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I tried to make H-bridge by TIP 122 transistor. I used 9V for a VCC. I used push button to control H-bridge, and it's fine. Then I used Arduino 2560 with two digital pins for driving H-bridge. But the output voltage was only 5V. And also, I tried with VCC= 15V, output still be 5V.

Could you please give me an advice? enter image description here enter image description here

Wouter van Ooijen
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Than
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  • Read [this answer](http://electronics.stackexchange.com/a/93851/29792) and [this question](http://electronics.stackexchange.com/questions/93016/bjh-h-bridge-going-in-reverse-but-not-forward-ll-transistor-overheating). There I present a link to [a better BJT bridge](http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html) that is able to handle 5A (with proper heatsinks) and does not allow the user to short the power supply (like Wouter implied). – Ricardo Feb 27 '15 at 13:37

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The upper TIP122's are wired as emitter-followers, so their output voltage can never be higher than their input (base) voltage. (In fact it will be ~ 2 x 0.6V lower.)

When you fed the inputs with the full Vcc that was not much of a problem, but when you feed it with the 5V Arduino outputs you will get no more than 5V from the outputs.

One solution is to put a level shifter between the Arduino outputs and the H-bridge. But it will still be a crappy H-bridge. (Do you realize what will happen when you make BOTH inputs high?)

Wouter van Ooijen
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