Newbie making a treadmill windmill with questions

[MN Ben]

I am a green horn so please bare with me and help me learn.
So I picked up a treadmill and the motor reads....

Perminant magnet DC Motor
Model #B4CPM-o75T
Class B Insulation
CW rotation
Electrical rating @ 90vdc FF.1.0 AOM
40 HP treadmil duty
4200 rpms 5.4 amps

The blades make this motor turn counter cw. Is this an issue?
Does this motor output AC?
Do I need a bridge rectifier? I understand a rectifier keeps the current flowing in one direction. Does it also change the current from AC to DC?

I have a small hobby volt meter but only know the basics on using it.
These were the readouts when I spun the motor with my power drill.....counter clockwise
97 ACV
44 DCV

When I switched the volt meter to see how many amps it was putting out, there seemed to be a lot of drag on the motor. Is this considered "load"? The amps read about 4.7

Ben

[Flux]

The big problem is speed. If it reaches 90v at 4200 rpm then it will reach 9v at 420 rpm. To get cut in for a 12v battery you are looking at over 600 rpm.

Any blades capable of reaching that speed will be tiny and will only  produce significant power in high winds. Even fast 4 ft blades will need about 12 mph and I mean fast ( probably not the things you have or have looked at).

The anti clock rotation will not matter unless it relies on a screw thread keeping the blades on ( deadly).

Being dc you don't need a rectifier but you do need a series blocking diode to stop the thing from motoring.

Possibly a good learning project but don't expect much useful power. You would need a speed increasing drive and a larger prop to get much out of it on a normal wind site.

Flux

[tanner0441]

Hi

Plus if it is 5.4 amps it is only going to be rated at about 70 watts.

Brian

[snake21]

it will give you around 75 watts at 14.4v.try to find a permanent magnet motor with smaller rpm like 200-300.smaller rpm will start charging in lower winds.try to gear your motor if you want to use that same one.the ametek motors works best for a small system.i have an ametek 38vdc and im happy with the output.in normal winds,it give me around 3 amps and in high winds,it gives me around 6amps.small motors is a good start for a wind project.to get 75 watts,the motor will have to spin at around 4000 rpm which is impossible in normal winds without gearing.

[Isaiah]

divide the rpm's by the volts and this is volts per turn ,then multiply the figure by 15
 and that will give a rough idea on 12 volt cut in, or usable pwr.
2000 rpm  divided by 200 volts = 10x 15=150 rpm for cut in speed.
 keep your eye out for a ecm out of a commercial air conditioner and look for higher amps!
 Isaiah

[MN Ben]

Thank you guys. This is a cheep treadmill and I do not expect the motor to last long. I will look at gearing it as long as I can find some scrap stuff around to do that.

I would like to know what size of Diode to put in. Maybe there is one on the board that came w/ the treadmill. Do you see anything useful?

[Bruce S]

Thank you guys. This is a cheep treadmill and I do not expect the motor to last long. I will look at gearing it as long as I can find some scrap stuff around to do that.

I would like to know what size of Diode to put in. Maybe there is one on the board that came w/ the treadmill. Do you see anything useful?

(Attachment Link)

There's a whole bunch of useful stuff on there 
D10, D2 and the other one I can't quite make out but the same size. Also the big resistor R2 looks to be at least 1/2 watt .
If the treadmill is surely toast then harvesting parts off this board can reap you some goodies.
The Diode rating you can find by googling the number located on them.
If you're going the gearing route, you can go looking for an old kiddes battery powered rides. Most of these were geared down to nice and slow you can use it in reverse gearing to speed up the RPMs for this.
Depends on how handy with tools, but doable
Have fun!
Bruce S
PS> Don't be too tempted to use the DC motors out of the toy rides, they're usually 6Vdc and don't put out squat. I've tested a dozen and they're all better off as high torque solar movers.

