current??

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Re: current??

Postby ABSF » Wed Jul 10, 2013 7:27 am

For low voltage and low current to operate a DC motor. I would not recommend the use of BJT and use MOSFET instead. On the top of my head, 2N7000 and BS170 are good choice. And looks like BS170 is better. They can conduct with a gate voltage of 2.1V typical and in pulsed mode the BS170 has a max current of 1200mA...... But of course you wont try to do that or else its life will be shortened. And dont forget to put a diode like 1N4007 across the motor to prevent back emf from the motor.

I wanted to upload the datasheet for 2n7000 and BS170 but the pdf format was not allowed. So you have to get the datasheet yourself...

Allen
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Re: current??

Postby pic16 » Fri Jul 12, 2013 11:17 pm

ABSF WROTE:For low voltage and low current to operate a DC motor. I would not recommend the use of BJT and use MOSFET instead. On the top of my head, 2N7000 and BS170 are good choice. And looks like BS170 is better. They can conduct with a gate voltage of 2.1V typical and in pulsed mode the BS170 has a max current of 1200mA...... But of course you wont try to do that or else its life will be shortened. And dont forget to put a diode like 1N4007 across the motor to prevent back emf from the motor.

I wanted to upload the datasheet for 2n7000 and BS170 but the pdf format was not allowed. So you have to get the datasheet yourself...

Allen





ABSF, I read a post and never understand why PWM signal from uC suddenly become sine wave signal after go thought many resistor and capacitor.....(n-th order low pass filter)????
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Re: current??

Postby pic16 » Sun Jul 14, 2013 4:49 pm

I so curious how pwm become sine wave, could anyone explain to me, at least drop me some information for me to read :roll:
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Re: current??

Postby Brian Griffin » Tue Jul 16, 2013 8:46 pm

That is the low-pass filter in the circuit diagram. It's to get rid of extra noise and to get a clean sine wave. You need to find:

1.) Sine-wave generation using PWM on microcontroller.
2.) Low-pass filter.
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