Feasibility of F & P Motor @ 1 rp hour

Dear Ardunio Gurus

I'm hoping a brave soul might offer an opinion or alternate for a design concept I'm working on.

Moneys too tight to mention but fortunately I have some time.

I am a reasonable confident programmer
– (fools rush in) and have good basic electrical skills but I am not trained in electronics and struggle when things get too technical.
PC power supply 5 & 12 volt
Ardunio 5 volts
Ardunio can control an AC SSR to turn on 240 volt or a DC SSR can be used to switch on DC.

I'm involved with an amateur theatre group and have accidently volunteered to create a prop for a theatre production.

The prop involves the horizontal rotation of a mass with a diameter of about 2.8m
Weighing about 25kgs at about 1 rev per hour forwards then back. (No lifting just rotation.) So say 360 clockwise then 360 anticlockwise.

I did a similar job a couple of years ago using small geared AC motor rotating an arm that connected to the prop about 200 mm out from the centre of the prop.

Down side of this was
mechanical jams,
broken gear boxes,
not 360,
fairly expensive motor gearbox combo,
no way to vary the speed.

So I started thinking hmm . . stepper motor.

Then I got gifted a Fisher & Paykel Smart Drive Motor out of a washing machine.
The Smart Drive Motor is basically a 3 phase Brushless DC motor.
Check this

Moving on
Silicon Chip did an article
Converting The F&P SmartDrive for Use As A... Motor

and if you click on the pic in the bottom right of the page and scroll thru the pages you get a table titled
Six step commutation sequence with Hall Effect outputs.

Coil Input
A+B-
A+C-
B+C-
B+A-
C+A-
C+B-
And respective Hall Outputs
001
011
010
110
100
101

So the plan is to buy 6 DC SSR’s (not pretty but. . .) A+,A-,B+,B-,C+,C-

http://www.ebay.com.au/itm/Solid-State-Relay-SSR-DC-DC-10A-3-32VDC-5-220VDC-/300553670794?pt=AU_B_I_Electrical_Test_Equipment&hash=item45fa65108a

And an Ardunio Mega

http://www.ebay.com.au/itm/ATmega2560-16AU-Microcontroller-Board-USB-Cable-For-Arduino-mega-2560-Module-/400509180781?pt=AU_B_I_Electrical_Test_Equipment&hash=item5d40351b6d

–say about $80aus
Join 2 gifted PC power supplies in series to give 24 volts DC and write some code using the Hall outputs as inputs to the Ardunio and sequentially power up the SSR’s using PWM so it doesn’t snap 60 degrees.

My concerns go to
Smooth rotation.
Possibly of having to reconfigure standard wiring of the Smart Drive Stator coils if it doesn’t work standard.
But that shouldn’t be too hard.
Issues between the PWM frequency and the SSR’s
That is, maybe the standard PWM frequency from the Ardunio is too fast for the SSR’s.
But I figure I could probably run something slower in the Ardunio code it just needs to be fast enough & proportional across the coils.

Maybe a generic stepper motor kit would be a better way to go.
But I haven’t used stepper motors before and they look light at the right price or expensive as they get heavier.

Maybe I could use an Electronic Speed Controller instead of the 6 SSR’s
but I’m not sure what ESC would be appropriate and
I only want very slow rotation and
I note in the video with the RC ESC he found it reluctant to start the motor rotating with standard wiring on 48 volts.

Feel like I’m out on the edge here but I like the country.
I found from experience that it can be smart to seek wise and experienced council at this stage.
Is this a feasible plan given my constraints and resources ?
Is there a better – cheaper way to do it ?
I’m guessing most have left the room by now, but if anybody feels they can offer an opinion I would be grateful.

Thanks for sharing.
I’m not in a rush.
Henry

A clock has an hour hand that moves at the speed you want : one revolution per hour. That will be the speed controller. The hour hand is photographed by a camera. The image of the hour hand is analysed in software. The platform position is compared with the position of the hour hand. The platform is mounted on an air table so it is lifted up 0.3mm to reduce friction. Small fans propel the apparatus so it moves to match the clock control standard. A digital clock can also be substituted for the analog hour hand and camera. If the fans are too weak, small rocket engines can assist in moving the platform.

How much torque does your drive mechanism need to provide? If you're only rotating 25 Kgs and assuming it's mounted somewhere close to the CoM, this doesn't feel like a project that will require any great complexity or cost, and multiple SSRs and big mains voltage motors repurposed to work as stepper motors feels like overkill to me. (I suspect this is what AmbiLobe was hinting at, too.)

It may be hard to dismiss the gifted motor, but you should.
You can use a smaller motor, with a gear box, and use a motor control shield. Lot less expense. You may need to calibrate the timing, to get the 1 rmh, but that shouldn't be a problem.