Speed control for shaded pole projector motor
Posted 03 July 2005 - 06:30 AM
I need to vary the speed on my movie projector for converting film to video. How do I speed control a shaded pole motor? Is it as simple as using a "ceiling fan" type speed control (the wall switch replacement, rotary type) ?
Can I simply wire it into the motor wires (so not to effect the lamp voltage) ?
Any info would be greatly appreciated.
Posted 03 July 2005 - 06:47 PM
You can usually control the speed of a shaded pole motor by varying the voltage and a light dimmer type circuit will usually work.
The problem you may have, is the reduction in voltage just reduces the torque, it does not change the synchronous speed. You may find that the load torque is not constant and so the speed regulation could become a problem. In the case of a fan, the torque is continuous and reduces with the square of the speed, so the speed can be controlled by varying the torque (voltage control). In you projector, I expect that there will be changing torque loads and so you may find the speed reduction is not consistent. The only way is to try it!!
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