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Topic: How Can I Control This Stepper with ONLY 2N3904's???? (Read 2499 times) previous topic - next topic

TECH GEEK

I have a unipoler stepper motor that says 1.2Amps per phase, but the only transisters i own are 2n3904(NPN) &2n3906(PNP)...
i know the max amout of amps they can use is .200 aka 200mA...

Any idea on how i can control this motor without buying more items?
As always... Thanks for posting!!!

amanmazleigh

just saying my opinion. If I were you, I rather go out to buy components than stay in to see my stuffs exploding around. hehe. just saying!

TECH GEEK

well i have about 200 of them and i don't drive yet and i am not planining on heading out any time soon..
As always... Thanks for posting!!!

David_W

It could be done by using 1 to drive 6 in darlington (the emitter of the 1 feeds the base of the 6) configuration.

CrossRoads

You could try putting 6 in parallel with current limiting resistors on each so no one can try and sink all the current itself.
Maybe wire it up like this.
Full on, the transistor will have Vce of ~0.3V. So with 12V for the motor, (12V - 0.3V)/0.2A = 58, use 68 ohm resistors and add another transistor in parallel.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Grumpy_Mike

Best of luck, getting transistors to share current is almost impossible. FETs are another matter they share nicely but voltage / current characteristics mean transistors naturally want to hog all the power.
So one gets all the power and blows so the next one takes over and blows and so on.
One way of trying to make them share is to put small emitter resistors in.

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