Re: LED Charge Indicator

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Jan Wagner <jwagner@xxxxxxxxx>

Tesla list wrote:

> Original poster: "Dan" <DUllfig@xxxxxxxxxxxxx>
>
> some industrial equipment that have built in capacitors, have a red 
> LED on the front panel to indicate if the capacitor is holding a 
> charge. Can this be done with the capacitors in a TC, or are the 
> voltages just too high?

It's a bit "low tech" but you could use a neon glow tube (glimm lamp, 
guide light, ...). Just add multiple normal 1/4W 500Vmax carbon or 
metal foil resistor in series with the lamp, or just a single HV 
resistor, to keep the tube current down and below 1mA.

http://www.exo.net/~pauld/summer_institute/summer_day15current/Neontubes.html

It'll glow until the capacitor voltage drops to a few ten volts, 
which should be a safe level.

However if you have added the recommended(!!) bleed resistor accross 
your capacitor, the cap probably drains its charge so fast you just 
see a short "blink" of the glow tube before the cap is empty.

- Jan