This is a placeholder topic for “Turbo Metal Gear Worm Motor (12V 160RPM 2.2kg.cm)” comments.
The turbo metal gear worm motor uses a metal gear box for durability and a high torque output. Due to the special mechanical structure of the worm drive the motor output shaft is self locking and can not be rotated.
Read moreCan you please recommend a controller for this motor (PMW?) need to slow this down to about 1rpm, and a suitable 2pole slip ring.
Thanks in advance
Any microcontroller, Arduino, Raspberry Pi etc will be able to do that, however it is not going to have much torque at all at that rate.
This is 160rpm motor, to go to 1 rpm you need to slow it down 160 times or roughly a PWM of 1.6 out of 255.
What is the usage that you need 1 rpm for?
A better option is to gear down the gearmotor further, but it will need a multi gear reduction.
Hi Paul,
Andrew is on the money. We’ve got a few options with a higher gear ratio, giving you more torque and control.
How precise does the speed have to be? You might need an encoder if the answer is “very”.
If you want a standalone “just works” controller, Pololu have a few options in that area:
Or if you’re happy getting your hands dirty with some simple Python code, a Pico and a motor driver should be enough (driver choice depends on how big your motor is)
Let us know what you think of those suggestions, keen to see your project come to life!
-James
I use those 50RPM DC gear motors in a project, with encoder, they are really torquey little motors, dont let the size fool you, I lift 3kg of camera and lens on a rail with them, and they are quite accurate.
However, I still gear them down as 52RPM is too high for what I am doing, but going from 52rpm to 1 rpm is a MUCH easier task.
Appreciate the prompt reply.
The project is to build a flying Santa, sleigh with reindeer for next year. The sleigh is at the end of a rotating counter balanced beam. The sleigh is made of wire and mesh with coloured 5v LEDs (approx 5kgs at the end of a 3m span). Plan was to periodically turn on LEDs and ramp-up to start the sleigh rotation, and use a trip switch to trigger stopping the rotation (ramp-down) and turn off the LEDs. Chain and sprocket with split pin as the weakest point. The target rpm is approx 3 rpm (don’t want a real flying Santa).
Parts list at the moment is:
Done some Arduino programming with addressable LEDs.
Early days, only 11 months of head scratching to go.
Regards
Paul
OK so by counter balanced you mean that the net load on the motor will be almost zero?
I would not use the small DC motors in that case the potential for the load is far too great.
Make sure that you have hard stop end points for it to move between because if something catastrophic happens like the counterweight falling off, you wan to limit the damage.
You’ll need a gear motor and still gear it down, PWM decreases torque substantially so while it will spin slowly it wont be able to move much.
This one that James included would be pretty good:
But I would look at the gearbox that it uses and see if I could get anouther one and run them sequentially. You will then have a 12v gear motor that could lift a car! 9joking, but that one is 50kg @1cm, doubling the gearbox would substantially increase that.
They will be loud though, so keep that in mind.
Hi Andrew
Don’t quite agree with that. The benefit of PWM is the higher torque available at low speeds when compared with just applying a lower voltage. The difference is that full voltage is applied while switched on. Albeit for very short times at low speeds.
The following is an answer to a question from an Electrical Engineering site which sums it up.
Quote.
Power efficiency The induction of the motor will cause the current to average. At the same time the transistors in PWM mode have very low impedance and therefore a low voltage drop and low power dissipation. In case of a series resistor a lot of power is dissipated in the series resistor.
Speed control behavior With PWM the motor will ‘see’ a very low power supply impedance, even though the power supply is constantly switching between high and low voltages. The result is that the motor has a much higher torque. With a series resistance the motor will experience a very weak power supply and it will be easy to stall the rotor.
Control circuit For a control electronics (eg. a microcontroller) it is very easy to switch on/off transistors. Outputting an analog voltage or controlling a series resistor requires much more expensive circuitry and in turn will cause more power dissipation.
End Quote.
Cheers Bob
While I accept the technical response, I have a couple of comments.
Whenever we implemented PWM speed control the motor stalled FAR easier than without, and I am only talking ‘light’ PWM such as 80%.
100% I agree with the concept that the torque of PWM is FAR greater than using voltage alone for speed control, but slowing a motor down using PWM doesnt increase the torque from running without PWM, in a real world scenario.
Hi Andrew
Didn’t say it did. But I did effectively say this.
I do agree with this
Especially if the motor in question is driven by the now popular “H” bridge.
I have noticed that with most H bridge circuits (I can’t say all as I just non’t know) that switch diagonally opposite Mosfets to apply the voltage you almost always NEVER get a flywheel diode (or in this case 2 diodes in series) Directly across the motor. One always gets to the motor via the motor supply. This has the effect of clamping the reverse voltage to the supply value and effectively applies a reverse voltage across the motor. This can be easily observed using an oscilloscope (with the mains ground disconnected so no accidental shorts) directly across the motor. Starting from standstill apply the PWM. you will see the positive ppm voltage but also a negative voltage the same amplitude and width as the wanted pulse. Net result, zero volts and no movement. This could continue until something like 20% duty cycle or maybe more. When the width of the PWM exceeds the negative pulse the motor starts to move. At this point the width of the negative pulse rapidly decreases and the motor will race up to about 20% speed. It can then be backed off a bit but never to a slow crawl.
This is digressing a bit and is not really the subject under discussion. I have oscilloscope pictures demonstrating this and can post them along with a description if enough interest. I have found that where this slow start is required using a relay to change direction produces better and predictable results. There are lots of scenarios where a slow start from standstill is required.
Cheers Bob
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