Arduino-(TLC5940)-MOSFET/TRANSISTOR-3W RGB LED

Hey guyz,

I'm trying to get some 3W RGB LED's (6 pins and 350mA/channel) to work. The powersupply is 5V. I could change to 12V if necessary.

The setup initially is to work with a TLC5940 and a mosfet. And trying to make my life a little easier if possible also to connect the same mosfet directly to the arduino. (For future lighting idea's :))

I red a lot of topics concerning the TLC5940 and/or mosfet. So much that I'm actually totally lost.

If I understand correct with a TLC5940 it is possible to generate a constant current through a mosfet? So that there is no need to have resistors in the led circuit.

My second questions is which mosfet can do the job? I was thinking about a 500mA mosfet. And is it possible to use the same mosfet directly connected to the arduino? I guess I need to add a current limiting resistor.

Just as mention, I got 3 IRLD024 mosfet's lying around.

Kind regards,

Tom

The TLC5940 is a constant current sink driver. You connect the LED between the positive supply and the TLC5940. That's it, however it only drives 120mA per channel so you will have to common-up 3 outputs at a time to drive your RGB LED. I think that can be done.

You cannot use it to drive a MOSFET, it is already a set of MOSFETs!

Hey MarkT,

Correct, to get 350mA I need an extra component, a mosfet/transistor.

T_O_M:
Correct, to get 350mA I need an extra component, a mosfet/transistor.

You want a PNP BJT, not a MOSFET.

Seems more logic.

Transistor is current based, mosfet is voltage based but I found other threads speaking about a mosfet. To limit the output current, I need to limit the current at the base. But doesn't that mean more (to much) losses over the transistor or do I need to add then current limiting resistors?

T_O_M:
but I found other threads speaking about a mosfet.

You could probably use a P-Channel MOSFET. But if you really only need 350mA, that seems like over kill.

T_O_M: Correct, to get 350mA I need an extra component, a mosfet/transistor.

Not correct. On the product webpage are seven Application Notes. This one is relevant... Paralleled Outputs Provide High-Current Outputs