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Author Topic: Almost enough volts but not quite! - Presses stopped, nixies working!  (Read 16394 times)
raygungothic
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« on: September 23, 2009, 03:59:38 PM »

I reckon I've done something wrong while assembling. The voltage between ground and my test point reads 170v with my trim pot at one extreme. Turn it to the other and I get... 173v. My limited understanding of the circuit suggests it should be able to make a *bit* more difference than that.

Unfortunately, the data sheet for my tubes appears to say that I need 200v to get the blighters out of bed and shining. My Russian is not great, but the stats list is
Voltage (something), V, (something)... 200
(Something), mA... 2.5-4.5
Voltage (something), V, (something)... 100
(something I have no idea about), c, (eh?)... 0,5
so I guess the 200v is what I need to hit to light them up.

I have a 12v supply and the 47pF cap the kit came with. I have a 5.6pf cap somewhere but I'm not at all sure it's rated for 500v; I think I'm going to run out of patience and risk it fairly soon. The worst that can happen is bits of cap in my eye, and I've had worse.

In the meantime, does anyone have any hints as to things to check for if the trimpot has bother-all effect on voltage?

Many thanks!

Ray
« Last Edit: September 24, 2009, 04:11:58 PM by nonentity » Logged

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« Reply #1 on: September 23, 2009, 04:08:15 PM »

I reckon I've done something wrong while assembling. The voltage between ground and my test point reads 170v with my trim pot at one extreme. Turn it to the other and I get... 173v. My limited understanding of the circuit suggests it should be able to make a *bit* more difference than that.

Unfortunately, the data sheet for my tubes appears to say that I need 200v to get the blighters out of bed and shining. My Russian is not great, but the stats list is
Voltage (something), V, (something)... 200
(Something), mA... 2.5-4.5
Voltage (something), V, (something)... 100
(something I have no idea about), c, (eh?)... 0,5
so I guess the 200v is what I need to hit to light them up.

I have a 12v supply and the 47pF cap the kit came with. I have a 5.6pf cap somewhere but I'm not at all sure it's rated for 500v; I think I'm going to run out of patience and risk it fairly soon. The worst that can happen is bits of cap in my eye, and I've had worse.

In the meantime, does anyone have any hints as to things to check for if the trimpot has bother-all effect on voltage?

Many thanks!

Ray

Ray, you're going to want to use that 5.6pf cap, most definitely.   If you don't have one, I will mail you one, email me at bradley@robotpirate.com

Secondly, the trim pot should give you a larger range of voltage than that, not sure why it wouldn't be, but that is a bit odd.. Can you take some closeup pics of both sides of the board and send them to that same address?

With the 5.6 pf cap, you'll want to run 9 volts.  12 with that cap would most likely get too high voltage.

Brad
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Masoste
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« Reply #2 on: September 24, 2009, 12:37:00 AM »

I just got a board with some IN-4 tubes together the other day. It looked great with a single tube but when I started plugging in more tubes I though I had shorts or had just done a shoddy soldering job. It looks like I just wasn't getting enough juice to drive them with that 46pf cap so I upped it to a 7pf cap that I had hanging around and that got things working. I'm still not getting quite what I'd like for these tubes (although it drives some B-5750S http://www.tube-tester.com/sites/nixie/data/b5750s.htm tubes great). I suppose I'll change it again to the suggested 5.6pf cap and see if that does it. Unfortunately I have a set of 6 tubes but one's bad so I'm waiting for another tube to arrive from Russia before I'll really be able to finish this project.
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raygungothic
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« Reply #3 on: September 24, 2009, 03:40:06 AM »

Bradley - thanks very much for the help and the v quick reply!

