Custom nixie clock [FINISHED] - Page 1
Forum section: electronics / projects

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 04:23:29 am
content: Finished it!Thanks to everyone who helped me!-----------------Sure, everyone makes these, but.. So am I. As a gift for my girlfriend, birthday and christmas.So I'm doing it too. I'm using 595's to control the nixies in direct drive mode, a DS3231 spi module thing for timekeeping, MAX771 to step the voltage up, arduino because thats what I'm comfortable with, and PWM on the anode HV supply for dimming. And a photoresistor for auto control. I only blew it up once so far!This will serve as my project log.I was already here earlier when this very helpful forum helped me fix my MAX771 issues, so thank you to everyone who helped in that thread!And now I have blown up the resistors for the pwm drive, because I am using a PNP transistor to turn on and off the HV supply to the tubes, and I had a 10k 0805 resistor, R11 and R13, to NPN's, to the micro.Yeah, I know. 0805's don't like it when you try to dissipate 3.24 watts over them. I found that out with a lot of smoke.They are now 220K's and are operating fine, it seems!So now I have pwm fading working, I realized that I was a little too conservative with the anode resistors (even at 100% duty cycle its meh) so I'm gonna swap the 15k resistors to 10k. Should brighten things up a bit, so I can then PWM them back down.

author: JoeB83
author_rank: Regular Contributor
timestamp: December 07, 2015, 04:55:05 am
content: Very cool, and very professional-looking PCB!

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 04:57:26 am
content: Thank you!! I worked very hard on it..I've now left it running for a while, as I was afraid of how how the anode resistors might get. Good news, they don't get that hot! It's noticeable but certainly not bad, at around 121F max after five minutes. That's acceptable, right?

author: Cyberdragon
author_rank: Super Contributor
timestamp: December 07, 2015, 05:50:24 am
content: Oh noes! Not again! I've already saved a Fairchild 7000 from one of you lot. Savages! Always afta me tubes!Nixie tubes should not draw very much current at all. The anode resistors shouldn't get that hot unless they're too small. Make sure you use the recommended voltage and current for the tubes. If you run them too bright you can shorten their life, they should run around a quarter watt each.

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 06:01:33 am
content: The anode resistor is 0805 1/8w and on a section of pcb with tiny tracks and very little cooling, and it only heats up to 121 F. Does that sound bad?And also, its a IN-14 tube, 180V and a 10K anode resistor. Not sure how much current but I don't think its a lot. I'll measure the resistor later.EDIT: I measured the anode sustain voltage on my nixie's right now are 145.9V. So 34.1V across the 10K resistor, which means 3.4mA on the tubes. Sounds about right.The tiny 0805's are dissipating 0.116w, so.. within their power rating of 0.125w. But probably at the warmer side of it.After 20 mins the inductor L1 got to 131F. I'm worried about that because I only had one tube in. But maybe it's not a linear scale and just running makes it warm.. I'll have to fire the other tubes up and run it for a while and see. Maybe I can add a heat spreader if I absolutely must, but.. probably don't need to.

author: Cyberdragon
author_rank: Super Contributor
timestamp: December 07, 2015, 07:02:54 am
content: The power draw is fine, the resistor is just a bit too small. Odd that the inductor is getting hot. Could be an efficiency problem. It probably won't overload but it's wasting power.

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 07:42:13 am
content: Would going up or down in inductance fix that?

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 07:17:10 pm
content: Well.. the project may be over before it really started.I transferred everything over to where my computer is so I can work on the programming, and stupidly like an idiot put the black cliplead in the red, and vise versa.. pop. I've replaced my LDO and my microcontroller heartbeat led is flashing again, however, I cant get any high voltage. I've replaced the max771 and the mosfet, which are the only two really sensitive components. Still no high voltage. I'm at a loss and I'm low on spare components, and spirits are low. I was doing so well, too.I cant seem to get more then 26 volts out of the hv converter.. Its a new converter ic, and a new fet. what else could be broken??? I told the micro to not turn on its hv output so nothing should be drawing..

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 08:46:40 pm
content: It just seems like its not even trying to boost the voltage and is staying at minimum power. Also, the frequency. When it was working it was under 100khz I think? Now its like.. 450khz.?Whats so confusing is that THEY ARE NEW PARTS. The only worry of mine is I replaced the max771 and tried it, and then the fet and tried it. I hope the fet wasn't blown out and then blew out my only spare 771.. I just dont know what else it could be. its getting feedback.I'm so frustrated by this. I have no idea what to do or what could be wrong, I feel like I've hit a brick wall. Everything was working with this setup, I've replaced all of the parts that could be malfunctioning.. It's driving the gate properly and boosting voltage and getting a proper feedback voltage (that is low so it should be upping its duty cycle) and the scope shows everything and everything checks out but.. What is happening? What do I do to move forward? I don't have anymore max771's.. I'll have to get more.

author: Ian.M
author_rank: Super Contributor
timestamp: December 07, 2015, 08:58:28 pm
content: As it had blown the FET, could it have smoked the inductor? It would only take one shorted turn to explain your problem.

