Re: [neonixie-l] Re: Multiplexing noise

2015-02-24 Thread gregebert
I used direct-drive on my first nixie project only because my gut-instinct 
was to keep it as simple as possible; I've stuck with that ever since.
Too many postings about 'noisy nixies', choosing the correct 
cathode-current, bleeding, flickering, RFI, etc. I've even seen 
scary-looking blue arcs between anodes in a panaplex.
Even my wristwatch is direct-drive (lucky me, the SP-151 has separate pins 
for each cathode segment...)

Since I dont sell anything, the extra cost for direct-drive isn't an issue 
for me.

That said, I have an unusual 9-segment (not a typo; it has 2 more segments 
in the middle so you can display characters like T, W, etc) display that 
requires multiplexing, and I hope to make a clock out of it in the near 
future. Fingers crossed I wont have any weird problemsjust wish I could 
find a few more of these units for spares.

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Re: [neonixie-l] Re: For Steampunk Nixie Clock Fans..

2015-02-24 Thread Paul Parry
Hello Nick,

I can feel this wandering off Topic slight.. Again.. LOL

What a wonderful use for a 5C/3023. I did mention earlier that I had a bit 
of a fondness for Vintage aircraft, I had a complete Vampire T11 in my 
possession a few years ago XD515 (long story) not the smallest things to 
house so I donated it to RAF Cosford where it resides in the sheds at the 
back awaiting re-assembly.
Not come across the 'Resin' on the lighting panel, but I know a lot of 
planes of the era had UV lighting in the cockpit that illuminated all the 
dials as they had radium? paint inside that glowed very nicely under UV. It 
could possibly be used to switch on the UV lamps? It was certainly the case 
in my T11.

Is that your Firefly?



On Monday, 23 February 2015 13:26:04 UTC, Nick wrote:

 On Monday, 23 February 2015 12:34:56 UTC, Paul Parry wrote:

 The part used on Gemini was a MK IB Directional Gyro as fitted to the 
 Spitfire / Lancaster / Mosquito and most of the other planes of the era. 
 They are abundant and you can get them on eBay for a couple of pounds, I 
 used a scrapped one so there was no chance it would ever go up in the air 
 again anyway


 Hi Paul,

 I, too, have a rather eclectic collection of ephemera... My workshop 
 lights are controlled by an MOD 5C/3023 switchbox as used in Lancasters, 
 Mosquitos, FIrefly Vs etc. - the MOD liked to use the same kit in multiple 
 aircraft as it made store-keeping/spares easier to manage.

 Enclosed is an image of my 5C/3023 which I acquired NIB for just a few 
 pounds, and a photo of the inside of the cockpit of a Firefly V undergoing 
 restoration, showing the same model box (look closely!).

 EDIT: The RESIN switch controlled lights for a type of IFF system - 
 there is much discussion, even today, on the exact nature of this, most 
 choosing to believe that it was IR rather than visible-light based...

 Cheers

 Nick

  


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Re: [neonixie-l] Re: For Steampunk Nixie Clock Fans..

2015-02-24 Thread Nick
On Tuesday, 24 February 2015 08:18:16 UTC, Paul Parry wrote:

 I can feel this wandering off Topic slight.. Again.. LOL


It doesn't matter in this case. Believe me :)
 

 What a wonderful use for a 5C/3023. I did mention earlier that I had a bit 
 of a fondness for Vintage aircraft, I had a complete Vampire T11 in my 
 possession a few years ago XD515 (long story) not the smallest things to 
 house so I donated it to RAF Cosford where it resides in the sheds at the 
 back awaiting re-assembly.
 Not come across the 'Resin' on the lighting panel, but I know a lot of 
 planes of the era had UV lighting in the cockpit that illuminated all the 
 dials as they had radium? paint inside that glowed very nicely under UV. It 
 could possibly be used to switch on the UV lamps? It was certainly the case 
 in my T11.


