Hopefully this is a quick question, i have a lock, it needs 5v to open, i am using a Arduino Diecimila and when i connect this lock to the 5V Power and Gnd connection on the board it opens and my meter shows the 5v connection.
But when i connect to say one of the digital outs and GND and have it digitalWrite( 3, HIGH) it does not open.
When i do not have it connected to the lock, the digital out shows that it is putting out 5v(read from a meter) but when i connect it to the lock it only reads out about have that 2.5v
Probably because the arduino can't output enough current, so the it's output voltage drops off. Use a transistor (or FET or whatever) to drive it, This should help : Arduino Playground - HomePage I know it's for a solenoid but it'll work for the lock.