Author Topic: Using a small motor as a dynamo.  (Read 2354 times)

Offline Gas_mantle

  • Full Member
  • ****
  • Posts: 1334
  • North Yorks - UK.
    • My Youtube channel
Using a small motor as a dynamo.
« on: November 09, 2018, 09:35:32 PM »
Hi all,

I'm looking for a bit of help in using a small mains voltage electric motor as a small dynamo to be driven from a steam engine.

I bought this little motor for £3 at my local club auction night so for what I paid it's no great loss if it doesn't work but I'd like to put it to use if I can. I've hooked it up to a small LED (I think it is a car headlight lamp) but can't get any sign of it lighting. I've tried the motor in both directions and also reversed the polarity of the leads but still nothing  :(

Admittedly the spec says 5200rpm and I'm only so far running it in my lathe at about 1100rpm but I'd have expected a glimmer of light ?  :headscratch:

As it is an AC 240v mains motor presumably it will supply AC? Do LED lamps need DC ?

Any help greatly appreciated, thanks  :)




Offline crueby

  • Full Member
  • *****
  • Posts: 8895
  • Rochester NY
Re: Using a small motor as a dynamo.
« Reply #1 on: November 09, 2018, 10:16:01 PM »
Most LED's are DC, if it is a car light, definitely DC. If you have a voltmeter, try hooking that up to see if you are generating anything at all with the motor (on AC setting, I would assume).
As for what it takes to make a AC motor generate electricity, that is way too long ago to my AC circuits classes!

Offline Gas_mantle

  • Full Member
  • ****
  • Posts: 1334
  • North Yorks - UK.
    • My Youtube channel
Re: Using a small motor as a dynamo.
« Reply #2 on: November 09, 2018, 10:22:21 PM »
Thanks Chris  :)

Unfortunately I don't have a Voltmeter, I'll see if I can find a torch bulb to try tomorrow.

I'm not even sure if AC motors can be used as generators the same way that DC ones can  :headscratch:

Offline crueby

  • Full Member
  • *****
  • Posts: 8895
  • Rochester NY
Re: Using a small motor as a dynamo.
« Reply #3 on: November 09, 2018, 10:31:05 PM »
Thanks Chris  :)

Unfortunately I don't have a Voltmeter, I'll see if I can find a torch bulb to try tomorrow.

I'm not even sure if AC motors can be used as generators the same way that DC ones can  :headscratch:
If you google 'generate electricity from ac motor' you will get a bunch of articles on it.

Offline Florian Eberhard

  • Full Member
  • ****
  • Posts: 432
Re: Using a small motor as a dynamo.
« Reply #4 on: November 09, 2018, 10:31:17 PM »
Hey Peter

Does this Motor have magnets (in other words, is it a dc motor) or is it a universal motor with field windings?
If its the second you won't be able to use it as a generator as it is. (it could probably work if you use an exciter to build up a magnetic field but i don't know if anything else is required for it to work)

Florian

Offline Gas_mantle

  • Full Member
  • ****
  • Posts: 1334
  • North Yorks - UK.
    • My Youtube channel
Re: Using a small motor as a dynamo.
« Reply #5 on: November 09, 2018, 10:47:29 PM »
Thanks, I suspect it is an AC motor, it came of a mains powered sewing machine.

I'll have a bit of a tinker with it tomorrow and possibly take a look inside. When I bought it I didn't consider the fact that AC may be unsuitable for what I want  :(

Offline Florian Eberhard

  • Full Member
  • ****
  • Posts: 432
Re: Using a small motor as a dynamo.
« Reply #6 on: November 09, 2018, 11:01:02 PM »
Hey Peter

These motors can be quite handy for driving small milling Spindle or similar (held in the toolpost of your lathe for example)

By the Way: you should look for a motor with low rpm to get some useful voltage out of it. The lower the rpm per volt rate is, the more volts you get when you drive it with a steam engine.

Florian

Offline Don1966

  • Full Member
  • *****
  • Posts: 5996
  • Morgan City, LA (Along the Gulf Coast)
Re: Using a small motor as a dynamo.
« Reply #7 on: November 10, 2018, 01:25:04 AM »
This motor looking like a universal motor can run on AC or DC it is however serie connected and can be a generator but the load must be attached to it to put out voltage. Some my not have enough residual magnetism to do that only trying it with a load will tell. Good luck!

