Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: WaldoDTD on April 09, 2008, 04:42:37 PM
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Ok, so I am trying to create a transistor switching circuit so that when i put voltage on the base pin of a Bipolar junction transistor (NPN) it will turn on a motor current. After much frustration the circuit doesn't work. I have the motor wired from the emitter pin to the ground and +9 VDC on the collector. My microcontroller pulls the base pin to 5VDC. Should I use a opto isolator? Or should I rethink the transistor circuit? Thanks!-Waldo
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Whipped up this one just now. Let me know if you problem with this one.
There is wide leeway for resistor values. R1 should be greater than 10*R2. And R2 should be such that when enable signal is asserted enough current flows through base-emitter diode to turn on the transistor. In the current case with 5 volt signal about 5mA flows, which should be enough to turn on the transistor.
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The $40 robot does this:
http://www.societyofrobots.com/member_tutorials/node/59