6 position Stepper Motor Air Pump HACK

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
Yesterday I bought a used CPAP machine. It works, but I'm not looking for a CPAP. I have a newer unit which I hardly use.

OK, the hack! It has an air pump in it. Turbo type with a three wire motor. The motor has three wires colored Black, Red and Yellow. The PCB it plugs into has some kind of (probably) MOSFET (or something similar) that runs the motor. Based on computed information received from three air pressure sensors it will run the motor at a programmed RPM. There is no discernible markings on the motor so I just did some experiments. Knowing the power supply delivers 12 VDC I took an old sulfated 12V SLA battery and did some poke testing. When I apply a voltage on various pins the motor snaps to given positions. Since I don't know what the manufacturer called the 12 oClock position I just picked one and went from there. Here's the results:
1683488444666.png
After testing I organized the positions into the above chart. The silk screen calls them Q16 through Q21 and each is marked 7N0607. There is a seventh; Q23 (same number) which is nearby but doesn't appear to be directly connected to the motor plug through L5, L6 and L7 (obviously a choke of some unknown value).

The desired result (what I'm after) is to power the motor directly using my own home brew motor switching circuit, but this is a good bit above my skill level. I can build but coming up with the design for this - - - I haven't a clue to start where. Obviously those transistors (I'm assuming due to Q labeling) are computer controlled which bases its output off of parameters and sensed airflow and pressure changes. Don't want to hack the board, at present I assume it could be put back together. It won't run continuous without some sort of reprogramming. I've been through all the settings and can't find anything that would allow me to just use it as a simple air pump.

Why you ask? I'm building a large pond and want to infuse air into the water column in some way or another as yet to be determined. Aquarium pumps are just too noisy and don't pump near enough air, so I'd like to use this small 12VDC Stepper Motor (I'm guessing it's a stepper) because it uses low power and amazingly can produce quite a bit of a push of air.

A chip of which I don't know powering similar rated transistors along with a variable sweep through the positions is what I think I want. I said I THINK I want. Obviously I'm open to alternative suggestions. And no, changing the motor but keeping the turbo pump is not an option. It's quite specialized. And for a buck - not a bad price to get something that can be repurposed.

Speaking of ponds, I'll be out back cleaning the 105 gallon pond I currently have. Later this year I'm planning on a 1000 gallon pond (approximately). As for filtration, I have that sorted out. Sort of anyway. The water pump is going to be 120VAC from either a dishwasher or a washing machine drain pump. Waterfalls and jets to circulate the water around the pond. And the air bubbler in the middle.

For those extra curious I'm planning a side basin that is filled from the waterfall but not a part of the pond. In that is going to be an ultrasonic mist unit and its mist is going to flow down a different path into the pond. It may be a year before I get that far. Assuming I'm even able to get the pond built in the first place. Back issues. Son-in-law will help, but I still want to be thoroughly involved in the project. Lots of concrete work along with sealing of the pond against leaks.
 
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Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
Thanks. Excellent suggestion. But here's where my lack of skill, experience and understanding come into play: The control wires - - - how would I power them? What signal source would I use? I have no experience with that module. Willing to learn though.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
The motor does not appear to be "Brushless" other than it likely has a permanent magnet spun to various locations via the input on the power lines. That module might work (probably) but I don't know that for sure. I can generate in excess of 7VAC when I force blow into the turbine. More of a 3 phase motor than a brushless motor. Can you spin a brushless and get an output? My thinking is that you can't.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
Well, I'm going outside now. Will be back later this evening to see what others are saying.
Thanks all.
 

geekoftheweek

Joined Oct 6, 2013
1,180
Thanks. Excellent suggestion. But here's where my lack of skill, experience and understanding come into play: The control wires - - - how would I power them? What signal source would I use? I have no experience with that module. Willing to learn though.
Unfortunately I don't have any experience with them myself just yet. Actually I think this particular one may be designed to be used with a potentiometer. I can't say for sure as they always seem to have ultra vague descriptions.

The motor does not appear to be "Brushless" other than it likely has a permanent magnet spun to various locations via the input on the power lines. That module might work (probably) but I don't know that for sure. I can generate in excess of 7VAC when I force blow into the turbine. More of a 3 phase motor than a brushless motor. Can you spin a brushless and get an output? My thinking is that you can't.
As far as I know a brushless motor is essentially the same as a three phase motor and works the same as far as power, but not exactly the same in physical design (if that makes any sense). They work on the same principles, but physically they are different. I'm guessing the permanent magnet vs induction is a big part of the differences.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
Again, I speak from ignorance, but I seem to think a brushless motor can be something with a circuit board in the motor that commutates switching to the motor to cause it to spin. Things like hard disk drives, maybe computer fans and a few others. I have a pump from a dishwasher that definitely has a circuit board in it and will not generate any power if spun mechanically.
 

geekoftheweek

Joined Oct 6, 2013
1,180
I see where you are going. If the controller is on the motor itself it won't produce a voltage when spun by hand. It will be dissipated by the controller through EMF clamping circuits to protect the controller. The controller in the link would essentially be built in to the motor itself.

