I have a project where I want to make something like a 7-segment display using neon tubes.

Using neon tubes is a hard requirement, so I cannot use LEDs etc.

I do not want to use one 12 ⇒ 5 kV transformer/power supply per segment; since that will get expensive very quickly.

Is there a way of (inexpensively) multiplexing N neon tubes to a single HV supply?

Each segment would use less than 5 watts .

One idea I have had is to use some 240 V opto-TRIACs on the HV side, and a relay (or something) on the 12 V side. Switching the 12 side off, before switching the HV side.

Would that work, or is there a better way?

  • 1
    \$\begingroup\$ What size and specs are these neon tubes? \$\endgroup\$
    – MOSFET
    Commented Jun 22 at 1:35
  • 2
    \$\begingroup\$ I think you’ll find that anything that can handle switching 10kV will cost at least as much as a separate power supply, and likely a great deal more. Eg. H24-1A69 About $90 ea. and better not to switch under load. There are no high volume/ low cost applications that require this. Even modern ICE cars use one coil per cylinder. \$\endgroup\$ Commented Jun 22 at 1:53
  • \$\begingroup\$ @MOSFET let's say 30cm long, so less than 5 watts (if driven continually) So if we use a 5kv supply that would be 1mA (maybe a bit more to strike, so let's say a peak of 25mA maybe). \$\endgroup\$ Commented Jun 22 at 1:54
  • \$\begingroup\$ Multiplexing neon tubes? Did you consider switching time for the tubes? \$\endgroup\$ Commented Jun 22 at 1:57
  • \$\begingroup\$ @Ale..chenski Since this is meant to look 'retro' a long (100-300ms) switching time would be ok. \$\endgroup\$ Commented Jun 22 at 2:00

1 Answer 1


As an idea for individual 12V->HV supplies, here's a high-volume, novelty quality power supply for a neon tube in the 30cm range.

It was the silhouette of a skating hockey player, in a couple of colours, similar idea as the below, from here:

enter image description here

I think it was something like $10 retail about 10 years ago. The tube got broken, but it was roughly similar. Modern ones are almost entirely fake neon made from LEDs and lack the appearance such as the plasma snaking around inside the glass tube.

Here's the PSU innards which operate from an AC adapter - just a CMOS 555 driving a power MOSFET and a potted HV transformer. Very primitive but it outlasted the tube running some years 24/7. Plasma balls use a similar HV transformer.

enter image description here


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