Magnetic operated bicycle lights help please!!

Africaman

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Mar 29, 2016
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Hi all,

I am a missionary going back to work in Africa very shortly, and I could do with some help. I have seen bicycle lights that operate with the use of a coil and magnets. These would be life savers in Africa where the people cannot afford batteries. I am not electrically minded so need all the help I can get.

1. I know I need some copper wire but don't know which is the best gauge to buy to obtain the brightest LED light.

2. I don't know what voltage the LED needs to be?

3. I don't know how the LED should be soldered as there is an earth and a live?

Any help with the above would be very much appreciated...

Thank you,
Africaman...
 

Steve K

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Jun 10, 2002
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Peoria, IL
wire coils and magnets are what what are inside generators and dynamos. These dynamos and generators were designed by engineers who understand things such as electricity, Maxwell's equations, bearings, material science, magnetism, etc. They created the methods for manufacturing thousands of these, with the result that they are much, much cheaper and better than you could ever build yourself.

You might consider purchasing a very low cost generator light such as this:
http://www.sears.com/universal-chro...-SPM8005143029?prdNo=1&blockNo=1&blockType=G1
 

iggs

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Oct 19, 2007
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It's an interesting question. What would be the current Africa light of dynamo systems currently available

It needs to be very cost effective

It needs to be user field serviceable where needed (bearings)

It needs to be reliable

It needs to be very resilient

The Toyota hilux of lights. What would it be?

Shimano or SP hub?

Which light?
 

Savvas

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Jun 11, 2010
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222
There have been quite a few commercial magnetic induction bike lights that have been designed and marketed - at least since 1984 when I bought my first one (it's still going btw). Some have been expensive and some have been dirt cheap. I haven't seen the Reelights (the current, expensive, Danish ones) but there are quite a few very cheap Chinese ones available. Apart from the fun of experimenting one wonders why you'd try to make one when they are readily available for around $10. Surely, even in Africa this is relatively cheap.

My biggest concern would be that the less sophisticated induction lights (I haven't tried the Reelights) are really extremely limited as bike lights. The older one I have is well made but it's very(!) low powered. Maybe the more modern ones are a bit brighter. It flashes only - no steady beam - and only works when the wheel is turning. Because of their usual location on the chain stay somewhere or down at hub level they seem very vulnerable to damage when lying the bike down or from minor parking collisions with other bikes, light poles etc. Pretty difficult to see in dusty or rainy conditions too. I think it's important to have a think about what you want these affordable lights to achieve. I think induction lights are likely to be quite ineffective as 'to see' lights. Unless quite a sophisticated design is involved, I suspect you are still looking at quite limited lights, even as 'be seen' lights.

I think it's worth appreciating the the biggest investment in value-for-money bike lighting is a decent rechargeable battery. In my experience there's good value to be had for both 'be seen' and to see' lights from just using decent NiMH batteries such as the Sanyo AA or AAA Enneloops in reasonable quality Chinese-made lights, either no-name or something like to Cateye EL-135/Omni3 combination. This sort of combination can provide excellent lighting in most every-day utility bike situations which I presume is what the OP has in mind. Personally I don't think the goal of dirt-cheap, robust & effective, easily made induction bike lighting is achievable. For experimentation purposes there are quite a few designs available online - see here. If you are working in a local community some sort of group-buy might be the go...

Sam.
 

jdp298

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Mar 22, 2011
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With your sister, somewhere you wouldn't like
The best kind of bike generator is a hub dynamo, and the cheapest seems to be the Shimano DN3n20 or 3n30 (I have 2 of the latter). Plenty of second hand or old stock on ebay going for not much more than 25GBP each. However, then you need rims, spokes, someone to build it and tyres and so on.

So for fitting to something already there I'd lean on the bottle dynamo. There are lots and often cheaper. But they do wear out sooner (my paper round bike destroyed 2).

As for the lights, it's a luxury that I make my own, but it costs more in components than cheaper imports off the internet.

Then there's the Magnic Light here, but it's not cheap for what is a very small thing. In fact, there was a thread on this forum about how it couldn't possibly work. Then it did. I think page 7 of that thread is where you start to see how it all works.

But barring all else, get some solar rechargeable/wind up torches and velcro straps.
 

niggle

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Sep 26, 2016
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Hi, first post on here :wave: and this topic is interesting to me, I am a keen cyclist with experience of all types of bicycle lighting and have built quite a few bike wheels including dynamo hub ones.

