the original 'main'. For it to move to the next
main, the other guide has to be lowered first, then as the prior guide
raises its level, the glow will transfer to the 2nd guide. When the
2nd guide rises, the glow will now jump to the next 'main'. Do this 10
times, and the glow will make a full circle thru all cathodes. one of
the main cathodes usually has a resistor tied to it and ground, and is
used as the 'index'. When the glow is sitting at its position, a
voltage will develop across that resistor, that's traditionally used
as a 'carry' signal.

To simplify controlling a dekatron from a uC refer to the drawing below:

<http://images6.theimagehosting.com/Dek_uC.gif>

The guides are here a biased to +90V, but the main cathodes are also
raised above ground to ~50V. This is done to simplify the drive
circuit. Dekatrons have a low operating current of about 350uA, so
biasing them is fairly simple (a cheap way to make a -50V supply
without really doing it). With modern circuitry we can operate them
much like a stepper motor. That is we can pause the glow at any
cathode, either guide or main. In the old traditional circuits, the
glow was usually only paused at a 'main'. The guides are controlled
from the uC thru two ouput port bits, thru a pair of MPSA42 Hi-V
transistors. Note, that they are rigged as common-emmiter, hence
inverting. That's actually perfect, so a one on the port bit will turn
on a transistor, dragging the guide voltage to ground. In this case
thats 50V below (or more negative) the mains, causing a tranfer to
that guide. It'll stay there until the next action, or step. You can't
do that with capactive coupled schemes. Note for proper transfer to
occur at the next step, there should be a little overlap when
switching between guides. This overlap should be a minimum of ~100uS
for most dekatrons. To go forward, sequence G1-G2-M-G1-G2-M. To go
backwards, sequence G2-G1-M-G2-G1-M. During the 'M' period both guides
are 'off', and the voltage on both should float back to +90V. An
'index' detector is also shown in the circuit. Its a MPSA92 (hi-V PNP)
hooked up in a 'common-base' configuration. When the glow is at the
'index' cathode, the current flowing thru the emitter will be routed
thru to the collector, showing up as a logic one at a uC input port.
This configuration keeps the voltage on the index cathode from rising
to high (only 0.7V) relative to the other main cathodes, and it also
performs level translation from the +50V plateau, to ground. The uC
input must have a high impedance of at least 200K minimum. That leaves
out many 8051s, since many have internal pull-up resistors. Check the
specs of the uC that your using.

I've started drawing an animated .GIF that will show the glow transfer
from cathode-to-cathode of 'common' 2-guide, double pulsed, dekatrons,
but it might take a while.

Common type dekatrons fall into two groups, 'counters' and
'selectors'. In a selector, each of the 10 main cathodes is brought
out to its own connector pin. In a counter, most of the main cathodes
are tied together, internally, while only one (and upto 4) have their
own separate output pin. Any of the 'separated' main  cathodes can be
used as an 'index'. The index will let your uC know where the glow is.

Hope this helps.

Item numbers 300022695669 & 300022695664.

(Not my auctions.)  MM5314 is the chip used in those old B-7971 Nixie
clock schematics, and I think Sal built a couple Numitron clocks with
them also.

- Chris W.

[edited by A.J. - please trim quoted material]
--- In NEONIXIE-L@yahoogroups.com, "Walter Jann" <walterjann@...>
wrote:
<snip>
> My Dad is coming in town and we need a project.  He's an old tube
> theory guy (he helped me rebuild my predicta tube TV last year)
> and I thought this would be a fun project.  If I can figure out
> how to control a dekatron with my basic stamp, we can design and
> build a cool clock.
<snip>

FYI - I have reviewed the info in the database files, I found a
schematic for a micro controlled dekatron, but I don't fully
understand it.  I clearly understand microcontrollers but don't
understand how to control the dekatron with it.