I've looked at some photos of XD515 - http://flickrhivemind.net/Tags/xd515 - 
it was really in poor shape - do you think that it'll ever fly again or 
will it be a static display? A major task if ever there was one. Top marks 
for stopping it rotting completely - certainly a long-term project !
 

 Is that your Firefly?


Regrettably (or maybe, thankfully) not - it was from another forum 
(Britmodeller) where we were discussing the true nature of RESIN - lot of 
argument about it as it was classified and seems to have changed its nature 
during its life. It was definitely IFF - not cockpit - the real question 
was was it just very dim/near-IR red lights or true IR - no-one seems to 
know for sure - some speculation too that is relied on other aircraft 
having a Tabby system on board... 

Cheers

Nick

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[neonixie-l] Re: Russian 100x100 array

2015-02-24 Thread Alex
Those have been on ebay for a good while from the same seller, I was 
tempted a while ago but they are just too high a $ for my taste. The 
displays panels themselves are, if i recall from reading somewhere, a 
nightmare to drive as they use glow transfer to scan in data, so 
essentially gas based multiplexing. Those for 250 do look like they come 
with some soviet era wizardry in the box and he states are parallel 8 bit 
interfaces (LPT port...).

I think I actually looked around at the time and discovered they were used 
on soviet CNC machines - I even found a Russian companies website offering 
LCD replacements for them. 

- Alex

On Monday, 23 February 2015 13:36:45 UTC, Mike Mitchell wrote:

 Has anyone done anything with the Russian IMG-1 100x100 neon array?
 I've seen a few ebay postings

 http://www.ebay.com/itm/Rarest-NOS-NIB-NIXIE-MATRIX-screen-100x100-1-Z568M/321346505250
 and

 http://www.ebay.com/itm/Rarest-NIXIE-MATRIX-screen-100x100-1-Z568M-tube-vfd-IN-18/321356330231

 It looks interesting...



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Re: [neonixie-l] Re: Multiplexing noise

2015-02-24 Thread Joe Croft
Hi Yall,

I've attached a picture of the display pcb layout and a pdf of the
schematic for it. The cathode drivers are just the MPSA42 with a 100K ohm
base transistor and the collector is tied directly to the cathode and the
emitter is tied to ground.

-joe

On Mon, Feb 23, 2015 at 10:58 AM, gregebert gregeb...@hotmail.com wrote:


 I will try the biasing. would biasing both sides help? This would be sort
 of like terminating the lines.


 No need to worry about termination at this frequency, as in reflected
 waves, unless your PCB traces are several feet long...
  I did check the datasheets for the MPSA42/MPSA92 and they are a good
 choice because they have low leakage and high Vceo.
 Therefore *driver* leakage is not your problem; can you post a schematic
 of the driver  predriver circuits ? It could be the predriver.

 It's possible the device driving your PNP anode driver is leaky, causing
 the PNP to turn-on slightly. Are you using a NPN predriver -- PNP driver
 arrangement ?
 If so, your NPN device could be leaking 0.1uA and your PNP will conduct
 beta times this. This is easy to fix with a resistor across the PNP's
 base/emitter to shunt-away
 the predriver leakage.

 It's also possible there is noise entering the predriver; this is where a
 scope will help. If you dont have a scope, then proceed with debugging he
 predriver.

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display_schem.pdf
Description: Adobe PDF document


Re: [neonixie-l] Re: Multiplexing noise

2015-02-24 Thread 'Terry S' via neonixie-l

Joe -- the anode driver I borrowed from the open-source clock looks 
slightly different than yours.
 
It uses the same transistors, but the MPSA92 has 100K directly across the 
BE junction, and a 470K between the MPSA42 collector and the MPSA92 base. 
 
In other words, imagine moving your R22 to the left of R21, and making R21 
470K. (Temp 10 tube)
 
Also, mine has a 33K from the driver to the base of the MPSA42, as opposed 
to your 100K. A little stiffer drive.
 