Recently I bought a Novatec EDH-2 dynamo hub, still on Ebay at the moment for £22.54, complete with some cabling and a set of incandescent lights: http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=361733606215 This guy has sold a few already but he might do you a deal on whatever stock he has left.

The lights are obviously inferior to and less reliable than LED ones, but the rear Soubitez rack light does not look too rubbish and both might work adequately with LED replacement bulbs. I have not tried the ones I got and the front has no switch anyway so not really ideal for a hub dynamo (you can have the pair for your project for cost of postage if you want them, PM me).

The Novatec hub dynamo would suit the project very well, better than a Shimano IMO as it has fully accessible and serviceable cup and cone bearings on both sides, unlike all Shimanos where access to the right bearing is not possible without extreme care to avoid breaking the live connecting wire. It isgenerally considered a robust and serviceable design criticised for being slightly more draggy than even the cheapest Shimanos and in particular with lights off it has slightly worse drag than with them on (but over all still barely detectable without sophisticated test bed equipment).

It has been suggested that this is due to the zener diode included to provide overvoltage protection, which would be necessary for the bundled light set. However all modern StVZO German standard approved LED front lights have this built in including to protect the rear light, so the zener diode can be removed, which is child's play as detailed here: http://wiki.openstreetmap.org/wiki/User:Zapfen/EDH-2-Mod I have temporarily detached the end connected to earth on mine and I can definitely feel increased resistance with lights on compared to off, but I could be imagining that...

Best cheap but usable LED front light is, according to reviews, the Axa Pico, circa £12 on line at Ebay or Amazon, switched and un-switched variants probably exist but I have not checked. For your project I would suggest the best option for the rear would be a rack mounted one assuming bike has a rack, failing which a mudguard mounted one. Attaching one to seatpost or seat stay (the frame tubes that run from the back wheel hub to the seatpost) is probably not the way to go if a bike is likely to have large loads attached.

You can buy large reels of suitable cabling, if rated for 1A it will be absolutely fine, or you can re-use domestic appliance wiring as it is much thicker and more durable, and more than capable of handling the current. The twin core stuff is ideal for this but you can also use 3 core just fine, e.g. should be able to pull out the extra: send out an appeal to friends, family, etc for them to cut it off the appliances they throwing out and send it to you.

Getting LED polarity right is no biggy, if does not work one way round then swap and it should do- as I understand it you cannot harm an LED by wiring it the wrong way round: techies please correct me if I am wrong!

Bottle dynamos are an alternative to wheel building but as said they are not as durable, the best ones from B&M etc. are no cheaper and still not as good as the cheapest hub dynamos. They all suffer from issues of alignment difficulties, potential for slipping into the wheel which would be a particular hazard at the front- never fit a bottle dynamo behind the front fork and preferably not at the front at all, only in front of the rear seat stays.

Wheel building takes a bit of learning but I managed after a couple of attempts, the only absolutely essential tool is a spoke key and you can use the bike frame or forks as a 'truing stand'. I would not be surprised if a few locals already have a good grasp of this, but if not there are numerous Youtube videos to help plus lots of guidance on the Cycling UK forum http://forum.cyclinguk.org/index.php?sid=ad4698b9e16c2253e6df1a2c4587537a particularly anything posted by Colin54 who used to be the wheelbuilder at Spa Cycles, building wheels for the demanding needs of cycle tourists. If you join and post on there you will probably get lots of help.

Generally you can re-use the wheel rim but will need new shoter spokes- the exact length will need carerful measruement of the rim and calculation using an online spoke calculator, e.g https://leonard.io/edd/ I fancy the bikes you will be working on will either have the MTB 26" rim size or old fashioned British sizes like 26 x 1 3/8", best to find out and take measurements- if they are all similar you can buy boxes of spokes in bulk, possibly from a wholesaler if you ask around local bike shops. For you purposes almost any spokes will do and stainless is not necessary, galvanised should last for decades if not exdposed to road salt regularly.

Regarding Reelights etc. these are not adequate for riding on unlit UK roads let alone anything less well surfaced, they are not bright enough and generally only work in flashing mode- OK for lit streets but do also give a bit of hassle in terms of needing careful alignment and frequent re-alignment.

I hope that all helps :)
 

niggle

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Sep 26, 2016
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Sorry the wheel building chap on Cycling UK forum is 531colin, not Colin54.
 
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