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 09:06:12 pm
content: I'll replace it now and see. I don't know if it blew the fet, but it was hooked to an unregulated supply at the time. I moved it from my current limiting supply at the bench to my beefy atx bench supply at my computer. So when it went, it really went..

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 09:20:36 pm
content: Nope.. new inductor did not make a difference. Fet drive is still going very low duty cycle and making a whopping 18 volts from a 12v supply..

author: c4757p
author_rank: Super Contributor
timestamp: December 07, 2015, 09:22:04 pm
content: Start taking parts off the board and testing them individually. Don't skip any.

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 09:25:31 pm
content: It appears that the entire digital side is okay (and it wouldn't affect HV generation anyway so)I'm a bit new at a lot of this, how can I test parts like the fet and the like?Also, how do I test the MAX771? I'm actually reading its feedback voltage right off its input pin, thus testing the pcb traces and stuff. It just doesn't want to up its duty cycle. Could I have blown the new one out too?In the meantime I'll just shave off that entire corner of the board with the reflow gun and test the passives out of circuit.

author: ajb
author_rank: Super Contributor
timestamp: December 07, 2015, 10:13:44 pm
content: Have you replaced that 100uF cap on the 12V rail? I'd be surprised if that didn't blow up from the reverse polarity, or at least let the magic smoke out. Inadequate input capacitance will definitely cause problems with any switching converter.

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 10:32:11 pm
content: I did, but it didn't help.The components I replaced were:First thing, 7805 regulator. The microcontroller came back to life, presumably the shift registers too. Completely independant of the HV supply.Noticed it still wasn't working. Replaced MAX771 regulator IC. Nothing worked, still.Replaced Mosfet. Still not working. Concerned at this point, measure voltage, see around 20 volts??Replace input cap on the 12v rail and inductor. Still not working??? What on earth is left?At the state it was before I desoldered the entire board, it appears the max771 was working, but at minimum power. It was only sending the bare minimum pwm, as if it thought it was already at high voltage. I could understand this behavior from the chip that saw -12v, but this was a new chip from the spares pile! What gives??

author: Ian.M
author_rank: Super Contributor
timestamp: December 07, 2015, 10:41:30 pm
content: Maybe it thinks its over-current. Check the resistance of the 3x1R || shunt.

author: ITman496
author_rank: Regular Contributor
timestamp: December 07, 2015, 11:34:01 pm
content: ......THAT MAKES SO MUCH SENSE. That entire thing was made up of 0805 resistors, had a total resistance of probably 0.25 ohms, and got exposed, minus a fet body diode drop, to 12v..they must have blown out. I wish I could have measured them directly before I took it all apart. Time to put it back together. I'll keep you posted!

author: ITman496
author_rank: Regular Contributor
timestamp: December 08, 2015, 12:58:17 am
content: sigh. nope.it appears in desoldering the chip to get it out of circuit to check other things, putting it back.. its dead. And the other chip, dead too. Both are dead, don't have any more.. have to wait for digikey. UGH. I wish I had just tried the resistors first.. I just want to start programming this thing and look at nixie tubes glowing and stuff.. now I have to wait a few days and do nothing.

author: AustinEngy
author_rank: Regular Contributor
timestamp: December 08, 2015, 02:22:23 am
content: Keep your spirits up! You're gonna end up with a totally awesome project when you're finished and I look forward to seeing you solve these problems. I'm too new to this type of thing to be of much help, but admire that you're making this as a gift. I wish you the bestYour girlfriend will love it, I'm sure!

author: ITman496
author_rank: Regular Contributor
timestamp: December 08, 2015, 02:28:58 am
content: Thank you.. I've replaced every component and now I dont have a gate drive signal anymore, so.. i assume that's whats happening. On the bright side I've learned a lot about how to use my scope. Tomorrow I'll start attempting to machine the wood case for it. This is my idea of what it'll look like.

