Motor/Gear help for my project

Other Hardware Motors, Mechanics, Power and CNC
1

I am trying to do my first home project. Basically it is going to dispense (upon button press) an exact serving of whatever food you want. I have most of the programming and wiring done. The next thing I have to do is figure out how to turn the knob on the dispenser using a motor. I have this motor (http://i.imgur.com/Kk0OLRQ.jpg) . I am willing to get another motor if I need to. Here are pictures of the apparatus, and the knob I need to turn.

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http://i.imgur.com/BXOFSKh.jpg [3]
http://i.imgur.com/1ToVv3H.jpg [4]
http://i.imgur.com/7cydjXK.jpg [5]

I have a kitchen scale under the dispenser, and I want it to stop dispensing when the scale reads 28g (for example).

The knob is glued onto the axle, which sticks into the paddles on the inside. For now, I am thinking that I should remove the knob, and attach the motor to the axle, and basically just bypassing a knob. I would need a different motor, but I am not sure exactly which one to use. I am thinking about a servo motor.

Any advice is greatly appreciated.

2

You will probably need a motor with gear reduction to get the speed down and the torque up. You can get them from many robot supply places using a search for "gearmotor" or "gear reduction motor".

Like this: http://www.robotshop.com/en/pololu-80rpm-right-angle-plastic-gear-motor.html

3

Hello shanefontaine, welcome to the forum. I suppose it's possible to turn that knob using the motor you have, but you would have to come up with a drive train and that would be a project of it's own. If it were me, I would reject that motor as a candidate in this project because it is just too small. There are many small, yet powerful motor/gear assemblies available at low cost that you could use. You will first have to determine the torque required to turn the knob in order to know what the drive capabilities must be and then perhaps double that to ensure consistently good operation. - Scotty