I'm trying to control a higher voltage power source with my arduino and general purpose NPN-transistors but I am getting nowhere.
I've got the charging circuit from here; http://www.i-hacked.com/content/view/207/44/'
And I don't need the "Don't charge those batteries"-speech, I know the risks involved.
My arduino is monitoring the voltage on the battery as it is charging, and i would like to use the arduino to cut the power when the voltage has reached a specific value. How would I implement a transistor switch, base-controlled by the arduino, into this circuit?