Author Topic: Dissapointing Stepper Motor Output (Read 3170 times)

gotwind · « **on:** April 19, 2006, 02:02:39 PM »

I bought this size 34 -14 v stepper motor on eBay for £25.($60)

I get 12volts at approximately 200rpm, and then rising to about 60 volts (open circuit)with increasing the shafts speed, using a cordlessdrill to power the motors shaft.

The current seems to limited itself to only 0.32 Amps. Therefore using ohms law W=I x V

12v x 0.32A = 3.84 watts @ 200 rpm.

I thought i might get a lot more current, it's rated at 14v with 1.8 degree steps, have i hooked it up wrong prehaps?

Also why does this board stretch all my images, it was uploaded at a pixel size of 360 X 400?

Thanks

Ben

ghurd · « **Reply #1 on:** April 19, 2006, 10:59:12 AM »

Thats really good output for a stepper motor. Really good.

I probably average 0.4W 30ma. Not sure I ever broke 250ma. And I have a LOT of different steppers.

The last one I had big hope for is 24V, 2.5A, 0.6 ohms, 0.93mh. Sounds good.

Open circuit at 400RPMs is 3.35VAC. Dang.

I bet output will go up using 2 bridges, one for each coil set. Never can tell for sure. Some work better one way, some work better another way.

Use 200 or 400PIV bridges.

Inductive reactance will keep the amps down too.

My machine shows the photo at 690 x 767 pixels, 27.6kb. Fine by me.

G-

Opera House · « **Reply #2 on:** April 19, 2006, 11:05:26 AM »

Not exactly sure how you have that wired. I assume this is a 5 wire stepper motor and one diode for each winding producing half wave rectification. 5 wire steppers are a little hard to deal with. Add another four diodes to rectify the opposite polarity and double the voltage. Inductance is also a problem that will limit the available current.

gotwind · « **Reply #3 on:** April 19, 2006, 12:21:31 PM »

Thanks for the reply guys..

It is a 6 wire stepper - 4 windings and two commens joined together.

I just wired the 4 winding cables through an IN4001 diode, as in picture.

If thats all the power i can achieve, i think it may go back on eBay and put the money towards one of these beasts - 1.2 Kw PM Alternator - £150

Take a look, i've put a piece on my website

http://www.gotwind.org/FuterEnergy_Gen.htm

SmoggyTurnip · « **Reply #4 on:** April 19, 2006, 12:50:18 PM »

That is a nice looking genie.

According to their web site it puts

out 1000 watts at 12.5 m/s.

Any idea what RPM it is operating at at 12.5 m/s.

10 volts per 100 RPM unloaded only tells part

of the story. I wonder what it's internal

resistance is?

tecker · « **Reply #5 on:** April 19, 2006, 02:27:23 PM »

The treadmill motors routinely go for around 30 to 50 bucks good output there

gotwind · « **Reply #6 on:** April 19, 2006, 02:29:04 PM »

I've found a bit more info on eBay - They sell a few on there in the UK.

Weighing only 7Kg, and producing 1000W into 24V batteries at only 500RPM, they are ideal building blocks for a wide range of energy generation products.

· Ideal for Wind Turbine designs

· Ideal for Water Turbine applications

· Ideal for Waste Oil fuelled generators

· Output voltage from 12V to 48V depending on RPM

· Output voltage 10V per 100 RPM (off load)

· Maximum Power Output 1200W

· 3 Phase AC output power (requires rectification for DC applications)

· Delta Connected Windings

· No Gearbox required, these are Direct Drive PMG's

We have decided to continue to sell these as separate items, despite us having launched our 1KW wind turbines, which all use this PMG. The main reason for this is that these PMG's have proven very useful in many applications that we are not currently involved in. With the launch of The Renewable Energy Challenge on our website we felt that these PMG's would make ideal power sources for a wide range of products that can be entered through the Challenge. It is therefore in our most logical opinion best to allow these and other items to be sold as `building block products' for other enthusiasts.

The key feature of this PMG is that the main axle (18mm in diameter by 50mm long) is held stationary, with the main body of the PMG doing the rotation. This means that we have been able to place the rare earth magnets around the outer perimeter of the generator, giving us 16 pole changes per revolution, in a casing measuring under 180mm in diameter. It is this configuration that gives our PMG's a smooth and powerful performance, while remaining light-weight and very compact. The stator windings do not move in this design, since they are mounted to the main axle. The power cables for each of the 3 phases (delta connected) protrude through the centre of the main axle, and are around 30cm in length.

