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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 Answered

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?
 

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steveastroukBest Answer (author)2009-10-12

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

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Jayefuu (author)2009-10-12

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 />

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