I'm not saying either one is better -- just pointing out a difference. I 
haven't built this circuit yet, so it may need tweaking.
 
I do think Niek has an astute observation regarding coupling -- I went to 
great pains in my layout to keep the low V drive circuit lines short and 
far away from the high V switching noise. Put my driver pairs right next to 
the decoder, and the lines from the connector to the decoder are as far 
from anything else as possible. 
 
Observing what flickers on and what other lines are switching at the time 
should point you right to the crosstalk source.
 
Terry S.
 
On Tuesday, February 24, 2015 at 6:15:37 AM UTC-6, joenixie wrote:

 Hi Yall,

 I've attached a picture of the display pcb layout and a pdf of the 
 schematic for it. The cathode drivers are just the MPSA42 with a 100K ohm 
 base transistor and the collector is tied directly to the cathode and the 
 emitter is tied to ground.

 -joe

 On Mon, Feb 23, 2015 at 10:58 AM, gregebert greg...@hotmail.com 
 javascript: wrote:


 I will try the biasing. would biasing both sides help? This would be 
 sort of like terminating the lines.


 No need to worry about termination at this frequency, as in reflected 
 waves, unless your PCB traces are several feet long...
  I did check the datasheets for the MPSA42/MPSA92 and they are a good 
 choice because they have low leakage and high Vceo.
 Therefore *driver* leakage is not your problem; can you post a schematic 
 of the driver  predriver circuits ? It could be the predriver.

 It's possible the device driving your PNP anode driver is leaky, causing 
 the PNP to turn-on slightly. Are you using a NPN predriver -- PNP driver 
 arrangement ?
 If so, your NPN device could be leaking 0.1uA and your PNP will conduct 
 beta times this. This is easy to fix with a resistor across the PNP's 
 base/emitter to shunt-away
 the predriver leakage.

 It's also possible there is noise entering the predriver; this is where a 
 scope will help. If you dont have a scope, then proceed with debugging he 
 predriver.

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Re: [neonixie-l] Re: Multiplexing noise

2015-02-24 Thread Niek
Does the issue happen more to certain tubes/digits than to others? If so, 
it could have something to do with the layout of the traces: i'd be 
especially worried about long runs of high voltage lines parallel to the 
lines switching the transistors. E.g., in your PCB, the trace at the very 
bottom (originating out of M at the header) is a low voltage line that 
controls the anode switch transistors, and if you follow it up, it runs 
parallel to some high voltage lines. The high voltage line's fast switching 
could induce a smaller voltage spike at the base of that transistor, which 
could then turn it on. If this is the cause, it probably would show up more 
to certain digits/tubes than others.

If it's the same for all, then there might be some problem with the program 
controlling it: e.g. you need to make sure to wait a small while after 
turning off one anode, then switch the cathodes, then turn on the next 
anode. Are you doing that?



On Tuesday, February 24, 2015 at 1:15:37 PM UTC+1, joenixie wrote:

 Hi Yall,

 I've attached a picture of the display pcb layout and a pdf of the 
 schematic for it. The cathode drivers are just the MPSA42 with a 100K ohm 
 base transistor and the collector is tied directly to the cathode and the 
 emitter is tied to ground.

 -joe

 On Mon, Feb 23, 2015 at 10:58 AM, gregebert greg...@hotmail.com 
 javascript: wrote:


 I will try the biasing. would biasing both sides help? This would be 
 sort of like terminating the lines.


 No need to worry about termination at this frequency, as in reflected 
 waves, unless your PCB traces are several feet long...
  I did check the datasheets for the MPSA42/MPSA92 and they are a good 
 choice because they have low leakage and high Vceo.
 Therefore *driver* leakage is not your problem; can you post a schematic 
 of the driver  predriver circuits ? It could be the predriver.

