How do I control a device running from another power source using arduino?
I have board of LEDs (about 16 x 10mm bright LEDs) that i made which is running off a 9v DC850mA adapter salvaged from an old Casio keyboard. Basically I want to flash the lights in sequences determined by my Arduino. I have plugged the LEDs directly into the board (which, at the time, I hadn't realized was potentially hazardous to my board) and it worked just fine. Problem is, when multiple boards are plugged in they can't get bright enough, and I want to use ALOT of these LED boards. so yeah, I am just looking for some advice on what to research, or even a schematic you may already know of. I know very little of transistors. And i know nothing about relays (not even sure if thats what might be used). Any help is greatly appreciated. thank you.