Alternative Power sources - Motor/generator questions

Author

Motor/generator questions

uioped1

2006-02-15, 6:21 pm

Hi everyone,
It's been a while since I posted here, hope there's still some
regulars. I'm building a pedal-powered generator, mostly because I
can't stand using a regular exercycle that doesn't _do_ anything.

Anyway, I've gotten to the point where I need a generator, but I
don't really know what to look for. There is a junkstore nearby that
has a good selection of surplus motors. What should I look for? What
will indicate good efficiency when run as a generator in a low input
power range? (I guess that I can put out about 200 watts, but don't
really base that on anything. Can probably do more for short periods.)

Am I correct that if I run the motor in reverse at the same
speed it runs at on wall current, that I will get the same voltage and
hz output?

Thanks!

meow2222@care2.com

2006-02-15, 6:21 pm

uioped1 wrote:
> Hi everyone,
> It's been a while since I posted here, hope there's still some
> regulars. I'm building a pedal-powered generator, mostly because I
> can't stand using a regular exercycle that doesn't _do_ anything.
>
> Anyway, I've gotten to the point where I need a generator, but I
> don't really know what to look for. There is a junkstore nearby that
> has a good selection of surplus motors. What should I look for? What
> will indicate good efficiency when run as a generator in a low input
> power range? (I guess that I can put out about 200 watts, but don't
> really base that on anything. Can probably do more for short periods.)
>
> Am I correct that if I run the motor in reverse at the same
> speed it runs at on wall current, that I will get the same voltage and
> hz output?
>
> Thanks!

you'd get the majority of your V_out, but not all by any means.

Stepper motors would work without gearing, but be too low v and too
little power for you.

NT

Harry Chickpea

2006-02-15, 8:21 pm

"uioped1" <alexw@cs.pdx.edu> wrote:

> I'm building a pedal-powered generator, mostly because I
>can't stand using a regular exercycle that doesn't _do_ anything.

Have you considered direct drive to a bug-zapper? How about making a
big honkin' pedal powered wimhurst machine?

SQLit

2006-02-15, 9:21 pm

Nick Hull

2006-02-15, 10:21 pm

In article <1140039812.027837.68640@g44g2000cwa.googlegroups.com>,
"uioped1" <alexw@cs.pdx.edu> wrote:

> Hi everyone,
> It's been a while since I posted here, hope there's still some
> regulars. I'm building a pedal-powered generator, mostly because I
> can't stand using a regular exercycle that doesn't _do_ anything.
>
> Anyway, I've gotten to the point where I need a generator, but I
> don't really know what to look for. There is a junkstore nearby that
> has a good selection of surplus motors. What should I look for? What
> will indicate good efficiency when run as a generator in a low input
> power range? (I guess that I can put out about 200 watts, but don't
> really base that on anything. Can probably do more for short periods.)
>
> Am I correct that if I run the motor in reverse at the same
> speed it runs at on wall current, that I will get the same voltage and
> hz output?
>
> Thanks!
>

You can't pedal the motor at full speed, what you want is a 120 volt
motor that you pedal to get 12 volts out. An electric weed-wacker motor
is close to what you want.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/

Allison-nospam@nouce.bellatlantic.net

2006-02-15, 11:21 pm

On 15 Feb 2006 13:43:32 -0800, "uioped1" <alexw@cs.pdx.edu> wrote:

>Hi everyone,
> It's been a while since I posted here, hope there's still some
>regulars. I'm building a pedal-powered generator, mostly because I
>can't stand using a regular exercycle that doesn't _do_ anything.
>
> Anyway, I've gotten to the point where I need a generator, but I
>don't really know what to look for. There is a junkstore nearby that
>has a good selection of surplus motors. What should I look for? What
>will indicate good efficiency when run as a generator in a low input
>power range? (I guess that I can put out about 200 watts, but don't
>really base that on anything. Can probably do more for short periods.)
>
> Am I correct that if I run the motor in reverse at the same
>speed it runs at on wall current, that I will get the same voltage and
>hz output?
>
>Thanks!

What might work better is DC motor of the type used for treadmils
or so called DC servomotors. Without a load these motors require
little effort to turn but the bigger the load or the faster (more
output) the harder it will be.

You cannot get the right HZ and voltage unless you can assure the
correct shaft rpm for an alternator . Getting .25hp out of a human
for a sustained time requires a well conditioned athlete. Figure a
lot less say .1hp (about 70W) and even doing that for 30minutes will
be a significant workout. Half that again for average people would
likely be more resonable but still a fair amount of power(25-35W)
for small TV or fan.

