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I do like mystery eBay control modules, so I got one of these actuators for us to explore.
This unit is intended for Chinese 220V, but does operate on 110V too, but at much lower power (1W). It still has decent torque for some applications at the lower voltage.
Its purpose is to rotate a plate (damper) inside a duct to select between full airflow or nearly none. There's no intermediate position with this unit - just on and off, and there's also no feedback to show it has operated successfully other than the actual airflow happening.
I guess this could also control water valves and many other devices that use a rotation of 90 degrees. As with all cheap eBay industrial stuff, I regard this as suitable for hobby or prototyping use. I don't recommend using grey import items in commercial products.
The operation is incredibly simple. Just a very standard 4W geared synchronous motor and two end of travel switches. No fancy direction control. Just relying on the motor stalling and reversing at the end of its travel.
You can find these on eBay if you search for the keywords air damper actuator. Typical cost should be 10-15 pounds/dollars/euros.
Be aware that the open and close connections can backfeed to each other, so should always be treated as being live while experimenting.
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Let's take a look at another random control module from ebay - and this is an actuator for use with air ducts. The listings for these and there's lots of them tend to describe it as 220 volt actuator for air damper valve electric air duct motorized damper, wind uh. The information is very vague. I could not find data on this for the actual use of it, and the text is so small that the translation app just struggled a wee bit with actually even identifying what it was.

I used a zoomed up image and it gave me a line of text which was no help at all. It gave me a rough idea of the indication uh of what it did, but uh not really a decisive indication of what it does. So it has a connector on it and it has three connections. I opened it up in the end and worked it out.

It was actually a lot uh simpler than i was expecting. I was thinking it was going to be like one of our water control valves as the spring return motor, with a switch output and uh dc braking side. Our water valves are quite complex. That way.

This is not complex. This has a motor and two switches, so let me show you what this does first and then i'll power up show you operating then we'll open it up. So the idea of this is - and i shall zoom down this a little bit the if you have an air duct with air flowing through it, you can have a metal plate around metal plate in that duct that rotates to actually block or allow the air to Flow through and initially i was thinking well, it's going to take quite a lot of force if that's quite high pressure, but it's quite a clever idea, because if this is rotating that direction, you'd think this would be pushing back against the air. But in reality, while it is the other side is being pushed by the air, so it takes a lot of the pressure off it, and all that does is then rotate to that position there, and it means it can open and close quite easily, even with quite Strong airflows, that is more or less it the schematic for it i'll show you the schematic before you even show it working, because it's incredibly simple, there's a synchronous motor.

It's non-directional, it's one of those bi-directional ones that just stalls against the end of travel. I was thinking, there's going to be capacitors in here for direction. When i didn't detect, there was a spring-loaded return and what happens is that you've got a common going to the motor which is rated for watts? I guess they do these in other voltages. I'd expect them to do them in 120, volts 24 volts, but you've got a live for the open and alive for the close and and they close and they go via end of travel switches so that when the motor gets say, for instance, you power up say Open the motor will wind in that direction until it hits that switch and when it does so, it kills power to that.

It's worth mentioning, though, that during that time, this connection, which has not been used, is actually live. So i'm going to have to be careful while i play about with this, because uh the wire that is not connected will become live, but to get the change of direction. If you then disconnect the open and you connect the closed to actually move it to the other position, the motor it's stalled against that position. It can't go in that direction, so it runs in the other direction.

But if it's in the mid position it will actually run in a random direction. So supposing you want it to close, it will actually, and it was in the mid position. It might either go straight over to the closed position or it might go to the fully open position, hit the end of travel, limit, reverse and then come over until it hits that switch. And likewise, if you power both these, it will just go backwards and forwards continually because it's getting fed power all the time that is it.

It's not complicated. Let's demonstrate operating by stuffing live wires into connections so i'll stuff, a bit of blue tack down here, because this is a little accurate, a bit and i'll use this opener thing as an arrow, and i shall just stick that onto there. I shall bring in the cliff quick test, a piece of electrical test equipment and i shall put that wire in there. I don't know which wire this is i'll, just stuff it in and the other wire.

I shall um basically tuck out the way, so i'm not going to just put my my snips on like that and when i power it up, it's going to do something it hit the end of travel. Now it's going to that position. It will stop when it gets to the fully closed position. I guess that's it right now, if i connect the other connection - and i just place this out here, so i don't get zapped, it's gone in the wrong direction, initially stalled, and now it's going over to the other direction, and that is it: it's not that sophisticated.

Now we're sure what happens if you just connect both up and it does its little dance backwards and forwards so i'll stuff. This wire in here people always ask this is the cliff quick test? It's a really common. It's designed for test workshops. It's got a need indicator to show it's active, but it's got blade terminals in here and a fuse and when you open up it disconnects both the live and neutral.

But when you close it down, it makes connection so that these things can be tested. So this thing is now going to travel to its fully open position, and then it's just going to stall against the end of travel, reverse and go to. The other position makes a slight humming. Noise goes an opposite direction, doesn't really draw much more current.

It draws a consistent for watts when it's in motion, and that is it. Okay, we have seen it running. I shall disconnect the wires and we shall open up the chinese data sheet says it's rated for 50 000 cycles. It's made of plastic.

