Science Buddies: "Ask an Expert"

I am having an issue. I followed everything as per the directions. I put every jumper wire, transistor, wires, correctly as the diagram. When i left the bot alone for 3 minutes, the batteries became so hot. the switch does nothing. I don't know what is wrong with it.

Hi - if your batteries are getting hot then you definitely have a short circuit somewhere. Please carefully check and double-check all of your wiring to make sure it matches the diagrams in the project exactly. A single wire misplaced by just one row on the breadboard can cause a short circuit.