Problems with Power Transistors

Forum 2005-2010 (read only) Hardware Interfacing
1

Hello!

Right now i try to attach several RGB Leds to my Arduino with the help of 3 mosfet power transistors and a 6V external power supply. Its the first time im working with power transistors, and as always the problems are big.

Diagram looks like this: (same for every color)

Digital output --> 10k resistor ---> G
6V + ---> D
6V - ----> LED cathode ---> 220 resistor ---> S

I hope this is understandable. The Problem is, i dont know where to attach the Arduino ground. Each time i touch one transistor, the colors are changing. It seems not very stable right now..

Anyone knows help? :wink:

Thanks

2

I would try hooking it up like this:

+6V----220R-----LED anode

LED cathode------D

-6V----------------S
Arduino GND-----S

Digital output-----G

3

Thanks for your reply!

The problem is, i've got common cathode rgb leds and want to control them with 3 mosfets.
So i think i have to control the anodes of the led with the transistors?!

Greets

4

Witn common cathodes you'll need a "high side switch" similar to this:

If you google "high side switch" you'll see many more just like it.

5

Thanks alot. I already solved the problems with some PNP MOSFETs.. Hope all will be fine..

Greets