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Author Topic: Hand-cranked stepper motor as a generator  (Read 19597 times)

Offline conradelektro

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Hand-cranked stepper motor as a generator
« on: July 17, 2013, 08:14:40 PM »
By chance I found this web page depicting a hand-cranked stepper motor http://bjblaster.homedns.org/projects/renewable/hand_power/index.html and I decided to try it myself.

My video http://www.youtube.com/watch?v=qec_qsDseCY shows a hand-cranked stepper motor, a rectifier circuit and a Joule Thief circuit.

The stepper-motor is more than 20 years old and I bought it some time ago for very little money from a surplus dealer in Germany. The face plate of the stepper motor has a side length of 80 mm. A heavy and sturdy stepper motor with six wires. The axle has a diameter of 10 mm.

The hand-cranked stepper motor first drives eight white LEDs which seem to get too much power. A rectifier circuit allows to measure the output power (at about 60 rpm or one crank turn per second) which amounts to approximately 0.8 Watt. It does not help to turn the crank much faster as shown in the video, the output will not rise much.

The hand cranked-stepper motor and the rectifier circuit first drive a radio and then a Joule Thief which lights a 200 Volt / 1 Watt Led-lamp and alternatively a gutted CFL (compact fluorescent lamp, spiral shaped gas discharge tube, ignites at ~800 Volt).

Unless you find a person who is willing to crank the stepper-motor, this idea will not be very useful. But it is an interesting experiment.

Greetings, Conrad

Free Energy | searching for free energy and discussing free energy


Offline gyulasun

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Re: Hand-cranked stepper motor as a generator
« Reply #1 on: July 17, 2013, 10:51:33 PM »
Hi Conrad,

Nice and simple setup, thanks for showing.  Did I notice correctly that the cranking force needs to be a little bit higher for the LED lamp than for the gutted CFL?  Or just the small difference between left and right hand cranking?

rgds, Gyula


Offline conradelektro

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Re: Hand-cranked stepper motor as a generator
« Reply #2 on: July 18, 2013, 09:46:31 AM »
Did I notice correctly that the cranking force needs to be a little bit higher for the LED lamp than for the gutted CFL?  Or just the small difference between left and right hand cranking?

Yes, the Voltage over the 47000 µF cap rises to about 3 Volt when lighting the CFL (not so much power consumed) and only to about 2 Volt when lighting the 200V / 1W LED lamp (more power is consumed, more effort is needed to crank).

The stepper motor produces about 0.8 Watt when cranked at about 1 turn per second. It is possible (although not comfortable) to turn it by hand at up to 3 turns per second, but the output does not rise significantly. Why is that? May be it has to be turned much faster to see a difference? Or is some sort of satturation reached soon?

On the back of the motor where the specifications are imprinted on a aluminium foil, one reads "@ RPM 60 CPS" (on the left side, beneath "STEP ANGLE 1.8°", see the photo attached to my firts post in this thread). What does this "@ RPM 60 CPS" mean?

This person also made a video about a stepper motors as generators http://www.youtube.com/watch?v=cPMkBfuo824 (more tests, stepper motor on a bicycle to light some LEDs).

It seems that I have to spin the stepper moto much faster to get more power out of it:
 http://www.solarheatengines.com/2011/01/28/generating-power-with-a-stepper-motor/

If you think about it, there could be useful applications, e.g. on a bicycle or a very simple wind turbine. Conversion efficiency is not such a big issue in a quick and dirty hack, costs and simplicity of build are more important.

The advantage of a stepper motor as a generator is that one gets some power out of it even at a low turn rate, which allows to drive it without gears (directly driving the axle with a slowly turning source like a wind wheel or water wheel).

