Homebrew high voltage nixie power supply

[Kevin A.]

Just wanted to share a nixie related project I've been working on for a few weeks now. I've got the boards ordered for my latest revision. Looking for any feedback and to see if this interests anyone. 

https://neonkev.com/2019/08/18/project-20-watt-high-voltage-boost-converter/

Since I got into nixies, I've found that good high voltage power supplies are a major asset to any successful design. Instead of relying on Chinese eBay stuff or other unsustainable sources, I wanted to build my own using the latest in boost controllers and high power semiconductors in addition to using the highest quality, brand name components in the actual construction the supply. It's not a design built down to the lowest cost but one built for silent, reliable, and continuous low-ripple operation at rated power. 

This will be made open source once I've matured it to a reasonable degree. I hope that the latest revision will prove satisfactory. 

[Nicholas Stock]

That’s a really nice write up Kevin!

Sent from my iPhone

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[Kevin A.]

Thanks Nick! I'd like to do more if I could find the time. 

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[Kevin A.]

Update; I designed a scaled down 10 watt power supply for use with the popular MOD SIX clock. It works a treat!

[Bill Notfaded]

Looks good Kevin... 10 WATTS is some juice!

Bill

[Bill Notfaded]

I might like one of you big 20 Watt versions to drive my longer B-7971 smartsocket array... as it is now it's requires multiple Taylor supplies.  For safety I've not been eager to drive more than 2 or 3 tubes per Taylor supply.  If you add up powering all the segments from the datasheet it looks like many people exceed the specs or just assume they won't light all the segments on all the tubes at once?  So this means using 4 or 5 Taylor power supplies for a longer smartsocket array.

Regards,

Bill

[Kevin A.]

In order to make sure my design is suitable for your needs, how many tubes are you driving and do you anticipate driving them with all cathodes on? The Burroughs datasheet gives a max "all cathode" current of 21ma per tube for the 7971. 

The mod six is a proven 7971 design and usually 1 taylor module or equivalent (40-50ma max) power supply seems sufficient for 6 tubes. 

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[Bill Notfaded]

So maybe two of your supplies then for 10 smartsockets?  That's better than possibly 5 Taylor... at least that's how I see it!

Bill

[Kevin A.]

Let me see what I can do. I have some ideas about how a 40 watt version would be possible without too many tweaks. I'll take a stab at that if you're not in a rush. 

On Fri, Sep 6, 2019, 4:22 PM Bill Notfaded <notf...@gmail.com> wrote:

So maybe two of your supplies then for 10 smartsockets?  That's better than possibly 5 Taylor... at least that's how I see it!

Bill

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[Bill Notfaded]

Take your time.  No rush at all.  I've got 10 projects going and more on the way.  I love this stuff.  It helps keep me sane from other real work work.

Bill

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[Kevin A.]

Here's what I was thinking. Major difference from the 20 watt version is the main switching MOSFET, which is over twice as beefy. The inductor I used on the 20 watt was overkill so this should take better advantage of it. Size is the same as before; practice makes perfect! 

You'll also need a 5 amp 12 volt adapter to get the kind of juice you're looking for out of this thing! 

[Bill Notfaded]

Kevin-

I know just the place to get the 12V power supply supplies.  I regularly buy 3A for most things so I have usually more than enough power.  The same seller I buy from has a 5A as well.  I've found the price is good for US distributer.  He markets them as 5050 LED strip power supplies.  I've never had a problem with them and they're cheaper than anywhere else I've found and he ships usually the day I order them.

They come in these sizes all 12V:

1A/12W

2A/24W

3A/36W

5A/60W

6A/72W

8A/96W

10A/120W

15A/180W

20A/240W

25A/300W

30A/360W

40A/480W

50A/600W

He gives me quantity discounts too.

Best Regards,

Bill

On Fri, Sep 6, 2019, 7:33 PM Kevin A. <ka...@scarletmail.rutgers.edu> wrote:

Here's what I was thinking. Major difference from the 20 watt version is the main switching MOSFET, which is over twice as beefy. The inductor I used on the 20 watt was overkill so this should take better advantage of it. Size is the same as before; practice makes perfect! 

You'll also need a 5 amp 12 volt adapter to get the kind of juice you're looking for out of this thing! 

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[gregebert]

Budget about 4 watts per tube (b7971); 160 volts at 25mA is slightly above the max recommended current per the datasheet.

Also be aware that you will need to deal with the generated heat from these tubes, if they are in a fully-enclosed case. Vent holes on the top and bottom should suffice; convection will handle it from there.

They actually do get slightly warm after a few minutes of use, but not at all hot like vacuum tubes such as radio/TV/stereo.

