homemade dynamo unit

[billj pump]

i want to add a dynamo unit to run off my stationary steam engine, it only needs to generate around 4 volts to power some small bulbs, the stuart dynamo is very costly item and im sure works very well but im not willing to splash that much dosh out on such an item, im wondering if there is another way round this by using maybe a bicycle dynamo or a way of converting a small electric motor, anyone with any ideas please?

thanks

billj

[baggo]

Hi Billj,

Any DC motor that uses brushes and a commutator will operate in 'reverse mode' and act as a generator. You'll probably have to experiment with the pulley sizes to get the right output at the rpm that you intend to run it at.

Another idea is to use a stepper motor as used in printers, scanners etc. These will give an AC output unless you add a rectifier but that is no problem if you are only going to run bulbs off it. I made a small 'toy' wind generator using one of these that gave about 100mA at 12volts.

Incidently, the generator in the famous wind up radios and torches is simply a DC motor used in reverse!

John

[ron]

John
Thanks for posting that info, I also fancy a generator to run off my Victoria but like Billj was a bit put off by Stuarts price.
Ron

[steammadman]

billjpump,
Yes you can use a cycle dynamo to power the lights off.
I used one to light up a carrousel i made some years ago
i took off the serrated wheel that runs on the tyre, and
replaced it with a pulley, obout3/4 inches diameter i think,
and then fitted a pulley of about 2 1/2" diameter on the drive
spindle, (motor),this increased te speed enough to light up brightly
a load of "pea" bulbs.
It looked very very effective lit up in a darkened room.

hope the above helps, and you have as much fun messing
around with the lighted set up as i did.
if you need any more info dont hesitate to ask, but if you need
the bulb quantities etc , it may take a little while as my grandson
has the carrasel now and he live a few miles away.

good luck

[Tel]

I've used bicycle generators to make a couple of these - the first was pretty crude, just the bare generator bolted down & driven on the existing serrated wheel by the 10V flywheel via a toothed belt (ex sewing machine I think).

The second effort was much better - the generator being housed in a brass case with appropriate ends and a small pulley. I'll dig it out & take a pic or two if I can remember

[billj pump]

Hi, thank you fellas for your interest, some great advice given, i like johns idea of converting a dc motor and then Tels idea of a new housing, the bike dynamo idea is great but im finding it difficult to get hold of one off an old bike, i have a few old dc motors knoking around so ill have a little fun experimenting as steammadman said, again ta fellas,,,,

billj

[raysputin]

Hi,

Bike dynamos come in three basic kinds; the hub variety needs the lowest RPM, followed by the variety that runs on the outside of the tyre (I think sanyo makes these) while those needing the highest RPM are those that run on the side of the tyre. The wattage from any of these is pretty low.
Another choice is the motors from electric scooters or powered ride-on toys. These are mostly 24V units with power consumptions from 100 to 500 watts. They can provide fairly good outputs if run as generators.
www.oatleyelectronics.com have some surplus motors at reasonable prices but they are running out of stocks.

[billj pump]

i got a stepper motor out of an old pc scanner, i just couldnt get it to work! the motor seemed to jam tight and wouldnt turn in either direction when power was applied, im going to look around for an old 6-12volt cordless drill and try that motor, i did manage to salvage the tiny flouresent light out of the scanner though its only about 3mm wide x 200mm long it'll come in handy for something!.

[baggo]

Hi Billj,

Stepper motors won't run if you just apply a DC voltage to the windings. They have to be driven by a special drive circuit (usually a chip) that supplies the windings with out of phase AC voltages. They work on a similar principle to an induction motor. If you are interested in how they work have a look at:

www.imagesco.com/articles/picstepper/02.html

There's a bit of a write up on the wind generator I made using one at:

www.baggo.copperstream.co.uk/re/Stepper%20Motor%20Genny.htm

The main problem with using stepper motors is sorting out the connections as they have several windings which can be wired in various ways to get the output. It's a lot esier to use a DC motor! As Tel suggests you can knock up some false ends and mounting brackets to make it look more like the real thing.

John

Wow, I knew I was well pickled but now I'm seasoned as well! ;D

[chris vine]

Hi,

I used a tiny stepper motor, from a computer tape drive, it was just to move the head from one track to another. It was about 1/2" dia and 5/16" long. Driven by a tiny oscillating engine it drove something like 20 leds.

To find out what it would do and what speed to run it at you can spin it with the lathe at a known speed.

Chris.

[billj pump]

hey john, i feel a right dork now, trying to connect a stepper motor stright to a 12 volt supply,,derr! now i know better thanks for the fantastic info, i liked the wind generator and i like your style of writing! good luck on the future projects, please keep us informed of them.

thanks for the usefull info chris

billj

[modeng2000]

The current edition of Every Day Practical Electronics, September 2006, has an article containing details about using a stepper motor as a generator to power leds.

From the EPE web site:- 'LED Torches — ideas for a range of deceptively simple LED torches (flashlights). This interesting article shows how a stepper motor can be used as a hand-cranked generator, in order to power an array of high-efficiency white LEDs. Plenty of scope for testing your resourcefulness and improvising from whatever surplus items you have to hand. Our article shows 'step by step' (no pun intended!) how to build your own LED torch, with a series of photographs and full guide notes. '

John

[billj pump]

hi,,, thanks for the info john, interesting article.

billj