What kind of motor should I use?

Hello! I am trying to create a coin counter/sorter and I was going to use a model similar to the above to sort the coins. My question is what would be the best kind of motor to drive the rotating wheel that sorts the coins. Servo seems simpler as I would not need a motor controller(to my understanding), but I am not sure which one to get and I am afraid of it not having enough torque. Would a servo or a dc motor be best in this situation?

Gear motor
https://www.google.ca/search?rlz=1C1AFAB_enCA475&biw=1440&bih=787&tbm=isch&sa=1&ei=RWywWtSZHOfcjwTkj4qYDw&q=6v+gear+motor&oq=6v+gear+motor&gs_l=psy-ab.3..0j0i8i30k1.24480.25551.0.29043.3.3.0.0.0.0.253.498.0j2j1.3.0....0...1c.1.64.psy-ab..0.3.495...0i13k1j0i8i7i30k1j0i10i24k1.0._5H438_updc

A servo is (usually) a DC motor with position feed-back and control hardware, making them really simple to use. Servos usually move only 180 degrees, it looks like your application needs more.

A regular geared DC motor is cheap and reliable and will do the job if you have some form of position feedback on your coin sorter. After all you have to know where you are and when to stop.

Another option is a stepper motor, it's much less power efficient and you still need some form of zero positioning feedback, as you have to know where you are when starting up.

Until you know how hard the small gear is to turn, you don't know what to use.

Looking at the 3D model, it would seem as though there would not need to be buckets or torque needed.

I would use a small magnet, a sensor, and a regular DC motor to drive it and get position (more magnets if needed) for a finer position feedback.

Regular DC motor has no position feedback by itself, so in that case you need a magnet under each bucket and a sensor to tell you when the next bucket is under the hopper.

You need an extra magnet and separate sensor (placed in a way that they don't interfere) as a zero position, to know which bucket it is that you placed under the hopper.

Or a single magnet and an array of sensors around the receiver, so the sensor that is activated can tell you which bucket is under the hopper.

In case of a stepper you'd need just the zero positioning. A DC motor is more efficient, but the overall positioning will be less precise.

Using magnets has the problem that they have a range in which they're detected. Optical sensors can be more precise, by having small holes in the top of the bucket or so.

One of the cheap N20 gear motors in the link in Reply #1 would be a good starting point. I think it will have enough torque and the cost will not be great if it has to be abandoned in favour of a more powerful motor.

...R

fall-apart-dave:
Looking at the 3D model, it would seem as though there would not need to be buckets or torque needed.

I would use a small magnet, a sensor, and a regular DC motor to drive it and get position (more magnets if needed) for a finer position feedback.

It's about friction. I can't tell just by looking how hard it is to turn the wheel.
It depends on the gear teeth which IME plastic gears don't all mesh smoothly as they should.
It depends on how the wheel turns on the axle.

Those little geared motors have quite some torque and indeed are cheap enough to just try. If it really doesn’t work, get a stronger one.

Of course the correct engineering way is to measure the torque needed to turn the wheel and get a motor that can handle this force 3-4 times over.