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small DC motor/generator shopping

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Prismseed

New Member
I want to play with getting electricity out of a dc motor. Power a few LEDs, be handy if I could take it apart and practice motor maintenance and brush replacement. Tips on what to look for?
 

MaxHeadRoom78

Well-Known Member
Most Helpful Member
What size and voltage/current are you interested in? Treadmill Motors have a bit of power. and generate 100v at full RPM.
Just run them slower for lower voltage.
At one time it was warned that removing the rotor on a PM motor without inserting a 'Keeper' resulted in a loss of magnetism, now with modern rare earth magnets it is not so much of a concern.
Max.
 

Prismseed

New Member
Reply well to start just some leds. How newb friendly would it be to get a higher amp motor, then practice stepping it down? I'm not familiar with them but there seems to be adjustable breaker switches, could that be a protective step to prevent burning out parts?
 

tcmtech

Banned
Most Helpful Member
On the more practical application sense being you say you want to only run a few LED's then you don't need much of a motor. Most anything that is rated at a lower RPM and voltage will work good for what you want to play with.

Personally if you want to get by cheap or possibly free stop by any local office supply and equipment repair place and ask their service department manger if you could have a few old copier machine motors of assorted sizes. Odds are they will have several junk units you can pick parts from for free. ;)

Good chance you will end up with a collection of low speed high torque brushed and brushless servo and drive motors and likely some stepper motors as well. If the guy is really nice you might even get a few old circuit boards and power supplies to go with them too of which many control panel boards are loaded with LED's! :woot:
 

MaxHeadRoom78

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The leds are only going to draw the current required, as long as the motor can supply or even higher is OK.
You just need to back feed or rotate the motor to produce your required supply Voltage e.g. if you have a motor rated at 90v @ 2000rpm, driving it at 1000rpm would give you a little less than 45vdc.
Max
 

MaxHeadRoom78

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If you go with too small a motor, you may find them difficult to take apart as often they are cheap style case and crimped etc making it hard to dismantle easily.
Max.
 

Colin

Active Member
5v from a Hand Cranked Generator
When the handle is turned fairly quickly, the output of the motor produces a maximum of 5.5v and has a current under short-circuit conditions of about 400mA. This project is fully described in the link below and shows how to increase the voltage of the generator by adding 100 turns to each pole of the generator and this will increase its charging current to a 3.6v Li Ion battery.
www.talkingelectronics.com/projects/SpotMistakes/SpotMistakesP8.html


GeneratorCct.gif

The diode and LED connected
to the generator


wind-up%20torchRadio.jpg

Wind-up Torch/Radio

Torch-1.jpg

THE HAND-CRANKED TORCH - charging current 175mA
(after the modification)


3.6vCell.gif

Close-up of the 3.6v Li Ion 450mAhr cell
 
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MaxHeadRoom78

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Most Helpful Member
The OP mentioned he also wanted something to take apart to find out about motor construction/maintenance etc?
Max.
 

schmitt trigger

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Discarded toys are an excellent source of small permanent magnet DC motors. And they should be capable of powering a few LEDs
 

tcmtech

Banned
Most Helpful Member
THE HAND-CRANKED TORCH - charging current 175mA
(after the modification)


Close-up of the 3.6v Li Ion 450mAhr cell.

So once the coin cell battery goes dead you have to crank the generator for a good 3 - 4 hours to charge it back up? o_O

Methinks there be a design flaw of practicality there. :oops:
 

Prismseed

New Member
My salvage options are pretty dry right now. A complication I'm having looking in stores is there is a lot of electric motors that don't easily say what kind of motor they are.
 

MaxHeadRoom78

Well-Known Member
Most Helpful Member
Look for the presence of brushes, an indication of DC brushed,
If you find a small motor that might be a small induction motor, connect the leads together and spin it if it spins freely, no braking, then it is probably not what you want.
Max.
 

spec

Well-Known Member
Most Helpful Member
I want to play with getting electricity out of a dc motor. Power a few LEDs, be handy if I could take it apart and practice motor maintenance and brush replacement. Tips on what to look for?

