Generator light

[FLYBYU44]

Wow I just found this forum, it's great! I've always been addicted to flashlights and bike lights so this fits right in there. I am totally ignorant when it comes to electrical stuff though and I want to learn more. I have Vista lights for my bike right now (I ride a recumbent by the way) and I'm having problems with the battery not holding a charge. It used to last for 2 hours+ but now it is down to around 30mins. What I really want is a generator that runs off the rim and powers a large LED light, like around 3watts (I have a 3 watt LED Maglite and it would be nice). I'm not concerned with a rear light or nothing like that. I have looked around the forums and several members have made things similar to this, but most are more complicated then what I want. I don't need a switch even because the rim generator can be taken away from the rim when it isn't needed. I've looked at some of the wiring diagrams you guys post for these lights and to be honest I am totally in the dark. What I need are suggestions on what to use to build it. I was wondering if the cheaper Schwinn generators that you see on ebay work okay, if not what ones do work okay? Can I add batteries or something into the system so that it remains lighted when I'm not moving for a little while? I got a book from the libary on teaching oneself electronics and plan to read it so I can better understand what the heck you guys are talking about. Thanks for any help...

 

[TorchBoy]

:welcome:

I don't know that I'd want anything making my pedaling job harder, even if it's only by 3%. Why not simply replace your present battery? What kind is it?

 

[FLYBYU44]

My battery is the Vista light one, it sucks because it takes 8 hours to charge and if I forget to charge it then it's no riding that night. I don't believe they make Vista Lights anymore, I couldn't find the web page for them anyway. I really wouldn't care about the generator, my bike is pushing 40lbs so it isn't easy to pedal to start with.

 

[TorchBoy]

I think the key word is "dynamo" - have you done a search on that? This one might inspire you. And, of course, the Where to buy dynamo thread.

Wikipedia also has some interesting info.

 

[n4zou]

You might try this Pioneer E-generator dynamo system.

It connects to the rear axel and is driven from the spokes. It has all the advantages of a hub dynamo without the extra cost of building a new wheel around an expensive hub dynamo.
It's available from ABS-sports.com for $99.95 and $6.95 shipping in the 48 states.
Here is a German language page with test data translated so it's almost readable!
http://translate.google.com/translate?hl=en&sl=de&u=http://www.enhydralutris.de/Fahrrad/Beleuchtung/node43.html&sa=X&oi=translate&resnum=1&ct=result&prev=/search%3Fq%3D%2522pioneer%2BELS-100%2522%26hl%3Den%26safe%3Doff%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-USfficial%26hs%3Dk1x

 

[rideatnight]

It sounds like a bottle dynamo would be the best for you. I don't have experience with the bottle dynamos, but the general rule of thumb is that the more you spend the more efficient the dynamo is.

As far as wiring goes, it is very simple to run one or more LED lights in series off the generator. Without a standlight, a simple full wave bridge rectifier will work fine: http://en.wikipedia.org/wiki/Diode_bridge

The dynamo will keep constant current output, so just run the AC into the rectifier, and out to the LEDs.

Having a standlight is a little more complicated. You can connect a 1F 5.5V supercapacitor (also known as goldcap) across one of the LEDs with a small resistor (like 10 ohms) to get a minute or two of light after you stop. It won't be as bright as when you're moving, but it would be enough light to see by.

I hope this helps a little bit.

 

[NateTheGreat]

There are some classy dynohubs wheels with built in generators. There is nothing to rub on these magnogenerators. Not the cheapest though.

One is made by Shimano and the other by $chmidt. Peter White cycles sells wheels built with the hubs.

Here is a link comparing efficiency of the two designs: http://www.vintagebicyclepress.com/VBQgenerator.pdf

 

[FLYBYU44]

It sounds like a bottle dynamo would be the best for you. I don't have experience with the bottle dynamos, but the general rule of thumb is that the more you spend the more efficient the dynamo is.

As far as wiring goes, it is very simple to run one or more LED lights in series off the generator. Without a standlight, a simple full wave bridge rectifier will work fine: http://en.wikipedia.org/wiki/Diode_bridge

The dynamo will keep constant current output, so just run the AC into the rectifier, and out to the LEDs.

Having a standlight is a little more complicated. You can connect a 1F 5.5V supercapacitor (also known as goldcap) across one of the LEDs with a small resistor (like 10 ohms) to get a minute or two of light after you stop. It won't be as bright as when you're moving, but it would be enough light to see by.

I hope this helps a little bit.

As I said I got a book on electronics from the library and I'm already starting to understand a little of this stuff you guys talk about. Thanks a bundle for the link and the advice. I'm just not sure if a bottle generator would work good. I want this just for a front light, I have a 20" front wheel on my recumbent, if I hook the generator to this wheel will it work better at lower speeds(spins faster due to smaller wheel)?

 

[rideatnight]

The bottle dynamo would work just fine on that small front wheel, because the tire is traveling at the same speed as a larger wheel. The wheel will be rotating faster, but the tire will be traveling at the same speed.

However, if you were to use a hub dynamo with the 20" wheel, the hub will cause more drag because the hub will be rotating faster. The faster a generator rotates for a fixed load (the resistance of the LEDs), the more back EMF there is. A way to think of back EMF is excess power coming back into the hub in the wrong direction. Shmidt makes a SON20 for 20" wheels to solve this problem, but unless you want to drop $200 on the hub alone, just buy a decent bottle dynamo. Plus with a bottle dynamo, you can pull it off the tire when you're not using the light.

All that said, the SON20 hub would be a great long term investment, if you have the capital. Less overall resistance, incredible reliability, better efficiency and less to muck with.

 

[FLYBYU44]

The bottle dynamo would work just fine on that small front wheel, because the tire is traveling at the same speed as a larger wheel. The wheel will be rotating faster, but the tire will be traveling at the same speed.

However, if you were to use a hub dynamo with the 20" wheel, the hub will cause more drag because the hub will be rotating faster. The faster a generator rotates for a fixed load (the resistance of the LEDs), the more back EMF there is. A way to think of back EMF is excess power coming back into the hub in the wrong direction. Shmidt makes a SON20 for 20" wheels to solve this problem, but unless you want to drop $200 on the hub alone, just buy a decent bottle dynamo. Plus with a bottle dynamo, you can pull it off the tire when you're not using the light.

All that said, the SON20 hub would be a great long term investment, if you have the capital. Less overall resistance, incredible reliability, better efficiency and less to muck with.

I would go with a bottle dyno but I ride mostly in the winter at night, so I think that the wheel would slip on the tire wouldn't it?