Hand-cranked stepper motor as a generator

[Paul-R]

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?

[conradelektro]

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/

[ALVARO_CS]

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

[mariuscivic]

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

[TinselKoala]

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/