hi!

i have almost made a line following car (toy) but i have 1 problem.... my transistor gets hot after a while... am using about 7 volts power supply, i have 2 transistor as a darlingon " bc337 transistors "( when i put the light off the dc motor run very fast like i want ) but when i touch the transistor 2, is hot! )

then i changed the transistor 2 to a 2N2219 ( it was working okei, but also hot, and i think its broke, cuz it doesnt work anymore ) then i used a BD243 transistor, its still alive, but it gets hot 2,

i use resistors, so i dont know what to do....

 

Since you didn't post the circuit diagram, all I can suggest is that you put a heatsink on the transistor getting hot.