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copper wire following robot: building a dual Hbridge to drive a robot. but my transistor TIP 42 and TIP 120 overheat

i have a dual hbridge but its overheating im a beginner in electronics and i dont know how to fix this   i have attach a schematics of my circuit...i used 4 npn transistor (TIP120) 2 to control the Hbridge and 2 others that form the hbridge , 2 pnp transistors (TIP42G) ,  (4) 1Megaohms resistors. TIP transistors are able to take up to 150 degrees...i heard of heat sink  and voltage follower to help with the overheat . but i cant make it work. is my circuit correct..if yes how can i get rid of the heat?
 


You haven't switched the transistors properly - you have both transistors in one leg coming on together, or you aren't driving them into full saturation. That said, MOSFETS are probably better in an H bridge these days.

Steve
souandji (author) 6 years ago
thanks guys
Jayefuu7 years ago
I've never used one before, but I'd suggest you check your connections against this instructable. It seems to be well documented and maybe they've done something you've missed?<br />