Neon flickering flame bulb in overdrive

[Yohan Park]

We all know the flickering flame candle bulb (if you don't, what are you doing here?)
I was wondering if there's a way to get this to glow stable.
So I removed the base and found a 30K 1/4W resistor in there (230V model)
I replaced this with a 10K 1W model to see what would happen.
Well, things happened...
It was glowing way more intense but still flickering and after 5 minutes or so I noticed the rich bouquet of brûlante resistance (the resistor was melting and you know the smell...)
So I contacted a certain YouTuber for advice and he told me perhaps it would be possible but I need to use a combination of a resistor and a capacitor (with discharge resistor across it) to get higher current with less heat a combination.

All good advise (I guess) but I have no idea about capacitor values etcetera.
Can anyone help me in the direction to solve this?
Thanks in advance

[gregebert]

At 60 Hz, a 0.27uF capacitor has 10K ohms of impedance. You would need to use a non-polarized cap that can handle the ripple current, something under 12mA.

I cant vouch for how well that will work; it's a non-linear circuit so the capacitor is not exposed to a steady sinusoidal waveform, so it's effective impedance is probably much different.

If I have some extra time, I'll run a SPICE simulation.

[Grahame]

Adding a bit more...

Capacitive reactance (its "resistance") Xc = 1 / (2 * Pi * F * C)

So swap round Xc and C to be able to work out the capacitance required for a required resistance. For me in f = 50Hz land, Xc = 10k gives

1 / (2 * pi * 50 * 10000) = 0.00000032 = 0.32 uF - so I would start with a 0.33uF standard capacitor, a PET type perhaps.

About the resistor required across the capacitor. The capacitor can hold a charge when the circuit is switched of. Sufficient to charge give an unpleasant shock. Use a 1M resistor across the capacitor to dissipate the charge. Make sure you use a resistor with sufficient voltage rating - usually it will be a 0.5W part to get this. Cheap Chinese capacitive droppers often use a 0.125W part which will not have the required voltage rating.

Hope this helps, Grahame

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[Bill van Dijk]

There are a number of on-line calculators to determine capacitor reactance, for example:

http://www.sengpielaudio.com/calculator-RC.htm

Also, if you do use a capacitor make sure you use a class “Y” capacitor; they are designed for use in an AC line. Anything else is a danger and / or fire hazard!

 

Bill

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[Yohan Park]

Thanks all
Received a personal email saying the electrodes are coated with a substance meant to make these flicker so it could be difficult to make them glow steady.
Too bad :(