Prebuilt PSU boards - recommendations?

[David Pye]

Hi all,

I'm working on a project which is a series of daughter boards for different tubes (eg IN12, IN14, IN18), which then has a common driver-board which provides the brains of the clock (processor/HV/RTC etc) to provide 8 digit clocks.

I want it to be possible for people to fit different HV modules (within reason of the footprint size of the board I can allocate).

What are common ones? What I would like to do is to ensure that you can plug/play several of the current boards if I can get the footprints to overlap.  Requirements would be to run off 9-12V input voltage.

So far, I've added footprints for the two I am most likely to recommend (the NCH8200HV and CH6100HV which Yan sells)

I'd like to know if there is a particular smallish PSU board that's your go-to PSU for clocks, and if so, I'll see if I can make room on the board for a pinout for it.  Great thing is, provided the pinouts don't clash, I can put them on top of each other (if that makes sense).

Cheers

David

[Dekatron42]

Tayloredge have prebuilt psu’s and Tortugascuba (Michael Moorrees) have kits that are easy to assemble and they both work very well.

/Martin

[threeneurons]

Speaking of power supplies, I've been running a few experiments using HVAC 24VAC transformers. I choice this type of device, since almost all Radio Shack stores have closed, since 2015. I still have one near me, in Tehachapi, CA (a franchise). Also, in recent months, the Fry's chain is clearly in trouble. They have empty shelves, and will most likely close just after the new year. But HVAC supply stores are relatively common, and they all carry 24VAC transformers, that are used to relay thermostat data (simple switch closer) back to the heating & AC system. They currently sell in the $12 ballpark.

To get 170V+, from these transformers, doesn't even involve a switching suppy. I got some numbers off a simple multiplier circuit:

With the capacitors used, and a 40VA transformer, this thing can deliver upto 70mA, before the output drops below 170V. Note, that's the average voltage, shown on a meter. Any peak in the ripple, exceeding 170V, will strike a nixie tube.

As a baseline, I hooked up one of my switching supplies. It was modified so that the coil got the full DC rectified & filtered voltage (~36V), but the control circuit was limited to 12V, as not to destroy the power FET. Also the coil value and timin cap value were altered. Though the coil, was still a small drum coil, of the same series.

I surprisingly got 100mA output, with the supply only getting comfortably warm. Using fullwave rectification, smaller 20VA & 30VA transformers can be used. Note: I got 20W (120mA) out with the 20VA transformer. NO IT WAS NOT 100% EFFICIENT ! The 20VA transformer was just putting out more power than its rating. So, this kind of load, should only be presented intermittently, else that transformer will eventually fail.

Of course to make this usable, +5V, or some other low voltage needs to be drawn from the same transformer. If less than 50mA is needed, a 680 ohm 2W resistor, and 4.7V (1W) zener, should do the trick. For higher currents, a switching buck converter can be used. The MC34063 can handle up to 40V, and should safely deliver a few hundred mAs.

[Dekatron42]

Nice!

Two questions:

1. How do you calculate the capacitance for the electrolytic capacitors in the tripler circuit?

2. Can the switcher be modified to output 300V or more (600V) without using an external tripler?

/Martin

[blkadder]

For my uses, I have used the NCH8200HV and CH6100HV power supplies  you describe in your message.  My favorite kits are the ones from Pete, and his are usually included with the kit.  Not sure if he has them available as stand alone units though.  You can check with him at pvelectronics DOT co DOT uk.  Hope this helps.

Ron

[David Pye]

Thanks all for the input!

I have had Pete Virica's PSU modules before, and have one clock using it, but I don't think he seems very keen to sell them in large numbers.

I think the NCH6100HV will be the main one I will support, as it is reasonably priced, and will fit on the board.  Might certainly arrange to support others in future.

Thanks again!

David

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[Michail Wilson]

B-7971 on ebay.

For a untested/parts only auction, I think $170 each is quite expensive.

But, they have 13 tubes.

 

https://www.ebay.com/itm/254418708775

 

 

Michail

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