Don

Offline MJM460

  • Full Member
  • ****
  • Posts: 895
  • Melbourne, Australia
Re: Using a small motor as a dynamo.
« Reply #8 on: November 10, 2018, 08:26:02 AM »
Hi Peter, I would suggest a car headlight, even LED type, as a test load would be a bit like trying to power a large truck with a motor scooter engine.  You need some little LED's from an electronics supply outlet, about 10c ea, and a small collection of resistors.  And I suggest that you really need a digital voltmeter to work out what's going on.

A cheap voltmeter will do, but it will not be long before you want a very low voltage scale, say mV, and one with a thermocouple for measuring your steam conditions, both available in relatively low cost meters these days.  Get some 1ohm resistors and a five ohm as a load for your generator and measure the voltage across them for current using ohms law.

A normal LED has a forward voltage drop (when it lights up) of about 1.2 V, but needs a series resistor to limit the current to something in the range of 1 to 20 mA so as not to burn it out.  So you need to know the maximum likely voltage to calculate the required resistor.

Once you are getting some output, you can measure it and then see what you can do to increase it to something more useful.  Or just power a string of LED's.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 830
  • North Wales, Great Britain.
Re: Using a small motor as a dynamo.
« Reply #9 on: November 10, 2018, 11:44:14 AM »
Good morning Peter.

From the photo I can see that there's a four pin socket under the motor. I presume for the foot operated speed control. I also noticed a cable at the back with two wires. If you're looking for a voltage from that wire you're not going to see one because part of the circuit is missing/open.

Are you able to remove the box with the socket attached? If you can you should be able to see the wires that go into the motor itself. As Don has pointed out it's a small " Universal " motor capable of being run from either AC or DC. Hopefully there will be just two wires going into the motor body itself and it's those where you'll need to attach your bulb to.

Don't forget that some LED lamps are " polarity conscious " and your motor will be outputting DC when driven, this is where a cheap voltmeter would come in handy. Alternatively find an incandescent bulb of reasonable wattage instead.

Cheers Graham.

Offline Ian S C

  • Full Member
  • ****
  • Posts: 1065
  • Stirling Engine Maker Darfield Canterbury N Z
Re: Using a small motor as a dynamo.
« Reply #10 on: November 10, 2018, 12:02:59 PM »
Forget it, the easiest to find is a small DC motor (old printers and that sort of thing), or find any small motor With permanant magnets either stator or armature, if it has brushes you get DC, if it's brushless AC. If you get adventuristic  you can do some modifications to a motor, and turn it into an alternator.
I took a small shaded pole motor, and remove the armature, and made a new one similar to the shape of one in an automotive alternator, but with a magnet inside the claws of the armature. I did cut the shading rings on the poles of the motor, but there was little if any difference in the output of the alternator.  This is suitable for driving from one of my hot air engines that has a shaft power of about 5 Watts at last test. This is only one of about half a dozen generators / alternators that I use on my motors.
Ian S C
         
« Last Edit: November 10, 2018, 12:12:33 PM by Ian S C »

Offline Gas_mantle

  • Full Member
  • ****
  • Posts: 1334
  • North Yorks - UK.
    • My Youtube channel
Re: Using a small motor as a dynamo.
« Reply #11 on: November 10, 2018, 12:39:16 PM »
Many thanks for all the replies, it's given me a few things to think about.

I think Graham may have hit the nail on the head in mentioning there would have been a foot operated treadle attached and in the present state the circuit may be incomplete. I'll have a bit of a play around over the next few days and see what I can manage. I have a vertical engine near completion and bought the motor as an impulse buy thinking it may be worth trying to get it power a small bulb etc, it only cost £3 so if it doesn't work its no great loss.

Offline pgp001

  • Full Member
  • ****
  • Posts: 656
  • West Yorkshire - UK
Re: Using a small motor as a dynamo.
« Reply #12 on: November 10, 2018, 05:32:07 PM »
Peter

You may have looked already, but there is a generic wiring diagram available on the net. This is one of many similar ones.

https://www.quiltingboard.com/vintage-antique-machine-enthusiasts-f22/snap-crackle-pop-t250376.html

Phil

Offline Admiral_dk

  • Full Member
  • ****
  • Posts: 1401
  • Søften - Denmark
Re: Using a small motor as a dynamo.
« Reply #13 on: November 11, 2018, 08:36:41 PM »
Most LED's are killed if you expose them to more than 5V reverse voltage => AC is an absolute NO, NO  :zap:
and as mentioned you also need a series resistor and the size depends on voltage .... all in all - don't use LED's for testing - or perhaps - only use single LED's or better two anti-parallel connected with a series resistor.

