[simpits-tech] Resistor for LEDs?

[Joseph Fagner]

Hey Ben, I am planning on using some different power supplies I found on
eBay that provide both 5 and 12 volts and were used for disk drive
enclosures.  Could you diagram what your saying as it's hard to
visualize, but a picture goes a long way.  I would like to uses this way
to power my back lighting as well.

Thanks
Jay

-----Original Message-----
From: simpits-tech-admin@simpits.org
[mailto:simpits-tech-admin@simpits.org] On Behalf Of Ben Jones
Sent: Wednesday, December 25, 2002 8:29 AM
To: simpits-tech@simpits.org
Subject: Re: [simpits-tech] Resistor for LEDs?

Guys,

Can i suggest from a electrical background , not using your computer
power
supply to power led's and there associated resistors,
for the simple factor that if you have a "misfortune" with a led or
associated wiring having a blow out or melt down , this could cause the
power supply to your pc to either fail or cause dammage to the boards if
a
spike was created.

the power supplys being load dependant will constantly vary the amperage
tho
maintain a constant voltage, if there was any big load changes on the
supply
there is a chance that your led's will vary in light intensity being
given
off..

My suggestion to solve this problem ( or anticipated problem) is to have
a
separate filtered and proctected powersupply being of 12 v dc ,
supplying
your leds by a 12 v bus ( a parallel circuit)  , this is easy to tap off
the
12 v needed take the active through your switched contact to turn the
led
off and on , then through the  power dissapation resistor  onto the led
and
out to  the 12v bus neutral,  because this is all in parallel  only the
1
wattage resistor is needed for each led , and because the supply is
constant
where ever you tapp off ( given the powersupply can handle the full load
plus 10%) there should be no drop in intensity throught each led , as
would
the cas be in a series circuit.

The only reason i suggest this is because the power supply is feeding
some
pretty expensive gear and it works best just powering the computer,
which is
the way it was designed for.

If there is any electronic techo's out there please correct me if i'm
wrong..

regards

ben

****************************
bjones@pipecomp.com.au
*****************************************


----- Original Message -----
From: "Joseph Fagner" <crease-guard@attbi.com>

> That's simple, don't really need to know the load, just use an free
> molex connector from one of the systems running your simulator.  Your
> computer will provide the load.


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