[Flux]

Your motor rated at 5.4A will probably stand peaks of 10A

The big diodes D8,D9,D10 if I have the numbers right are 6A devices. It is not ideal to parallel them, but doing so will get you up to the rating the motor can stand and will be good enough for a trial.

Flux

[madlabs]

Ben,

Not long ago, I completed a mill from a similar, but a little better, motor from a treadmill. Like yours, I had to use short blades with a high TSR to get the RPM to be able to pull anything out of it. It needs 12mph + to get going and then doesn't make much power. It was an AWESOME project, I enjoyed doing it and building a 40' tower. However, it is a toy. It doesn't and can't make any real useful power. So, as long as you are in it for the fun of the project (which I was) then go for it and have fun. If you really want to make some power, go another route. The treadmill motors just aren't that great a starting point.

Just my .02

Jonathan

[whythehecknot]

I bought four similar to the one you have and had varying degrees of luck with them. Flux hit the nail on the head about the speed that these need, and the narrow thin blades that it takes to get that speed. And the biggest problem I had with mine is that they were too hard to start, that is they offered resistance when spun by hand and therefore no good for the thin two bladed prop that would have spun it fast enough to make 12 volts, but was unable to because it just couldnt get it going.

[MN Ben]

Thanks Guys.
This motor takes a good gust to get it spinning which means if I gear it, it will need even more. It just doesn't spin well with the fingers, maybe the drag from the brushes. I'm not all up on blades yet, but maybe I will put 4 of the thin pvc ones on the hub.

I will be using two of the larger black diodes. The markings on them are MS 6A4 on the opposite side is the number 2. Is sounds as if I will need to hook up two in a row.

This is a learning project.

[TomW]

"2 in a row" or in electronics speak "Series" may not be what you want. Almost certainly you want 2 side by side or in electronics speak "Parallel" .

Good Luck with it.

With gearing you could use longer blades to get the startup to work a bit better.

Many ways to defur a feline, you know.

Tom

[MN Ben]

Parallel, got it Thanks. I just watched a video on parallel, in that case, resistors.

[taylorp035]

Just as the other people have said, the "cut-in" rpm is a bit too high to have any practical value for charging.

4200 rpm / 90vdc = 46.6 rpm /volt.  --> about 600 rpm to start charging a 12v battery.  The blades would have to be too small, and then the windmill would never start spinning.

My treadmill motor was ~33 rpm / volts  --> ~400-450 rpm cut in.  The wind at my house was rarely high enough to hit 400 rpm.   For your next motor, search for one in the 15-20 rpm / volt range and the results will be much better.


Since you already have the motor, I would highly suggest to keep going with what you have and make some blades for ~ 4ft diameter.  Then watch it and read the voltage you get off if it.  Maybe you can charge some Nicd's at 4-6 volts.


Good luck!  Keep us updated.   

[MN Ben]

Thanks. I'll set it up to see whet I get out of it. The diameter is just over 4'.

I found the diode info from the above picture here...
http://www.datasheetcatalog.com/datasheets_pdf/6/A/4/6A4.shtml
MN Ben

[MN Ben]

It is up and flying! I need to add some guy wires. The wind speed is about 14 mph according to the school 12 miles east of me. The volts read 8 to 10 and the amps read 0.7 to 1.4.

http://youtu.be/hw8O2zRqlzg

I have yet to hook it to a battery as I have nothing to run 

Ben

[Bruce S]

It is up and flying! I need to add some guy wires. The wind speed is about 14 mph according to the school 12 miles east of me. The volts read 8 to 10 and the amps read 0.7 to 1.4.

I have yet to hook it to a battery as I have nothing to run 
Ben

Ben,
That's a nice setup, BUT tie a battery to that thing please, even a dead car battery!! Letting it fly unloaded is asking for trouble.
The very least is a burnt up motor. Worry about the output later.
IF NO battery short the wires together, put the wires across an old toaster or something 
Too much good work in it to see it smoke.
Cheers;
Bruce S

[ghurd]

Do Not confuse open circuit volts (Voc) times short circuit amps (Isc) with potential charging watts.
The dishonest/unknowledgeable sellers do that to sell crap.

