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b.r.b.
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Posted: 03 October 2008 at 2:12am | IP Logged Quote b.r.b.

Hi everyone - I'm going to build the mini mill to get my feet wet so I just found an old laser printer with a 24V 48 Step (7.5 degrees) stepping motor in it.

http://www.digchip.com/datasheets/parts/datasheet/304/M42SP- 5.php

Because the steps are so low - can I reasonably expect this to charge a 12V battery? I do plan on doubling the volts to 48 by using two full wave bridge rectifiers.

I'm very new to this and am excited to try this tiny one out - so if anyone can give me guidance - that would be great!

I'd like to have this motor charge a 12V battery that will be used to power a handful of white LED lights - so I can light up my barn. Is that doable with this thing?

I live on the coast of Maine - and get a lot of ocean wind - not sure how hard but enough to spin this thing, I think.

John


Edited by b.r.b. on 03 October 2008 at 2:36am



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KiwiJohn
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Posted: 03 October 2008 at 6:33am | IP Logged Quote KiwiJohn

There is only one way to be sure John! Of course we dont know how big your barn is or how much wind your get or how often you would have the light one, or... etc etc!

I suggest you go ahead and build the mini mill as one thing for sure, apart from the fun of it, you will know more at the end of the exercise.

You wont get the placard volts, at least not all the time, but there are various ways of arranging things to trade amps for volts.

So go ahead, build the mini mill and keep us informed of progress and I am sure there will be plenty of suggestions to help as you go along.

John

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b.r.b.
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Posted: 03 October 2008 at 6:48am | IP Logged Quote b.r.b.

John - thanks for the quick response!

You're right of course - and I do plan on doing it anyway!

I think the thing that concerns me the most is that the motor seems kind of stiff to turn. The holding torque is: 78.4mNĀ·m

I don't really know what that means, though and am wondering if someone here knows enough about that number to tell me if I'm going to need some big blades to turn this thing.


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KiwiJohn
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Posted: 03 October 2008 at 7:10am | IP Logged Quote KiwiJohn

As a simple test try turning the motor then short all the leads together and try again. If there is a considerable increase in difficulty with the leads shorted you have a good generator for a low impedance load, just what you need!

Big blades mean starting earlier in low winds but lower top RPM (I think). If you make big PVC blades they are quite easy to make into smaller blades though it is difficult to reverse this process!

Hold torque I presume refers to the motor's ability to resist rotation when it is energised.
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b.r.b.
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Posted: 04 October 2008 at 12:19am | IP Logged Quote b.r.b.

By shorting all the leads together do you mean just connect them to each other?

Yes, as far as I know, holding torque just means the amount of torque it takes to turn the motor from a standstill.

I made some really sh*tty blades last night - and ran a fan at high speed and couldn't get my motor to turn. My blades were made from a plastic bottle though so I don't think they were a good test - even for prototyping purposes.

I'll be sure to post pics when I get some PVC pipe and get the right size figured out!


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KiwiJohn
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Posted: 04 October 2008 at 4:29pm | IP Logged Quote KiwiJohn

Yes, just twist all the ends together, if that makes it very hard to turn you have a potentially effective generator.
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b.r.b.
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Posted: 05 October 2008 at 2:11pm | IP Logged Quote b.r.b.

Excellent. I tried that and it certainly feels harder to turn. I don't know enough about motors to say if it's "very hard to turn" but there's a definite increase in resistance.

I've been busy making the blades for this thing - I'll post some pics after I get them off my camera. The knob on the motor was way too small to drill holes for bolts through - so I had to wing it by using JB Weld and a large washer. I'm going to use that as my blade mount. Hopefully the cold weld epoxy will hold!



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deaftodd
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Posted: 15 April 2009 at 3:44pm | IP Logged Quote deaftodd

Hi, I have the same motor, too. Today was really windy and thought the exactly the same thing as BRB did. I am trying to find the wiring diagram so I can know which places I can add diodes.
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DaViD
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Posted: 16 April 2009 at 1:03am | IP Logged Quote DaViD

Hi b.r.b., I've used that motor with three blades each at 1 1/2 feet in length and it started in a 6 to 7 mph wind if that helps any

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gb237
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Posted: 31 August 2012 at 10:47am | IP Logged Quote gb237

Well, I'm a little late (4 years) to this party, but I've just taken apart an old Laserjet 4 and found the same motor. So I'm curious: how did the turbine perform in the end?
At the moment I'm more interested in the other motor in there, though. Assuming you had a Laserjet you might have found the same. After A LOT of searching, it turns out the main drive motor is a Nidec RH7-1171, 24v, 1.1 ohm. There's very little about the spec online, and I don't know much about them, but from what I can tell it's a 3-phase hybrid stepper motor. It's a really nice design, which lends itself to turning it into a VAWT with very little trouble. You could literally just stick a set of arms/fins to the top. The question is, how best to wire it for maximum output?
I can't open it up (three screws in the top just refuse to budge) but to me it looks like there are four inputs: three coils, which are all joined at one end. I've used an LED against the four inputs in all combinations, and it works in all (which supports that theory - in each case there's at least some coil between them). Like this: http://www.osm-steppermotor.co.uk/img/3-phase-nema-17-steppe r-motor-wiring.jpg
So, how to use that to best effect...?
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Downwind
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Posted: 01 September 2012 at 6:24pm | IP Logged Quote Downwind

There looks to be 2 types of wiring types for the motor you have, do your motor have 3 wires or more (how many wires)





The basic wiring for a generator will require 6 diodes to make a 3 phase rectifier.

Honestly i feel you will be fighting a loosing battle with that motor for a generator, due to the fact of its strong cogging effect, and is likely to not spin until there is a cyclone approaching.

Over all the power output might charge a couple of Nicad cells but will be next to useless.
That said and understood its still worth making a wind generator from it just to learn how hard it is to extract energy from the wind and make power with it, dont expect to disconnect from the grid anytime soon.

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Warpspeed
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Posted: 02 September 2012 at 2:09am | IP Logged Quote Warpspeed

One thing to be aware of.

It is normal practice to always connect three phase alternator windings in star connection.

The reason for this is that if the voltages generated are not three perfect sine waves, connecting the three windings in closed delta will result in circulating currents around the three windings. That could well waste power and heat up the windings all for no useful purpose.

You can test this for yourself by breaking into the closed delta connection at one point, and measuring the circulating current (if any) with a low impedance amp meter.
It may not matter, or it could be a significant problem, depending on what you have.

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