precision motorized turntable?

[seco93]

hey,

im a computer guy and an animator. right now i am trying to build something called a stroboscopic zoetrope, which basically is a turntable with models in different animated positions on it, and when the lights are strobed to match the timing of the table spin, the objects will move before your eyes. i need to be able to spin a table with a considerable weight at 30-40 rpm.

i really dont remember much about motors or anything from my high school physics classes. so far i think im going to get a DC motor and hook it up to a variable transformer so i can have control of the speed of the motor. and for the lights i was going to use a hall effect switch and magnets around the edge of the table to strobe the lights rather than relying on strobe lights.

first off, if there is anything wrong with what ive said, or you have better ideas, please let me know. next ive been looking online for some of these devices but i dont know what im looking for exactly. im not sure what i need to know about the power of the motor, the specs of the transformer or the hall effect switch. if anyone could point me in the right direction so i dont buy something that wont work or something unnecessary, this is out of pocket so id prefer to spend as little as possible for my first attempt. not only do i need to know what im looking for but also how this stuff can be hooked up to itself, assuming that i already have a working turntable device. looking at the motors and switches and stuff makes sense in theory but completely alludes me when it comes to putting it together.

any help is greatly appreciated. thank you

 

[zekeman]

The DC motor is OK for a cheap,open loop drive and a full wave rectified and filtered variable transformer( variac)output will work to drive the turntable. The motor has to be sized and geared down (pulleys are probably cheapest) enough to take the friction load plus enough to accelerate the mass within a reasonable time. You might try to buy a used turntable drive with more precision
I would use a proximity switch with appropriate bosses where you would have magnets for the pickup and amplify the signal to drive the strobe light.
Good luck .

 

[tygerdawg]

"precision" = "costs money"

How much are you willing to spend? If you have some reasonable funds, then you can get a lot of sophisticated motion control. Zekeman has a good response, but if you really need precision then you may put in a little engineering to better define your needs (rotational speeds, response times, masses, accelerations, etc.). Then this info may guide you into the kind of motion control you really need. It may lead you to simple syncrhonous motors, steppers, servo, and then the power transmission components (gears/belts) in order to move the part.

If not too sophisticated, then is quite likely you can get acceptable used equipment from the internet somewhere.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[SincoTC]

seco93

As you said "I'd prefer to spend as little as possible for my first attempt". Why not start off by experimenting with an old record deck. The motor and drive problems are already sorted and the range of RPM you mentioned fits neatly. So long as you maintain a reasonable balance and don't load it up too much, it should prove the concept and highlight any shortcomings without much investment in time or money. Stick with non-contact switches (opto or hall effect) operated my tiny magnets or slots in the rim, so there's no cyclic friction to interfere with the already rotation demanded by reasonable music reproduction.

Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK

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