Until the battery voltage is reached, and passed up, there are no charging amps.  0W.

Consider a bridge rectifier for the blocking diode.  Cheap, and easy to heat sink.
(change Ametec to treadmill motor)



"When I switched the volt meter to see how many amps it was putting out, there seemed to be a lot of drag on the motor. Is this considered "load"? "
No.  That is considered 'shorted'.  It is often a good way to stop the mill from all that drag, in some situations.
It is not a good idea with that type of motor.

You can make it work.  It will not be great, but it could work a bit.
Have a look at this,
http://www.fieldlines.com/board/index.php/topic,140404.html

Get the guys on it before it crashes.
Keep the output wires shorted together too.
G-

[MN Ben]

OK, I shorted the output wires.
I have two 6A diodes I removed from the treadmill board that I will use to block the current.

Ghurd,
I received your dump load in the mail and hope to put that together today.


Ben

[ghurd]

 

[Norm]

Ghurd.....if he had a capacitor collecting the current it would allow
the TM to spin faster....then have a brush and a commutator segment
that would connect to the battery that would allow the capacitor to
discharge to the battery each turn.
Would work with the right size capacitor/s ?
Norm.

[ghurd]

Norm,  I don't think there would be any gain.
The cap would not charge any higher than open circuit volts,
and it would not discharge lower than the battery volts.
G-

[MN Ben]

Newbie rule #1 tie down the mill.............. The 40+ gust along with the contstant 25+ winds just knocked it over. The base of the stand kicked out and the whole thing landed nicly on the ground. My wife just said it looked 'OK".

Next to understand......
I need to learn to make it furl (sp?) or apply a break system of some sort as I can see a county officer come up and want it stopped because I know the count requires a breaking system on windmills.


Charge Question......
Will my 12 volt battery only start to charge if my genny produces more than 12 volts? And with that, the battery is only getting the amount of amps my genny is producing above 12 volts, correct?

My neighboring town school is reporting winds of 20 mph with 28 as the high.
Just before it fell I recorded 18 dcv and 3 amps output from the genny.

Ben

[Madscientist267]

The 'shorting' currently is your brake.

You gotta get that thing tied down before something besides "nicely on the ground" is found in the description of the aftermath.  

As far as charging goes, yes, the mill will need to reach a Voc (open circuit voltage) that is higher than the battery's OTV (colloquially the same as Voc) PLUS the drop in the blocking diode(s).

So, if you have yer standard everyday silicon diode, there is a typical voltage drop of 0.6-0.9V (depending on current, usually "counted" as the nominal value, or about 0.7V) across the diode.

Let's assume your 12V (nominal) battery is resting at 12.6V and you need to charge it.

For this to happen, your genny needs to hit (approx.) 13.3V just to begin charging. But at that point, the current flow will be nil, because the genny+diode combination is only matching the battery's voltage.

To actually charge, the mill needs to increase speed from this point (called "cut-in").

This is where the limitations of the motor/blade combination will become apparent. A rotor that can spin fast enough to get above cut-in for your particular motor needs to be small, so that the centrifugal forces at the blade tips don't rip it apart at operating speeds. The problem with a smaller rotor is, it can't grab as much wind. Less wind to grab = less power to harvest.

Steve

EDIT - Question - What did you have it loaded with when you were measuring the 18V @ 3A?

[MN Ben]

The 'shorting' currently is your brake.

I had the two wires coming from the motor twisted together, the motor still spun. Are you saying the motor should not move when the wires are shorted?

EDIT - Question - What did you have it loaded with when you were measuring the 18V @ 3A?

Nothing, I un-shorted the wires to get the reading.

Thanks for your help steve.

