I'm working on a project for lighting foam pumpkins and syncing them to music, I have everything worked out, using vixen in my laptop to play music and pass the switching direction to the mega. the trouble is the LED's I'm using. I'm a sign repair tech, and i came by some parts from an old LED billboard. basically its a small block with 4 pixels each made up of 2 green, 2 red, and 1 blue LED. common anode. I have worked out wiring to make all four pixels do the same thing at once to add brightness. but the blue channel pulls 400mA, Green pulls 500mA and Red pulls 200mA. so i need a way to get the logic 0 from the arduino to drive the LED's but the draw is way too high...
Im sure its a simple solution.
Use transistors or an LED driver. Lots of examples on the web, e.g. Arduino Playground - HomePage
Do not power the LEDs from the Arduino -- use a separate supply and make sure everything has a common ground.
THanks for the link, I was actually looking at that one earlier but when i put it all on a breadboard it turns on from a logic High, I need it to turn on from a Low because of the rest of the project. The code im using can be set to use a low or high to turn on things but all of the 32 outputs im using must be the same ether low or high. the relay modules im using for switching 120v are low triggered. was thinking about just using inverters like 7404's but was hoping not to add a bunch of extra chips to my plans, I intend to expand quite a bit more over the next few years and have a christmas light show as well.
Why couldnt my free parts just be easy to use lol.
If your LEDs are powered by 5V, you can use a "upside down" PNP transistor instead. This will be activated by a LOW. See attached. This won't work if the LED power supply is greater than 5V, though.
