Re: ATM A little electronic help on my Foucault tester

[Michael Lindner <mikell@optonline.net>]

On Tue, 04 Dec 2001 09:14:43 -0500 (EST), Leftfieldstar@aol.com said:

>   That's a nice handy method for figuring the resister values. Do you have a 
>  reference for other convenient data computation like that?

Thanks. Unfortunately, that's a "one-off" for me of ohm's law (E = IR, where E
= volts, I = amps,and R = ohms). Back in the old days, when I learned
electronics (with vacuum tubes!) there were only 3 things you had to know:

	E = IR	(voltage is current times resistance)
	W = EI	(power in watts is voltage time current)
	sum(I) = 0	(the sum of currents into and out of any point is 0)

They're still all true, but some devices act funny (like the LED, which has a
constant voltage drop across it).

There is a good site for lots of optical formulae:
http://www.atmsite.org/contrib/Tasso/formulae/

I suppose one for ATM-related electrical and one for mechanical formulae would
be nice as well. Any volunteers?

By the way, in the face of opinions otherwise, I usaually use a 9v battery to
power my LED devices. The reason si that the 9v battery clips are so darn cheap
and convenient, and the 9v battery lasts nearly forever, since as the cell ages
the voltage can go waaaay down without significantly affecting the performance
of the device. My LED flashlights are 4 years old now, and I've never changed a
battery, despite my kids leaving them on all the time.

-- 
Michael Lindner
http://home.att.net/~mikel
http://www.starastronomy.org
http://www.atmsite.org
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