Building a pedal power bicycle 12 volt generator, ghetto style - Page 8

camimfajardo · 05-04-09, 10:45 PM

Hi,

This is a great Idea turned cheap. I love it.
Can you please explain a little more about the electrical connections?
I think that the generator goes connected to the battery with a switch in between, and then the power inverter goes connected to the battery (with a switch as well?).

So, it seems that when you connect the battery to the generator/motor the motor will start spinning, and you only have to get on the bicycle and pedal against the motor? is that right?

Also, I'm debating whether to use a car alternator or not. I am planning to go to a junker and buy a car alternator. Do you think that the car alternator would require a high (too high?) pedaling speed to work? on the other hand, what would be the best way to get a used 12 volts permanent magnet motor?

Thank you,

Regards,

MetroMPG · 05-20-09, 07:53 AM

Quote:

Originally Posted by camimfajardo

Can you please explain a little more about the electrical connections?
I think that the generator goes connected to the battery with a switch in between, and then the power inverter goes connected to the battery (with a switch as well?).

That's right. Except the inverter's "switch" was just a set of small alligator clips.

Quote:

So, it seems that when you connect the battery to the generator/motor the motor will start spinning, and you only have to get on the bicycle and pedal against the motor? is that right?

Right again.

Quote:

Also, I'm debating whether to use a car alternator or not. I am planning to go to a junker and buy a car alternator. Do you think that the car alternator would require a high (too high?) pedaling speed to work?

It will require a LOT of effort, unless you modify the alternator's field circuit to reduce its strength.

Watch this video. This is an unmodified car alternator, and the rider is out of breath after a minute of powering a light:

YouTube - Exercise bike generator uses car alternator

Quote:

on the other hand, what would be the best way to get a used 12 volts permanent magnet motor?

eBay, probably. And junk yards are full of 12v permanent magnet motors (in cars - for electric windows, seats, wipers, blowers, etc.)

Thank you,

Regards,[/quote]

NiHaoMike · 05-28-09, 03:37 PM

http://techno-fandom.org/~hobbit/cars/boost-hack/
Maybe try that trick to get more voltage at lower speeds? I actually tried it with the motor for my hybrid bike. By turning the motor by hand (I don't have it installed yet) without the circuit, it only generates about 2v. But with the circuit, it goes up to over 200v!

MetroMPG · 05-28-09, 03:43 PM

I'm not ashamed to admit that Hobbit & Lee Hart are over my head.

(You too, NiHaoMike!)

NiHaoMike · 05-28-09, 10:40 PM

It really has to do with Faraday's Law and Lenz's Law. The voltage induced in a coil of wire is proportional to the rate of change of magnetic flux, which is proportional to the speed of the generator shaft. Therefore, at low speeds, the generator will not normally generate enough voltage to be useful. But at those low speeds, if you short the generator output, the current induced in the coil generates another magnetic field to oppose the incoming magnetic field. Then remove the short and the magnetic field that was opposing disappears, causing a fast rate of change of flux and a corresponding high voltage. The transistor acts as the switch to connect and disconnect the short circuit and the rectifier automatically routes the boosted voltage to the rest of the circuit. (That is actually remarkably similar to how a magneto works.)

BTW, that description was based on Stephanie Wood's (a friend of mine) explanation of how it works. (She is actually really into Hobbit's articles.)

jimmo · 12-07-09, 10:09 AM

not sure if someone mentioned this above, didnt have time to read it all, but by installing a cheap diode the motor will not turn the wheel and you will produce a lot more current. I made a pedal generator last year and use it all winter long. I can sustain about 80 watts avg for a good length of time so a lap top should be no problem with a diode in the positive line.

MetroMPG · 12-07-09, 10:26 AM

Hi jimmo -

Got any pictures of your setup?

Quite a few people have mentioned the diode in the YouTube comments. I didn't add one because it wasn't in my junk pile, and honestly I wouldn't know how to choose one for the job from Radio Shack (or wherever).

Quote:

by installing a cheap diode the motor will not turn the wheel and you will produce a lot more current.

I thought the diode was only a "one way door" that prevented current flow from the battery to the motor. Are you saying that adding one would increase the electrical output for the work being done?

jimmo · 12-07-09, 02:50 PM

I cant say for shure but I think energy is being wasted on magnetising the coils in your motor even though you are spinning it faster than it will on its own. I could be wrong. I am going to try to bypass my diode and pedal mine the same way. If I can't sustain the same power as when I am using the diode then my theory is correct.
I got away with using radio shack diodes all of last winter but this year I upgraded to a 40 amp diode from ebay because I installed a watts up meter in line. If my radio shack diode failed it would ruin the meter and I was pushing the limits of those diodes. I had two installed in parallel.
I will take some photos of it and post em later.
In the winter I use it almost everyday. I power a television during my workout. Its pretty cool. I never realized how many people out there are doing things like this.
lots of good info on this site... David Butcher: Pedal Powered Generator - DIY Plans

MetroMPG · 12-07-09, 03:00 PM

Thanks for the info, jimmo. Looking forward to the photos!

jimmo · 12-07-09, 07:15 PM

OK, here are some photos of mine. Gonna try bypassing the diode, Ill let ya know how it works. One thing I just realized is that this motor is a 24v 350 watt and I am using it to charge a 12 volt system and inverter. This might have something to do with its efficiency. As you can see I have a large diameter roller because it doesnt take many rpms to make 15 volts from this motor. Also the large diameter creates a lot less rolling resistance and runs cooler and quieter. this set up is a lot quieter than the roller that came with the trainer from the factory.