Hi Prism,
Just a thought- most cars (autos) are jammed with motors- from very small (mirror motors) medium (seat, wiper) to massive (starter). I would think you would be spoilt for choice and one thing you can be fairly sure about is that they will all be 12V DC. Any car breakers yard would be able to get you a suitable motor for a low cost.

You mention brushes but many small motors, like personal computer (PC) DC fans are brushless. Instead of brushes and an armature, the commutation is implemented by hall effect sensors and switching transistors. I would think you could have some fun with a computer fan motor and they are dead easy to work with. Once again, you should be able to get a computer fan from many sources for next to nothing- make sure you don't get an AC type though.

As you probably know, there are various types of DC motor, but in broad terms you will find that the permanent magnet types will be better suited for your investigations because they are simpler to use.

spec
 

MaxHeadRoom78

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Although for practicing brushed motor maintenance as the OP mentions, a PC fan is virtually useless and is usually a throw away item if it fails.
Max.
 

spec

Well-Known Member
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Although for practicing brushed motor maintenance as the OP mentions, a PC fan is virtually useless and is usually a throw away item if it fails.
Max.
The OPs opening statement is that he would like to get electricity out of a motor to light some LEDs. and I am saying that a permanent magnet motor would be easiest for that purpose. Many motors, including power tool motors are moving away from brushes over to solid state commutation, so if the OP wants to get experience with motors in addition to the old brushes and commutator type it would be wise to investigate the new wave.

I an not sure what you mean by your statement throw away items. If you mean people don't bother to service them, then that is correct, but that is probably true of most small motors and often large motors in view of the high labor costs these days. I know they are generators, but often a car (auto) alternator will be scrapped because the brushes are worn or one of the bearings have gone- both simple repairs.

As for fan motors, they are normally changed either because they have become noisy or they have ceased up entirely. Both faults are easy to fix. The other thing is that a fan motor would make an excellent little alternator by taking the output directly from the coils and possibly using diode rectifiers to produce DC. The advantage of a PC fan motor is the small size, simple disassembly, free availability and also that the operation is clear to see when they are opened up. In that sense they would be educational. This is not the case with most motors.
 

shortbus=

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but often a car (auto) alternator will be scrapped because the brushes are worn or one of the bearings have gone- both simple repairs.

If you can find the parts. A lot of whats made today, there are no supply side outlets for the DIYer, they are only available to the "big guys".
 

MaxHeadRoom78

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On the same line a wish to practice motor maintenance was also expressed and changing brushes etc, which virtually limits it to DC brushed and Universal motors.;)
Max.
 

spec

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If you can find the parts. A lot of whats made today, there are no supply side outlets for the DIYer, they are only available to the "big guys".
I can get brushes for any alternator from a number of local car spares shops. I don't know about your part of the USA, but you can certainly get alternator brushes by mail order.

For any obscure or or old alternator or motor for that mater you can always fit brushes from a unit with bigger brushes and simply file them down. By the way, the brushes on an alternator have a real easy time.

https://www.jcrsupplies.co.uk/products/ALTERNATOR_REBUILD_PARTS

**broken link removed**

https://www.google.co.uk/#q=alternator+brushes&tbm=shop
 
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spec

Well-Known Member
Most Helpful Member
On the same line a wish to practice motor maintenance was also expressed and changing brushes etc, which virtually limits it to DC brushed and Universal motors.;)
Max.
I want to play with getting electricity out of a dc motor. Power a few LEDs, be handy if I could take it apart and practice motor maintenance and brush replacement. Tips on what to look for?
I would like to see you light a few LEDs with a universal motor. The OPs post is about learning about motors not specifically about only learning about brushes.
spec
 

dr pepper

Well-Known Member
Most Helpful Member
Have aplay by all means, brushes in most motors except expensive ones are not replaceable.
A stepper motor is a good way to light leds at low speeds.
 
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