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Microwave Oven Carousel Drive Motor Reversing

05/07/2012 3:11 PM

I have a motor from an old microwave oven that was used to drive the microwave oven carousel. I want to use the motor (that happens to have just about the right rotational speed and torque) to drive an auger that will be used to provide feed to my fish pond. The problem is the motor alternates in rotational direction when the power is switched ON-OFF-ON... at least most of the time that happens. I'm powering the motor with a 16 volt transformer - it's a doorbell transformer. I want just one direction and I want to select which direction (CW or CCW). Any suggestions?

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Pathfinder Tags: microwave carousel motor
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#1

Re: Microwave oven carousel drive motor reversing?

05/07/2012 3:21 PM

See the 3 wires on it? On the side that has two, one of them is the Fwd, the other is Rev. If you only power one of them (and the other side), it will not change direction. In your microwave, they had a relay that changed possition every time you turned it off so the next time, it powered the other lead.

Side issue: At 16VAC on a motor designed for 21VAC, you are at 76% of design voltage, which means your motor will only provide 58% of it's design torque. It will also pull more current as it attempts to avoid slipping a pole (it is a synchronous motor), so most likely it will burn up relatively quick. If I were you I would get a 24V transformer and use a trimming pot to reduce it to what the motor is designed for.

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#2
In reply to #1

Re: Microwave oven carousel drive motor reversing?

05/07/2012 4:38 PM

JRaef - the yellow and white wires are connected together (in parallel) to one input of the motor. The motor reacts the same if I use both wires tied together, or just the yellow or white wire alone (along with the second input terminal-the other yellow wire). The motor has just two input terminals. I was intuitively aware of the voltage issue so I've been running the motor for the last 8 hours or so and the temperature rise has been ok and the torque is suitable for my purposes. If I end up using this motor it will likely be ON for less than 1 minute in 24 hours. Thanks for the reply, any other thoughts?

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#14
In reply to #1

Re: Microwave oven carousel drive motor reversing?

05/08/2012 4:54 AM

GA

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#3

Re: Microwave oven carousel drive motor reversing?

05/07/2012 4:39 PM

Grillmark Rotisserie Motor (BBQ-480940)

$15 online



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#4
In reply to #3

Re: Microwave oven carousel drive motor reversing?

05/07/2012 4:52 PM

SolarEagle - that's the kick I needed - guess what I re-discovered (fortunately in a plastic bag) in the cabinet below my 7 year old bbq. Thanks!

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#6
In reply to #3

Re: Microwave oven carousel drive motor reversing?

05/07/2012 4:58 PM

SolarEagle - Oops I guess I spoke too fast - just checked the Rotisserie motor and it does the same thing re changing direction when it is turned ON and OFF and ON. Back to the drawing board.

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#5

Re: Microwave Oven Carousel Drive Motor Reversing

05/07/2012 4:55 PM

The way those motors are designed, whatever direction they get going in they continue unless it stalls. If you stall it while it is running, it will reverse direction. You could build a mechanical ratchet type device to select the direction, although I don't know if it is worth it.

FYI the BBQ grill rotisserie motors do the same thing.

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#7
In reply to #5

Re: Microwave Oven Carousel Drive Motor Reversing

05/07/2012 5:02 PM

Thanks frankd20. Looks like I will have to go with the surplus dc gear head motor that I have on hand. Wanted to avoid dc power supply or battery but right now this seems to be the best option.

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#8
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Re: Microwave Oven Carousel Drive Motor Reversing

05/07/2012 5:27 PM

To give you a motor idea if you are buying something, I have a 24v ac motor that turns in one direction. I believe it is for an old clock, about the same size as your microwave motor. It has some sort of mechanical stop built in it, so even by hand you can only turn it in one direction. A search for timer motor should yeild some good results on ebay or elsewhere.

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#10
In reply to #8

Re: Microwave Oven Carousel Drive Motor Reversing

05/07/2012 7:04 PM

Right. I disassembled the timer motor out of a clothes washer. It had a little plastic ratchet device that only let the motor run one direction. Since these little motors don't have any starting winding, they're equally happy running either direction .

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#16
In reply to #5

Re: Microwave Oven Carousel Drive Motor Reversing

05/08/2012 3:40 PM

frankd20 - Stalled the motor multiple times today and found that your info is correct. I like this motor (size, mounting, power needed, shaft size, free) for the auto feeder application that I have in mind so now I want to try the ratcheting idea. Will post results if they seem worthwhile. Thanks.

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#18
In reply to #5

Re: Microwave Oven Carousel Drive Motor Reversing

05/18/2012 7:21 AM

Got the automatic fish feeder up and running now... ratcheting works just great. Here's a photo. Thanks for the help. (you can view a video at: http://youtu.be/A5dsESVhh1I )

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#9

Re: Microwave Oven Carousel Drive Motor Reversing

05/07/2012 6:19 PM

From memory these are permanent magnet motors, the direction will be determined from the last position it stops.I don't believe there is anything you can do to get a fixed direction.It does not always spin the opposit direction when it stops.

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#11

Re: Microwave Oven Carousel Drive Motor Reversing

05/08/2012 1:41 AM

I'm guessing that there is an internal capacitor that is bad because there are two wires and not three. A synchonous motor has 2 windings with a common tap. The two windings have an AC capacitor between them.

Power is applied to the common and an end of the capacitor depending on the direction.

The erratic behavior is a symptom of a bad, inadequate or missing capacitor. It could be internal because I can only see two wires to the motor.

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#15
In reply to #11

Re: Microwave Oven Carousel Drive Motor Reversing

05/08/2012 5:43 AM

KeepItSimpleStupid - Kind of think the motor itself might be operating normally as I've observed over the years (on several microwave ovens) that the rotation of the carousel reverses each time (or at least most times) when it is turned ON again. Up to now I thought that this action was intended to give better wave coverage for the food - now it seems that the change in direction is simply due to the type of motor selected (?)

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#12

Re: Microwave Oven Carousel Drive Motor Reversing

05/08/2012 2:04 AM

I believe the rotation depends on the which half of the ac cycle is when its applied to the motor. Therefor motor does not always reverse when power is supplied. You may be able to use a half wave rectifier and a little higher voltage source to run the motor in the direction you need. Since its only running for short time period.

I have never done this so I'm not sure of the outcome.

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#13

Re: Microwave Oven Carousel Drive Motor Reversing

05/08/2012 3:42 AM

here http://hurst-motors.com/permanentmagnetacsynchronous.html you have it explained. Both the voltage and the capacitance affect directional stability.

I've used these motors before.

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#17

Re: Microwave Oven Carousel Drive Motor Reversing

05/08/2012 3:48 PM

Intermatic manufactures mechanical timers (for lighting, pool pumps, water heaters, etc.), and they contain unidirectional motors with a reduction gear train combination. They sell replacement motors that come in common voltages, including 120 V at 60 Hz; no transformer required. See Grainger catalog items No. 1PNJ8, and 1PNK1. Electrical supply distributors should also have them in stock.

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Users who posted comments:

Andy Germany (1); bigg (1); eltech (1); frankd20 (2); JRaef (1); KeepItSimpleStupid (2); metalSmiths (1); SolarEagle (1); Thomas J. Becker (1); vgsdvawt (7)

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