Hi all. I'm looking to do some PWM on some high power LEDs. PICwise,
everything is working great. Now comes to the EE part, where I have much
less skill. I have to power 5 LEDs with a current of about 20mA each.
It's easier for me to provide higher current rather than higher voltage,
so I was thinking about paralleling them. But, I'd like to only have one
current limiting resistor for the string of 5. According to my
calculations, it worked out to something like 40 ohms. I can't remember
the exact equation I used, I don't have the paper in front of me.
However, if I want to PWM 100mA of LEDs what would be a good value to
use? Also, what would be a good transistor to use? I was thinking about
a TIP31 just off the top of my head, but I have a feeling it's a bit of
overkill. I'm PWM'ing at about 20kHz.

I'd appreciate any help!

BTW, I saw this, and it made me think of you Jinx:
If at first the idea is not absurd, then there is no hope for it.
- Albert Einstein


Thanks,
Josh

--
A common mistake that people make when trying to design something
completely foolproof is to underestimate the ingenuity of complete
fools.
        -Douglas Adams

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu