Power System for Bicycle Lights

[Rasori]

Hallo Alle,

I'm posting from Deutschland here, on a foreign exchange. Naturally, I ride the bike a whole lot more here than back in the States, and that includes night riding.

 

My bike has lights and a commercial dynamo for them, but the dynamo's broken and I have time so I figure I'd like to try to rig something up myself. I'm pretty good at making circuits and switches (which can be triggered in a near infinite amount of ways), but that's about it; consider me a fresh recruit on the electrical bandwagon (as in, transistors, resistors, capacitors, etc. are just fancy names to me). So, I suppose one of my first questions is where to get a nice base knowledge of the vocabulary and common equations necessary for electrical systems.

 

Now, I have a list of needs and a list of wants. I'll post both, and if you can, let me know how feasible the wants are (the needs are basic).

 

Needs:

---Two lights (headlight and rear/brake light).

---A power generator (which can take power from something on the bike that moves; often a wheel)

---The lighting of the lights.

---A water (and preferably temperature, esp. low temperature) resistant design.

 

Wants:

---My dynamo now does contact the wheel, and it adds a noticeable increase in resistance (then again, it's broken) when connected. If I could sneak in something that perhaps creates less energy per second but also gives less resistance to me, that'd be nice.

---I'd really like to have a rechargeable system, where the generator charges a battery (or, if what I think (and wikipedia says) a capacitor is is correct, a capacitor//capacitor bank) which can then power the light--good for if I've been spending the night the German way and should be walking the bike home.

---If I could have a rechargeable system, I'd also really like a charge meter--perhaps simply a red, yellow, green LED--to prevent overcharging.

Two completely manual switches: one to open/close the charge circuit (again, prevent overcharging), one to turn the lights on/off.

---If possible, two intensities for the rear light (night light and brake light intensity). I think this could be done simply by putting a bit more power into it when braking, ie two circuits going to the rear light, one turns it on when the switch for lights is on, the second when the brakes are pulled. Perhaps have the first circuit a double-switch (I'm almost certain that term is incorrect) so that pulling the brakes also activates that circuit if the main switch is off (as, to be able to see during the day time, the brake light would need a decent intensity).

---I think I'd also like the ability to transfer from bike to bike, as I'm borrowing my current bike for the next couple of months and will be switching afterwards. I think this mostly depends on the way I mount the whole system though.

 

Now, like I said, I'm pretty good with circuits and switches, mainly what I need is a list of parts and how to rig the more advanced stuff up. Some of it may be completely the stuff of dreams, but I really think a decent amount of it could be done.

 

I know it would be easier to buy a commercial dynamo (possibly more reliable and even cheaper, as well, as I have no parts to start with), however I have free time and I'd like the self-satisfaction of having made it myself, so as long as the project won't bankrupt me I'll be happy to attempt it (let's set a price limit at 50 Euros, but I'd be willing to go higher if that's completely unfounded... feel free to link me to online suppliers of what I might need).

 

Any online guides that might help with the whole project are also appreciated. I'm looking at this as my introductory project to intermediate circuitry, so if you can come up with more nifty features (regardless of necessity) to be a good learning exercise, feel free to suggest them.

 

Thanks, all!

[Dak]

are we talking motor- or pedal-bike?

 

if pedal, then break lights are a bit ott, as you (probably) use your breaks to fine-controle your speed, and not just to stop or slow down suddenly.

[insane_alien]

Dak, for a pedal bike when riding at night you are required to have a red light on at the back by law. it doesn't have to respond to brake usage. just be constantly on.

[Dak]

yes, i know. but a break light is still ott

[Klaynos]

Just a note, but I believe that Germany has similar bicycle lighting requirements to the UK (I think there's a EU regulation which means the two are highly similar) and that means you're lights have to have past a certain standard to be allowed as the only lighting on the bike...

[Crooked Mick]

Looked into this a few years ago. You will need a generator/alternator that can be driven by a wheel. You will feel resistance as the power has to come from somewhere and that is you pushing. If the source produces alternating current, to charge a battery the AC must be turned to DC by a rectifier using diodes. These are available as rectifier packs. A capacitor across the output will smooth it out a little. Then a zener diode can cut out harmful peaks in the output from riding fast downhill. Your battery will have to be a rechargeable type. For the tail lamp a series of say four red LEDs with another four as a brake indicator - maybe. While white LED headlamps are sold for bicycles, the more conventional incandescent type may still be better even though they use more current for the same light.

 

Frankly I think it is a waste of effort. Blinking or steady red rear lamps using a few LEDs are available from chain stores for a few dollars and a pair of penlight cells lasts for many hours of operation. I have a four penlight cell headlight with a two-intensity setting which uses an incandescent bulb and the cells have a few hours life.

 

It might be worth your while though to check the bicycle stores or the net for this sort of system. I have seen systems with all sorts of batteries from a lead-acid to strings of nicads.

 

Crooked Mick

[Rasori]

One (covers many things said); yes, a brake light is odd, and yes it probably is a waste of effort. That doesn't change the fact that it would also be a good excercise to get myself familiarized with some of these things.

 

Two; I know I will feel resistance, as you can't get energy from nothing. However, is wheel-driven the only way? Nothing that can get power by acting like a baseball card in the spokes or something? There probably isn't anything like that, but one can never tell these days. I just have a feeling that wheel-driven is about the most resistant method there is, and other (less efficient but workable) methods should be available. These may not normally work for the power for these lights, but the concept is that I can charge the battery for a long period when the light isn't needed, and needn't run the lights direct from the generator.

[Spyman]

A hub dynamo is a small electrical generator built into the hub of a bicycle wheel that is usually used to power lights. Most modern hub dynamos are regulated to 3 watts at 6 volts, although some will drive up to 6 watts at 12 volts.

http://en.wikipedia.org/wiki/Hub_dynamo

[Crooked Mick]

"I just have a feeling that wheel-driven is about the most resistant method there is, and other (less efficient but workable) methods should be available."

 

Actually that's right. I once had a Raleigh cycle with a "Dyno-hub" which contained a power source and 3-speed epicyclic gears, this seemed to give less drag when on than a dynamo driven by the side of the tyre. The type that engage the rear wheel just behind the front sprocket I have no experience of, but I have heard that they can give trouble in the wet.

 

Voltage was a nominal 6 I think. These things are now rare I believe. Miller cycles of the USA made something similar.

 

Crooked Mick.

[Rocket Man]

i met someone who used a drink bottle to house a bundle of NiCad rechargables. he went mountain biking with it so he had a good intensity on the front. he claimed 3 hours continuous light which was feasable considering the kilo of batteries.

 

reed switches on the brake cables would be a simple mechanical problem.

 

run the tail and head lights constantly with additional (brake) lights via the reed switches.

 

if you can get a regulated dynamo and a matching voltage rating on the battery, you wouldn't need to worry about over charging.

 

did you want to wind the dyno yourself? that's a lot of work.

[gcol]

A recent re-examination of road casualty figures in the U.K. has shown cycling to be akin to a death-wish, my excuse for giving it up.

 

But when I did it, my backside got so hot and sweaty I wondered if a salt water cell built into the saddle might might make my discomfort somewhat productive.

 

Note to YT: Yes, this is meant as a joke (you know what I mean).