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In Reply to: RE: LED indicator light for Quickie posted by bainjs on September 21, 2009 at 02:49:41
The heater supply is dual 1.5v (they float so each tube needs its own). That's not enough voltage to power an LED.
The high voltage supply is not switched, so an LED across it would drain the battery and stay lit until the battery died. Not a good idea! If you added a switch, then even 1mA drain (a fairly dim LED) will still reduce battery life 20%.
However ... just put the LED in series with the high voltage supply! That way it will draw 4mA when operating, and only lose 1.5-2v out of the 36 volt nominal power supply.
Follow Ups:
no dropping resister needed?
Nope. Just solder in the LED and you're done.
Thanks
It's hard to think 36vdc as high voltage!
How about 12v? If you've ever had your hot sweaty body resting on a fender sanded down to bare metal while you worked on the engine and your elbow hit the positive battery terminal, you'd know what I mean. :-) I can tell you it is very unpleasant to get a shock that enters your elbow and exits your solar plexus. No fun at all, but of course we are talking about a huge available current with a car battery.
-- Jim
I've experienced the car battery "burn" as well. No fun!
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