Motion control for a rotating a cylinder

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Discussion Overview

The discussion centers on controlling the rotation of a horizontal cylinder using an electric motor, with a focus on achieving precise positioning and programming multiple start/stop times. The context includes mechanical and electrical considerations, as well as potential sensor solutions for accurate control.

Discussion Character

  • Technical explanation
  • Exploratory
  • Debate/contested

Main Points Raised

  • Mark seeks a method to control a cylinder's rotation with a 1hp motor, requiring it to return to the same position after each cycle.
  • Some participants question the accuracy needed for stopping at 360 degrees, considering the motor's momentum and the gear reduction ratio.
  • There is a suggestion to use an adjustable sensor that stops the motor slightly before reaching 360 degrees to account for momentum.
  • Bob proposes using a retro-reflector and photo-detector or a micro-switch for stopping the rotation, noting that a DC motor could provide better accuracy than an induction motor.
  • Mark expresses interest in the micro-switch idea due to its robustness in harsh conditions, asking for suppliers of necessary components.
  • Bob mentions that while microswitches are available, they may require a relay or contactor to handle the motor's power needs.

Areas of Agreement / Disagreement

Participants generally agree on the need for accurate positioning and the potential use of sensors, but there are differing opinions on the best approach and components to use. The discussion remains unresolved regarding the optimal solution for Mark's requirements.

Contextual Notes

There are limitations regarding the assumptions about the motor's performance, the effectiveness of different sensor types, and the specific requirements for the relay or contactor needed for the motor.

Whynotreuse
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Hi, I am an inventor with mechanical expertise but I am a novice with electrical controls. I want to control the rotation of a horizontal cylinder so it rotates 360 degrees, returning to the same start/stop position each cycle. The cylinder is being driven by a 1hp 110v electric motor, at a rate of one revolution every 124+- seconds. The solution should also include a means to program 1 to 6 start/stop times on a 24 hour basis. I imagine some sort of angle position sensor is available. I would appreciate any thoughts.

Mark
 
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Welcome to PF Whynotreuse.
I am assuming you are using some gear reduction between the motor and cylinder? I would think the momentum of a 1hp motor would make it difficult to get it to stop right at 360 degrees. How accurate do you need to be?
 
dlgoff said:
Welcome to PF Whynotreuse.
I am assuming you are using some gear reduction between the motor and cylinder? I would think the momentum of a 1hp motor would make it difficult to get it to stop right at 360 degrees. How accurate do you need to be?

Thank's for your reply.
It has to be very accurate. I was thinking the momentum would be relatively constant (6o:1) reduction ratio. Therefore my thoughts would be an adjustible sensor which stops the cycle perhaps a degree or two before 360 degrees. This should allow for the (X) degrees of movement from momentum. The cylinder is driven by sprocket and chain with a tension device removing the slack. More data available should you need it.
 
You could put a retro-reflector and a photo-detector on the outside of the cylinder, or a small hole in the cylinder with a light behind it, or a micro-switch, to stop rotation every 360 degrees. After a pause, you could have a timer that starts the motor again. You could get very accurate positioning if you used a dc motor rather than induction, but they are more expensive.

I have (in my hand) an isolated single phase solid state switch that is rated at 120 V, 25A that I paid ~$10 for about a year ago. I don't know how good it is for inductive loads.
Bob S
 
Last edited:
Very helpful. I like the idea of a micro-switch since this device operates under harsh conditions and a photo sensor may get dirty. Any idea who supplies the kit necessary to get this done?

Thanks

Mark
 
Whynotreuse said:
Very helpful. I like the idea of a micro-switch since this device operates under harsh conditions and a photo sensor may get dirty. Any idea who supplies the kit necessary to get this done?
Some industrial supply hardware stores have microswitches, but they can drive only an amp or two. So you will also need a relay or contactor that can drive the 1 HP motor.
Bob S
 

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