Switching 5 kV for a neon sign

Question

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?

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:

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.