Looking to create a small mechanism that spins 180 degrees, stops, and then goes back to 0 degrees and repeats this constantly. Needs to be a small motor (similar to the link https://www.walmart.com/ip/1773915605?sid=1f0d9c60-e2cf-4aaf-b932-2984307d66bb) and the object it will spin is less than one pound. Any leads on the type motor I would need?

 

How do you intend to couple that motor to the spinning object? If you are planning on rotating the object at the same speed as the motor shaft, that is not going to work. The motor is 5000 RPM at full load, so it would rotate 180° in 6 msec.

I think a gear motor would be much better.

 

How do you intend to couple that motor to the spinning object? If you are planning on rotating the object at the same speed as the motor shaft, that is not going to work. The motor is 5000 RPM at full load, so it would rotate 180° in 6 msec.

I think a gear motor would be much better.

When I put the link of the motor that was just a reference for the size it would need to be to fit my project. I would like to go direct to motor shaft but wasn’t sure if someone knew or has used a motor similar to what I’m using. I do not want it to spin very quickly

 

Then you definitely need a gear motor. I used a 60 RPM gear motor like this to rotate a barbie doll on a music box as a prop and it worked beautifully. It is tiny but plenty powerful with that gearing.

To rotate 180° and stop you will need limit switches. This is a standard arrangement. What controls when it goes and when it returns?

 

Then you definitely need a gear motor. I used a 60 RPM gear motor like this to rotate a barbie doll on a music box as a prop and it worked beautifully. It is tiny but plenty powerful with that gearing.

To rotate 180° and stop you will need limit switches. This is a standard arrangement. What controls when it goes and when it returns?

Preferably it would go to 180, maybe pause 2 seconds, and then go back to 0, pause 2 seconds, and repeat

 

If you happen to be competent with Arduino (or any other microcontroller) that would be the route to go. If not, I am sure someone will suggest a digital logic solution.

 

If you happen to be competent with Arduino (or any other microcontroller) that would be the route to go. If not, I am sure someone will suggest a digital logic solution.

That’s what it’s looking like. I have never worked with Arduino or servo motors but it’s looking like I’m gonna learn soon

 

Have you considered one of the smaller automotive windshield wiper motors?
No electrical reversing needed just the stop position and pause timer of some kind.

 

Have you considered one of the smaller automotive windshield wiper motors?
No electrical reversing needed just the stop position and pause timer of some kind.

if I can find a motor that works like that. Some windshield wipers work on a crank rocker with the wipers attached to the rocker. I’m working with a lightweight mannequin head so that may make it go a touch too fast if I can’t think of a way to slow it down but otherwise that’s brilliant

 

What makes a lot more sense is a crank arrangement so that the motor and gear train runs constantly in the same direction, but the output turns back and forth with a sine-wave velocity profile. consider that is a much more natural and believable scheme. also a whole lot less complex. The wiper motor scheme would be vastly over powered for the application. Also, much to large.

 

if I can find a motor that works like that. Some windshield wipers work on a crank rocker with the wipers attached to the rocker. I’m working with a lightweight mannequin head so that may make it go a touch too fast if I can’t think of a way to slow it down but otherwise that’s brilliant

@Colebrx This one is a smaller version that may satisfy the size, the effort for your application would be minimal, so a simple series resister or lower voltage may work to slow it down.

 

What makes a lot more sense is a crank arrangement so that the motor and gear train runs constantly in the same direction, but the output turns back and forth with a sine-wave velocity profile.

Yes, I thought of that, but I am much better at electronics than mechanics, so I have a personal bias.

Also, it does not satisfy the pause requirement:

Preferably it would go to 180, maybe pause 2 seconds, and then go back to 0, pause 2 seconds, and repeat

Although someone good with mechanics might know how to do that.

A servo or stepper would give you a lot of flexibility with the speed profile, and would not need limit switches I could see going that way.

I could also see using a motor like the one the TS linked and a rim drive directly off the shaft or a belt and pulley arrangement. Many ways to do this.

 

OK, not a crank, although a crank with a bit of lost motion would do it quite well. But certainly a CAM, with some dwell included at each extreme position will do it. Getting a whole 180 degrees rotation would require a bit of complex linkage, though.
So at this point a programmable logic device with four time intervals will work: drive one way for T1, pause for T2, then drive the other way for T3, and pause for T4. Then loop back. Add stops at the end points and a series resistor to allow the motor to be stalled momentarily without damage.
Open loop control can work because position accuracy is not a huge requirement for this application.

 

Simple rotary to horizontal crank provides continuous motion in for any length required, just a momentary timer needed for the pause period? !!

 

Depending on the relative timing, the pause could also be created by adding a lost-motion segment to the linkage. OR, if a cam arrangement is used, a dwell section in the cam profile.
The cam I had manufactured for a project a while back was done with a CNC cam machine, based on a numerical description of the cam. THAT was really convenient and got it exactly correct the first time!