author: Ian.M
author_rank: Super Contributor
timestamp: December 08, 2015, 07:51:20 am
content: Its a pity you jumped straight to replacing parts.Swapping the regulator was a good decision, but as soon as you found the boost controller was blown, you should have removed it then cold checked the boost circuit discretes in-situ.Also, when designing a one-off like this, its worth providingsolderpad jumpersso that various modules can be isolated for testing without having to hack up the board or desolder delicate parts.Good luck, and have fun making gerbil bedding!

author: ITman496
author_rank: Regular Contributor
timestamp: December 08, 2015, 08:33:20 am
content: Yeah.. Lessons learned for the next projects, right? I certainly won't be making any of these mistakes again. Using a weird not made anymore boost controller with not vetted by forum design for boost converter, not making isolating pads for stuff.. plugging things in backwards. debugging technique.Alas I think I replaced everything necessarily, as in everything was blown, but my second pull of the parts is what killed the driver ic.I am planning on it. Trying to think of what to use. Can I make a 2x4 look good, or do I have to use a weird wood..

author: Ian.M
author_rank: Super Contributor
timestamp: December 08, 2015, 08:52:01 am
content: How good are your carpentry skills?At the very least, if you are going for the correct period 1950's domestic style, you'll need it to be nicely veneered. It would probably be a lot simpler to style it as period test equipment. Sides done in 1/2" hardwood, with lightly rounded finger-jointed corners with triangular reinforcing pieces on the inside and a rebate in the top edge for a Tufnol top panel. Chunky rubber feet on the bottom to raise it up for ventilation and an expanded metal mesh bottom cover to keep out curious fingers. Shellac and wax polish all the woodwork.

author: krivx
author_rank: Frequent Contributor
timestamp: December 08, 2015, 08:57:42 am
content: Do you have design files for the nixie sockets? Do they stay cool enough not to melt?

author: v8dave
author_rank: Regular Contributor
timestamp: December 08, 2015, 09:01:50 am
content: For your reference I used the same MAX771 to build my Nixie clock and it works fine so hope you can get it working again. Attached is the schematic of the HV generator circuit which looks similar to your design other than a few differences.

author: ITman496
author_rank: Regular Contributor
timestamp: December 08, 2015, 09:34:42 am
content: Hm. I have no woodworking experience. This is gonna be interesting!And you used a 330uH huh.. I am using 100uH now, but I was using 220uH before, but it was established that it was not a good idea.Glad it works though. Still never gonna use it again ever ever.As for the sockets, they aren't really sockets. They are just mounts. The tubes sorta friction fit into them, after I solder wires onto them, and then I hot glue pot them into the socket to secure the wires from snapping off the legs. I can still get you the file if you wish.

author: v8dave
author_rank: Regular Contributor
timestamp: December 08, 2015, 10:07:18 am
content: Yes, the inductor is quite large but I used what I had lying around and this one just worked and has been for months. It's a little high in regards to DC resistance but as it works, I am reluctant to change it.ELC09D331F is the part number I used.

author: Ian.M
author_rank: Super Contributor
timestamp: December 08, 2015, 10:22:56 am
content: Quote from: ITman496 on December 08, 2015, 09:34:42 amYep. Its going to look like a dog's breakfast. No nice finger joints. Probably your best bet would be mitred corners assembled with square reinforcing pieces on the inside, screwed from the inside and epoxy glued. You probably don't have the tooling to do a rebate on the top edge for the top panel either, so use thinner sides and sit it flush on the ends of the corner reinforcements and glue and pin in square section battens for the edges to sit on.QuoteThat's not good, unless the mounts have an O ring to retain and cushion the tube. Fortunately Nixies don't have a heater, otherwise you'd be in for a world of grief.

author: Gyro
author_rank: Super Contributor
timestamp: December 08, 2015, 05:20:17 pm
content: Quote(One for next time) Never be too proud to include a reverse biased protection diode directly across the supply input of anything you're prototyping or that is externally powered. An abused 1A rectifier will normally fail short-circuit and still protect your circuit even in a high current reversed supply situation.

author: ITman496
author_rank: Regular Contributor
timestamp: December 08, 2015, 05:58:15 pm
content: Every single design for now on is getting disconnect jumpers and reverse protection and input protection and every protection... And I'm going to order 1 more spare parts then I think I need.I have a cnc mill, so.. Maybe I can be creative with it. I just need to find some cheap hard wood.The tube mounts seem okay, but yes, I am banking on the bottoms not being very hot. But they aren't, as far as I can tell. They friction fit pretty well into the 3d printed piece, it's printed to match the curve of the bottom of the glass tubes and cups them, and I use the glue as reinforcement for the pins, in retrospect 3d printed holes probably would have been better but I wanted to keep it slim.