[Neil]

Very impressive write up Kevin. Like Bill, the first thing that came to mind was “can I get one?”. I’ve started the resurrection of an unfinished 8 x ZM1350 SmartSocket project and had just done the power supply calculation and realised I needed 8x roughly 14mA = 112mA for all segments on. I don’t plan on that happening much if ever but am going to use two Taylor supplies. This should mean I can cover that worst case, while having loads of margin and hopefully cool running for normal operation. I look forward to following your progress with the 20w supply and if you do eventually have any for sale I may be interested.

[Kevin A.]

Thanks Neil. I'm working on getting this new transistor design up and running within the next two weeks. For my own sake, I can make the 20 watt and 40 watt versions use the same topology (since the major differences are limited to the transistor and input protection fuse). Current limiting for the specific application can also be adjusted by changing the current sense resistor, as the TPS40211 is a current mode controller. Stay tuned! 

[Richard Scales]

Please could you add me to the list of interested parties. I have some projects based on B-7971 and ZM1350 and would really appreciate it if i could use power supplies that were within spec for what I want to do.

These projects include 6, 8 and 10 tube variations.

Please could you confirm whether or not you include a logic driven enable/disable (I did see EN1 on the picture of the PCB on your project site). Also, am I right in thinking that to drive smart-sockets from 180V as opposed to 170V there needs to be a change in the value of the common anode resistor R31 (from a link to some resistance that deals with the slight increase in supply voltage)?

I am in the UK - I hope that isn't a show stopper!

Kind regards

Richard

[Kevin A.]

Hi Richard,

Thanks for the interest. Yes, there is a logic controlled enable/disable which can switch the high voltage output on and off. In normal operation, there is an internal pull-down on this pin in the controller IC to keep the output on. If this pin is pulled above 1.2 volts, it will signal the controller to turn the output off. The maximum voltage permitted on this pin is 10 volts. I will include a terminal block for easy access to this feature.

The difference between 170 and 180 volts should not require an additional resistor on R31. Looking at the smartsocket cathode resistor values for each segment, they are the same as those used in the mod-six 7971 clock, which operates without issue with 180 volts at the anode. The ~6% increase in power dissipated between 170v and 180v is minor and will not noticeably affect the longevity of the tubes or driving electronics. 

I've never sent a package overseas, but I could certainly try! Hopefully customs doesn't panick at the sight of mysterious circuit boards. 

Thank you,

Kevin

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[Jon D.]

Kevin,

Please add me to the list of those interested as well.  I, too, have some B-7971 and ZM1350 Smartsocket projects in mind with 6-10 tubes each.

Jon J.

[Richard Scales]

Hello and thank you for your speedy response, that all sounds perfect then. Please keep me posted on developments, I shall follow this thread.

Kind regards

Richard

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[Kevin A.]

Update:

A quick test shows that the 40 watt version works! It turns out, however, that 12 volts in is a bit too low for this design at this power level. By upping the input voltage to 24 volts (which is reasonable - there are plenty of cheap 24 volt wall warts as well), the design functioned as intended (all components within rated spec at 24 volts as well). Output across a fixed 876 ohm load settled at 179 volt ~201 milliamps for a 24 volt 1.65 amp input, which translates to 91% efficiency. There really isn't any practical benefit to running at 12 volts with double the input current. Efficiency would drop and heat would increase throughout the circuit to attain the same power. 

If any clocks or systems out there need a lower operating voltage and you want to run off of one power input, I can add 24 volt breakouts for your own DC-DC converter. A second option would be to build in a second switcher to step the input 24 volts down to an adjustable voltage between 1.2V-24V. This is fairly straightforward using a controller like the LM2576T-ADJ. It will, however, increase size and cost (current size is 3.3 inches x 2.1 inches). 

I want to perform some thermal testing when I have access to my infrared camera this week as well. I did some poking around to see what was warm after the supply was turned off. As expected, the transistor and diode did produce some heat, but they were only warm to touch. My 100 watt load resistor, however, was getting pretty warm!

[Kevin A.]

And to be clear, it does run at 12 volts as well. However, the controller will turn the HV off at around 110-130 milliamps as the inductor duty cycle approaches 100%. 

[Bill Notfaded]

Sounds great!  I have some 18v supplies as well.

Bill

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[Kevin A.]

Out of curiosity I'm going to try changing the switching frequency and increasing the inductance, with the aim of meeting my original goal of full output at 12 volts. Can't hurt to try. 

[Bill Notfaded]

Either way like you said 24V could also be doable.  Great work!