Offline Gas_mantle

  • Full Member
  • ****
  • Posts: 1334
  • North Yorks - UK.
    • My Youtube channel
Re: Using a small motor as a dynamo.
« Reply #14 on: November 11, 2018, 09:32:33 PM »
Thanks guys I realise now that an LED may not be the best light to use as a test so I'll get hold of a bulb and do further tests in a few days but it looks like my idea of powering a small lamp isn't really possible without getting involved in modifications etc.

It's probably worth me buying a cheapo multimeter tho, there have been a few occasions recently where one could have been useful.

Just as a matter of interest, has anyone got a Stuart or a PMR dynamo? I rather like the retro look but the Stuart seems hideously expensive at over £200 for the castings  :o  I'm sure with a bit of thought it can't be too difficult to make one for a lot less.
« Last Edit: November 11, 2018, 09:37:56 PM by Gas_mantle »

Offline Don1966

  • Full Member
  • *****
  • Posts: 5996
  • Morgan City, LA (Along the Gulf Coast)
Re: Using a small motor as a dynamo.
« Reply #15 on: November 11, 2018, 10:58:47 PM »
Most LED's are killed if you expose them to more than 5V reverse voltage => AC is an absolute NO, NO  :zap:
and as mentioned you also need a series resistor and the size depends on voltage .... all in all - don't use LED's for testing - or perhaps - only use single LED's or better two anti-parallel connected with a series resistor.
You can put a diode reversed form the LED forward voltage to protect it using A/C with a ballast resistor if you use One LED or two LED back to back with opposite polarity !

Don

Offline steamer

  • Global Moderator
  • Full Member
  • *****
  • Posts: 10316
  • Central Massachusetts, USA
Re: Using a small motor as a dynamo.
« Reply #16 on: November 12, 2018, 10:16:12 AM »
There is a vast world of brushless motors on fhe market that should work just cine  both in runners and outrunners
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Alyn Foundry

  • Full Member
  • ****
  • Posts: 830
  • North Wales, Great Britain.
Re: Using a small motor as a dynamo.
« Reply #17 on: November 12, 2018, 10:24:41 AM »
Good morning Peter.

Glad to read you're going to have a " poke " around inside that casing, however....

Like Ian I'd strongly suggest an alternative, there's an amazing amount of permanent magnet motors fitted to motor cars. Having a PM field the armature will automatically start to deliver a voltage as soon as it begins rotating. Early Vauxhall cars had a large size motor for the radiator cooling fan.

You could then fabricate a suitable casing to " hide " the motor in. Obviously, patterns and a casting would be my suggestion!! :)

I've just remembered that Andy, Chipmaster, posted some photos on the Retlas thread, I'll link them as an edit.

Cheers Graham.

As promised....    http://www.modelenginemaker.com/index.php/topic,5720.msg141827.html#msg141827
« Last Edit: November 12, 2018, 10:38:00 AM by Alyn Foundry »

Offline Ian S C

  • Full Member
  • ****
  • Posts: 1065
  • Stirling Engine Maker Darfield Canterbury N Z
Re: Using a small motor as a dynamo.
« Reply #18 on: November 12, 2018, 12:01:39 PM »
Here is a small selection of my generating machinery. On the engine is a DC motor from a large printer, on the table left rear is a Sturmy Archer hub dynamo (AC) that I had set up for a wind mill. Right rear is the alternator from my post above, front left, the black tube hides a DC motor from a kitchen stick mixer, and the one on the right is a little DC motor from a HP printer.  You only get out what you put in, so it's the one with the best bearings that wins, all of these 5 end up the same with that or similar power motors.
« Last Edit: November 12, 2018, 12:09:22 PM by Ian S C »

Offline Roger B

  • Global Moderator
  • Full Member
  • *****
  • Posts: 3987
  • Switzerland
Re: Using a small motor as a dynamo.
« Reply #19 on: November 12, 2018, 06:30:39 PM »
Permanent magnet 'hobby' motors work well as dynamos for model engines (if you are into IC engines they can also be used as starter motors).
Best regards

Roger