H-Bridge Question

singalls

Hello,

I have built an H-Bridge from the following nuts & volts article

http://www.parallax.com/Portals/0/Downloads/docs/cols/nv/vol1/col/nv23.pdf

I built the one in figure 23.5. It works fine but I would like to add an external power supply for the motor. How/where would this go? Any help is appreciated.

Steve

Prettybird

You need to attach more imformation for anyone to help you. I am new here but have alot of experience with electronics but lack programming skills

singalls

What else do you need? The wiring diagram is in the nuts & volts article

Steve

curt66140

Break the·connection·between the·+ 5 of the circuit·and the stamp, and apply your external 5 volts·there to power the circuit.· Keep the grounds between the stamp, circuit and the external power supply all connected together, if you have any other questions just ask.

Curt

singalls

Curt,

Thank you very much.

Steve

Beau Schwabe

curt66140,

There is a better solution (read below)... the circuit in figure 23.5 .. With the open collector configuration to the rails it will act more like a voltage regulator that tracks the input voltage to the transistor BASE's. Even if you apply 10V to the collectors of the NPN transistors, the motor will still only "see" about 2.6V when a 5V signal is applied to the transistor BASE.(<-- ...and the transistors will get very hot) In this example if you applied a 10V signal to the transistor BASE as well as the collectors of the NPN transistors then the motor would "see" about 7.6V

singalls,

A much better circuit for what you want to do is from the same article in figure 23.7 ... With this circuit, the voltage loss to the motors is only 1.2V as opposed to 2.4V, so even with a 5V supply the the Emitters of the PNP transistors, the motor would "see" 3.8V ... that's a 46% increase in power with the same voltage!

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 5/13/2009 3:57:12 PM GMT