A DC motor used as a generator running a light or charging a battery
to run a 12V TV would be a more reasonable task (typically 12V at
1-1.5a for those small 5" sets). By charging a battery your more
assured of a constant voltage for the equipment.

Allison

RoughRider

2006-02-15, 11:21 pm

I agree 100% about doing something useful like charging a battery or making
some power from the exercise... perhaps enough to keep a TV working to ward
off the boredom.

Solar Flare

2006-02-15, 11:21 pm

I have tried that too and they had a V belt mechanism
on it. Don't need any friction with a V belt. Don't
tell the US car manufacturers though.

"SQLit" <sqlit@qwest.net> wrote in message
news:AWPIf.39$_t6.992@news.uswest.net...
>
> "uioped1" <alexw@cs.pdx.edu> wrote in message
>
news:1140039812.027837.68640@g44g2000cwa.googlegroups.com...
there's still some[color=darkred]
mostly because I[color=darkred]
_do_ anything.[color=darkred]
need a generator, but I[color=darkred]
junkstore nearby that[color=darkred]
should I look for? What[color=darkred]
generator in a low input[color=darkred]
watts, but don't[color=darkred]
for short periods.)[color=darkred]
reverse at the same[color=darkred]
the same voltage and[color=darkred]
>
> The Industrial Science and Industry Museum in Chicago
used to have a bike
> generator. It was all I could do to get a single 100
watt light bulb (120v)
> up to full bright. I was a LOT younger then. I
could only hold the light
> bulb at full bright for a few seconds before wearing
out.
>
>
>

GMM50

2006-02-16, 10:21 am

For simple cheap why not use a car alternator and voltage regulator
into a battery.
You can play with the gearing to get the desired mechanical loads.

Next more complicated is car alternator into a better regulator,
something form the PV industry.

Keep us posted

meow2222@care2.com

2006-02-16, 10:21 am

GMM50 wrote:
> For simple cheap why not use a car alternator and voltage regulator
> into a battery.
> You can play with the gearing to get the desired mechanical loads.
>
> Next more complicated is car alternator into a better regulator,
> something form the PV industry.
>
> Keep us posted

A good idea if you can pedal at 15,000 rpm

Innovate808

2006-02-17, 7:21 am

Hi, If you go to www.futurenergy.co.uk and get a PMG from them, these have
been used on several Bike Powered stuff already, and you can expect to get
100 to 150W if you're reasonably fit, and more if you're in a hurry.

They ship to anywhere, and this is tried and tested, unlike some other
suggestions you may receive.

"uioped1" <alexw@cs.pdx.edu> wrote in message
news:1140039812.027837.68640@g44g2000cwa.googlegroups.com...
> Hi everyone,
> It's been a while since I posted here, hope there's still some
> regulars. I'm building a pedal-powered generator, mostly because I
> can't stand using a regular exercycle that doesn't _do_ anything.
>
> Anyway, I've gotten to the point where I need a generator, but I
> don't really know what to look for. There is a junkstore nearby that
> has a good selection of surplus motors. What should I look for? What
> will indicate good efficiency when run as a generator in a low input
> power range? (I guess that I can put out about 200 watts, but don't
> really base that on anything. Can probably do more for short periods.)
>
> Am I correct that if I run the motor in reverse at the same
> speed it runs at on wall current, that I will get the same voltage and
> hz output?
>
> Thanks!
>

uioped1

2006-02-17, 2:21 pm

Thanks for the replies.

It seems that maybe my power output was over-estimated, unless that
generator in the museum was terribly inefficient. . .

My main reason for trying to approximate wall current was that I
thought I could put out enough wattage that I could do something
usefull. Got the 200 watts figure from the 'net, figuring that I was
not in as good shape as a cycling enthusiast. Never expected to be
able to run my microwave or anything, but my laptop does draw about 175
watts, which I hoped I could at least approach after (in)efficiency
losses.

Why were people saying I couldn't run the motor at full speed? I was
planning to do some gear stepping?

Am thinking now that I will put a big flyweel on it as well, to help
stabilize the output.

I am looking for a cheaper solution than the PMG, so perhaps an
alternator would be the way to go. For some reason I never even
considered that

I didn't want to go with the battery solution, because I had figured
that the terrible inefficiency of the system would be too bad. Maybe
what I need is a _Really_Big_ flyweel

I kindof like that... It
wouldn't have to hold a charge very long, so the friction losses might
not be too great. I'm going to think more about that; I'll let you
guys know.

So my original question was what kind of motor will work well as a
generator.
Will certain types not work? If I get an overpowered motor and don't
run it at spec, will that be more efficient than getting an
under-powered motor and running it over?