author: ITman496
author_rank: Regular Contributor
timestamp: December 14, 2015, 06:55:56 pm
content: It's alive again!And.. my god. I nearly blew it up again by offsetting the connector for the power by one pin, making the polarity reversed, but thankfully I was on my current limiting supply.GOD. I ALMOST DID IT AGAIN FIRST THING AFTER FIXING IT! Why am I so bad at this. I've never almost blown something up / blown something up so much. For reference, the amount of damage my accidents have caused on this ONE project exceeds how much I've screwed up and blown up every other project I've worked on for the past seven years!Anyway. Back to business.And if anyone has a small lab supply with constant current that they are willing to sell (or trade for a tdk lambda 20v 10A constant voltage constant current power supply) please let me know. That thing is too big.

author: Ian.M
author_rank: Super Contributor
timestamp: December 14, 2015, 07:44:42 pm
content: Add this to your future design rules:* Use connectors with a shell on the header, and if they are dangerously electrically incompatible, for %DEITY%'s sake make them physically incompatible!

author: ITman496
author_rank: Regular Contributor
timestamp: December 14, 2015, 08:20:17 pm
content: I agree wholeheartedly! Polarized connectors and reverse polarity / overvoltage protection for now on! This has been an expensive learning experience. Unfortunately those are usually the ones that stick..This reminds me of the time I decided I was never going to use DEANS connectors again on my drones and switched to anderson power poles.My zephyr drone uses two 4s 5200mah LiPo batteries in parallel, one in each wing.I had deans connectors, which look like:Male end on plane, female on battery, Y harness on aircraft of the male type. Can you see where this is going.I plug one battery in. The positive exposed end of the Y harness other male connector jostled when I was holding the other end of it, and fell..onto the SMA bolt of the uhf control radio, a dragonlink.Now, to make it better, I had waited for that dragonlink RX because it had been out of stock for... Six months! Six months, I waited for it. About to do my first flight.As soon as I plugged that battery in. It shorted through the heavy 8 gauge wiring, the batteries were capable of pulse discharges of well over a thousand amps into a short..Two board design on the radio.. BANG. The receiver literally exploded, the male end of the deans connector melted and dripped through the bottom of the airplane, and the entire ground wiring of the entire aircraft detonated. It was intense. And upsetting.I no longer use deans or any un-shielded power cables. I guess I should follow that rule for everything else, too.story_time_over();

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 08:22:44 pm
content: Quote from: ITman496 on December 14, 2015, 08:20:17 pmDidn't you learn to use fuses?

author: ITman496
author_rank: Regular Contributor
timestamp: December 14, 2015, 08:52:31 pm
content: fuses in the main power system of an rc aircraft? I don't think I've seen anyone use fuses in them. Typically the motors draw upwards of a hundred amps anyway (or at least mine does) and pulses of far more then that when starting. With the size of the fuse, it would explode anything it touched anyway.(Also I don't want a fuse blow to essentially unplug the battery on my plane mid flight when it could theoretically blow out whatever caused the issue and carry on flying)

author: Fungus
author_rank: Super Contributor
timestamp: December 14, 2015, 08:57:13 pm
content: Quote from: ITman496 on December 14, 2015, 08:52:31 pmYou said:Quote from: ITman496 on December 14, 2015, 08:52:31 pmFuses don'thaveto be in the main power system. A fuse in that part of the circuit could have saved your electronics.

author: ITman496
author_rank: Regular Contributor
timestamp: December 14, 2015, 08:59:05 pm
content: A fuse on the ground path of the low power system, you mean? That makes way more sense.. Sorry, I misunderstood.

author: ajb
author_rank: Super Contributor
timestamp: December 14, 2015, 09:05:02 pm
content: Quote from: Ian.M on December 14, 2015, 07:44:42 pmAlso: fuses and TVS diodes are cheap insurance, especially if your project uses a standard barrel connector that may wind up connected to the wrong wall wart.

author: ITman496
author_rank: Regular Contributor
timestamp: December 14, 2015, 09:10:31 pm
content: Do you know of a good guide to using tvs diodes?

author: AustinEngy
author_rank: Regular Contributor
timestamp: December 19, 2015, 05:31:59 am
content: Quote from: ITman496 on December 14, 2015, 09:10:31 pmHere's a good introductory guide, may be a little bit high level, though.http://www.semtech.com/images/promo/What_are_TVS_Diodes.pdf

author: ITman496
author_rank: Regular Contributor
timestamp: December 20, 2015, 08:33:31 pm
content: It's working again! I pretty much wound up having to replace the entire hv section. But look!

