Tiny neon bulb driver circuit

[themadhippy]

Doable, but it's a pain to put a hundred plus turns onto a 4mm core

A cordless drill makes it more bearable

[Zero999]

There are neon bulbs that can be powered by 120VAC, directly from the mains (perhaps through a resistor of some sort).

Why do you need a transformer?

Two possible reasons:

1) A battery powered device.

2) Controlling the neon from a microcontroller and it's easier to switch 5V, than mains.

[Xena E]

Size you're looking for will be a hard ask for a 200mW inverter.

I've used miniature CCFL inverters for neon driving: find on the auction sites for very little coin.

If you want to roll your own there's loads of inspiration from prior art, just search CCFL circuit... but the inductor as always will be the chore, personal advice, unless you want the challenge I'd buy a solution...

X

[RoGeorge]

Is this for production, or for a one-off art installation?
How many of these Neon-LEDs do you need?

[Langdon]

There are neon bulbs that can be powered by 120VAC, directly from the mains (perhaps through a resistor of some sort).

Why do you need a transformer?

Two possible reasons:

1) A battery powered device.

2) Controlling the neon from a microcontroller and it's easier to switch 5V, than mains.

120V can easily be switched with a relay or SSR; the amperage is not great.

If it's battery powered, why would you use neon?

LEDs are usually the way to go for battery power.

[Analog Kid]

If it's battery powered, why would you use neon?

Go back and read the original post:

The end goal is to be able to use neon NE-2 bulbs in a circuit the same way as you would use a LED, for a retro aesthetic.

Same reason some of us like to use nixie tubes instead of LED/LCD displays.

[themadhippy]

good luck getting a ssr to turn off just a neon

[prosper]

Is this for production, or for a one-off art installation?
How many of these Neon-LEDs do you need?

Once i come up with something I like, I envision making up a bunch of small round PCBs, then 3d printing some lamp holders that contain the pcb and bulb. A bulb, a base, and two leads that i could run off an MCU, or whatever.

Just for personal use, but I do have about a thousand old ne2 bulbs, so, more than I'd want to hand-wind.

[RoGeorge]

1kpcs. hand-made of whatever item (doesn't matter what item) will be painful to manufacture by yourself, no matter the technical solution.  No matter what you would hand-made, when it's above 100pcs., hard work and determination is not enough.  It will need serious thinking about manufacturing processes.

Maybe search on Alibaba a small assembly house that can manufacture it for you.  They can do a custom coils/transformers, too, if needed, or maybe repurpose existing coils/transformers from LED light-bulbs.

[eliocor]

TDK ATB3225 mini transformers series, perhaps ?

Edit: sorry: Wolfram already suggested them...

[TurboTom]

I would try the following: Use one of the flash lamp trigger coils as I suggested here and drive it with a tiny class D audio amplifier chip like a PAM8302A. Short the inputs together, properly bypass the power supply and maybe install a small cap in series with the primary of the coil in order to limit power -- you may as well use a resistor in series with the output. Three / four tiny components and you're good to go.

[prosper]

i have a handful of various coils and chips suggested on order. I do have a bunch of similar audio amps in my stash, so I'll definitely give them a try

[prosper]

sorry, i didnt mean to suggest that I'd be making 1000. More like thats the absolute upper limit of what I'd consider. And definitely not all in one go, either. I have a project in mind that would need about 60 in total, so thats a more realistic first batch size.


Now that I think about it, I might also 3d print some 8x8 matrices too, and do up some sort of blinkie with them.... but for something like that, I'd build up a single larger power supply, not a few dozen small ones

1kpcs. hand-made of whatever item (doesn't matter what item) will be painful to manufacture by yourself, no matter the technical solution.  No matter what you would hand-made, when it's above 100pcs., hard work and determination is not enough.  It will need serious thinking about manufacturing processes.

Maybe search on Alibaba a small assembly house that can manufacture it for you.  They can do a custom coils/transformers, too, if needed, or maybe repurpose existing coils/transformers from LED light-bulbs.

[TurboTom]

i have a handful of various coils and chips suggested on order. I do have a bunch of similar audio amps in my stash, so I'll definitely give them a try

Just be sure they are class D since the PWM frequency is used to drive the coil and not the (non-existant) modulated AF. Also, the frequency should be somewhere in the 150...300kHz range, of course also somewhat depending on the coil's primary inductance.

[PCB.Wiz]

Also, the attached works; a classic 'joule thief' type oscillator. Various transformers work with it; the smallest one I've found was to wind a few dozen turns around the body of one of those 'resistor-style' axial inductors. (specifically, 50 turns with a tap at 25t over a 10mH '1W' inductor) Surprisingly, efficiency is actually quite decent; lighting a neon bulb at about 30mA/1.25V.
Stability is poor though, and it's very picky about supply voltage.

You can add a RC element to the base drive, so the base-emitter junction DC restoration gives a sort-of AGC action, to make it 'less picky'.
Next step would be current or voltage regulation.

Addit: eg current regulation diodes like WS7628(27.5-28.5MA) WS7612(11.5-12.5MA) WS7614(13.5MA-14.5MA) have useful 0.7-14V operating regulation regions.

What voltage do you want to run this from?

Does it light both electrodes?

It does, but not very well/evenly, as you noted. Capacitively coupling the output also makes the circuit that much more finicky, too

Maybe adding a resonant cap can make the secondary waveform more symmetric, and improve that electrode effect?

Of course, all of this edges up the BOM & size.

[Analog Kid]

If you have any interest in winding your own transformer you could check out this post I made which includes that in a project. May or may not be helpful.

[squadchannel]

https://www.analog.com/en/resources/technical-articles/small-highvoltage-boost-converters-guide.html

6mmx8.5mm 
 

[prosper]

What voltage do you want to run this from?

ideally, from 3-5V.

[prosper]

https://www.analog.com/en/resources/technical-articles/small-highvoltage-boost-converters-guide.html

6mmx8.5mm 
 

I've seen that AN before, had forgotten about it. Might be a good candidate for a capatitor decoupled experiment

[Zero999]

120V can easily be switched with a relay or SSR; the amperage is not great.

An SSR won't switch a neon. A mechanical relay is bigger and uses more power than a tiny voltage boost circuit.

[Langdon]

120V can easily be switched with a relay or SSR; the amperage is not great.

An SSR won't switch a neon. A mechanical relay is bigger and uses more power than a tiny voltage boost circuit.

Why can't an SSR switch it?

[themadhippy]

ssr's dont fully turn off,they leak a few milli amps,and as a neon will light up on mouse farts theres enough leakage current to keep them glowing

[Analog Kid]

I just confirmed that experimentally. Connected to a SSR, the neon bulb will glow even without any applied control voltage.

That's 10 minutes of my life I'll never get back ...

[Langdon]

If it's battery powered, why would you use neon?

Go back and read the original post:

The end goal is to be able to use neon NE-2 bulbs in a circuit the same way as you would use a LED, for a retro aesthetic.

Same reason some of us like to use nixie tubes instead of LED/LCD displays.

Why not just use Red LEDs and make them look like Neon?

Who could tell their actually fake?

[Analog Kid]

Why not just use Red LEDs and make them look like Neon?

Who could tell their actually fake?

You really don't understand the aesthetic here.
Why would anyone want to use nixie tubes when there are much easier to use low-voltage numeric displays available?
You're young, so you can be forgiven.