On Sat, Sep 21, 2019, 11:59 PM Kevin A. <ka...@scarletmail.rutgers.edu> wrote:

Out of curiosity I'm going to try changing the switching frequency and increasing the inductance, with the aim of meeting my original goal of full output at 12 volts. Can't hurt to try. 

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[Richard Scales]

12v or 24v are both good for me, as you say, 24v to 12v conversion (or whatever voltage you need for logic and associated circuits) is easily accomplished. I am looking forward the next installment!

[Kevin A.]

I've published another post covering changes and further refinement to the design: https://neonkev.com/2019/09/27/40-watt-boost-converter-running-into-physics/

With another Digikey order on the way, hopefully my next tweaks will get me down to 12 volts! If not, the design is still perfectly functional as-is, and I expect to be releasing it before the end of the year. 

[Bill Notfaded]

Looks great Kevin... nice work!

Bill

On Fri, Sep 27, 2019, 2:50 PM Kevin A. <ka...@scarletmail.rutgers.edu> wrote:

I've published another post covering changes and further refinement to the design: https://neonkev.com/2019/09/27/40-watt-boost-converter-running-into-physics/

With another Digikey order on the way, hopefully my next tweaks will get me down to 12 volts! If not, the design is still perfectly functional as-is, and I expect to be releasing it before the end of the year. 

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[Richard Scales]

I am properly excited by the work that you are doing and am looking forward to it's formal release.

I'll take a couple in the UK please - and if anyone else in the UK would like to combine shipping etc - PM me.

Keep up the good work.

RIchard

[Kevin A.]

Another update for those following:

After several spreadsheets and some experiments, I was finally able to get the design to function at a full 200 milliamps down to the 12 volt mark (and even slightly below). 

As I discovered, more inductor was required in addition to the changes in switching frequency. Some of the current sense control loop parameters also needed changing for stable operation over this wide input range. You can see the experimental dual inductor arrangement on the successful test board.  

Other changes include a transition to through-hole electrolytic capacitors, for ease of assembly and future serviceability. 

Another update will follow once I have assembled and tested the new revision as shown in the CAD image!

[gregebert]

Are the 2 inductors paralleled ? 

[Kevin A.]

Yup, 2 inductors are in parallel. Couldn't find a single inductor with the desired spec. I guess my design is sort of atypical compared to the majority of boost converters. 

On Fri, Oct 4, 2019, 3:57 PM gregebert <greg...@hotmail.com> wrote:

Are the 2 inductors paralleled ? 

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[gregebert]

With such a high boost-ratio, the other alternative is a flyback converter, which is almost identical except there is a secondary winding that goes to the high-voltage side.

Basically to get more voltage out of a boost-converter, you need more current. There are only 2 ways to do that if you've maxxed-out your duty-cycle:

1. Increase the supply voltage (which is not an option)
2. *Reduce* the inductance in order to increase the current.

By paralleling the inductors, you went with option 2. By doing so, you cut the peak-current in half, which keeps you away from saturation, and it also reduces the RMS current, which reduces heating losses.

Glad to see you got it working!

[Kevin A.]

Thanks! 

That's right; at 15:1 for 40 watts, its unusual to see a single inductor boost stage. Like you said, the usual solution would be a flyback transformer. The duty cycle for this design is around 94% at max load, but it works! 

Why do anything the conventional way if your goal is to power a ton of huge nixie tubes? 

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[Bill Notfaded]

I agree and it looks great too!  The size is reasonable too considering what it's doing... Really really cool Kevin I love it.  I think it's actually really neat with the dual coils!

Bill

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[Richard Scales]

Are you in any position to suggest maximum dimensions of a completed unit yet? No pressure whatsoever but I am just in the throws of designing a housing for a clock that has your power supply firmly in its sights and was wondering particularly what the maximum height of the constructed power supply might be?

[Kevin A.]

The dimensions of the board are currently 3.81 x 2.20 inches. The tallest components are 1.3" which are the inductors.

I will provide some 3D images with dimensions when I get home this evening.

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[Kevin A.]

Here are the images showing the maximum dimensions, as well as the mounting hole spacing and dimensions.

Please note that this board uses some through hole components and should either be on standoffs or insulated on the back side, to prevent accidental shorts against your mounting chassis. 

[Richard Scales]

Those images are great, I'll work to those dimensions remembering to allow for suitable standoffs etc. Please keep us posted regarding developments.

[Kevin A.]

Update: new design fabricated and works! See: https://neonkev.com/2019/10/15/success-201-boost-at-40-watts-without-a-transformer/

[Bill Notfaded]

That's awesome I like the website too really neat!