The PMG's are painted in a silver colour, but this may change without notice.

The mounting face of the generator is fitted with 6 x 6mm bolts (20mm long) with nuts and washers, and are positioned 40mm from the centre of rotation of the PMG, in a hexagonal format. This can be seen in the spec sheet on our website. Our PMG's are not guaranteed for use with your own bridge rectifier solutions, so if you intend to use it to provide DC output, we would suggest that you purchase our 3-Phase Bridge Rectifier Kit with this item.

tecker · « **Reply #7 on:** April 19, 2006, 02:37:17 PM »

That pig tail is not a 1000w size .what is the wire size? the pic is at a bad angle.

gotwind · « **Reply #8 on:** April 19, 2006, 03:33:02 PM »

Not sure what your refering to?

The thread has moved on to the Futerenrgyy 1.2Kw hub now. Image below.

There is something wrong with the way the images are processed on this board.

They are Stretched to some odd dimensions, and loose clarity.

Sorry,The reason I mention it, is because it is what I do for a living.

www.enhanced-images.com

Ben

Gotwind

Jon Miller · « **Reply #9 on:** April 19, 2006, 03:44:56 PM »

3.84 watts, thats very good for a stepper, my first stepper turbine 2 or 3 years ago only did 2 watts max!

There it is

tecker · « **Reply #10 on:** April 19, 2006, 06:35:05 PM »

1000 watts at 12v sounds like 84 amps maybe 48 at 20 is what their talking about

dinges · « **Reply #11 on:** April 20, 2006, 01:54:58 PM »

Does anyone have an idea how steppers stand up to continuous outdoors use? The bearings aren't meant for continuous use, I think. Plus there's the rain that seeps into the bearing.

These considerations are the only reason I haven't bothered more seriously with steppers, though I have some lying around. For a quick and simple generator, with limited output, they would be great if it weren't for my initial 2 worries.

Curious how your experiences in this respect are.

Peter.

ghurd · « **Reply #12 on:** April 20, 2006, 02:50:55 PM »

Mine do fine outdoors.

Damp basement for 2 years, and a motor that was taken apart 100 times, well... it didn't do so well.

The laminated kind have very nice bearings. The tin can kind have bushings.

May as well make one. The stray steppers will get deeper if you do not!

My uncle pointed out... "Use it now, or have you kids throw it away when you die."

I think he is correct.

G-

ghurd · « **Reply #13 on:** April 20, 2006, 06:10:52 PM »

Could be many people (like me) have a hard time believing something that size can substain a 1KW output without melting.

More so given the 100 RPM for 100V. Sound a lot like a stepper...

I have a stepper or 50 that will do that, but only make 5ma at 12V.

Got some induction conversions that are about the same, but I call them 6 or 8 watt.

WXYZCIENCE · « **Reply #14 on:** April 21, 2006, 09:50:48 AM »

Stepper motors are great for accurate controlled movement. They are the very last choice for generating electrical power. Rub two sticks together you will get better results. Joe

SmoggyTurnip · « **Reply #15 on:** April 21, 2006, 10:23:24 AM »

I think the specs are 100 RPM for 10 volts.

.

dinges · « **Reply #16 on:** April 21, 2006, 02:16:50 PM »

I've just tested a few steppers myself.

The best one is a 5V/1A stepper. By hand spinning, I can get .3A (!) short circuit, and about 15V open circuit.

I tested a few 24V/.18A and 12V/.4A ones but they only supplied about 30mA max, like Ghurd's. 40+V are easily attainable by hand turning.

I think I'm going to build something around that 5V/1A stepper. It has 4 completely independant coils. Per coil I should get about 5W max output. 4*5W=20W. If this holds up in practice then I am very happy camper!

Am now thinking about the prop; I think it should be relatively low RPM; 6 blade instead of 3? Diameter? TSR? etc. Still a few things to figure out, as you can see. Building it mechanically sound so it will survive at least a few years of outdoors use is my biggest problem right now.

The results you get are very good as far as steppers go. About as good as my best stepper (have only one of the 5V/1A version )

Peter.

ghurd · « **Reply #17 on:** April 22, 2006, 08:57:45 AM »

Just a typo.

G-

ghurd · « **Reply #18 on:** April 22, 2006, 08:58:39 AM »

Might want to wire it up and check the output into a battery... First!

G-

dinges · « **Reply #19 on:** April 22, 2006, 09:04:52 AM »

Ehm...