author: ITman496
author_rank: Regular Contributor
timestamp: December 21, 2015, 05:29:05 am
content: starting the final tidying.

author: ITman496
author_rank: Regular Contributor
timestamp: December 21, 2015, 06:22:11 am
content: Does anyone know what causes the IN-3 dot displays to have the neon like.. sorta wander around in the bulb? It starts at the bottom and then works its way to the top before it turns off. It's strange.

author: Ian.M
author_rank: Super Contributor
timestamp: December 21, 2015, 06:42:00 am
content: Are you running them at their rated current. At low currents the discharge can move about a bit and often moves upwards due to convection. It could also be a sign of old age, and possible decay of the trace of radioactive gas that is often added to the fill to reduce the dark effect.

author: ITman496
author_rank: Regular Contributor
timestamp: December 21, 2015, 06:54:57 am
content: Hm.. Not a bad point. I changed the anode resistor to be 10x what it was to dim it down, I should reduce slightly.

author: ITman496
author_rank: Regular Contributor
timestamp: December 21, 2015, 08:38:23 am
content: IT WORKS! Yay!Nixie test

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: December 21, 2015, 06:35:34 pm
content: Quote from: ITman496 on December 21, 2015, 08:38:23 amNice job! Glad you got it working! And blowing things up is also part of the learning experiance

author: ITman496
author_rank: Regular Contributor
timestamp: December 21, 2015, 10:13:05 pm
content: It certainly teaches lessons that you will never forget..

author: ITman496
author_rank: Regular Contributor
timestamp: December 23, 2015, 03:58:25 am
content: Question. When I pwm the tubes to dim them down (for night mode) very low, I can hear a faint.. hissing noise from the board. I assume its the coil. And I think it's hissing at the pwm frequency. Will this harm anything or is it okay? Everything still works and has been for ten minutes, nothing seems really hot.. But I wasn't expecting it to be audible. Will this destroy anything in the long run?

author: ITman496
author_rank: Regular Contributor
timestamp: December 23, 2015, 04:27:09 am
content: I analyzed it in audacity and I get peaks at 490hz, 980hz, etc etc. So its definitely the pwm frequency because.. That's also what frequency the default analogWrite function of an arduino sends.As long as it isn't harmful, I don't really mind. Once its in its case, it won't be audible. It's very faint. Just wanted to make sure something wasn't about to explode!

author: ITman496
author_rank: Regular Contributor
timestamp: December 23, 2015, 07:14:44 am
content: I'll check on that tomorrow! For now, however, I will end on a high note~

author: ITman496
author_rank: Regular Contributor
timestamp: December 24, 2015, 04:27:11 am
content: Wood base made! God that was the hardest part. I am not a wood worker, and there are still a lot of flaws in the case, but.. its 'okay'.

author: Ian.M
author_rank: Super Contributor
timestamp: December 24, 2015, 06:56:58 am
content: You are getting there. Its certainly not 'fine woodworking' and all the exposed screw heads make me wince, but it appears to do the job. What do you plan to do to keep the dust off the tubes and protect them?

author: ITman496
author_rank: Regular Contributor
timestamp: December 24, 2015, 07:47:13 pm
content: I actually did the screws that way on purpose because I like them lol..And.......... not sure. Ask nicely to make sure nothing knocks into them and that one sprays some compressed air at them once in a while?

author: Cloud
author_rank: Regular Contributor
timestamp: December 24, 2015, 10:06:23 pm
content: Very nice, I am planning to do something like this for quite some time now, but it still hasn't moved from schematics drawing in KiCadI am planning to do just hours and minutes and pack it into dark wood or maybe anodized aluminium

author: ITman496
author_rank: Regular Contributor
timestamp: December 27, 2015, 06:05:53 am
content: thank you!It's officially done now. Just needs its transport box and bottom cover.The wiring is not as neat as I intended. I accidentally made the wires for the tubes too short and the board had to be flipped upside down. Still works, but oh well.

author: TiN
author_rank: Super Contributor
timestamp: December 27, 2015, 07:17:18 am
content: Now time to think about adding fade-in/fade-out for nixies

author: AustinEngy
author_rank: Regular Contributor
timestamp: December 30, 2015, 07:40:43 pm
content: Awesome job! I'm sure your girlfriend is loving it as much as we are

author: BillyD
author_rank: Regular Contributor
timestamp: December 30, 2015, 11:24:03 pm
content: Great project, well done!

author: ITman496
author_rank: Regular Contributor
timestamp: January 06, 2016, 07:54:12 am
content: thank you all! Would not have been able to do it without your help!