 It's possible the device driving your PNP anode driver is leaky, causing 
 the PNP to turn-on slightly. Are you using a NPN predriver -- PNP driver 
 arrangement ?
 If so, your NPN device could be leaking 0.1uA and your PNP will conduct 
 beta times this. This is easy to fix with a resistor across the PNP's 
 base/emitter to shunt-away
 the predriver leakage.

 It's also possible there is noise entering the predriver; this is where a 
 scope will help. If you dont have a scope, then proceed with debugging he 
 predriver.

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Re: [neonixie-l] Re: Multiplexing noise

2015-02-24 Thread David Forbes

Greg,

I concur that these are fine things to do. I adjsuted my base-emitter resistor 
so that it would have about 0.3V across it if the base were disconencted form 
the circuit and the driving signal was on.


Also, short wires from the driver to the tubes are helpful to reducing 
crosstalk. I made multiplexed clocks with direct PCB traces from tube to tube 
under the sockets, and did the timing things you mentioned.


Most importantly, ensure some dead time (~100 usec) between turning off the 
anode and switching the cathode driver to the next digit's value. That's where I 
ran into trouble.



On 2/24/2015 10:12 AM, gregebert wrote:


Before you start hacking-up your PCB, can you try adjusting the timing of your
anode drivers so there is some 'dead-time', say 50-100usec, after 1 anode is
turned off, and the next one is turned on ? Also, if you can turn off all
cathode drivers during the dead-time, that might help. This will ensure the tube
is no longer ionized, and that should either reduce the unwanted glow or make it
more difficult to re-ionize from leakage. And to be safe, dont turn off the
anode  cathodes at exactly the same time (stagger by ~1usec); otherwise you
could create a di/dt problem from the stray inductance of the wiring.

Now, if that doesn't work, next thing to try is a true base-emitter resistor,
for example, moving the connection of R22 to the other side of R21 (see Terry's
note). I dont think the resistor values are critical as long as they are at
least 100K and they are 1/4 watt (or larger). You dont want them to overheat
P=Vcc^2/R, so with Vcc=160V, R=100K, a 1/4W resistor is at the limit. If your
local Radio Shack store hasn't shut the doors yet, grab some resistors. (I just
got some stuff last night at a 95% discount)



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[neonixie-l] Re: Russian 100x100 array

2015-02-24 Thread Terry Kennedy
On Tuesday, February 24, 2015 at 5:40:53 AM UTC-5, Alex wrote:

 Those have been on ebay for a good while from the same seller, I was 
 tempted a while ago but they are just too high a $ for my taste. The 
 displays panels themselves are, if i recall from reading somewhere, a 
 nightmare to drive as they use glow transfer to scan in data, so 
 essentially gas based multiplexing. Those for 250 do look like they come 
 with some soviet era wizardry in the box and he states are parallel 8 bit 
 interfaces (LPT port...).

 I think I actually looked around at the time and discovered they were used 
 on soviet CNC machines - I even found a Russian companies website offering 
 LCD replacements for them. 


I have a 512x512 VFD version in my collection. It is either a prototype or 
a part that failed testing, since there are no printed markings on it, just 
a number of comments like Dud scratched into the glass on the back (in 
Cyrillic). I was unable to get it to do anything at all, unlike the 
submarine one I posted about earlier. I guess it is just blue-green, though 
it is possible it is multi-color or RGB. Here are some pictures:

http://www.tmk.com/transient/6F5S8652-s.jpg
http://www.tmk.com/transient/6F5S8654-s.jpg

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Re: [neonixie-l] Re: Multiplexing noise

2015-02-24 Thread Joe Croft
Hi Yall,

Okay, I scoped the board and I have almost 500us of total dead time between
digits. This was measured on the digital outputs from the CPU. My code is
written in a way that I turn off all of the segment and digit signals one
at a time in a for loop so they are not all triggering at once. They are
turned on in a like manner. I do not know the time between these, but the
app know's nothing about the actual port and bit that is being turned on or
off so I assume the time is in the 1us ball park if not more. I am using a
16MHZ ATMega328.