Greetings, Conrad

Offline gyulasun

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Re: Hand-cranked stepper motor as a generator
« Reply #3 on: July 19, 2013, 12:04:17 AM »
Hi Conrad,

Yes I think it is a kind of saturation, both the LED and the CFL are non-linear loads (like Zener diodes) and able to limit voltage across themselves.
IF you also found a limit in output power when you hooked up the 10 to 100 Ohm resistors and no lamps, and you found the 0.8-0.9 Watt output limit,  this may come from core saturation due to load current I suppose or rather the effect of the "impedance protection" (see it also imprinted in the Alu foil) which may mean a provision to compensate for inductive reactance increase when the rpm increases. This is a special feature for the better, more precise stepper motors I think. 
I am not very good at stepper motor specs, what you ask I read as RPM @ 60 cps i.e. RPM at 60 Hz (cycle per second), if this makes sense but the real RPM data is missing? Should be in the rectangular box below the 60 cps but the box is empty...
Here is some definitions on AC and DC stepper motors but for slo-syn motor types (slo= slow syncron?) and not for rapid-syn ones, maybe still useful, see pdf page #18,  steps per second definition. etc: http://mcsupplyco.com/uploads/images/drawings/pdf1/SYNCGUIDE.pdf

Also, see this ebay offer where a 34H-600 type Rapid Syn stepper motor is shown and the step angle is defined as 72 RPM instead of the normal angle.  And below it, again the RPM @ 60 cps with an empty box:  http://www.ebay.com/itm/RAPID-SYN-34H-600-COMPUTER-DEICES-STEPPER-MOTOR-/271035025677?pt=LH_DefaultDomain_0&hash=item3f1af2490d
(A step angle of 1.8° obviously means 200 steps per revolution,  200 x 1.8°=360°  and this must be corresponded to rpm.)

rgds,  Gyula


Offline conradelektro

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Re: Hand-cranked stepper motor as a generator
« Reply #4 on: July 19, 2013, 11:39:27 AM »
@Gyula: you found nice infos about stepper motors, helps to understand better.

I found some stuff in German http://www.rafoeg.de/10,Forschungsprojekte/90,Schrittmotor/Schrittmotorversuch_RaFoeG.pdf, which contains some esoterics (Lenz force is lower at higher rpm) but also useful curves about output versus rpm (only useful for German speaking readers, the graphs may be useful for everybody).

I did some more measurements over the 10 Ohm and 100 Ohm resistor as a load: the voltage rises when I turn faster. And I will do some more tests with an electric drill to spin the stepper motor faster than by hand.

So it seems, the saturation was in the load (CFL or 220V/1WLED lamp, or even the 8 LEDs without rectification). There is of course a limit for output, but at very high rpm (several thousand revolutions per minute).

Greetings, Conrad

Free Energy | searching for free energy and discussing free energy

Re: Hand-cranked stepper motor as a generator
« Reply #4 on: July 19, 2013, 11:39:27 AM »
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Offline Paul-R

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Re: Hand-cranked stepper motor as a generator
« Reply #5 on: July 19, 2013, 05:24:06 PM »
There are plenty of usually good stepper motors in scrapped or dumped
printers, scanners etc. A small one in hard drives, CDdrives.

Has anyone driven such a motor with an electric drill and scoped the output?

Offline conradelektro

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Re: Hand-cranked stepper motor as a generator
« Reply #6 on: July 19, 2013, 09:07:02 PM »
There are plenty of usually good stepper motors in scrapped or dumped
printers, scanners etc. A small one in hard drives, CDdrives.

Has anyone driven such a motor with an electric drill and scoped the output?

I showed a link to such tests.  http://www.solarheatengines.com/2011/01/28/generating-power-with-a-stepper-motor
 
I did some scope shots, they show the expected sine waves with a 180° phase shift between the two windings of a stepper motor (the unipolar type with 6 wires has two mid point taps, which can be ignored when used as a generator). Bipolar stepper motor (4 wires) or unipolar stepper motor (6 wires), you need two full bridge rectifiers (one for each winding), as I show in the first post of this thread.

