Small DC motors

[angelodp]

Hi I have a few pickup winders that I created with left over parts. One of the winders works exceedingly well in that the circuit for the variable speed revs up to about 1800rpm and when the potentiometer is dialed back the winder stops...dead stop.

This is nice as I can check the pattern on the bobbins and then continue in rapid order.

The second winder is using the very same circuit with an LM317T and it does not behave the same way. In this unit the motor keeps spinning after I bring the potentiometer all the way down. The inertia just keeps the platten spinning?

Is that I have two different design motors and one obviously allow of the immediate stopping.

Please school me on DC motors. We are talking DC 6-12v

What type DC motor is correct for the quick stop. Brush or brushless - other? I do not know from the outside what these two DC motors are (bought at a model hobby shop, and have no markings)

Best Ange

[reTrEaD]

Hello, Ange.

I don't know enough about brushless motors to say whether they could provide any inherent braking action. Here are some other factors to consider:

Mass of the rotating assembly. More mass = more inertia = slower rate of reduction of speed when power is removed.

Gearing ...
Greater gear reduction = quicker rate of reduction of speed when power is removed.
Type of gears matters. A worm pinion is more effective in reducing speed when power is removed, than is a flat pinion.

(I saved the best for last)
Dynamic braking ...
If you simply open the circuit that supplies the power, this is less effective in slowing the rotation when power is removed, than is shunting the motor to ground.  In essence, you're turning the motor into a generator and loading it heavily with the shunt.

[angelodp]

Thanks for the input. I have ordered a small PMW device which might do the trick.

Best A

[kitwn]

Mar 10, 2024 22:32:22 GMT -5 angelodp said:

Thanks for the input. I have ordered a small PMW device which might do the trick.

Best A

PWM will give you better speed control at slow speeds, a gradual pickup instead of a sudden leap into life.

For the ultimate control of speed, including automatic acceleration and deceleration when starting and stopping, plus the added bonus of automatic turns counting then a stepper motor controlled by a microcontroller is the way to go. This does require a bit more of a learning curve though.

If you're concentration is as good as mine then such a machine could be programmed to stop after a specified number of turns. All you have to do is daydream while guiding the wire onto the bobbin. This would be a big bonus for me!

Kit

[angelodp]

Ok got in the PWM unit and it works like a charm. I am amazed at this little $7 unit. It allows the motor to start with full torque and at slow speed up to hi rpm. And.... little to no heat dissipation.

Thanks Again.

A