Braking a DC Motor

Other Hardware Motors, Mechanics, Power and CNC
1

Hi, I have a geared dc motor which runs at 100 RPM,to brake I was sending DirA & dirB LOW which worked fine accept that it took One revolution to stop. As I would like it to brake faster I have sent both HIGH added a delay then both LOW. It now depends on the delay as to how fast it will stop. The problem is I am not sure if sending the motor High and stopping too quick will damage it. The stopping code:

void Brake(){
   digitalWrite(DIR_A, HIGH);
    digitalWrite(DIR_B, HIGH);// Stop ----Stops quick
    analogWrite(PWM, 0);
    delay(5);
    digitalWrite(DIR_A, LOW);
    digitalWrite(DIR_B, LOW);// Stay --- Stopped 
    analogWrite(PWM, 0);
}

Any comments would be useful. Thanks
Terry

2

Telboy:
Hi, I have a geared dc motor which runs at 100 RPM,to brake I was sending DirA & dirB LOW which worked fine accept that it took One revolution to stop. As I would like it to brake faster I have sent both HIGH added a delay then both LOW. It now depends on the delay as to how fast it will stop. The problem is I am not sure if sending the motor High and stopping too quick will damage it.

Well that's a good question, and its certainly the case that with large industrial motors the braking current/torque
on shorting the terminals can exceed the safe limit.

But for small motors it may be perfectly fine.

So please supply details of the motor - and you can also try measuring the current to the motor as it brakes
directly if you have a suitable range on your multimeter...

The way you do controllable current limited braking if needed is to use PWM to switch between open and closed
circuit - industrial motor controllers usually have a big high power dump resistor to dissipate the energy when
this happens (rather than push the DC rail higher and higher).

3

Thanks for your reply MarkT, the motor is a GW 370:
Specifications:
Voltage: DC12V
Load torque: 10KG.CM
No-load speed choice : 0.6rpm/2rpm/3rpm/10rpm/25rpm/100rpm/120rpm
Suitable for: Widely used in windows, a door opener, miniature winch and other occasions.

I was thinking also about using PWM as a braking source.

4

Tiny motor, no problem shorting that.

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