You obviously know something I don't? Will check it out ASAP, hooking up to a cordless drill. But like I said, short-current of .3A & open voltage of 14V sounds good to me.

It was my best stepper; all the rest were just, well, like I said. Plenty of volts but very little current.

Have searched this board for more info on steppers but found very little. If you know things the rest of us don't (regarding steppers ) I'd be very interested!

Also, I thought total output is 4* output of single coil (4 coils total). Am I correct here?

Peter.

ghurd · « **Reply #20 on:** April 22, 2006, 11:46:25 AM »

Long story short. You cant tell!

One that first tested went well, 90VAC open by hand, far over 100VAC with a drill. Over 1A short per coil. Maybe 150ma total into a 12V battery.

Some must have 'The Dreaded 5th wire' (9th wire maybe in your 8 wire motor?) inside, because they do better with only 1 coil connected.

Some do better with half wave, some with full wave.

An 8 wire may do better with all 4 coils seperate, or maybe 2 series pairs.

Some do better with ALL the coils in series. Wonder how that looks on an O-scope!

The famous 6W at 12V... I never saw it, or part numbers for those who claim it.

I have broke 6W at 6V, maybe 8~9W at 4V.

Bigger ($$$) doesn't seem to help me. I have a couple that weigh 4~5 pounds.

One is a Jerry Rig / Delta, 6 wires out, no magnets. Another is a 24V (28?) Vopen peaks at 3V.

G-

dinges · « **Reply #21 on:** April 22, 2006, 12:14:16 PM »

Understood.

Just did some measurements. Not in a battery, but in lightbulbs (6V and a 12V one).

With the 6V bulb, I get about .25A output. No matter how fast I turn (by hand), I can't go above 7.5V.

With 12V bulb I get about .2A output.

Before I made this setup I calculated internal resistance of the stepper (one coil): Vopen/Ishort=14/.3=50ohm. This seems like a lot.

I got about 1.5 W per phase; let's just say that with 4 completely separate coils (which they are) and rectification, this should give about 6W total. Minus some losses from rectification; plus some extra voltage due to higher RPM (than my hands can deliver); let's just say 5-6W. I am thinking about putting 2 (rectified) outputs in series; this should give about 13-14V. And then paralleling both of these 14V-output, so I should get about .5A. Let's say 12V at .5A, for the moment. But I will make some more measurements before I commit any time to building a genny out of it.

A bit less than my original 20W... Think I'll spend my precious time on the 10ft Dan-design genny. Am right now building the coil-winder. But that stepper; well, when the correct brainwave hits (i.e. I know how to build it mechanically), it will be built too. At least the output is way more than my very first stepper experiment, 2-3 years ago, where I got about 30mA...

Peter.

fungus · « **Reply #22 on:** April 22, 2006, 01:42:54 PM »

On my stepper motor (4 wire) I can get 13-14v open circuit and 0.2 A into a lightbulb. I got it from a laser printer. I measured the resistance and it was 6-ohms per phase, 13 ohms overall. I could make about 4 watts with it.

ghurd · « **Reply #23 on:** April 22, 2006, 07:34:00 PM »

I expect you could make one in an hour or 2.

PVC and scrap wood.

Usually...

RPMs don't help with the amps as much as I expected. Impedence gets crazy high, I think.

Higher torque blades get it going a little sooner.

All 4 coils make less than 4X one coil. Not sure why that is.

A 5 wire (center taps internally connected) does best with 1 negative (common) and 4 diodes in the 4 positives.

Darn near any of them can smoke LEDs.

G-

ghurd · « **Reply #24 on:** April 23, 2006, 01:23:36 AM »

Shopping today.

Thought of an old conversation after looking at a camera case.

"Fits all cameras that fit inside"

Is you gas cap tight?

IntegEner · « **Reply #25 on:** April 23, 2006, 07:26:25 AM »

To the point. The Internet is fast gaining a reputation as a haven for junk peddlers. It is the warm puppies that are most to be wary of, cute and cuddly but not yet housebroken.

An image under the "XYZ" name of a three bladed 24" diameter aluminum rotor appeared under a different post, the "15 Watt Generator", I believe, and it is with some curiosity that I make mention of this. If more information is available on this, I would appreciate seeing it.

Anthony C.

www.integener.com

dinges · « **Reply #26 on:** April 23, 2006, 07:53:37 AM »

I HATE YOU!

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Author Topic: Dissapointing Stepper Motor Output (Read 3170 times)