By the way, laptop charger has wide range of acceptable inputs, and I'm
not too concerned about potential damage.

Pal

2006-02-19, 10:21 am

uioped1 wrote:
> Hi everyone,
> It's been a while since I posted here, hope there's still some
> regulars. I'm building a pedal-powered generator, mostly because I
> can't stand using a regular exercycle that doesn't _do_ anything.
>
> Anyway, I've gotten to the point where I need a generator, but I
> don't really know what to look for. There is a junkstore nearby that
> has a good selection of surplus motors. What should I look for? What
> will indicate good efficiency when run as a generator in a low input
> power range? (I guess that I can put out about 200 watts, but don't
> really base that on anything. Can probably do more for short periods.)
>
> Am I correct that if I run the motor in reverse at the same
> speed it runs at on wall current, that I will get the same voltage and
> hz output?
>
> Thanks!
>

More of a curiosity than of any technical assistance right now, but a
system such as this was widely used in the Australian outback to run a
two way radio system. It was invented by one Alfred Traeger who was born
in the late 1800's. http://www.wilmap.com.au/people/traeger.html this is
the only link I could find at short notice, but his system was used in
several places around the world, including Canada I believe.

Regards,

Pal

Bob Eldred

2006-02-21, 10:21 pm

"uioped1" <alexw@cs.pdx.edu> wrote in message
news:1140039812.027837.68640@g44g2000cwa.googlegroups.com...
> Hi everyone,
> It's been a while since I posted here, hope there's still some
> regulars. I'm building a pedal-powered generator, mostly because I
> can't stand using a regular exercycle that doesn't _do_ anything.
>
> Anyway, I've gotten to the point where I need a generator, but I
> don't really know what to look for. There is a junkstore nearby that
> has a good selection of surplus motors. What should I look for? What
> will indicate good efficiency when run as a generator in a low input
> power range? (I guess that I can put out about 200 watts, but don't
> really base that on anything. Can probably do more for short periods.)
>
> Am I correct that if I run the motor in reverse at the same
> speed it runs at on wall current, that I will get the same voltage and
> hz output?
>
> Thanks!

The best bet is a permanent magnet DC motor of approxamately 200 to 400 watt
rating (1/4 to 1/2 HP). The motor will need to turn relatively fast say 2000
to 3000 RPM depending on the particualr specs.You will need to gear it up
from the pedal wheel to get sufficient speed. The voltage and current output
will depend on the motor rating and speed. It is true that as a generator it
will produce nearly the same voltage it consumes as a motor at the same
speed, especially when unloaded. These motors range in voltage from 12Volts
to 120Volts DC depending on the particular device. Loading it and regulating
the output may be a bigger deal given the uneven drive of human power. Under
optimum conditions you can expect the efficiency to be about 80% power in to
power out.

Another option is to use an automotive alternator which is a sort of DC
generator because it contains internal rectifier diodes and outputs DC.
Other alternators and AC generators may also be used but they are much more
complex and require constant speed for constant AC frequency. That's tough
on a bicycle. Furthermore, many of these devices require excitation which is
an externally supplied current to energize the internal magnets. That
totally complicates the issue. That's why a permanent magnet device is to be
prefered. Some generators are self exciting also complicating the design.

Single phase AC induction motors, the most common type out there are not
suited to be generators, so stay away from them. Good luck.
Bob

Chopper

2006-02-23, 9:21 am

Hi

"uioped1" <alexw@cs.pdx.edu> wrote in message
news:1140039812.027837.68640@g44g2000cwa.googlegroups.com...
> Hi everyone,
> It's been a while since I posted here, hope there's still some
> regulars. I'm building a pedal-powered generator, mostly because I
> can't stand using a regular exercycle that doesn't _do_ anything.
>
> Anyway, I've gotten to the point where I need a generator, but I
> don't really know what to look for. There is a junkstore nearby that
> has a good selection of surplus motors. What should I look for? What
> will indicate good efficiency when run as a generator in a low input
> power range? (I guess that I can put out about 200 watts, but don't
> really base that on anything. Can probably do more for short periods.)
>
> Am I correct that if I run the motor in reverse at the same
> speed it runs at on wall current, that I will get the same voltage and
> hz output?
>
> Thanks!

Many years ago, a guy calling himself 'Peter Pedals' did this sort of thing.
He powered washing machines, generators etc whilst reading, watching TV etc
etc

You may still find him or info at the "Rainbow Power Company"

http://www.rpc.com.au/

Hope this helps

--
Regards

Chopper

<Remove 'Chopper' in Email address>

>

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