DIY Generator - Page 4 - Electronic Circuits Projects Diagrams Free

audioguru · 26th October 2005, 02:33 PM

Like a guy on another electronics chat forum who wanted to use a computer fan as a generator to power many LEDs and charge Ni-MH cells on his bicycle.

The fan actually powered a single LED very dimly when he was going as fast as he could go downhill. It would take weeks to charge his little battery.

I suggested reversing the connections so the little fan was powered from his battery and it could propel him along. Its thrust was about 10 grams. :lol:

**Nigel Goodwin** · 26th October 2005, 03:18 PM

Quote:

Originally Posted by williB

no i havnt tried a dc motor/generator ..
i'm gonna keep plugging away , i wouldnt say all the results so far are poor..
with the single phase generator i was getting a lot more voltage but the coils were bigger .
i've ordered some 20 gage wire ( .032 '' ) which should give better results for a three phase genny..

It's not voltage that's important, it's power!, all the results you've mentioned so far are only very low power. Remember the little DC dynamo's you get on push bikes?, they produce enough for the lights whilst taking very little effort from the rider.

I'm very impressed with the effort you're putting into it, but the results are rather disappointing.

williB · 29th October 2005, 02:28 AM

Whew !!
almost done !!
it still needs a little tweaking, like adjusting the air gaps .
i ran out of brass screws , and had to use stainless.
and i still have to solder some of the connections.
this is my first 18 coil 24 magnet three phase generator !
the last phase was the easiest to attach because there was only one spot left to put the coils :lol:

Someone Electro · 29th October 2005, 06:02 AM

Big mess of wires. :lol:

You have to triple check here to make shure evrything is wired up right.

The easyest mistake to make is conecting the coil the worng way round becose bouth wires are identical.

williB · 29th October 2005, 05:51 PM

Well the results are in..
I was close when i said the open circuit voltage would be 11v it is actually 12.5 to 13.05 Volts depending on which meter i use ..
the measured resistance of each phase is 0.5 Ohms and the line to line resistance is 1.0 ohms..
all measurements are DC and are recitfied with six diodes, and all current measurements are taken with the meter on the 10A scale..
into a 1 ohm resistor at one speed i got 3.9V @ 4.05 A = 15.75 W
at a faster speed also into a 1 ohm resistor i got 4.16V @ 4.28A = 17.8 W
and with the output going directly into the meter on the 10A scale 6.67A @ 1.97V = 13.14W
not too shabby for (24) 1/2 '' magnets and some wire ..
I cant wait till the 20awg wire gets here..

audioguru · 29th October 2005, 08:07 PM

Watts (what's) the efficiency? A couple of hundred watts of work to get 15W out?

williB · 30th October 2005, 03:15 AM

Quote:

Originally Posted by audioguru

Watts (what's) the efficiency? A couple of hundred watts of work to get 15W out?

please dont post in my threads anymore, thanks

williB · 30th October 2005, 03:45 AM

I've found a new source for Neo-Magnets, but havnt tried them yet..
http://www.magnetsrc.com/neo_NdFeB_m...isc_magnet.htm

below is a new generator designed with 7/8'' dia x .5'' magnets, it should give , an open circuit , output of at least 32 V with 20 AWG wire , current estimates are unknown at this point .. :lol:
oh the coils are 1.75'' dia., twice the magnet dia..

**Nigel Goodwin** · 30th October 2005, 07:53 AM

Quote:

Originally Posted by williB

Quote:

Originally Posted by audioguru

Watts (what's) the efficiency? A couple of hundred watts of work to get 15W out?

please dont post in my threads anymore, thanks

It's a VERY valid question, so far your designs appear to be very low efficiency, and you don't seem to be testing how well they work?.

williB · 30th October 2005, 02:17 PM

How would you test them ?
ps my apologies audioguru

**Nigel Goodwin** · 30th October 2005, 03:25 PM

Quote:

Originally Posted by williB

How would you test them ?
ps my apologies audioguru

How about 'the perpetual motion way'?.

Use a DC motor to spin your generator, monitor the current to the DC motor and the voltage across the motor - simple VxI gives you the input power to the drive motor.

Apply varying resistive loads to the output of the generator, again monitoring both current and voltage (FOUR multi-meters would be useful here!), simple VxI gives you the output power. You should be able to find a load value that gives the most power (largest VxI). It will give you the opportunity to post some more nice diagrams, this time of the load versus power graphs.

By comparing the input power and the output power, and at different load levels and speeds, you can get an idea of how efficient it is. Using different speeds might be informative as well?.

Obviously, this introduces the unknown efficiency of the drive motor, but you can ignore that as you're not wanting absolute values, just a comparative test of which might be better.

As I mentioned previously, try a commercial dynamo or alternator, or a DC motor backwards, and see how your generators compare - if you're not beating them it's rather a pointless exercise? - but VERY educational!.

williB · 30th October 2005, 07:01 PM

Nigel , i think that sounds like a lot of work .. and to what end?? i know it works.. and works well..!!