Greetings, Conrad


It seems that I have to spin the stepper motor much faster to get more power out of it:
 http://www.solarheatengines.com/2011/01/28/generating-power-with-a-stepper-motor/


Free Energy | searching for free energy and discussing free energy

Re: Hand-cranked stepper motor as a generator
« Reply #6 on: July 19, 2013, 09:07:02 PM »
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Offline ALVARO_CS

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Re: Hand-cranked stepper motor as a generator
« Reply #7 on: December 17, 2014, 11:36:10 AM »
hello Conrad
(or anyone with knowledge enough in measurements)

I made a simple setup with a small bipolar stepper motor driven as generator by a DC motor.
I need your help in an explanation of a behavior I do not understand.

the DC motor is feed via a PC power supply (modified with a  voltage regulator)

The input to it is 9V  (not changed in the following tests)

The output from the stepped m. is via two BR made out of 4 4007 diodes in paralel buffered with electrolytic cap 120uF 400V (see schematic)
Output measurements made at the cap terminals

The tests show the following data:
----------------

input: 9V at 400mA (with no load)
out: 18V

input:9V at 450mA loaded with a 100 Ohm/4W resistor after the cap.
out: 7.5 V
------------------
input: 9V at 350 mA with out terminals shorted (max load ?)
out: no V (as expected). . .speed of motor notoriously increased
------------------
May someone explain this motor speed up and lowering of input ?
any help greatly appreciated
cheers
Alvaro

Offline mariuscivic

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Re: Hand-cranked stepper motor as a generator
« Reply #8 on: December 17, 2014, 01:52:27 PM »
Hi guys! I'm also using a stepper motor in this vid: https://www.youtube.com/watch?v=Tn2lFxpxPa0&feature=youtu.be  and works realy good.


Let me propose you an experiment:
-grab a stepper motor(an powerful one)
-spin the axle by hand with nothing attached at the wires: you will see is not spinning free
-connect all the wires together as dead short and spin by hand  the axle:
                      1. at low rpm it will spin much harder
                      2. at high rpm it will spin free once you passed rpm sweat spot         


You dont need to reach 2000rpm;just spin it a little faster by hand and you'll see the difference. 
The motors i have spin better with the wires in dead short



Offline TinselKoala

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Re: Hand-cranked stepper motor as a generator
« Reply #9 on: December 17, 2014, 02:24:48 PM »
Examine your assumptions. Is a dead short _really_ the maximum load you can put on a generator? Does it really require the most turning torque? Remember Jacobi's Law.

You may be interested in studying the graphs presented on this page:

http://www.solarheatengines.com/2011/01/28/generating-power-with-a-stepper-motor/

Free Energy | searching for free energy and discussing free energy

Re: Hand-cranked stepper motor as a generator
« Reply #9 on: December 17, 2014, 02:24:48 PM »
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Offline ALVARO_CS

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Re: Hand-cranked stepper motor as a generator
« Reply #10 on: December 17, 2014, 02:38:26 PM »
thanks TK
(to say the truth I was expecting your opinion as well as MH´s one)
Lots to learn yet, that´s why I posted my question.

Offline mscoffman

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Re: Hand-cranked stepper motor as a generator
« Reply #11 on: December 17, 2014, 03:17:16 PM »
hello Conrad
(or anyone with knowledge enough in measurements)

I made a simple setup with a small bipolar stepper motor driven as generator by a DC motor.
I need your help in an explanation of a behavior I do not understand.

the DC motor is feed via a PC power supply (modified with a  voltage regulator)

The input to it is 9V  (not changed in the following tests)

The output from the stepped m. is via two BR made out of 4 4007 diodes in paralel buffered with electrolytic cap 120uF 400V (see schematic)
Output measurements made at the cap terminals

The tests show the following data:
----------------

input: 9V at 400mA (with no load)
out: 18V

input:9V at 450mA loaded with a 100 Ohm/4W resistor after the cap.
out: 7.5 V
------------------
input: 9V at 350 mA with out terminals shorted (max load ?)
out: no V (as expected). . .speed of motor notoriously /noticeably/ increased
------------------
May someone explain this motor speed up and lowering of input ?
any help greatly appreciated
cheers
Alvaro

These measurements are indeed within theoretical expectations.