Thank you also for the kind offer of a capacitor, but as your last package took several weeks to get through customs - and they charged me a disproportionate amount of money for the privilege of evaluating that the customs duty would be very small - I think I'd rather try to find one in the uk. I know they shouldn't charge for a tiny package but I don't trust them  Undecided

Also, since it seems something else is not right, I would like to try to diagnose and fix that before I change the cap, otherwise it might not have the desired effect. I guess I must have screwed up a solder joint somewhere, although it looks OK to my untutored eyes. I did do quite a bit of connection testing with a multimeter while I was assembling, but I got a little impatient after a while and stormed on. Still, if I get 170v and can send it to the anode pins using the Arduino, *most* of it must be working as designed! So it shouldn't be too hard to narrow down if I control my impatience and get systematic.

(I noticed this morning that the metal plate on the back of the FET runs 100v. Shouldn't it be at ground? That might be a hint, I'm definitely looking into that in more detail this evening)

Masoste - thanks, I'm sure you're right about needing the right cap for the tube. Unfortunately I don't have any other tubes to try.
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raygungothic
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« Reply #4 on: September 24, 2009, 03:00:34 PM »

Stop the presses!

My Arduinix is working after all.

I didn't change anything, just scraped the trim pot back and forth a few times and now it lights an IN-8 beautifully. My guess would be that the trim pot had something on the contact. All good now. (12v supply, 47pF C3 - I haven't tried changing the cap)

Thanks so much for all your help.


http://pics.livejournal.com/raygungothic/pic/000g1r0t

« Last Edit: September 24, 2009, 04:00:17 PM by raygungothic » Logged

nonentity
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« Reply #5 on: September 24, 2009, 04:08:40 PM »

Stop the presses!

My Arduinix is working after all.

I didn't change anything, just scraped the trim pot back and forth a few times and now it lights an IN-8 beautifully. My guess would be that the trim pot had something on the contact. All good now. (12v supply, 47pF C3 - I haven't tried changing the cap)

Thanks so much for all your help.


http://pics.livejournal.com/raygungothic/pic/000g1r0t




Awesome news, Ray!  Looking forward to seeing more from your project!
Bradley
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nonentity
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« Reply #6 on: September 24, 2009, 04:14:16 PM »

Congrats raygungothic, and thanks again for your purchase.

-Emblazed
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Masoste
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« Reply #7 on: October 04, 2009, 10:34:33 PM »

Well, It looks like I'm almost there.
I'm using a power supply that's rated for 1A at 9v but it's actually putting out a voltage near 12v.
I've decreased c4 to 7pf which gets me a reading of up near 220v without any tubes plugged in. But my Russian in-4s aren't lighting up all the time. I've got a configuration like that in the 6 tube layout with three tubes per cathode and two tubes per anode (anodes 2, 3 and 4). When I hook up my tubes the voltage tests at about 140v from the test point to the grounds pins on the arduinix board. Does that sound about right?

I've reduced the resistors on the anode outputs to about 2.2kohms which made the tubes a bit brighter when they're glowing but I'm still not getting every cathode to light up. Actually cathonde 4 if the second didget of the seconds display only occasionally lights up. I've checked my connections to the tubes though. Could it be the nixie controler chip?

I'm also curious if I should have individual resistors for the anode of each tube or if a resistor on each anode output is fine. That's how I have it configured now because I didn't think it would matter. I've tried a resistor to each tube's anode but it doesn't seem to make a difference.
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Masoste
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« Reply #8 on: October 04, 2009, 11:51:54 PM »

Here's a pic of what I've got set up now. The loose wires on the far right are for setting the time.



Most cathodes are working fine, like this



but some just don't wont to turn on



or even weirder is that I get a ghostie of a cathode that is not supposed to be lit lighting up. It'll be a cathode the same cathode as that of a different tube on the same cathode output.