05-28-09, 03:37 PM	#73
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	http://techno-fandom.org/~hobbit/cars/boost-hack/ Maybe try that trick to get more voltage at lower speeds? I actually tried it with the motor for my hybrid bike. By turning the motor by hand (I don't have it installed yet) without the circuit, it only generates about 2v. But with the circuit, it goes up to over 200v! __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

05-28-09, 03:43 PM	#74
MetroMPG Infrequent noob Join Date: Aug 2008 Location: 1000 Islands region, Ontario, Canada Posts: 402 Thanks: 37 Thanked 20 Times in 19 Posts	I'm not ashamed to admit that Hobbit & Lee Hart are over my head. (You too, NiHaoMike!) __________________ . To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

05-28-09, 10:40 PM	#75
NiHaoMike Supreme EcoRenovator Join Date: Oct 2008 Location: Austin, TX Posts: 1,154 Thanks: 14 Thanked 257 Times in 241 Posts	It really has to do with Faraday's Law and Lenz's Law. The voltage induced in a coil of wire is proportional to the rate of change of magnetic flux, which is proportional to the speed of the generator shaft. Therefore, at low speeds, the generator will not normally generate enough voltage to be useful. But at those low speeds, if you short the generator output, the current induced in the coil generates another magnetic field to oppose the incoming magnetic field. Then remove the short and the magnetic field that was opposing disappears, causing a fast rate of change of flux and a corresponding high voltage. The transistor acts as the switch to connect and disconnect the short circuit and the rectifier automatically routes the boosted voltage to the rest of the circuit. (That is actually remarkably similar to how a magneto works.) BTW, that description was based on Stephanie Wood's (a friend of mine) explanation of how it works. (She is actually really into Hobbit's articles.) __________________ To my surprise, shortly after Naomi Wu gave me a bit of fame for making good use of solar power, Allie Moore got really jealous of her...

12-07-09, 03:00 PM	#79
MetroMPG Infrequent noob Join Date: Aug 2008 Location: 1000 Islands region, Ontario, Canada Posts: 402 Thanks: 37 Thanked 20 Times in 19 Posts	Thanks for the info, jimmo. Looking forward to the photos! __________________ . To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

12-07-09, 07:15 PM	#80
jimmo Lurking Renovator Join Date: Dec 2009 Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	OK, here are some photos of mine. Gonna try bypassing the diode, Ill let ya know how it works. One thing I just realized is that this motor is a 24v 350 watt and I am using it to charge a 12 volt system and inverter. This might have something to do with its efficiency. As you can see I have a large diameter roller because it doesnt take many rpms to make 15 volts from this motor. Also the large diameter creates a lot less rolling resistance and runs cooler and quieter. this set up is a lot quieter than the roller that came with the trainer from the factory. Attached Thumbnails

05-04-09, 10:45 PM	#71
camimfajardo Lurking Renovator Join Date: May 2009 Posts: 1 Thanks: 0 Thanked 0 Times in 0 Posts	Hi, This is a great Idea turned cheap. I love it. Can you please explain a little more about the electrical connections? I think that the generator goes connected to the battery with a switch in between, and then the power inverter goes connected to the battery (with a switch as well?). So, it seems that when you connect the battery to the generator/motor the motor will start spinning, and you only have to get on the bicycle and pedal against the motor? is that right? Also, I'm debating whether to use a car alternator or not. I am planning to go to a junker and buy a car alternator. Do you think that the car alternator would require a high (too high?) pedaling speed to work? on the other hand, what would be the best way to get a used 12 volts permanent magnet motor? Thank you, Regards,

12-07-09, 10:09 AM	#76
jimmo Lurking Renovator Join Date: Dec 2009 Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	not sure if someone mentioned this above, didnt have time to read it all, but by installing a cheap diode the motor will not turn the wheel and you will produce a lot more current. I made a pedal generator last year and use it all winter long. I can sustain about 80 watts avg for a good length of time so a lap top should be no problem with a diode in the positive line.

12-07-09, 02:50 PM	#78
jimmo Lurking Renovator Join Date: Dec 2009 Posts: 11 Thanks: 0 Thanked 0 Times in 0 Posts	I cant say for shure but I think energy is being wasted on magnetising the coils in your motor even though you are spinning it faster than it will on its own. I could be wrong. I am going to try to bypass my diode and pedal mine the same way. If I can't sustain the same power as when I am using the diode then my theory is correct. I got away with using radio shack diodes all of last winter but this year I upgraded to a 40 amp diode from ebay because I installed a watts up meter in line. If my radio shack diode failed it would ruin the meter and I was pushing the limits of those diodes. I had two installed in parallel. I will take some photos of it and post em later. In the winter I use it almost everyday. I power a television during my workout. Its pretty cool. I never realized how many people out there are doing things like this. lots of good info on this site... David Butcher: Pedal Powered Generator - DIY Plans