Most 'ordinary' leds need about 20mA. Calculate a series resistor assuming
the led will have around 1.5 to 2V or so across it (it depends on colour).
You can find out what the actual voltage drop is after you've fitted the
resistor by putting your voltmeter across it.
If the supply to the lamp was ac, then you will need a diode (any small
type) across the led in the opposite direction to prevent it blowing with
too much voltage: most are rated around 5V
Let's say you have a 24V ac supply, the led will conduct in one direction
and the protection diode in the other, so, it doesn't matter which is which.
Start with a resistor of 1k, power rating at least 1W, it will get fairly
hot. The led will run cool. If you have a high intensity led, it will be
bright with perhaps 2mA, so.... do the sums :o)
David
G3UNA
How to I replace the 12 volt incandescent bulb in my Yaesu G-800DXA rotor
control unit with an LED bulb? The incandescent bulb is a fuse looking
bulb with wires out each end. I tried putting an LED in, it worked for a
while then went out. Do I need a resistor in the circuit?
.
Thanks and 73,
.
Joe N9VX
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
