10 wires stepper. How to use it?

[claude]

Hello,

I recently found a BERGER LAHR motor that has 10 wires out of it. It has double axes and so far I managed to identify 5 pairs of wires that seem to bring out a max output of about 3.2V at ~200mA each. No common wires seems to exist between these 10 wires. The motor is rated 5.2V at 1A, and it's 0.72 degrees.

Sorry for not being able to post any photos but my home connection is down right now. Perhaps i'll be able to post them in a few days.

My question is how should I wire this fellow? If someone can show me some sort of scheme I can use it would be great. Thanks.

Claude

[maker of toys]

I think you'll find that experience here has not been favorable to stepper motors as gens.  The magnets tend to be weak, and the windings are optimized for low current draw, hence low current OUT. . . and low effieciency.  Their cogging tends to make them hard to start, too.  

(As you might have guessed, my experiment with steppers was not a success; I never got to the point of putting blades on it. . . .)

that said, we'll need to know what output voltage you want before we can help wire it to (maybe) get that voltage.

[claude]

Yes, I know it won't be a great gen. All I'm hoping is to succeed in charging a small SLA batery rated at 6V 4Ah, for emergency lighting. Perhaps I will be able to do that with this one. My goal I guess should be 6-7 Volts at 0.5-1 Ah.

I need to know why are there 10 wires (never saw that many in a stepper) and what should I use (bridge rectifiers or diodes) and how to wire it. Thank you for your input, maker of toys.

[ghurd]

My first guess is it has 4 coils and a tach.

Test each pair of wires for ohms. The pair that tests different is the tach. Ignore it.

That leaves 4 pairs, and 4 coils. It is an 8 wire motor.

Now it gets fun. Choose a pair (A) to connect to all 3 (B, C, D) others and test voltage output into a  500 or 1000 ohm 1 watt resistor. Then switch around the ends of B, C, and D.

There are 2 matching pairs, say A and B. And C and D.

A matching pair connected in series will have the highest voltage. If one coil is reversed, the voltage will be near 0V.

Then there are 2 seperate generators in the motor, and they need rectified seperately.

Rectified to DC will be about 7.9VDC open circuit.  The amps will be very low.

G-

[claude]

Thanks ghurd!

I managed to make some photos of the motor. Sorry for the quality, it's a webcam but still.. Maybe it's useful to see what is all about. And wether I'll manage to charge a 6V 4.0Ah SLA battery with this one.

[ghurd]

Looks like a fairly standard heavy duty stepper.

The numbers look OK.

Sorry. Steppers are a shot in the dark.

The only way I know to find out if it'll work is try it like above.

Different brands and models with the same specs are totally different for outputs.

The output numbers you gave are a little vague, but it sounds maginal on the voltage.

I would full wave rectify it, with matching coils in series, and try it into a battery at around 300 RPMs.  I would call 100ma total into a battery good.

Might be a little to gain using 8 Schottky diodes to make 2 of your own rectifiers.

Part 1N5819 40PIV 1A.

If it doesn't work with full wave rectification, I would find another motor. Maybe 8 to 12V.

G-

[claude]

I just measured the resistance of the 5 pairs. They are all exactly the same, 3.3 Ohms.! How about that? No tach wires anywhere...

I connected one pair to a full bridge rectifier and got at 400 rpm the following readings (short-circuited): 2.2v at 80mA. I then random picked another pair and connected (in series) with this one and hooked it to the same full bridge rectifier. The readings doubled. Should I connect all the pairs in series and just rectify the final wires? There has to be a way to do that. I will then hopefully gather something like 11V at 400mA which would be great.

[ghurd]

Thats new to me. Never saw a 5 coil stepper. Did you buy it?

Sounds like you got lucky, picking the proper coils to connect the right way.

Seriesing all the coils will have things well out of phase, fighting each other. Not good.

Seriesing in phase coils is good for getting the voltage higher, not the current. It needed more voltage to charge a 6V battery.

Short circuit current does not have a voltage reading, that 2.2V is probably diode losses.

Short circuit is the most amps that can be gotten. If you need 2 coils to pass 6V, then total short circuit is 160ma (2 pairs of 2 coils). It will be far less into a battery.

Thinking out loud...

If it has 5 coils evenly spaced, it may be possible to wire it 5 phase star?  Lots of trial and error I expect. Peak voltage would be a little less. Could be interesting.

Did some googling, it is 5 phase. I don't think I would change much of what I said for you.

But I would have a go at 5 phase star, just for kicks.

G-

[claude]

Yes, I think too it's a five phase stepper. I'm interested in connecting it as a 5 phase star but I don't know how. The stepper was disassembled from an old Linotronic 300, a film imagesetter. It was responsible for film transportation so I guess it's high-torque or something. Anyway, I think i'll use diodes for all five pairs and paralell them for maximum amps. The problem is I don't know how many diodes should I use. 5? 10? A scheme for this or for 5 phase star would be great. Thanks.

[ghurd]

"paralell them for maximum amps"

The volts will not be high enough.

"A scheme for this or for 5 phase star would be great"

Add 2 legs to the link's star diagram.

http://www.fieldlines.com/story/2003/9/11/84741/6758

[claude]

Hello Ghurd, it's been a while. Today I finnaly got my stuff together to apply your suggestion. The motor is 5-phase so star configuration should be used. Easier to said than done. I identified the pairs and then connected one at the time to another one permanently checking the AC output when spun by hand. I figured the wrong connection should return null results, and I was right. Three hours later I managed to get the 5 output wires. Got 3 full bridge rectifiers and a 47uF cap on a veroboard along with 5 PCB connectors. As things began to get together I was increasingly impatient and when I finnaly connected the multimeter to the output wires I started turning it with a hand drill.

My drill doesn't have precise rotation speeds so it was all on me. At minimum speed (I estimate 150-200 rpm) I got 10-12 Volts and 0.250 Amps shorted. At about 300 rpm the voltage was 46 (!) while the amps stopped at 0.5A. Man, that was a joy! Worked like a charm. I'll make a mill out of it. It should be able to charge a 12 Volts SLA, isn't it?

Anyway, just wanted to thank you for your advice. It's been helpful.

Claude

[ghurd]

My drill doesn't have precise rotation speeds either!

But if you are getting 10~12V open and 0.25A shorted, it should do a tiny bit of charging at 12V.

Remember short blades turn very fast, and they must turn very fast before POWER is taken from the blades.

And 200 RPM is very slow for that much power.  Fast small diameter blades will be better.

Try PVC blades at 0,5 meter diameter.  It will not be great, but it WILL work.

That number is just a very bad guess, but it is what I would try next.

Then you can try better blades.

Do not make the mistake of trying to make power at very low wind speeds.  I did that. It did not work.

It is very nice to hear how things are going!  I often wonder.

Thank You!

G-