Motor overload automatic reverse- please help spec/identify 2

[salukikev]

Hello,
I am working on a project that would benefit from a motor that automatically reverses direction upon overload or stall. An example of this type is attached. In the example, a novelty Christmas ornament "animator" plugs into a light strand socket, and drives a winch. The winch: 1. Pulls the cord in 2. The hook stops at the enclosure 3.The motor reverses and lowers the hook again. This cycle repeats as long as the motor is powered.

I'd like to find a scaled up version of this, but more importantly, I'd like some terms to indicate this particular motor type or feature for specification and research.
Thanks for any help!
-k

 

[Skogsgurra]

What power range? What suply voltage is available? I would google +overcurrent +reversing and then refine the search from there.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[salukikev]

I can match the power range to the motor, its more a general question of type with this post. You could say 30 watts for the purpose of this question.
I did google using those and similar terms, but so far haven't found a great specification or search term matching a motor that operates this way.
I'm more looking for a motor intended to operate throughout its lifespan, rather than one with an emergency shut off or reverse system. I'd also like to avoid a micro controller or current sensing PCB if possible (as in the example, there is no PCB involved- it seems that an overload simply causes a phase shift and consequent reversing of the motor).

 

[waross]

There are small motors made with two identical windings and an internal capacitor. the windings are connected at one end and bridged by the capacitor at the other end. Three wires are brought out. One is common and the other two come from the capacitor-winding connections. When power is applied to the common and one other wire the motor turns. When the other wire is energized the motor turns the opposite way.
Mount this motor on a reaction plate, restrained by a spring and two position detent. When the motor torque exceeds the setting and the reaction plate jumps to the other detent position, a double through switch may be operated by the action to energize the other winding and run the motor the other way.

Bill
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"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

That's a nice trick, Bill! Easy to implement and easy to understand.

There are elctronic systems that do the same thing - or electromechanical systems. If this is a volume application, you better look for a consulting engineer that can design it for you. That way, you can optimize every aspect. For a one-off or low volume application, I recommend Bill's approach.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[salukikev]

Do you think that is how this example motor works? I love the apparent simplicity of the design event though I don't understand fully how it operates. Keep in mind that this is an AC (light strand) powered motor, not a DC where you can simply reverse polarity.
I tried to get a closer macro pic (attached) to illustrate the simplicity. Looks like a simply a coil and a free floating permanent magnet. I'm not sure if you can see from the pic, but there is a tab attached to the radial magnet, and there is a free floating pinion with a corresponding tab. This allows the magnet to rotate about 350deg without contacting the gear tab which is driven by the magnet tab.

My thought is that because this is an AC motor, there is a phase shift that can somehow occur and allow the drive direction to change when stalled. It could be there is an internal mechanism/capacitor as you propose but from what I can see there is not.
Thanks for any further ideas!
-k

 

[salukikev]

Just a follow up to this thread: I found another source for a replacement sample of this motor, ordered and received it today. I am delighted to see a patent cited. Here this particular motor is described in detail:

http://www.google.com/patents?id=8ZMYAAAAEBAJ

I don't believe the method of reversal was cited in this thread, and I guess its an unusual type to describe for sourcing. I am going to see what I can find with this discovery, but for the time being wanted to post this for reference. I still wonder if this arrangement can be scaled up and/or found in production quantities.

Thanks!
-kevin