Bill

[Richard Scales]

Following this with eager anticipation - no pressure at all but I just designed the housing for my ZM1350 project built around your PSU. Seriously - no pressure at all - just let us know when we can place orders. 

Great work!

[Bill Notfaded]

Count me in Kevin... you put really nice parts into this too which I like!  That's a decent amount of copper too!  It won't be cheap but nothing really good ever is.

Bill

[Kevin A.]

Design is up for sale on Tindie! I have enough parts to make 6 as of now. If there is a larger demand, I'm keen to buying more. 

https://www.tindie.com/products/nexus/40-watt-high-voltage-nixie-power-supply/

[Jon Jackson]

I live in the U.S.  I'm getting a Tindie error as shown in this screenshot:

Jon J.

On Wed, Oct 16, 2019 at 1:35 PM Kevin A. <ka...@scarletmail.rutgers.edu> wrote:

Design is up for sale on Tindie! I have enough parts to make 6 as of now. If there is a larger demand, I'm keen to buying more. 

https://www.tindie.com/products/nexus/40-watt-high-voltage-nixie-power-supply/

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[Kevin A.]

Hi Jon,

Just fixed it. You should be all set!

Thanks,

Kevin

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[Jon Jackson]

Working now...

[Kevin A.]

Recieved the order. Thanks!

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[Richard Scales]

Order placed!

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[Kevin A.]

Got it! Thanks. 

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[Bill Notfaded]

Just bought mine Kevin!

Bill

[Kevin A.]

Thank you!

The first 5 went quickly. I'll have these shipped by the weekend, and work on getting more! 

On Wed, Oct 16, 2019, 7:46 PM Bill Notfaded <notf...@gmail.com> wrote:

Just bought mine Kevin!

Bill

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[Bill Notfaded]

I thought it was a needed thing and you made it happen! I really didn't prefer the idea a having to use multiple power supplies for one project... This solves the problem! Thanks Kevin!

Bill

[Bill Notfaded]

It looks really cool with the coils that way too! I know it's superficial but it does look good.

Bill

[Bill Notfaded]

Good parts and lots of copper = good power!

Bill

[Dave]

Are you sharing your board designs as open source?

Or will you sell bare PCBs??

[Kevin A.]

I have some boards in stock for the initial orders which I am assembling; I'll see if there are any left at the end of this batch (20 total; 5 of which are already accounted for, with more requests on tindie). 

On Thu, Oct 17, 2019, 2:15 PM 'Dave' via neonixie-l <neoni...@googlegroups.com> wrote:

Are you sharing your board designs as open source?

Or will you sell bare PCBs??

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[Kevin A.]

I am pleased to announce that after many hours of careful assembly and testing over the past few days, the initial batch of orders is going to ship early this week. 

This project has been a very humbling experience so far; many challenges were overcome from not only a design but a manufacturing standpoint. I plan to produce more boards in the next week or two. Be sure to sign up for notifications on tindie if you are interested.

[Bill Notfaded]

Looks great Kevin!

Bill

[Kevin A.]

Gentlemen,

Looking forward to your feedback once you've had the chance to receive and check out your new units. Domestic orders have arrived; international orders are still on their way. 

I've gotten more demand than originally expected; next batch will be made this week and ready to go on Monday; 2 of 6 have already been accounted for, so there are 4 available units coming if anyone else is interested!

[Richard Scales]

USPS says package arrived UK six days ago, no update since and no package
Would you be able to check from your end?

[Kevin A.]

Sorry about the delay; I'll follow up with USPS tomorrow. 

On Wed, Oct 30, 2019, 6:43 PM Richard Scales <ric...@scalesweb.co.uk> wrote:

USPS says package arrived UK six days ago, no update since and no package
Would you be able to check from your end?

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[Bill Notfaded]

I've got mine!  Great stuff!  I had it last weekend.

Thanks,

Bill

On Wed, Oct 30, 2019, 3:43 PM Richard Scales <ric...@scalesweb.co.uk> wrote:

USPS says package arrived UK six days ago, no update since and no package
Would you be able to check from your end?

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[Richard Scales]

Thank you. Oddly USPS has it as having left London Heathrow on the 24th, no updates since. The UK handler Parcel force confirmed that it has not been scanned into their network ☹️

[Kevin A.]

I see that on my end as well. I do not send packages to the UK often, so I can't comment on whether this is normal or not. I did just submit a formal search request for this package through the USPS website and I'm calling USPS now. As it is after business hours, if I cannot reach anyone tonight I'll place another call tomorrow early in the day. 

I'll keep you posted with any updates. Worst case, if it is determined to be completely lost I can recover the insured value and send you another package (with a different carrier). 

