Which transistor to control brightness of 12 x 350ma LED from mega PWM output?

I am planning to control 12 ultrabright LED brightness with 12 PWM outputs from a Mega Arduino. I need help isolating the correct transistor/resistor arrangement. Here is the LED spec:


You need a constant current supply not just a transistor to control this.

Open drain shift register TPIC6A595 can control 8 350mA current loads.
(5V-3.4V)/.35 = 4.5ohm resistor for current limit.

6 LEDs on each device, lot of current. Have to watch cooling and good grounding.

Likely better off with a constant current driver, not sure what that'd be.

Does a constant current supply/driver need to be per LED or does it control several?

It can only control several if they are in seriese.

  1. what should I be looking for in specs?

  2. I think you mentioned needing transistors as well?


Might try a LM317 constant current source (with heat sink).
Or maybe a BuckPuck.

do Buckpucks and/or other constant current drivers/suppliers allow dimming from the PWM output of the Arduino?

I have not used this but the PDF says "External analog/digital intensity control (TTL compatible)"

I have used the LM317 with PWM and a MOS FET driver.