Tiny linear stepper motor, not as good as it looks.

Buzby

Senior Member
Searching around for tiny motors, I found this listing : http://www.ebay.co.uk/itm/272511958008

When they arrived I discovered that the plastic 'nut' is not threaded, it just slides freely along the drive rod.

Closer inspection revealed that the 'nut' has a tiny hook, which looks as if it should hold some unspecified bit of stuff against the thread, thus providing the drive I was expecting.

Not too worried about my financial loss, but has anyone any ideas as how I could make these useful ?

Cheers,

Buzby
 

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techElder

Well-known member
I would say that that "nut" is both a "nut" and a clutch. The weight of something holds it on the screw threads enough for it to move with the turning threads. Of course, over time they would be a bit more locked in.
 

neiltechspec

Senior Member
Those are the sort of motors fitted inside CCTV / Camcorder lenses.

The little lug should be engaged with the thread, quite common for the edge of the lug
to either break off or wear out (particularly on the focus motor). I have investigated a few
faulty lenses and found this to be the cause.

So I would suggest they are manufacturer rejects.

Just my opinion of course.

Neil.
 

AllyCat

Senior Member
Hi,

When they arrived I discovered that the plastic 'nut' is not threaded, it just slides freely along the drive rod.
----
...has anyone any ideas as how I could make these useful ?
Yes, I found the same - the "nut" is so loose that I doubt if it's "broken", but another component part is required. I pushed a piece of 30 awg copper wire under the "hook" which locks the nut onto the shaft to see how it's rotating. But it will need something finer than that for the screw to move the nut along the 1mm diameter shaft.

Also, perhaps I should have realised that the "outrigger" arm carries the second motor bearing, so it can't be removed to use the shaft with a normal worm/pinion gear at the end. I have some ideas how to couple (rotary) motion from the motor, but I've found that theory doesn't always work with these little steppers, so I need to experiment first.

However, I do know how to drive them at a cost of 20 pence and two PICaxe pins ;) . I started a thread a few weeks ago here and will add to it when I've devised some reasonable hardware and software configurations. The easy-to-use board can drive at least two (perhaps 4 or more) of these steppers with coils in parallel, since each coil is around 24 ohms.

The way I propose to make (reliable) electrical connections is to glue the back of the foil "cable" onto the motor body with Araldite (epoxy resin) and when set, cut off the surplus foil and solder 30 awg wires directly onto the pins. This motor and the one in my link both have 20 steps per revolution. They seem to work "best" with both coils energised "continuously" (i.e. a current reversal in one of the coils for each step) but the heating at even 3 volts is probably too high for anything more than short periods of operation. They do rotate with individual (even separated) pulses to each coil but it depends how much output "power" (or torque) is needed.
___

I think these really tiny motors are mainly going to be useful for "indicator" type applications. But I still have high hopes of using two of the slightly larger (6 mm) version shown in my link above to drive my (proposed) "AA" (cell) line follower, using differential steering / sensors. The "chassis" is a piece of Vero/perfboard 21 holes by 6 (52 mm x 16 mm) carrying a (DIP) 14M2. Actually I believe an 08M2 might be sufficient, but I want to retain the option of using it as a test bed to carry a "camera" based around edmunds' linear optical sensor. ;)

Cheers, Alan.
 

Buzby

Senior Member
... Yes, I found the same - the "nut" is so loose that I doubt if it's "broken", but another component part is required.
That's what I thought as well, but at cost of 6p each I think I can withstand the financial loss this month.

So you too are building a miniature line follower ?

That edmunds has a lot to answer for :)

Cheers,

Buzby
 

stan74

Senior Member
Et moi :) If you use a sd card converter you can adapt those plastic connectors and solder leads to the adaptor. Not these tiny motors but maybe strip leds or membrane keypad.
 

oracacle

Senior Member
these look very similar to the motors used in cheap compact camera (minus linear drive) to operate the zoom and focus on the lens.
 

edmunds

Senior Member
Dear @Buzby,

I have not done any business with precisely the motors you have obtained. However, I can recommend these as working. It is only operational as a linear actuator and you should not remove the metal support as already pointed out this leaves the motor without axle support that is, of course, necessary.

Quickly browsing what is available now, I would suggest these for linear actuator function as there would already be a support for the slider and thus confidence the motor can overcome the friction of slider support and some mechanism to move.

Of course, if you are looking for a supply for series production, a well known auction site will not work. In that case I can recommend to look for a company called MINBEA.


Good luck,

Edmunds
 

ZOR

Senior Member
Did they come from a company called Lar Fing Ow Woud?

Edit: Sorry my poor sense of humour. I have bought many small steppers of ebay, either so tiny could not solder or mount, or get mechanically connected to shaft. There are lots of motors that good in photographs but often blown up size or toom small to get any idea what they are like until you get them. Lots of smiling faces in China
 

erco

Senior Member
This hoarder has learned that some Ebay gambles don't pay off. Rather than beat yourself up finding a problem for this "solution", I suggest you develop a develop a thick enough skin to toss that dollar item into the trash bin and walk away with a clean conscience. Saving it for a potential future opportunity is a losing proposition. Even if you do need it a year from now, you won't be able to find in the pile, and they will still be available on Ebay, probably for less!
 
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