Author Topic: PWM and SN754410 (or other IC) question  (Read 2585 times)

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Offline arseniusTopic starter

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PWM and SN754410 (or other IC) question
« on: March 27, 2008, 07:02:50 AM »
I was just wondering if there is a difference between using the PWM pins on a motor controller (pins 9 and 16 on the SN754410) vs doing PWM on the input pins.  Isn't that essentially what you would do if you built your own H-bridge?  Would this simply not work, or might it damage something?  Possibly this would be dependent on the IC used.

Offline Ro-Bot-X

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Re: PWM and SN754410 (or other IC) question
« Reply #1 on: March 27, 2008, 10:56:27 AM »
The Enable pins (1 and 9, 16 is motor power...) let the outputs receive power or not. If you PWM them the motors will be ON and Coasting (off, but no power). If you tie the Enable pins to Vcc and PWM one of the direction pins, the motors will be On and Braked (both motor leads are shorted to ground). There is another method, Enable tied to Vcc and PWM both direction pins (eighter using complementary PWM outputs on the microcontroller, or using an inverter between the direction pins). This last method is the best because when the motor can recharge the batteries when the generated voltage is greater than the battery voltage (plus the protection diode).

So, for a good engineered drive system you should use DC motors with H bridges connected in the regenerative mode (the last method for PWM).
Check out the uBotino robot controller!


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