Thanks,

Kevin

On Wed, Oct 30, 2019, 7:13 PM Richard Scales <ric...@scalesweb.co.uk> wrote:

Thank you. Oddly USPS has it as having left London Heathrow on the 24th, no updates since. The UK handler Parcel force confirmed that it has not been scanned into their network ☹️

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[Kevin A.]

After a lengthy phone conversation with USPS representatives, they submitted an internal request for an update on the package. Hopefully it is still in transit to you, and maybe forewent some local scans in the UK. I shipped another unit to Australia the same week and the tracking history looks similarly sparse, with the package arriving just today.

Of course, I'll keep you posted. Thanks. 

[Richard Scales]

Much appreciated, thank you very much.

Sent from my Huawei phone

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[Richard Scales]

I got my friend in Hongkong to place an order from the second batch and his have just arrived in HK, I suspect he might be seeing his before I see mine!

On Thursday, 31 October 2019 00:36:44 UTC, Kevin A. wrote:

After a lengthy phone conversation with USPS representatives, they submitted an internal request for an update on the package. Hopefully it is still in transit to you, and maybe forewent some local scans in the UK. I shipped another unit to Australia the same week and the tracking history looks similarly sparse, with the package arriving just today.

Of course, I'll keep you posted. Thanks. 

On Wed, Oct 30, 2019, 7:32 PM Kevin A. <ka...@scarletmail.rutgers.edu> wrote:

I see that on my end as well. I do not send packages to the UK often, so I can't comment on whether this is normal or not. I did just submit a formal search request for this package through the USPS website and I'm calling USPS now. As it is after business hours, if I cannot reach anyone tonight I'll place another call tomorrow early in the day. 

I'll keep you posted with any updates. Worst case, if it is determined to be completely lost I can recover the insured value and send you another package (with a different carrier). 

Thanks,

Kevin

On Wed, Oct 30, 2019, 7:13 PM Richard Scales <ric...@scalesweb.co.uk> wrote:

Thank you. Oddly USPS has it as having left London Heathrow on the 24th, no updates since. The UK handler Parcel force confirmed that it has not been scanned into their network ☹️

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[Kevin A.]

Hopefully all packages arrive safely to their respective owners! I'm keeping a close eye on your tracking; you will recieve your order one way or another. 

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[Kevin A.]

Richard,

Just letting you know that I also reached out to parcelforce in the UK and submitted an inquiry with them as well. If none of the requests I've submitted turns up a result in one week's time (by November 8th, 2019), I'll be sending you a new package via. DHL.

Thank you for your patience, 

Kevin

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[Richard Scales]

All understood, thank you for your help.

Sent from my Huawei phone

-------- Original Message --------
Subject: Re: [neonixie-l] Re: Homebrew high voltage nixie power supply
From: "Kevin A."
To: neonixie-l
CC:

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[Kevin A.]

Richard,

Good news, looks like there was a new scan today. Package should be on it's way! 

To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/4oohsg7ppnixpuhf0j-vsdyg8i3p6fxk0xqp8-tpjmwp-wss8p8-unlirc-1y5lreromxghnc76urc021mc-pm54gm-gmsnk4t6sxs8igo5r6v3c820-u2bx4p-gwnhro-yutxdv-uk4onqhfnsqs-doak3i.1572618301317%40email.android.com.

[Richard Scales]

Hello, yes, I just got the same notifications and now  Parcelforce in the UK seem to be accepting ownership!

My friend in HK is very pleased with his and has been sending me pictures of it all afternoon which has been fairly depressing - until now!

Lets see how long it takes Parcelforce to work out how much to fleece me for import charges!

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[Kevin A.]

So now the true reason for the delay reveals itself! Again, sorry for that; a customs check just seems to be the luck of the draw. 

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[Richard Scales]

Hello!

After nearly a month after ordering - I am informed that the eagle has landed! (I am informed by Parcelforce in the UK that it is a busy time of year!). I am working away all week but my wife sent me stage by stage pictures of the package being unwrapped!

I am back Monday and will get it in to play on my ZM1350 development setup - Thank you for all your help. I look forward to reporting on progress.

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[Kevin A.]

Glad to hear it finally arrived! Looking forward to your feedback and seeing it in action on the ZM1350 project. 

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[Richard Scales]

Just got to my desk after working away and have looked at the PSU's.

First test - connect to 12V and set the output to 170V   all good.

My clock build has ten ZM1350 smart sockets - though only using six at the moment - it has been running reliably for 1 month or so using one of the NCH6100HV power supplies to generate the 170V.