That casts doubt into my mind: let us unplug the connector. It's nice they've got a little phoenixy type connector here and pull off my bit of blue tack and arrow there. We go. That's uh that out that way, grab a screwdriver and open it up.

So there are four screws holding this closed, you'll notice. This is curved, i guess it seems quite a ungenerous curve. You i mean it seems quite a tight curve. You'd think it would actually be quite a soft curve for the whatever it's designed to clamp onto.

I don't know if that's just a perfectly engineered curve that matches many things or if it's got adapter plates for different ducts. I was expecting this plate to protrude a little bit further just for extra support. It seems to kick over at an odd angle when it reaches end of travel and the motor is stalling against the switches. I think it stalls against end stops next to the switches.

I don't think it puts strain on them directly. What we have inside is a fairly standard synchronous motor on two little spacers here. This thing: whatever core does it have in here? Can i get that off? It's jammed on quite tightly uh. Let's pull it off anyway.

Let's pull it off. Is it going to come off or it might be, really jammed on very tightly? I don't think it's screwed on hmm, maybe not! Oh there's a pin right, okay! Well, that's why that wasn't coming out in a hurry, they've put a locking pin in here. So yes right here, that's that then that'll be why my efforts were in vain, so putting this back together again, there are the two end of travel switches, the two motor connections, one of them is coming over to here, then a wire link is going over to The other side, the other one, is going round to the common connection. Then they've just used bits of tin, copper wire.

It looks a bit shonky uh, but they've used those to bridge to the switches, and that is it it's this two little switches and i've to what i said there aren't end stops. It really is actually just stalling hard against those uh switches. Shall we zoom down in this? Shall we power it up again? Yes, we shall and we'll see it stalling. I shall just grab the connector here.

I shall stuff this little connection. There's another thing. The connector here is literally just a it's a printed circuit board connector, but they've put it through the holes here and just sewed it in place. I suppose it works.

This is made very cheaply, as many very popular industrial components are let's zoom down in this. This is not going to be very bright. Is it let's brighten up a bit as well? Can we just saturate it a little bit just so? You can actually see that that arm right, tell you what let's get the neutral in and the two lives and we'll just power up, so it does its little dance again and we'll see it smashing those switches and pulp when it reaches the end of travel. Begin.

The destruction so the distortion there, the slight movement over, is just the plastic flex. I guess that's, probably the most destructive bit slight 50 hertz means hum off that. That's it. How simple is that it's all it needs to be, but there we go.

That is the i'll just zoom back out. This is going to be super saturated now, zoom out tame it down uh, but that is it the very common. These things are about 10 pounds, that'll, probably translate to 10 euros and 10, given how things normally work out, but the very common actuator for ear damper. I could see it having other applications, make a little 3d printed adapter a little cube in here and uh put it on various things that will let you actually put it to two positions, but quite neat.

Quite a smart little mechanism, super simple just how things should be.

12 thoughts on “Inside a cheap ebay rotary actuator”
  1. Avataaar/Circle Created with python_avatars Bunny Killer says:

    50K cycles?? if it operates 15-18 times a day it will last for 7 yrs without any "safety factor", so in reality it will last 3-4 yrs…

  2. Avataaar/Circle Created with python_avatars PWN NATION says:

    Your description of how it works sounds very similar to the way some mini-split fan vanes operate.

  3. Avataaar/Circle Created with python_avatars Richard Brian Smith says:

    Awesome Video big Clive

  4. Avataaar/Circle Created with python_avatars Red Overdrive, the unstoppable confused daltonic!! says:

    that really looks like a microwave plate rotator motor, also the speed seems the same… i bet you can copy the design and make one yourself with a microwave one, switches included…. btw, that motor is not only syncronous so mains is precise in frequency and it is as well, and it's also an high voltage generator, if you take a microwave oven one and rotate it by hand it can even light up small fluo tubes, i did once and used too much force and apparently a plastic gear inside lost a pair of teeth LOL, now it jumps

  5. Avataaar/Circle Created with python_avatars Graham Stevenson says:

    You need more insulation on those live feeds for use at 220/230/240 V ! Those soldered connections are rubbish too. You're meant to wrap the wire around the terminal before soldering.

  6. Avataaar/Circle Created with python_avatars Ray Ceeya says:

    I imagine the use case for this is some sort of electric door lock probably. I could be wrong.

  7. Avataaar/Circle Created with python_avatars Evan Jones says:

    Reminds me of the old PAR 36 pinspot scanners…

  8. Avataaar/Circle Created with python_avatars Little Bear says:

    Joe Biden is the worst thing to happen to America.

  9. Avataaar/Circle Created with python_avatars Tech Gorilla says:

    Without watching first – as I do – I will go out on a limb and wonder if these are like the actuators that ElectroBoom just replaced on his hot water heating system. I'll go watch now.

  10. Avataaar/Circle Created with python_avatars MrWitchblade says:

    a butterfly valve controller.
    great on an exhaust pipe for performance vehicles. (lol)

  11. Avataaar/Circle Created with python_avatars Hola! Cucumber Man says:

    Used to call the quick test (LEN) live earth natural
    Nice video Clive looks handy that does

  12. Avataaar/Circle Created with python_avatars Mark A says:

    Rather use a Honeywell controller for a real application because that one will conk out on the hottest or coldest day.

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