# Rotary switch recommendations for controlling/isolating three manually powered stepper motors

#### wyo22ski

Joined Jun 14, 2022
2

I'm sure you are aware that connecting the leads of one stepper motor to another, and manually turning the rotor on one, turns the rotor on the other. To me this is pure magic and I'm wanting to make a little battery free project for my son using four stepper motors and a rotary switch.

The first stepper motor I'll call the controller motor and will be connected to the switch poles, the three others are selected via the rotary switch individually. From my basic understanding, I need a switch that has four poles, and four positions per pole. I don't believe multiple decks will help. With the single deck, each click of the switch allows me to control a different stepper motor from the controller motor.

From my research, it appears that the (in stock) Grayhill 57HS22-01-4-04N or 57M22-01-4-04N meet these requirements as they have 4 poles and 4 positions per pole. Problem is, these are $100-150. A bit pricey for my project. Any other suggestions? Am I missing any other alternatives? Thanks again for any advice #### Sensacell Joined Jun 19, 2012 3,011 Not really in the mood to look up the specs of your proposed switch- you will get better response of you post the data sheet itself. If you common connect one leg of all the coils, you only need a 2-pole, 4 position switch. #### MisterBill2 Joined Jan 23, 2018 12,424 What is fortunate is that there are no hazardous voltages involved, and that it is not likely that the motors will be moved while the switch is being operated. One cheaper choice would be two four-pole, center off, toggle switches. The small ones cost less than$10 each, and you would only need two of them. Not a rotary switch, but it will allow selecting one at a time. and it may be possible to link both to one lever that can push in any of four directions.

Also, rotary switches are available from many surplus sources.

#### boostbuck

Joined Oct 5, 2017
202
With four motors, one a master, you surely only need a 4 pole, THREE position switch.

These are available where I am (through Jaycar) for less than 5 dollars:

#### shortbus

Joined Sep 30, 2009
9,441
I'm sure you are aware that connecting the leads of one stepper motor to another, and manually turning the rotor on one, turns the rotor on the other. To me this is pure magic and I'm wanting to make a little battery free project for my son using four stepper motors and a rotary switch.
Not wanting to argue but can you give a link to where you saw this as a possibility? Was it on Youtube by chance?

This is a totally new concept to me at least. I can't believe turning one stepper will generate enough voltage in the correct sequence to move another motor.

Joined Jul 18, 2013
25,469
Not wanting to argue but can you give a link to where you saw this as a possibility? Was it on Youtube by chance?

This is a totally new concept to me at least. I can't believe turning one stepper will generate enough voltage in the correct sequence to move another motor.
Yes it has been done for quite a while now, the original servo principle was done likewise.
One application is a remote wind direction indicator where the vanes have the generator and the remote dial indicator has the slave.
Although the better method is the Synchro.

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#### Sensacell

Joined Jun 19, 2012
3,011
Not wanting to argue but can you give a link to where you saw this as a possibility? Was it on Youtube by chance?

This is a totally new concept to me at least. I can't believe turning one stepper will generate enough voltage in the correct sequence to move another motor.
Yes it works- but no guarantee of synchronism and the torque is feeble.

Joined Jul 18, 2013
25,469
Best using bi-polar versions IMO.

#### MisterBill2

Joined Jan 23, 2018
12,424
I should have tried this when I had access to a bunch of superior electric stepper motors.
I am certain that it depends on how fast the motor is rotated. But I have ZERO trust in what is shown on yoo toob.

#### shortbus

Joined Sep 30, 2009
9,441
Yes it has been done for quite a while now, the original servo principle was done likewise.
But to my understanding of how those work, they also have an outside power supply. I take the TS post as his is un-powered, only the one being manually turned to move the second one. I can't see a slowly turned stepper making even the name plate voltage when turned by hand.

I'm sure you are aware that connecting the leads of one stepper motor to another, and manually turning the rotor on one, turns the rotor on the other.

#### MisterBill2

Joined Jan 23, 2018
12,424
I have never experimented with that. I am aware that a PM stepper can generate enough voltage to serve as an encoder, cheaper and more rugged than a standard encoder and not needing external power. But triggering a digital input takes a lot less power.

#### wyo22ski

Joined Jun 14, 2022
2
Thank you all for the suggestions! I will begin experimenting.

Shortbus: As for the video, I can't remember how I found it, but it does exist. If I get a chance tomorrow to wire two stepper motors together to demonstrate, I will post a video. FYI, once two steppers are connected, the control stepper is way harder to turn, but still feasible.

I'm plan on getting some Nema 11 Steppers for the project and controlled them with a Nema 23 for the controller. The controller should be way easier to turn given the larger coils acting on the smaller coils of the Nema 11 steppers.

#### MrSalts

Joined Apr 2, 2020
1,840
Thank you all for the suggestions! I will begin experimenting.

Shortbus: As for the video, I can't remember how I found it, but it does exist. If I get a chance tomorrow to wire two stepper motors together to demonstrate, I will post a video. FYI, once two steppers are connected, the control stepper is way harder to turn, but still feasible.

I'm plan on getting some Nema 11 Steppers for the project and controlled them with a Nema 23 for the controller. The controller should be way easier to turn given the larger coils acting on the smaller coils of the Nema 11 steppers.
Note that the NEMA size is only the bolt pattern and spacing. It has nothing to do with the motor power, step size, etc.

#### shortbus

Joined Sep 30, 2009
9,441

Joined Jul 18, 2013
25,469
As per post 6, I mentioned the Synchro is the better option, if you need any kind of low RPM power.
The stepper version is OK for low current, low RPM indicator methods.

#### MisterBill2

Joined Jan 23, 2018
12,424
The syncro/selsyn certainly requires power,as does the the sine/cosine resolver. But both provide "infinite resolution" that depends only on the external circuitry.
And totally off-topic, a resolver is an interesting device for sending an instrument signal to the two channels of a stereo amplifier with speakers on opposite sides of the band. A kick wheel allowed the resolver to be rotated or even spun for amazing sounds.

Joined Jul 18, 2013
25,469
The syncro/selsyn certainly requires power,as does the the sine/cosine resolver.
Any (or most) motors that posses P.M. internally for field etc, will generate when rotated.
The typical Synchro does not have any PM, usually external field..

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#### shortbus

Joined Sep 30, 2009
9,441
Any (or most) motors that posses P.M. internally for field etc, will generate when rotated.
I agree wholeheartedly with that, but can't believe rotating a stepper motor by hand, step by step will cause a second one to move. If it wasn't so stinking hot I'd go to the attic of my shop to hunt up a couple of steppers to try it. But even the ground floor is over 100F the last few days.