As for direct drive, I am multiplexing because of a lack of pins and board
space. I wanted a nice small board as well as through hole parts because I
want to sell this as a kit. I just don't have room for a couple of more
DIPS.

I like the idea of the moving the resistors, I will try this. I will also
spread my segment lines out going between the 4 digits up top and the 2
digits below. I am still contemplating the ground plains they are easy to
do. I will have to ask a couple of people at work about the issue of them
possibly increasing the  coupling between the lines.

Biasing the lines is another idea I will try as well.I can do most of these
before the next board spin. Depending on how the other things I try go, I
will then decide on the plains.

-joe

On Tue, Feb 24, 2015 at 2:28 PM, gregebert gregeb...@hotmail.com wrote:

 I used direct-drive on my first nixie project only because my gut-instinct
 was to keep it as simple as possible; I've stuck with that ever since.
 Too many postings about 'noisy nixies', choosing the correct
 cathode-current, bleeding, flickering, RFI, etc. I've even seen
 scary-looking blue arcs between anodes in a panaplex.
 Even my wristwatch is direct-drive (lucky me, the SP-151 has separate pins
 for each cathode segment...)

 Since I dont sell anything, the extra cost for direct-drive isn't an issue
 for me.

 That said, I have an unusual 9-segment (not a typo; it has 2 more segments
 in the middle so you can display characters like T, W, etc) display that
 requires multiplexing, and I hope to make a clock out of it in the near
 future. Fingers crossed I wont have any weird problemsjust wish I could
 find a few more of these units for spares.

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Re: [neonixie-l] Re: Multiplexing noise

2015-02-24 Thread 'Terry S' via neonixie-l
Greg -- regarding the resistor size and power dissipation, if there are 6 
digits (7 in this case with the neons), can't you figure the resistor duty 
cycle is 1/6th, and therefore smaller wattage resistors can be used? The 
average dissipation is more like .043 watts, by my back-of-the-napkin math.

I realize the instantaneous dissipation is .25 watts, but resistors do have 
some thermal mass

If I'm wrong here please correct me. I know I've worked on a similar 
problem before and I recall the answer was not so obvious.

Terry

On Tuesday, February 24, 2015 at 11:12:19 AM UTC-6, gregebert wrote:

 I think this is the problem: The base-emitter of the PNP is not shunted 
 with a resistor (see note from Terry). The purpose of the base-emitter 
 resistor is to provide a path for the leakage-current of the NPN predriver.

 With the schematic as shown, roughly half of the NPN's leakage current 
 goes thru the base of the PNP. That current is them multiplied by beta, 
 which I think was around 130 from the datasheet. It's not a lot of current, 
 but it could certainly contribute to unwanted glowing.

 Before you start hacking-up your PCB, can you try adjusting the timing of 
 your anode drivers so there is some 'dead-time', say 50-100usec, after 1 
 anode is turned off, and the next one is turned on ? Also, if you can turn 
 off all cathode drivers during the dead-time, that might help. This will 
 ensure the tube is no longer ionized, and that should either reduce the 
 unwanted glow or make it more difficult to re-ionize from leakage. And to 
 be safe, dont turn off the anode  cathodes at exactly the same time 
 (stagger by ~1usec); otherwise you could create a di/dt problem from the 
 stray inductance of the wiring.

 Now, if that doesn't work, next thing to try is a true base-emitter 
 resistor, for example, moving the connection of R22 to the other side of 
 R21 (see Terry's note). I dont think the resistor values are critical as 
 long as they are at least 100K and they are 1/4 watt (or larger). You dont 
 want them to overheat P=Vcc^2/R, so with Vcc=160V, R=100K, a 1/4W resistor 
 is at the limit. If your local Radio Shack store hasn't shut the doors yet, 
 grab some resistors. (I just got some stuff last night at a 95% discount)



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