I removed the NCH device, mounted the new supply, connected GND and 12V on one side, then the 170V Output and the output control on the other side and fired the thing up - all looked good.

I have now had it running for almost an hour now and I am seeing some odd behaviour on the smart sockets in as much as occasionally some characters are corrupted or the seconds misses a single change (ie, displays 1 then 3,4) other characters display garbage and some transition effects change.

I have checked all voltages on the Smart Sockets and right now - the 5V is at 4.995V and the 170V is at 169.9V so I would expect that to be OK for the logic and the display.

The display blanking (processor disabling of the 170V output) is working perfectly - I am just getting corruption.

I have NOT connected GND on the output side as it appears to be the same connection as GND on the input side.

I have a small BUCk converter generating the 5V for the logic and that line appears to be clean.

I have mounted the new HV supply on one side of a perspex panel on 15mm standoffs, the smart sockets are on the other side of the panel with the same 15mm standoffs.

Is there any risk that some form of RFI is causing the issue that I am seeing?

I removed the PSU from its mount and moved it away from the smart sockets - around 20cm and the symptoms remained.

If I put the NCH6100HV back in the circuit then order is restored.

Could you suggest where I should be looking next?

On Tuesday, 12 November 2019 19:16:05 UTC, Kevin A. wrote:

Glad to hear it finally arrived! Looking forward to your feedback and seeing it in action on the ZM1350 project. 

On Tue, Nov 12, 2019, 1:46 PM Richard Scales <ric...@scalesweb.co.uk> wrote:

Hello!

After nearly a month after ordering - I am informed that the eagle has landed! (I am informed by Parcelforce in the UK that it is a busy time of year!). I am working away all week but my wife sent me stage by stage pictures of the package being unwrapped!

moved the I am back Monday and will get it in to play on my ZM1350 development setup - Thank you for all your help. I look forward to reporting on progress.

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[Bill Notfaded]

Have you tried hooking it up to a scope?

Bill

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[Kevin A.]

Richard,

The phenomena you describe seems to be quite interesting, and after thinking though the possibilities I have several ideas for you to try:

The 2 most likely scenarios I can come up with would be:

- Switching noise entering from the enable pin to the microcontroller. Try leaving the enable pin unconnected, and the power supply will stay on. If you find that this alleviates the problem, you can use an optocoupler to drive this pin and keep it galvanically isolated from your microcontroller. 

Or:

- Noise or large voltage ripple present on the 5V rail. I'm not sure which 12 volt power supply you are using to drive the whole system, but the introduction of a large switching power supply could be taxing your 12 volt source and/or introducing unexpected noise. If you have a scope, see if you can probe the 12 volt line and the 5 volt line with the NCH device installed, and then with the new power supply installed. If you see a lot of noise or higher ripple with one versus the other, try to smooth things out with some general purpose 220 or 470uF electrolytic caps placed close to your circuits across power lines.

I would also recommend using a linear regulator for powering logic such as your micro and the smartsocket controllers. You can pre-regulate 12 volts down to 8-6 volts, then use a high quality LDO (low dropout regulator) to provide clean power to your logic circuits. Switching power supplies can be very noisy and cause glitches just by output ripple present in normal operation. 

My suspicion is that the larger switching currents of the big supply may be inducing some noise on the low voltage side of your circuits, and seeing as the 5 volts is running directly off of a switching supply this noise is making it's way to the logic and causing glitches. You already tried moving the power supply away from the smart sockets and observed the same glitches, so I cannot imagine EMI/RFI emitted from the device itself is the issue. 

Of course, let me know what your findings are. We will solve this! 

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[Richard Scales]

Hello,

I scoped the 5V and it all looked just fine, I am using the same 12V Buck converter that I have used everywhere else - I will try adding caps next.

The 12V supply is capable of delivering much more than the required current and it is also driving a 6 digit B-7971 device at the same time

I removed the HV enable/disable line - no difference.

I will report back once I have added some capacitors.

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[Bill van Dijk]

Richard,

 

Adding caps is not likely to improve things since your ripple current will increase, and only serve to make things hotter. If you suspect the caps (very possible) just replace them with the same value.

 

Bill

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[Kevin A.]

Richard; If you could provide a few images of your setup and the wiring specifically, that would be very helpful. I'm not sure how your grounds are routed, but using several switching power supplies without adequate grounding could cause that switching noise to couple through other parts of your circuit. 

Another problem I see is using the $2 buck converter to directly power the logic. It provides little in the way of filtering and low noise output; it would be perfect for preregulating 12 volts to 8-6, but then using a linear regulator for a low noise 5 volt rail, which should alleviate power related glitches occurring with the your control logic. 

