Author Topic: phototransistor/motor driver circuit  (Read 3326 times)

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Offline WaldoDTDTopic starter

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phototransistor/motor driver circuit
« on: April 09, 2008, 04:42:37 PM »
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

Offline brijesh

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Re: phototransistor/motor driver circuit
« Reply #1 on: April 09, 2008, 09:59:18 PM »
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.

Offline Admin

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Re: phototransistor/motor driver circuit
« Reply #2 on: April 14, 2008, 06:56:33 PM »


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