I hope that these aren't too many photos. I just can't think of how else to describe it. In the bottom picture the fourth digit was supposed to be a 3 when the photo was taken.
I suppose I should mention that I've tried changing the update speed of the bulbs. It doesn't seem to make too much difference. 7 is about the longest I can stand before the flickering gets to me though.
I'm thinking that maybe it's either a short on the circuit or in my wiring because the barely lit cathodes. For a while the 2 cathode on my last digit just wouldn't quite go out.
« Last Edit: October 05, 2009, 12:26:37 AM by Masoste » Logged

nonentity
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« Reply #9 on: October 05, 2009, 08:25:55 PM »

Whoa, GREAT pics!!

Looks like you have a short in your cathodes...  Can you try just hooking that tube up to a different set of cathodes?  Like only that tube, hooked to a set of cathodes you know works.

Or, try switching tubes.  However, looks like your tubes are fine.  What hookup wiring diagram are you using?  can we get a shot of the back of your tube board?

I know when I get odd short here or there it causes weird things like that.

Looking great tho!
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nonentity
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« Reply #10 on: October 07, 2009, 02:44:25 AM »

A short would make sense. I've tried a few other tubes but keep getting the same thing. But a short in my cathodes or anodes?
I always get a faintly illuminated cathode that matches the same number cathode of a the fully illuminated tube that's running off the same cathode output but a different anode beside it.
A quick diagram would be something like this:

Although I've also got three more bulbs on the second set of cathode outputs and they share the same three anode outputs.

I can take a photo of the board that I've mounted the tubes on if you think it would help. I've checked it visually and tested for any shorts that I could figured that I could find with my multi-meter but didn't find anything. Would dirt or solder flux residue be enough? I've cleaned it with solvent too.
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nonentity
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« Reply #11 on: October 07, 2009, 03:52:07 PM »

Hmm, might not be a short in your wiring harness to your tubes, but it could be a slight short on the arduiNIX itself, did you check all the solder joints on the shield?

I am wondering if it could be a driver issue...   Did you socket your driver chips?

On second thought, It sounds like something to do with the multiplexing of the anodes.. As if the dimly lit tube has an anode that isn't being switched off correctly during the multiplexing sequence... might be a code issue.

When Jeremy gets back in town from his vacation, I'll see what he thinks about this.
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« Reply #12 on: October 09, 2009, 12:21:26 AM »

Well I've had some new success. I have all the cathodes firing now, but I'm still getting faint "ghost" cathodes lighting up.

I changed capacitor c4 again for one that's 5.6pf (rather than the 7pf that I had in there) just to make sure that wasn't a problem snce the 7pc capacitor was one I found that didn't have a voltage rating either.  And  when I was done I did a pretty vigorous cleaning of both sides of the arduinix board with Acetone. I also added a bit more heat to some solder points that looked less than perfect. It's possible that a solder point was preventing one cathode from firing and it does look a bit cleaner but I don't actually think that did anything. So, your suggestion about multiplexing of the anodes might make sense.

I've also played with the anode resistors a bit. I'm using a 5.1kohm resistors on the anode of each tube (8 in total). I wasn't able to get every cathode to light up before changing these from 10k to 5k although I think that that may have to do with these tubes. The in-4 tubes may require a bit more current/voltage than some other tubes. The tube-tester page has the most information that I can find on them anywhere (http://www.tube-tester.com/sites/nixie/data/in-4/in-4-sh1.htm).  

I've got my driver chips in sockets. Do you think that I should try swapping them for one another and see If that affects the faint ghost cathodes?
« Last Edit: October 09, 2009, 12:29:23 AM by Masoste » Logged

nonentity
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« Reply #13 on: October 09, 2009, 08:26:51 PM »


I've got my driver chips in sockets. Do you think that I should try swapping them for one another and see If that affects the faint ghost cathodes?

Yes, I would try that, and if it ends up being a driver chip issue, I'll send you a fresh set of chips.  Lightly salted, of course.
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nonentity
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« Reply #14 on: October 10, 2009, 11:02:57 AM »

Well it looks like that's it.
If I swap the two driver chips the tubes that have the ghost lit cathodes follow along. I either have an issue with the first three didgits (from one chip) or with the last three (from the other chip) but not both.
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