[Lab] human powered art

Richard Guy Briggs rgb at tricolour.net
Sat Jan 15 18:12:24 EST 2011

On Fri, Jan 14, 2011 at 07:14:29AM -0500, Darcy Whyte wrote:
> I would like to make a human powered generator for an art project.

I've been wanting to build one for a while now...

> I am curious if a couple of NEMA 34 motors is large enough to capture all
> the power that a human can generate.

My understanding is that a stepper is not the kind of motor that can be
used as a generator.  Wait!  I stand corrected!

What is most commonly used to generate DC is a commutated DC motor.

A car alternator will also work.  It is an AC generator with a
rectifier, but they tend to be a lot less efficient.  It also needs a
power supply bias to get started (say, a car battery under charge) since
there are no permanent magnets and it uses a field coil.

My understanding is that motors are typically 80% efficient, while
dynamos closer to 50%.

Do you have a link for your NEMA 34 motor specs?  I've seen anywhere
from 50W up to 500, so it sounds like those might work!

> I'm looking at a couple of applications.
> 1) To run a 120V toaster. I suspect this might need as many as 5 people to
> peddle. Also to run a 60W incandescence bulb.

A toaster is going to need 3 top athletes (400W ea) or about 8 fit
adults (150w ea) to run.  For kids (50w ea), it is going to be more like

> 2) To charge a 12V battery.

One will work here, it'll just take longer...

I wanted to power a TV, or at least to power the "on" circuit.  Other
ideas we had was to use a human powered generator to power parade float
lights or moving parts.

> I'm suspecting that a stepper motor is a good candidate to make the
> electricity. I think the first part of the project is to make up some BOMs
> that show what motor to use, the RPM that it would require and parts for a
> rectifier and whatever else is necessary to operate in these applications.

I've got lots of small ones, so I can try some tests and see.  I
wouldn't have thought they would work because the rotor I thought was
unmagnetized steel.

> Does anybody know of any existing projects or have any recommendations?

There are lots out there that I have tripped upon in the past...  I
threw together this page to summarize:

I just tripped on this site that may be of interest too:

	slainte mhath, RGB

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