Can anyone identify this type of motor? - Page 1
Forum section: electronics / general

author: MrAureliusR
author_rank: Unknown
timestamp: April 19, 2015, 10:15:14 pm
content: Hey everyone. A few weeks ago I passed by a home which had a huge box full of random electronics out front. Some of the stuff looked like it was from a home security system. Mixed in was this huge, very heavy motor, which I can't tell much about from the exterior, as I'm not really that knowledgeable when it comes to motors. I'm hoping someone here can answer a few questions about it!1) Is it AC or DC? (I know that might be impossible to tell for sure)2) What are the smaller control cables for?3) What was its likely purpose? (My guess is that it drove a belt of some kind)I almost think it's either from a washer, dryer, or garage door opener, but it doesn't seem big enough for those applications even though it's deceivingly heavy for the size (if you dropped it on your foot you would definitely break bones).Here's a bunch of pics:

author: Pillager
author_rank: Unknown
timestamp: April 20, 2015, 06:10:26 am
content: OK, looks like it's a brushed motor (the brushes could be those black screw sockets). If it's AC or DC, I couldn't say, the motor could be run on both.The other wires could be:-) NTC (2 wires)-) brake (2 wires)-) rotary encoder (2, 3 or 4 wires)Your best bet would be to start taking it apart. You can take off the black cover on the rear (the one with the 2 thin wires going in), and then the round aluminium plate underneath.Be careful, might be some mechanical assembly underneath, with springs that jump out and you might never find them again (speaking from experience here ;-).But go ahead and "take it apart". Or use a DC-psu on the RED (+) and BLUE (-) wires and try to get it to run. Just watch the current :-)

author: Gyro
author_rank: Super Contributor
timestamp: April 20, 2015, 10:22:36 am
content: I'd put my money on it being a high power permanent magnet DC servomotor. These often have 4 brushes.I'm mostly with Pillager on the other connections... Almost certainly an encoder (opto or more likely a tachogenerator) and probably a thermistor. Not sure about a brake though, don't think any of the other wires are thick enough and a servomotor would normally run closed loop so wouldn't need one. I doubt if there's any positional sensing as it seems to have a plain pulley.An easy way to tell for sure is to put a dvm across the spade terminals and spin it by hand - you should get healthy DC which reverses with direction. Shorting the spades together should make it pretty hard to turn.These motors tend to be able to put out surprisingly high torques at very low speeds (supply current permitting) which can yield some useful applications (coilwinder?). Try a few DC volts on it and see what happens.

author: TerraHertz
author_rank: Super Contributor
timestamp: April 20, 2015, 10:23:48 am
content: The pulley is not for a belt, but a cable that will wrap around it multiple times. That slot on the rim is for the cable end, which would have a tab of some sort crimped on. Is there a similar slot on the other side of the pulley?That it's driving a cable, shows the motor had to be reversible. Therefore it's a DC motor.Also the pulley didn't take many turns of cable, so the thing it moved didn't move very far.The black plastic cover almost certainly contains a bi-phase encoder disk, with an LED on one side (red and gray wires) and two photo transistors on the other side (the other 4 wires.)It was a motor in which absolute position was important.The aluminium vanes suggest the motor dissipated a lot of heat. So it was moving something either heavy, or that needed a lot of acceleration.I'm thinking something like a big old printer head driver. Maybe a daisy wheel printer?

author: amyk
author_rank: Super Contributor
timestamp: April 20, 2015, 01:48:48 pm
content: Googling the part number "40715-04" turns up what looks like a parts manual for a small aircraft... that and the Torx screws suggest maybe it's avionics-related?

author: MrAureliusR
author_rank: Unknown
timestamp: April 22, 2015, 01:15:09 am
content: Thanks for all the info guys!Touching the spades together doesn't make it any harder to turn. Spinning it really hard in one direction gives a couple hundred millivolts, in the other direction gives a couple hundred negative. So it does look like it's a DC motor.Quote from: TerraHertz on April 20, 2015, 10:23:48 amYes there is a slot on the other side as well. It's a funny looking beast. Here's a couple more close ups of where those wires connect. Four of them are soldered to copper traces which run off towards the center.

author: TerraHertz
author_rank: Super Contributor
timestamp: April 22, 2015, 01:41:43 am
content: OK, I was totally wrong about the sensor being optical. Now I guess that end structure is a like a printed motor, with two PCBs close together. The four wires go to traces on the stationary PCB, and the one next to it rotates with the motor. Signals from traces on that disk are coupled via the central transformer made of two half potcores.But which side is the excitation applied to? Is the end transformer supplying the drive, or transmitting the signals?I still think it's some bi-phase scheme, otherwise why not just two wires to each side?What they did has the advantage that there's no electronics, LEDs, etc to go wrong. Just coils and traces.

author: amyk
author_rank: Super Contributor
timestamp: April 22, 2015, 03:08:00 am
content: In keeping with the aviation theme, perhaps it's one of these?http://en.wikipedia.org/wiki/Resolver_(electrical)Anyone here familiar with small aircraft parts who can say whether such a pulley arrangement would be common?

author: Gyro
author_rank: Super Contributor
timestamp: April 22, 2015, 10:17:27 am
content: ... and it's not a tachogenerator eitherGiven the avionics connection, my bet would be on a synchro/resolver too. In the old days the rotor feed would have been via slip-rings but obviously things have moved on with the electromagnetic coupling. Excitation would be 400Hz (or possibly higher for this setup).In terms of decoding, I'm not sure how much effort you might want to put into actually trying to use this bit (unless for pure interest) as the will be both amplitude and phase to decode. Given that you have an exposed shaft available you could retro-fit whatever you want, be it slotted disk and led/opto, magnet and hall sensors / reed switch or nothing at all depending on what you decide to use it for.I'm a bit puzzled that you didn't see any increase in mechanical resistance when you shorted it. It might be worth taking a look at the state of the brushes, or it might just be the characteristics / operating voltage. If it had been me, I'd have had put a few volts on it by now!One thing's for sure your garage door opener hypothesis is out of the window by now - even if it might actually make rather a good one

author: Mashpriborintorg
author_rank: Regular Contributor
timestamp: April 22, 2015, 10:38:49 am
content: I am an aircraft parts collector, and as far as I can remember, I have never seen any Torx screw on any aircraft part... even on "modern" (post Y2K) parts. And the way the wires are soldered to that back aluminium disk do not look very "aircraft grade". The plugs do not seem very aircraft grade either.

author: Gyro
author_rank: Super Contributor
timestamp: April 22, 2015, 10:40:34 am
content: QuoteSorry, that wasn't quite the engineering spirit! If you've got a signal generator handy then it would be instructive to pump, say, 1kHz sine wave into the driving coil (the black bit) and scoping the other wires as you slowly turn the shaft.