Help locating hardware

Help & Support Robot Parts
1

Hello, I am a tinkerer attempting to build what amounts to a glorified braiding machine and am not sure whether a particular part I am looking for exists in the electronic world.

I seek a half-turn rotating device similar to but (I think) different from stepper motors and rotary actuators that I can find on the Internet. My requirements are:]rotation by pi and -pi radians on demand (direction matters, and no limit on amount of rotation accumulated over time)/:m]]stop rotating at multiples of pi radians (only two stopping positions), and ideally have some inclination to stay in that spot/:m]]relatively low cost (may expand up to 100 parts)/:m]]low error rate (again, 100 parts)./:m]Each device would be in charge of rotating a 2" radius wooden disc to which is attached two bobbins of yarn, and there wouldn’t be much resistance either, so I don’t think size or power should be an issue. Accuracy is not a big deal either, but error in stopping position location should be constant (not accumulative) over operating time.

I would greatly appreciate any suggestions of search terms for what such a thing would be called.

Thanks,
Eric

2

Since your motor needs to rotate an indefinite number of tuns on either side, you will most likely need a stepper motor or a DC motor with an encoder.

Stepper motors provide open-loop control but may skip some steps over time, which might lead to accumulative error. On the other hand a DC motor with an encoder, although a bit more difficult to control, will have very accurate positioning.

Since you only need half-turns, you might also be able to use a regular gear-motor with small switches or markers at the stopping points. You can then use a microcontroller with a simple program to activate a motor until one of the switches is hit.

Here is a suggestion of microcontroller with integrated motor controller you could use: RB-Dfr-36

As for the motor, you will need to make sure you determine the required torque before making a choice, you can use this tool to help you with the computation: robotshop.com/dc-motor-selection.html

Finally, please find here, all the DC motors with back-shafts or encoders we carry: robotshop.com/gear-motors-with-back-shaft.html