# Low RPM motor with 1 or 2 revolutions to stop



## gatz (Aug 31, 2021)

Looking for a small 110-120 v AC motor that is Low RPM and would start, then rotate only 1 or 2 revs then stop.
(1 rev would be probably be ideal)
By Low, I mean 1 to 4 rpm or in that range.
A simple push-button switch would initiate the cycle.
I'm trying to avoid latching relays and limit switches, but can go that way if need be.

I've looked on Surplus Center's site; not seeing any.
Anything out there ?
TIA
gatz


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## Firstram (Aug 31, 2021)

If the gear motor turns that slow you could use an adjustable timer relay, just pick your time range and voltage. 









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## projectnut (Aug 31, 2021)

You're probably going to need a gear reduction motor.  Merkle Korft makes several models with different speeds and different voltage requirements.  My Sheldon lathe uses one for part of the spindle speed change mechanism.  It's a fractional hp 120 volt ac motor with gear reduction that has an output of 1 rpm.

Here's a link to several Merkle Korft motors and reduction systems available on eBay:









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## Boswell (Aug 31, 2021)

how much power/torque do you need?  Could you just use a servo controlled by a simple microprocessor?


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## gatz (Aug 31, 2021)

The mechanism I want to make has to have a cycle that is constant;  1 revolution, then stop. (or possibly 2)
 An *adjustable *timer won't suffice.
As mentioned, the latching relay & limit switch may be the only way if the run/stop cycle is not part of the gear-motor itself.
It would be similar to a wiper motor on a car, however, there would only be 1 revolution......switch on, 1 rev, stop
I've made them before, but was trying to simplify things by finding a gear-motor with this feature built in


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## tq60 (Aug 31, 2021)

Somewhat easy with some simple relays.

If 1 remember gear motor then on part of the drive place a magnet.

Then a Reed switch to react to magnet.

Reed switch come in multiple flavors, normally open to normally closed with option to toggle as SPDT

use a latching relay to power motor and place Reed switch in the feedback loop that holds relay.

If you have normally closed Reed switch easy, if normally open you need another relay.

In detail, start button applies ground to coil of a DPDT with other side of coil to power (coil power)

One set of the 2 sets of contacts is for latch.

Connect common to ground and NO to same coil connection as the button.

Apply power and no action.

Push button and relay latches.

Pull power.

Now remove wire from NO terminal and attach to normally closed Reed switch.

Attach new wire from other side of Reed switch to NO terminal.

Apply power and push button and relay should latch.

Place magnet near Reed and relay should open.

Wire motor to other set of contacts.

If you use a DC motor you can add a BRAKE.

Add a 2P2T relay to the motor power lines.

The COIL of this relay is active when motor is running, so connect it to the relay above.

The C (common) go to the motor.

The NO connections go to motor power supply

The NC connections connect together.

When motor is told to run by latching relay the motor relay closes connecting motor to power 

When the shaft turns to where the magnet gets near the Reed it opens the holding loop and the latching relay releases.

This then releases the motor power relay.

The relay switches the motor from power to a short circuit so the coasting motor that now is a generator stops quickly.

Sent from my SM-G781V using Tapatalk


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## Alexander McGilton (Aug 31, 2021)

I'm curious of the application.
What comes to mind is the timing mechanism for older model public restroom hand dryers. Present ones simply have a timer circuit that allows for it only to be run for a set time. Older ones have a low speed and low torque motor the turns a paddle wheel to a micro switch, the heater and blower motor turns off when a paddle had come to off position of the switch. 

You may well get a replacment unit from a repair shop, study the design then scale up to your speed and torque requirements. 








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## RJSakowski (Aug 31, 2021)

You haven't specified the size of the motor,  Small could be anything from a Lego motor size to 1 hp.  

For a motor running only one or two rpm, this should be fairly easy.  How precise does your stop position need to be?  If precision is required, an escapement mechanism could be used..  

Does the motor have to be a.c.?  Windshield wiper motors are capable of a single rotation and the parking at the same position each time.  Presumably, you can even use the OEM control  electronics which has a one cycle then stop option. 12 vo;t power supplies are cheap and readily available.


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## pontiac428 (Aug 31, 2021)

Arduino plus variable reluctor positioning module equals very precise dial-a-just.  All depends on application, the big mystery!


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## Reddinr (Aug 31, 2021)

How about a stepper motor and a drive powered by AC?   Can run at a speed you need and start and stop +/- fractions of a degree.  Could work with or without gearing depending on the application.


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## MikeInOr (Aug 31, 2021)

Knowing what your application is might help us help you find the motor you are looking for?

My first thought is a gear motor with a round plate on the shaft with a notch taken out of it for the stop and a simple roller switch that opens when the roller on the switch falls into the notch.  Press a button and the motor turns engaging the roller switch to power the motor until the notch comes around again and the switch opens.  Wiring would be very simple.


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## pontiac428 (Aug 31, 2021)

How about a hand crank?   Squawk!  It's a living.


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## pdentrem (Aug 31, 2021)

Gear motors are common in robots etc. Check out robotshop.com
Pierre


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## Bi11Hudson (Sep 1, 2021)

I have a few motors salvaged from a hydraulic system. 120 volts, single phase. But they have been out in the barn for years(~20+), I don't know their condition. Maybe 1/4 HP, maybe less. The limitation is that they run one direction 320 degrees and stop. Then can only be run reversae 320 degrees. Came off a hydraulic valve that was remote control. Speed about what you're asking for, 1-2 RPM. Reversing through a single contact, the motor is wound for reversing specific service.

Email me if you're interested. Response might take a few days, I would have to find them. After I got motivated. . .

Bill Hudson
.


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