Ben

[ghurd]

Shorting does not actually "stop" turbines, just slow them down to a crawl.
Treadmill motors, and many other PM DC motors, have high enough coil resistance so that shorting will not "stop" them from turning, and many will not noticably slow down.

The 18V and 3A are Voc (open circuit volts) and Isc (short circuit amps).  It does not mean 54W.
18V was at 0A, 18 x 0 = 0, so 0W.
3A was at 0V, 0 x 3 = 0, so 0W.

Rough guess?  Very very rough.

18/3= 6 ohm coil resistance.

Taking Steve's cut-in voltage up to 14.0V leads to:

18V - 14V = 4V

4V / 6 Ohms = 0.667A of charging current at that RPM.

However, being driven with wind at the time creates problems.
The 3A reading was measured under shorted conditions.  Meaning the RPM was lower because it was shorted (as far as the turbine could tell).
At a higher RPM, like totally unloaded such as a the Voc reading RPM, the amps would read higher.
Meaning the 3A and 18V happened at different RPM, which means the rough guess of 6 ohms for the coils is incorrect, and that makes the 0.667A of estimated charging current incorrect.

It would be better being tested when driven from a motor at a known RPM.
It is not easy or practicle to 'adjust' that type of motor.
About the only thing that can be done is to tinker with different blades and see what works best.
If you get the blades suited to it, it will work.

Ain't this fun?
G-

[MN Ben]

It is fun.

Rather than trying to modify this treadmill motor I will most likely start a new genny with a different motor or try one from a cloths washer. When that happens, I will post the new thread link here.

Ben

[ghurd]

"Rather than trying to modify this treadmill motor I will most likely start a new genny with a different motor or try one from a cloths washer."?

Unless the clothes washer motor is an F&P or simlar, the results will be bad.

[artv]

Hi Ben,
It seems like this post has come to an end .So I hope you don't mind a question.
G-Hurd.."the cap will not charge any higher than open circut volts"
Are there any exceptions to this rule??
My Voc is 20.6vdc on one phase, with my seconds connected I can charge the caps (two 56volt, 12,000uf paralelled) to 28volts.
When I hook up 3 lights (2 headlights , 1 tail-light) the volts read 9.4vdc, and 13.7vdc at the caps and the lights shining bright enough that they will melt any wires that are touching them and or start burning into the wood there laying on.
Just wondering if there is any known arrangement to exceed VOC.......Thanks ..artv

[ghurd]

Art,
I meant "will not charge a battery".

Look up 'KVL'.
Amps flow from the high voltage place to the low voltage place.
Crap doesn't flow up hill.

There are many ways to interpret your question.

#1.  No.  You can not exceed VOC, because if you exceed VOC, the new VOC is the VOC.

#2. Yes.  You can get 100,000V from a 12V battery.  Neon signs, Jacob's Ladder, etc.

#3. Yes.  MPPT.

I expect you are confusing VACopen with rectified VDCpeak.

Like I told you before, do not confuse VOC with power.
I can get 100,000 VOC out of a 9V transistor radio battery.  But it will not power a small TV.
G-

[REdiculous]

Why not gear it? Sprockets are about $20 each and same for the chain. Go with #25 instead of regular BMX stuff and you can fit a a pretty big ratio in a small space.
 

edit to add; My 80t and 11t sprockets with chain just showed up!! I paid $58.50 for the whole deal, shipped priority mail. I'm looking to drive a 10" wheel w/ my treadmill motor, but yeah.

[boogerbr549]

just get one or two more treadmill motors. look for the ones that r 120volt and 20amps wire them in series use 6 blades at 20 inchs then u will get power.

[Bruce S]

just get one or two more treadmill motors. look for the ones that r 120volt and 20amps wire them in series use 6 blades at 20 inches then u will get power.

Can you explain in better detail? I'm thinking most of what you posted is pretty much wrong.
20 inch blades are NOT going to make enough of anything much less even charge a battery , might light a LED if you've got a 50mph wind coming in at the right angle.

Bruce S