Creating an electronic turn table

[Transition]

Hello everyone,

I have a project i need to start, but it requires that i set my product on top of a small surface that can spin in pre-defined increments (something like 45 degrees at a time). I'll need to be putting stuff that's ~20lbs on top of this to spin, so the motor needs to be relatively strong. Fast turning isn't required, i don't really mind if the thing spins ridiculously slow. Anyone have any ideas how i could make something turn in predefined increments like this? I wouldn't mind if i just had a knob to turn and there was a 1:1 knob to table turn ratio.

Thanks,

- RJ

[ElectroLawndart]

Transition,

You might try using a stepper motor geared to the turntable. You can move the turntable any amount based on the number of steps you turn the motor. It also has the added advantage of speed control.

Dart

[Transition]

Transition,

You might try using a stepper motor geared to the turntable. You can move the turntable any amount based on the number of steps you turn the motor. It also has the added advantage of speed control.

Dart

Thanks for the info Dart. Unfortuantely, i'm very un-educated in the world of electronics. Is there an 'easy' way to do this, or somewhere you think i might be able to purchase something as close to finished as possible?

If you look at the photo attached you'll kind of get an idea what i'm trying to do. You'll have a table w/ a small hole, then underneath a structure to support the shaft that will be going through the table. I'd like to be able to control the shaft by just adapting a stepper motor like you mentioned, to the bottom of the shaft.

[arx_n_sparx]

What you are looking for is called an indexing table. Try a Google search of that.

Brad

[Transition]

What you are looking for is called an indexing table. Try a Google search of that.

Brad


Hmm found lots of information on indexing tables, but their all super-expensive machines for CNC'ing. Looked on eBay even and they're several thousand dollars.

I'm trying to find a relatively inexpensive way to do this. $200 is probably even out of my range.

[lazy-b]

guys: you can just use an ordinary Servo Motor, and modify it to allowed continous rotation or may use a Stepper Motor, you would need a lots of torque if installed it at the center of the wheel, its better to install it at the circumference of the wheel.....you may use Gear but I guess its more simple just use a rubber wheel.....for getting the position, just use an optical encoderthis usually give 400 step per revolution....but this is very expensive, might just need a single micro switch, use for reference only, then just let the stepper motor count how many step have you been moved.

[LabDog]

I would try looking at servocity.com they have a good selection of shafts and sprockets for servos.
Paul

[vintage1]

Well forst off te mechanics of teh turntable are easy enough as people are tossing out old record players every day.

The issue of driving it is unclear.

I am not sure if ou need continuous rotation, or just +- 45 degrees..in the latter case a servo would work.

If you ned continuous, you either need a stepper motor, or some kind of mecahims that can read teh turntable position sio you can control the angle...but...is that what you want?

Or is it just a question of roughly moving a heavy object around? I mean a simple reversible motor could do that..

[gedaso]

How about a table driven by an electric motor (perhaps with a belt drive reducer) and some switches to stop it in chosen locations ? Switches could be either optical or microswitches with targets/contacts located around the perimeter of the table. You'd need to wire up a latching relay and a "restart" switch to drive the table on to the next position.

[Transition]

Well forst off te mechanics of teh turntable are easy enough as people are tossing out old record players every day.

The issue of driving it is unclear.

I am not sure if ou need continuous rotation, or just +- 45 degrees..in the latter case a servo would work.

If you ned continuous, you either need a stepper motor, or some kind of mecahims that can read teh turntable position sio you can control the angle...but...is that what you want?

Or is it just a question of roughly moving a heavy object around? I mean a simple reversible motor could do that..

I need increments like 45 degrees at a time, then stop. This table is going to be used for photography, but the key is there will be a cube/dome over the product so i can't see it, muchless touch it. So, i'll need to hit a switch, or turn a dial, then the table moves accordingly. This really needs to be as simple as possible. I just need a motor that can move at pre-defined increments (lets just say 45 degrees) then stops. Don't fuss about the mechanical details on how this will be adapted to rotate the shaft, i just need to figure out the electronic details.

[Majortomski]

Go to your local model railroad hobby shop and get an HO scale or bigger powered turntable. They are a variation on a Geneva mechanism, which turn a fixed amount incrementally from a constant rpm input

[Mr.RC-CAM]

The poor man's recipe: Take one Normally-Closed leaf actuated switch and mount it near the outside perimeter of the stationary base. Wire across it a nice looking Normally-Open push switch that the user can press. Connect this bundled switch assembly to your power source and motor. On the slow moving turntable, install eight pegs or cams, at 45 degree positions, that will interact with the NC leaf switch.

To start the turntable, just press the NO switch for a few moments. The motor will run until a peg hits a switch. The process will repeat if you press the NO switch.

[Dan Baldwin]

If I had to do this, I would probably go with a stepper motor driven by a PIC. I would calculate how many steps would be necessary to rotate the table 45 degrees, and have the PIC put out that many steps whenever a button was pressed, or based on time, or whatever you need. I use unipolar 4 phase steppers because they can be driven by 4 power transistors intstead of 8 for a bipolar stepper, and all 4 transisors can be driven directly from the PIC without voltage translation.

A DC motor and limit switches would be easier to implement.

Dan

[Acetronics]

Hi,transition ...

A simple Idea : It exists such rotating devices at your TV shop !!! : ask for rotary bases for Sat antennas ... knob or IR Remote to control it.

An example : www.CONRAD.fr choose 28 49 71 - 82 or 06 20 60 - 82 as a ref ( upper left of the screen )

Direct link : http://www2.produktinfo.conrad.com/cgi-bin/dlc/dlc.cgi?art=062060&ins=62&lang=EN

Alain

[Radiofly]

The antenna rotary drive might be a great suggestion. However, from what you've described, I don't see why you even need a motor. Just get a Lazy Susan turntable from Home Depot, place any circular platform on it (Eg., a circular cut piece of 3/8" MDF or plywood), mark the edge in 45 degree or whatever increments and turn it by hand. If the entire turntable assembly is covered, then just put any pulley under it, another pulley (same diameter for 1:1) some distance away and connect by a string, belt, brocoli tie strap, whatever. Mark the outside pulley in 45 degree increments and give it a whirl.