ATM Re: LED Control

[Dave McCarter <McCarterD@claven.fanshawec.on.ca>]

>It appears to me from recent posts that Electrical Engineering and Amateur
>Astronomy do not mix for some odd reason. 

It is always amazing to me how some emailers can get so wrapped up in these
kind of completely trivial issues.

I teach electronics, and from a PRACTICAL side all one has to do is place a
low value resistor in series with the LED, all into the old lamp base. 47
ohms being typical (I have used 10 ohms for one kind of LED that could take
the current, to 1500 ohms where I wanted a dim glow on a reticle) (gees I
spelled reticle right, I think :-)  )

A typical two "C" battery flashlight lamp draws 200mA, while a high
brightness LED might draw 10 to 30 mA, which is quite a difference. One
friend just turns on his flashlight all night, and his flashlight is still
going on the same batteries after a year of observing. (we get a lot of
clouds!!!!)

If you do want to use a switch mode device to control the LED a 555 circuit
would work, and use almost as much energy to run the circuit as it would
save. Besides the added complexity degrades reliability, adds cost and
size, but what a conversation piece.

As another poster often notes "worry less, do more".   :-)

David McCarter   McCarterD@claven.fanshawec.on.ca
R.A.S.C. London Centre VP & Observers Chair
ATM: Mirrors, Electronics, Heaters, etc.
Amateur Radio VE3GSO