A
Andrew Holme
Guest
henszey@gmail.com wrote:
need a current-limiting resistor in series with LED. You would be
better-off connecting the LED, in series with a resistor, across the 12V or
15V supply. Forget about VREG1 altogether. Calculate the LED current using
Ohm's law:
I = (Vs - Vf) / Rs
Vs = Supply voltage
Vf = Approximate forward voltage drop across LED (3.5V ish)
Rs = Series resistor
You need decoupling capacitors (try 100nF) on the input and output of the
other (remaining) voltage regulator.
With the fans, you're OK - they'll "draw as many amps as they need," but youHello,
This is my first time posting to USENET. I was wondering if anyone
could help me figure out if I have the correct circuit for what I am
trying to do. I have followed other peoples schematics before, and
this is the first time that I have tried to make something for myself.
You can see the schematics that I drew up here:
http://img68.echo.cx/my.php?image=schem1wn.png
I want to run 4 things off of one power supply. The 15V 4.5A is an old
laptop power adapter. The two fans run at 12V and .01A-.02A. The LED
runs from 3.5V-4V. The peltier will run upto 15V and 15A. I did'nt
have any images for the fans and peltier so I just used some random
ones.
What I don't understand is does a device draw as many amps as it
needs? like the fans and the LED or does that need to be limited some
how?
Thanks
need a current-limiting resistor in series with LED. You would be
better-off connecting the LED, in series with a resistor, across the 12V or
15V supply. Forget about VREG1 altogether. Calculate the LED current using
Ohm's law:
I = (Vs - Vf) / Rs
Vs = Supply voltage
Vf = Approximate forward voltage drop across LED (3.5V ish)
Rs = Series resistor
You need decoupling capacitors (try 100nF) on the input and output of the
other (remaining) voltage regulator.