**Nigel Goodwin** · 30th October 2005, 07:05 PM

Quote:

Originally Posted by williB

Nigel , i think that sounds like a lot of work .. and to what end?? i know it works.. and works well..!!

I thought you were trying to make subjective tests?, but perhaps you're not bothered about how well it works? - as long as it works well enough!.

JimB · 30th October 2005, 09:05 PM

Willie,

At the risk of having missed the point somewhere here, there are two things which seem to be wrong with your generator.

The rather odd ratio of magnets and coils, I would have expected a ratio of 1:1 or 2:1, but I am not an expert on 3 phase genrators.

What are the coils mounted on? it looks like a wooden board, and they are held on with brass or stainless steel screws.
What are the magnets mounted on? I cannot tell.

You have a serious problem here, there is no magnetic circuit!
Have a look at (say) a simple permanent magnet motor. There will be two iron poles from the magnet. The poles are very close to the rotor, a very small air gap, and the rotor is its self made of iron.
Lots of magnetic material to make a magnetic circuit.

What is in your magnetic circuit? several inches of air and wood. Not good.

JimB

bryan1 · 30th October 2005, 09:36 PM

Hiya Willi,
As Jim stated above, it looks like you've mounted everything on plywood and not steel. All the stators I've looked at are suspended in fibreglass and held stationary. The magnets are mounted onto a disc of 3/8" minimun as this lets the flux generatored from the magnets to flow. This has been talked about heaps on the otherpower forum and atleast I find by reading otherpower posts I can avoid their mistakes and make up a working unit in 1 go.

Cheers Bryan

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26th October 2005, 02:33 PM	(permalink)
audioguru	Like a guy on another electronics chat forum who wanted to use a computer fan as a generator to power many LEDs and charge Ni-MH cells on his bicycle. The fan actually powered a single LED very dimly when he was going as fast as he could go downhill. It would take weeks to charge his little battery. I suggested reversing the connections so the little fan was powered from his battery and it could propel him along. Its thrust was about 10 grams. :lol: __________________ Uncle $crooge

29th October 2005, 06:02 AM	(permalink)
Someone Electro	Big mess of wires. :lol: You have to triple check here to make shure evrything is wired up right. The easyest mistake to make is conecting the coil the worng way round becose bouth wires are identical. __________________ Il give you shocking experience.

29th October 2005, 05:51 PM	(permalink)
williB	Well the results are in.. I was close when i said the open circuit voltage would be 11v it is actually 12.5 to 13.05 Volts depending on which meter i use .. the measured resistance of each phase is 0.5 Ohms and the line to line resistance is 1.0 ohms.. all measurements are DC and are recitfied with six diodes, and all current measurements are taken with the meter on the 10A scale.. into a 1 ohm resistor at one speed i got 3.9V @ 4.05 A = 15.75 W at a faster speed also into a 1 ohm resistor i got 4.16V @ 4.28A = 17.8 W and with the output going directly into the meter on the 10A scale 6.67A @ 1.97V = 13.14W not too shabby for (24) 1/2 '' magnets and some wire .. I cant wait till the 20awg wire gets here..

29th October 2005, 08:07 PM	(permalink)
audioguru	Watts (what's) the efficiency? A couple of hundred watts of work to get 15W out? __________________ Uncle $crooge

30th October 2005, 02:17 PM	(permalink)
williB	How would you test them ? ps my apologies audioguru

30th October 2005, 07:01 PM	(permalink)
williB	Nigel , i think that sounds like a lot of work .. and to what end?? i know it works.. and works well..!!

30th October 2005, 09:05 PM	(permalink)
JimB	Willie, At the risk of having missed the point somewhere here, there are two things which seem to be wrong with your generator. The rather odd ratio of magnets and coils, I would have expected a ratio of 1:1 or 2:1, but I am not an expert on 3 phase genrators. What are the coils mounted on? it looks like a wooden board, and they are held on with brass or stainless steel screws. What are the magnets mounted on? I cannot tell. You have a serious problem here, there is no magnetic circuit! Have a look at (say) a simple permanent magnet motor. There will be two iron poles from the magnet. The poles are very close to the rotor, a very small air gap, and the rotor is its self made of iron. Lots of magnetic material to make a magnetic circuit. What is in your magnetic circuit? several inches of air and wood. Not good. JimB __________________ Experience is directly proportional to the value of the equipment ruined.

30th October 2005, 09:36 PM	(permalink)
bryan1	Hiya Willi, As Jim stated above, it looks like you've mounted everything on plywood and not steel. All the stators I've looked at are suspended in fibreglass and held stationary. The magnets are mounted onto a disc of 3/8" minimun as this lets the flux generatored from the magnets to flow. This has been talked about heaps on the otherpower forum and atleast I find by reading otherpower posts I can avoid their mistakes and make up a working unit in 1 go. Cheers Bryan __________________ " The only way to avoid human error is to avoid the use of humans"