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[Richard Scales]

OK, here we go.

Here is the schematic for the layout of my project:

Here are some pictures of the actual thing (which is currently in bits as I decided to move the micros nearer to the PSU to shorten the data and HV control lines.

This is the board with the two micros and BMP sensor, it takes GND and 5V in, the NodeMCU TX connects to the Nano RX and the Nano outputs the Data and HVctrl to the Smart Sockets and HV PSU.

This shows the HV PSU and Buck Converter, some screws missing so not quite straight! - the Brown/Blue cabling is the 12V supply, Red/Black is the 5V supply, Green is used for both HV and HV control. You can see the backs of the smart sockets which are on the other side of the black perspex panel.

Here is the whole thing including the board with the micros - currently hanging loose - it was designed to be mounted on the four posts at the left hand end of the black perspex panel.

I left it all running yesterday and the corruption was there on and off - mostly on! All the time the HV and 5V 'looked' clean (according to my scope) though there were clearly issues. It could perhaps be down to something non related though when I switch the HV supply for the NCH module - running only 6 tubes, order is restored (with the same wiring).

All pointers gleefully received!

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[GastonP]

Hi Richard,

   What's the bandwidth of your scope? Is it a digital or an analog one? Did you check to not have bandwidth limit enabled when looking for noise in the lines? 

It could easily be that the scope is not up to snuff for the task of hunting for glitches.

Also, did you check whether the voltage in the data line (only one and no clock? Wierd...) is within specs?

Gaston

On Wednesday, November 20, 2019 at 5:51:18 AM UTC, Richard Scales wrote:

OK, here we go..

<snip>

[Richard Scales]

Hello, I was using a digital scope - I'll go and check settings. I also have analog scopes to hand so can do a comparison.

The Data line I speak of is the TX serial data out of an Arduino nano which is connected to the serial data input on the smart sockets - no need for clock. Yes, I believe it to be in spec - it's between 0V and 5V.

Richard

[Kevin A.]

Here would be my first 2 suggestions in changes to your circuit:

#1: I would definitely place the ground from my logic circuits straight to the main power ground, instead of routing it though the 5V buck module. The buck converter is also a switching power supply and this could very well be coupling noise through the rest of your circuit, especially if it is the only ground path for the logic.

#2: If #1 does not fully alleviate the problem, I would try placing an electrolytic cap of between 100-470uF on the 5 volt rail close to the logic circuits. This could help decouple the logic from any noise entering through the 5V rail.

Finally, if the above two do not solve the problem, I would use a linear regulator after the 5V module to provide a clean 5 volts to your logic circuits. It looks like the 5V module has a trim pot on it, so I would increase the voltage to 6 or 7, and then use a 5 volt LDO (low dropout regulator) to provide the final 5 volts. This certainly will alleviate a large amount of noise on this line that you might not even be able to observe on your scope, unless you zoom in quite a bit on the vertical (voltage) scale (so that you're looking at hundreds or even tens of millivolts per division). 

[Kevin A.]

Also, not sure if you guys watch David Jones from EEVBlog, but I sent him one of these to critique and share his thoughts on what I made. You can watch it on youtube here: https://youtu.be/pt2CgSphN58?t=2255

[Richard Scales]

I tried the first two suggestions and thought (initially) that all was good but upon watching in detail it would seem that it is the same.

I have a L78M05 to hand - is that going to do the job?

Otherwise I can get something like this https://uk.rs-online.com/web/p/low-dropout-voltage-regulators/1246447/ very quickly.

[Kevin A.]

Does it seem like the degree of glitching has been reduced, is the same, or worse with those 2 changes? 

An LM7805 could support your 5 volt rail depending on how you implement it. The higher the input voltage, the hotter it gets. If you can adjust your buck module to 8 volts, then put the 7805 after the buck module and see if that works. If your buck module will not go up to 8 volts, you could try using the 7805 directly from 12 to 5 volts if you're not pulling more than around 0.75 amps (power dissipation (heat) is increased because of the greater drop from 12 to 5 as opposed to 8 to 5). 

If that doesn't solve the problem then improving grounding is the next way to go. Ground paths ideally are short and use larger conductors. Having long, narrow ground wires strewn about may certainly be contributing to glitches from noise and undesirable ground loops. 

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[Mahdi Al Husseini]

Tremendous respect Michael. I am currently redesigning a boost converter using a LM3478. It’s a surprisingly involved process, especially if not well acquainted with power circuitry. I’ve found that, between refinement of component values and board layout design, it’s very much an art and science. Really liked the write up. Keep up the good work. 

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[Mahdi Al Husseini]

I said Michael, meant Kevin*, sorry!