Since in your case the motor and controller are separate you don't have the clamping action and are able to measure a voltage.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
YouTube - that wonderful place where you can learn how to build free energy devices that don't work, electronic projects that are ill-advised, and a whole host of other issues.

Please have a look at this and tell me if this is serious or is something I never want to ever try. Remember, my goal is to build a fish pond using these types of motors (3 phase) and need to power them. I don't want to start coding and making all kinds of things to go along with it. BUT I want it to last. Something that is going to filter the pond reliably for a long time before some unknown issue may arise.


I have an old dishwasher three phase motor to be used to filter the water, which I can not figure out how to run using the existing driver board inside the motor. So external is probably the only way I'm going to get it going. This thread initially started with the air pump hack, which I still want, but still don't know any other way to run other than what the video seems to suggest.

IS IT A GOOD IDEA OR BAD?
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
If it runs my motors, as long as it pumps water through the filter and runs the aerator pump, I'd be happy. That is IF it's "Reliable".
 

Jon Chandler

Joined Jun 12, 2008
980
Great Scot on YouTube tears to spreads a similar circuit and shows how to create a "real" one.

I do however strongly question your belief that the CPAP uses a stepper motor.
 

nsaspook

Joined Aug 27, 2009
12,743
YouTube - that wonderful place where you can learn how to build free energy devices that don't work, electronic projects that are ill-advised, and a whole host of other issues.

Please have a look at this and tell me if this is serious or is something I never want to ever try. Remember, my goal is to build a fish pond using these types of motors (3 phase) and need to power them. I don't want to start coding and making all kinds of things to go along with it. BUT I want it to last. Something that is going to filter the pond reliably for a long time before some unknown issue may arise.


I have an old dishwasher three phase motor to be used to filter the water, which I can not figure out how to run using the existing driver board inside the motor. So external is probably the only way I'm going to get it going. This thread initially started with the air pump hack, which I still want, but still don't know any other way to run other than what the video seems to suggest.

IS IT A GOOD IDEA OR BAD?
Bad, as in bad hack. You need a star 4 wire motor for it to have a chance to work correctly. Most common motors are three wire but some can be converted by hacking the coils.
1683589094843.png

Just buy a cheap controller for 3/4 wire motors.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
I do however strongly question your belief that the CPAP uses a stepper motor.
Please keep in mind that my expertise on motors is as extensive as those little DC motors that have a permanent magnet surrounding three coils and a commutator and brushes. As for AC motors, barely understand how a Shade Pole motor works. Universal motors have stator and armature coils along with commutators. In other words, I'm greatly limited when it comes to specialty motors.

This CPAP motor has three wires. When you power two of the three wires the armature swings to a given spot every time. Change polarity and it swings to a different place. Select two other wires and you get a whole new set of positions. So on and so on. I DO know what a stepper motor is. If you rotate the armature by hand it has very definite positions where it stops. Switching from one position to the next is something I don't know how it's achieved. I only know it works. You can tell a stepper motor to move five steps forward (or reverse, or any other number of steps). This CPAP motor does not snap to definite positions. Well, kind of, sort of, but if I called it a stepper motor I probably mis-spoke.
You need a star 4 wire motor for it to have a chance to work correctly. Most common motors are three wire but some can be converted by hacking the coils.
I have access to only three wires. If the motor is star wound I have no way of reaching the star point. The motor is completely enclosed in a plastic body and has two turbofans, one on each end. No way to check for a star (fourth) point without breaking the unit apart. I don't want to do that. All I know for sure is that a CPAP is good at forcing air into your lungs at some preset pressure, depending on the settings the CPAP machine computer has selected. MY most common setting has historically been 10cmH2O. But I've seen settings where it can be pushed up to 20cmH2O. I don't even know to what depth this motor will push air down to. This whole project might be a bust. But to find out I need to get that motor running at its max (without damaging it).
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
Just had a look at some numbers. 20cmH2O is a depth of 7 7/8". Seems like it might not work for what I want after all. Still, I want to pursue the project.

I've alluded to another motor, a 12V water pump from a dishwasher. That one IS a star wound motor. I do have access to the star point. This one I sincerely hope to use for the filtration system. ([edit] it may be a 24V motor)
1683642704502.png1683642514958.png
 
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Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,757
Coil resistance on the CPAP motor:
R > B = 5.1Ω
B > Y = 5.1Ω
Y > R = 4.9Ω

After extreme magnification I can not see any sign of a star point construction. This is not to say it isn't star point, just saying there's no way to tell for sure.
 
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