Aj808
Posts: 1
Joined: Thu Dec 24, 2015 8:12 pm

Rotary table

Thu Dec 24, 2015 8:23 pm

Hi all, this is my first post so please be patient . I am a electrical technician and I have been thinking about getting a pi and building a rotary table. I work for a tool company and have an old table that the control is obsolete. The way it was is like this, there was a 8amp dc motor to turn the table through a gearbox and an encoder on the shaft of the table to give a position read out to .00 degrees. On the old control you would type the position you want and the table would go there and stop and hold. Now, I want to make a new control, I'd love it to be touch screen but just to do the same as the old control. It would need to readout the position. Do any of you guys think this would be do-able or has it been done? Thanks for any help in advance

Aj

ame
Posts: 3172
Joined: Sat Aug 18, 2012 1:21 am
Location: Korea

Re: Rotary table

Fri Dec 25, 2015 7:06 am

Very do-able, but you're going to have to do a lot of fiddling.

Controlling the motor is easy. The simplest way is with a pair if relays. You can control on/off and direction.

There might be a problem with overshoot though, when the table moves a tiny amount after the power is cut. You could get round that by using a MOSFET to control the motor speed, or do it in software by turning the motor off before it reaches the desired point.

The position sensor might be more difficult. Or it might be extremely easy. Can you see how the position sensor works? Maybe you can hook into the raw signals and decode them, or maybe you can hook into the original control box and pick up some useful signals there.

Have fun. It sounds like an interesting project.

User avatar
RogerW
Posts: 285
Joined: Sat Dec 20, 2014 12:15 pm
Location: London UK

Re: Rotary table

Sat Jan 02, 2016 2:56 pm

Certainly can be done. You need a stepper motor and some drive electronics. Lots of people have done this using microcontrollers but usin a pi would certainly make a much better user interface possible.

Slackware
Posts: 131
Joined: Mon Jan 18, 2016 3:45 pm

Re: Rotary table

Sat Feb 13, 2016 8:07 pm

you can get rotary encoders that will measure to 9600 steps per revolution cheap enough. but that is only a 26th of a degree, to get hundredths you will need 36000. BUT if you measure at the gear you can multiply it out. But you should have everything you need already on the table. rip open the guts and just replace signal lines with RPi inputs. If it is that old you are dealing with very little surprises. single layer circuit boards, and no custom black box IC chips.

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