Re: LED Charge Indicator

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: BunnyKiller <bunikllr@xxxxxxx>

I would say that the voltages are a bit too high, the required 
resistance to keep the LED lit at upper end voltages would be in the 
near 1 megaohm rating. When the voltage drops in the cap ( but at 
still dangerous levels)  the resistor will reduce the needed current 
to keep the led lit thus giving you a false sence of security 
thinking the cap is discharged.....

for example   lets say the LED you chose needs .030 A to be lit at 
full power and turns off at a minimum of .008A.

15KV NST can easily charge a cap to 21KV
21,000/.030 = 700Kohm resistor needed to keep led alive at 
21KV  (given that the resistor wont arc over)

.008X 700,000 = 5600 V   will still be in cap when LED turns off

and lets not forget that the cap can hold a charge that is reversed 
of what the LED may need ( since the cap is an AC style cap) and the 
LED wont even light up in this senerio.

Scot D



Tesla list wrote:

> Original poster: "Dan" <DUllfig@xxxxxxxxxxxxx>
>
> All:
>
> 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?
>
> Dan