Thanks again and remember, once upon a time you guys were at my
primitive level of electronics... :)

W

--- In NEONIXIE-L@yahoogroups.com, "smrippe" <steveripper@...> wrote:
> I found the following description for the DS8880 which is very
> similar if not the same as the DM8880. Perhaps other members can
> provide information as to the differences between these two IC's. I
> have a PDF of the DS8880 datasheet and it can also be found at the
> following address:
> http://www.national.com/pf/DS/DS8880.html
>
> The DS7880/DS8880 is custom designed to decode four lines of BCD and
> drive a gas-filled seven-segment display tube.
<snip>

Here's a list of equivalent part numbers:
75480
DD-700
DM8880
DS8880
ECG2028
NTE2028

I think the rest of John's questions have already been covered.

A.J.

John:

I found the following description for the DS8880 which is very
similar if not the same as the DM8880. Perhaps other members can
provide information as to the differences between these two IC's. I
have a PDF of the DS8880 datasheet and it can also be found at the
following address:
http://www.national.com/pf/DS/DS8880.html

The DS7880/DS8880 is custom designed to decode four lines of BCD and
drive a gas-filled seven-segment display tube.

Each output constitutes a switchable, adjustable current sink which
provides constant current to the tube segment, even with high tube
anode supply tolerance or fluctuation. These current sinks have a
voltage compliance from 3V to at least 80V; typically the output
current varies 1% for output voltage changes of 3 to 50V. Each bit
line of the decoder switches a current sink on or off as prescribed by
the input code. Each current sink is ratioed to the b-output current
as required for even illumination of all segments.

Output currents may be varied over the 0.2 to 1.5 mA range for driving
various tube types or multiplex operation. The output current is
adjusted by connecting an external program resistor (RP) from VCC to
the Program input in accordance with the programming curve. The
circuit design provides a one-to-one correlation between program input
current and b-segment output current.

The Blanking Input provides unconditional blanking of any output
display, while the Ripple Blanking pins allow simple leading- or
trailing-zero blanking.

Steve R.

--- In NEONIXIE-L@yahoogroups.com, John Smout <whoop@...> wrote:
>
> On 10 Aug 2006, at 15:31, John Smout wrote:
>
> > The displays, looking closely, say Beckmann SP 351 and Beckmann SP
> > 352 respectively.
>
> OK I finally decided to take the display board off the motherboard
> and hopefully I can leave the panaplexes mounted on this pcb. There
> are some chips wired to the Panaplex segments that are DM8880Ns, one
> per digit. Does anyone have a data sheet for this chip?
>
> John
>

Hello Guys,

Thanks for your help a few months ago on upgrading the dying tubes
in my nixi-cron clock kit and thank you raymond for shipping my geek
klok kits.  Anyhow, I'm a noob and just figured out how to program a
basic stamp (sorry guys, I don't know C) to multiplex words using
74141s on my B7971 tubes(before I got the geek kloks).  Pretty
elementary by your standards but I did it myself.  I've searched and
can't find any posts that would help me understand how to control
dekatrons (which I own but have never used) with a microcontroller.
My Dad is coming in town and we need a project.  He's an old tube
theory guy (he helped me rebuild my predicta tube TV last year) and
I thought this would be a fun project.  If I can figure out how to
control a dekatron with my basic stamp, we can design and build a
cool clock.

P.S.    Is anyone (David Forbes?) selling scope clock kits?  I need
one and I have insufficient knowledge to design one myself!

Thanks Guys (and thanks for helping a noob),

-Walter Jann

> ripple blanking and the current programming input?

Ripple blanking is for leading-zero blanking. If Ripple Blanking In is
low, the display will blank and Ripple Blanking Out will be low when
the digit is zero. In a typical counter display you would tie the
least significant RBI high, so the least sig digit is always lit, then
tie the most significant RBI low and cascade its RBO to the next most
significant RBI, and so on down the line, so the blanking "ripples
through" from the MSD downwards and stops at the first non-zero digit
- a zero below this will not be blanked.

Current programming is to set the segment current limit, so you don't
need anode or cathode resistors. The current/resistance curve is on
page 3. A 3k resistor will give you 1mA segment current; 10k will give
0.35mA; over a wide range of anode voltages.