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my transistor gets hot, line follower/dark sensor

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leonheard

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my transistor gets hot, line follower/dark sensor
« on: February 01, 2013, 04:01:31 PM »
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....

Hero999

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Re: my transistor gets hot, line follower/dark sensor
« Reply #1 on: February 02, 2013, 12:12:24 PM »
Posting a schematic would make it easier for us to help you.

You obviously need to use a more powerful transistor and/or add a heat sink to keep it cool. Another option could be replacing the Darlington pair with a MOSFET or connect the collector of one of the driver transistor to +V, via a current limiting resistor.