Nixie Power Supply NK02

[JBro63]

Hi all.

I'm looking to incorporate a 12v -> HV power supply in to a PCB design rather then use the excellent external 6300/8200 Omnixie's. As a starter, have sourced the components for the threeneurons NK02. The only change was replacing R5/RX with a single 9.1k resistor.

Once assembled (all components soldered) it seems to work ok - lights up a neon or nixie as expected. I'm unable to get a reliable reading of the output voltage using a multimeter, the values are all over the place sometimes exceeding the 600v max of the meter which concerns me a little.

Anyone have any tips or insights on this behaviour?

The NK02 design is from this page.

Thanks.

[Nick Andrews]

You may need a higher impedance meter to measure high voltages, especially low current supplies as the typical meters will pull the measured voltage down.  If you use a 1 GOhm resistor to make a voltage divider, it's much easier to measure high voltages more accurately on these tiny supplies.

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[Joe Croft]

I found that with no load, switching power supplies can swing wildly.

-joe

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[JBro63]

I don't have anything that big lying around unfortunately. Would an oscilloscope be a better instrument? I have a very old Tektronix I can try.

I'm reading board layout is very important for these types of supply; currently this test piece is all soldered together adhoc with bits of wire so I think I'll built order a test PCB in the meantime.

Thanks.

[gregebert]

A scope will tell you a lot. I suspect the power supply is generating spikes and your meter is picking them up at different times, giving the impression of random voltages.

[Dekatron42]

Just check the maximum input voltage on the oscilloscope so you don't blow the input with over voltage!

Maybe buying a cheap digital multimeter would be th ebest solution here, just make sure it has the voltage range you need.

/Martin

[JBro63]

No joy with the scope. I think the probe that came with it is faulty. Some test PCBs arrived today so I've assembled one and amazingly it works perfectly. No smoke, no components getting hot. Output is a steady 180v with or without load, measured with the original multimeter. Happy camper.