1) Generator is unloaded - high voltage output due to lack of electrical load on generator ("LENZ LAW GENERATOR" electrical load acts
as mechanical brake), No power is being produced, as there is zero current in the load => low mechanical load on motor => high RPM's

2) Generator is loaded - generator acts as brake - motor input current rises due to mechanical load on motor - generator output voltage
is lower due to Ohms law in resistance of coil versus resistance of load. Real world motor(s) automatically adjust their operating current to
their mechanical load to some extent. This saves energy on average - causes the motor to "lug" under appropriate conditions.

3) Unique condition in Generator - shorting output coil collapses internal magnetic field - zero driver voltage => zero current (in a generator
circuit only). No power being generated <=> no mechanical braking force. In a generator circuit some driver voltage is required to cause
some current flow in load - if the generator doesn't supply this driver voltage where does it comes from? - it doesn't. Voltage is what
causes the electron Current to flow in a circuit.

One could use Ohms law math to calculate approximate generator output coil impedance(resistance) of generator coil.
 
This is a good experiment showing several unique and somewhat surprising conditions in a real world motor/generator set. Congrats.
Instrumentation readings helps one to understand what is occurring in the circuit.

:S:MarkSCoffman



Offline mscoffman

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Re: Hand-cranked stepper motor as a generator
« Reply #12 on: December 17, 2014, 03:33:02 PM »

If magnetic cogging force is to extract energy then there must be an integration time frame. If rotation is sufficiently fast then the
integration time frame is violated and less net energy will be extracted. This is a consequence of unusually rapid radius squared
interaction in magnetic fields. (you might want to consider the fast HHO interaction rates if you need to outrun magnetic interactions)

:S:MarkSCoffman

Offline ALVARO_CS

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Re: Hand-cranked stepper motor as a generator
« Reply #13 on: December 17, 2014, 05:19:42 PM »
Thanks again for all the kind explanations.
reading on the subject, I found this quote:

" Efficiency also approaches 100% if the source resistance approaches zero, and 0% if the load resistance approaches zero. In the latter case, all the power is consumed inside the source (unless the source also has no resistance), so the power dissipated in a short circuit is zero."

I found in the forums, that there is a common misunderstanding between efficiency and power transfer


Offline meiji_jap

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Re: Hand-cranked stepper motor as a generator
« Reply #14 on: June 25, 2016, 12:47:09 PM »
By chance I found this web page depicting a hand-cranked stepper motor http://bjblaster.homedns.org/projects/renewable/hand_power/index.html and I decided to try it myself.

My video http://www.youtube.com/watch?v=qec_qsDseCY shows a hand-cranked stepper motor, a rectifier circuit and a Joule Thief circuit.

The stepper-motor is more than 20 years old and I bought it some time ago for very little money from a surplus dealer in Germany. The face plate of the stepper motor has a side length of 80 mm. A heavy and sturdy stepper motor with six wires. The axle has a diameter of 10 mm.

The hand-cranked stepper motor first drives eight white LEDs which seem to get too much power. A rectifier circuit allows to measure the output power (at about 60 rpm or one crank turn per second) which amounts to approximately 0.8 Watt. It does not help to turn the crank much faster as shown in the video, the output will not rise much.

The hand cranked-stepper motor and the rectifier circuit first drive a radio and then a Joule Thief which lights a 200 Volt / 1 Watt Led-lamp and alternatively a gutted CFL (compact fluorescent lamp, spiral shaped gas discharge tube, ignites at ~800 Volt).

Unless you find a person who is willing to crank the stepper-motor, this idea will not be very useful. But it is an interesting experiment.

Greetings, Conrad

I like the idea how you made the crank handle to grip the motor -- anyway would you mind to explain as in your video why when you turn whether clockwise or otherwise it still generate energy because i have a motor...12  volt DC when i turn it only generate electricity when the connection is correct. -- it generate around 0.8 volt to highest around 5 volt

Free Energy | searching for free energy and discussing free energy

Re: Hand-cranked stepper motor as a generator
« Reply #14 on: June 25, 2016, 12:47:09 PM »

 

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