Question on choice of Mosfet Transistor in H-Bridge, and power amplification

Discussion in 'The Projects Forum' started by corrado33, Oct 22, 2009.

  1. corrado33

    Thread Starter New Member

    Oct 22, 2009
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    0
    Hey guys, I'm new here, but not new to electronics. So I'm following this diagram on how to build an h-bridge..

    http://www.societyofrobots.com/schematics_h-bridgedes.shtml

    And I have a quick question. I understand everything about the diagram, however I'm having trouble finding the correct transistors. I'm looking on Digikey.com and they have literally thousands of different types of transistors. So I really don't know where to start.

    Here is a previous thread made by me (on another site, that didn't get answered) concerning my problem.

    So here are the motors I'm using, and I'm running them at 24v. http://www.robotmarketplace.com/products/0-BHG31.html

    What transistors should I use? The tutorial mentioned something about PWM optimized mosfet's as well? Should I be looking for those since I'm obviously going to be using PWM? Could someone point me in the right direction?

    Also, the tutorial mentioned something about amplifying the signal coming from (most likely the microcontroller) to the transistors themselves... However, in the power amplification tutorial, he said that those circuits should only be used for amplifying low voltages, like a sensor or something. So, correct me if I'm wrong here, but most microcontrollers will output a 5V signal. So what should I amplify that 5V to? 9V? 12V? And also, how do I do it? I did find a 5V to 9V voltage converter on http://www.goldmine-elec-products.com/prodinfo.asp?number=G16902 however, it has a max amperage of.. well, something that's lower than my motors will be drawing, but does that matter since this'll only be attached to basically the "switch" of the transistor? What do you guys suggest in the voltage amplification department?

    Thanks for your help.
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Google around some more. There are complete H-Bridges already worked out with parts specs and interface logic to get beween your uC Port Pins to the high-side switches.
     
  3. corrado33

    Thread Starter New Member

    Oct 22, 2009
    8
    0
    Thanks Mike! I googled 24v H-Bridge and got a great result, however it doesn't say anything about power amplification. The only reason I mention this is because I read that transistors are more efficient with more voltage applied.

    Basically, the resistance of the transistor is controlled by how much voltage is applied, so high voltage will yield less resistance (and therefore LESS heat, which is a good thing).

    Any ideas about that?

    Thanks!
     
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