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[Kevin A.]

Thank you Mahdi! I highly recommend trying a hand at switched mode power supply design; it will teach you a lot!

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[gregebert]

There are drop-in replacements for the 'old-school' linear voltage regulators, and they use high-frequency switching to minimize the component sizes.

Recom Power makes several of these, and I've used them on several projects with no problems.

[Bill Notfaded]

Wow Kevin that's awesome that you sent it to Dave and he put it up on the mailbag!  I love EEVBlog and spend a lot of time there.  I like trying to converse with the voltnuts in the metrology forum even though some of those guys are way out of my league.  They're nice still and tolerate me.  Now in addition to Nixie tubes I've also got a vintage test gear habit!  I've even merged my addictions and have a collection of Nixie counters, voltmeters, and misc Nixie tube display devices made for things like X and Y in machining and more!  My most recent test gear addiction has me fixing up a Fluke 343A voltage reference and a set of L1 L2 GPS stations and I'm going to mount the antenna on back yard roof I think.  I got the big L1 L2 survey type antenna.  I figure if you want your volts stable and accurate gotta have accurate time too right?  Voltnuttery X timenuttery!  I think I want a rubidium oscilator now too... it's a lifestyle I guess??? 

Best Regards,

Bill

[GastonP]

Ugh... it seems you have become a TEA (test equipment addict). It's difficult if not impossible to get out of that place. If I weren't in a constant state of squalor (due to that addiction) my house would look like a lab.

My wife uses other words to describe it :D

[Richard Scales]

I put the 7805 in place but it made no difference whatsoever. I decided to change the position of things so that the HV supply was at the 'other end' of the clock and the CPU's were at the end where the signal goes to the Smart Sockets. There seemed to be some improvement, at one point i thought it was completely fixed though staring at the thing periodically I could see that it was not not totally 'fixed'. Reading your comment about ground wires I will beef-up the 0v and 5v connections to the logic boards as they are indeed skinny at the moment.

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[Kevin A.]

Glad to hear you're making progress. Interesting that moving the HV psu away before did not make a difference, but in the new position it did. Something must have changed with your electrical connections as well which resulted in that improvement.   

Grounding is crucial to signal integrity no matter the circuit. Keeping the ground path as short as possible with large, low impedance connections should definitely improve the situation. 

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[H. Carl Ott]

Hi Richard,

 Could you go into some detail on how your "HV control" signal operates? 

carl
--------------------------------------------------------
Henry Carl Ott   N2RVQ    hcar...@gmail.com

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[Paul Andrews]

Hmmm. Try changing the orientation of the HV board. Like either parallel to the chassis or perpendicular to it. I’m think magnetic flux lines. Transformer orientation is a big consideration in tube amplifiers.

[Richard Scales]

A quick lack of progress update - Having beefed up all cables I was still experiencing the corruption issue.

In an effort to make some progress I decided to put that issue to one side and add the remaining 4 tubes to make the 10 tube display complete - I could then work on the display code a little - knowing (hoping) that the corruption issue might get resolved on day.

I added the last 4 tubes and noticed that, on power up the HV supply would shut down (neon goes off) and then after what seemed an eternity (though most probably about 20 seconds) it would come back on. This was evidenced by the neon going off then on as well as the displays (most but not all of them) would light up.

I measured the current being delivered at this point and it fluctuated between 12 and 18mA depending on the data being displayed.

Crazy I thought. My expectations were that the HV supply would be up to delivering much more than that without difficulty.

In a last minute desperate attempt to make some progress, I removed the HV supply and put the NCH6100HV back in its place.

The thing powered up, all digits displayed, the clock runs and displays all required data and there was no corruption of data.

Something about using your HV supply is causing something somewhere to misbehave. 

I have now run the clock on the NCH6100HV for an hour and all continues to work well. Yes, it gets a little warm but, if left alone, the HV is disabled unless there is any PIR action.

In isolation, the supply appears to be fine. I have been running the thing from a 1.5A 12V plug top adapter.

My issues only seem to have started since using the new HV supplies, where could I look next?

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[Kevin A.]

Thers is certainly some usual interference between the power supply and the driving electronics. For the time being, I would recommend leaving the enable terminal unconnected from the controller. You can also tie a jumper between the enable and ground terminal blocks to ensure that it is being pulled down. 

I start each power supply under a 200 milliamp load on the High Voltage output and let it run for 4 hours without interruption, at 12 volts input. It is impossible that the high voltage load is causing the power supply to cut out and go into restart. 

I'll need to really exhaust all the possibilities I can think of and get back to you. Some consultation from my colleagues is in order too.

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