Contactless dynamo powering bike safety lights

Hello everyone!! On this instructable you will see how to build a simple contactless dynamo for powering a bike safety light from a relay coil and some hard drive magnets.

As you will see, the electric circuit is really simple and contains only 3 bright red leds and a 4700uF capacitor. The capacitor is used just to keep one of the leds steady while you are driving. The other two leds will be blinking as the magnets pass by the coil. To have all three leds blinking you can remove the capacitor if you want. If you decide to place some more capacitors in parallel, the steady led should keep on even when you're stopped.

On part two we have more 2 coils installed for powering 5 white bright leds for the front light. The circuit is completely independent from part one's.

For more information about how to improve this kind of system, just look around the site, there are several instructables on the subject. You will find different kinds of generators and other circuit ideas.

Step 1 The coil

To avoid spending time building your own coil, just look around for an old relay. I got this board from an old telephone central station.

The second picture shows the coil disassembled from the relay. On the bottom part you may notice that the magnetic circuit is open. In fact that's where the relay's moving parts were attached. I didn't noticed much difference closing the magnetic circuit with a peace of metal, so I just left it as it is. But theorically it should improve efficiency.

For a simple system like this, you should try to keep the coil's resistance between 100 and 200 ohms. This one has 200 ohms. With more than that you will generate more energy but efficiency drops because you also have more losses in the coil.

Comments

[The.zafootz]

This device is awsome I am learning to make one myself and hope to learn everything there is to know about contactless dynamos =D

[SinAmos]

Simple, yet awesome. I can't wait to try.

[jules15]

i did this and i was only getting .01 volts around there. I used a 5 volt relay. i don't know what to do :p

[scraptopower]

You're not using the DC setting on your meter are you ?

[loccci]

hi, i dont understand where to put the capacitor if i want one led or more to stay on constant. do you have to charge the capacitor intitially. why is the only place you could put it parallel with led3? why does it not get negative voltage? why arent all of the leds in parallel? led2 and led4 seem to be in series, why is this? sorry i just dont get it. thanks

[scraptopower]

I don't think it is possible to add capacitor smoothing to this circuit without adding a bridge rectifier (use schottky diodes for efficiency).

He has wired the circuit in that way because the waveform is not mirrored, so there's less load when the coil - wire is more positive. At least, that's what I think,,,

[yonutzky]

I have only one screw hole in my magnets. I tried to drill another hole in the panel the magnet sits on, with an ordinary drill, but it only dented the metal. It won't go through. Any suggestions?

Thanks

[bricabracwizard]

Use a proper drill for metal, they are a bit more expensive but they cut through metal like its cheese. Another thing is keep the drill cool while drilling they will stay sharper longer.

[The Insignificant User]

Something I've found that helps is to drill the hole and then use a hammer and a sturdy roofing nail to drive the rest of the way through. However, this works best with smaller diameter holes, so if you intend to use a larger bolt to hold it in place, that might not be the best method.
Best of luck.

[snowluck2345]

Could you give an example of some other windings you could use? For example would a toroid work? or a transformer?

[SuperKuper]

Where could I get my hands on some of these coils? Also are they sealed/waterproofed at all, and if not can the bike be open to the elements? (looks like there's a plastic coating on it)

[golddigger1559]

how long do you think it would take to charge a 200v 10000UF capaciter?

[ploomus]

Really nice project, i'm thinking about making my own but maybe i also want to use it for charging my Ipod. Well i'm not sure will it be powerful enough but i could find it out. I don't want usual dynamo because it feels boring and i love building myself =P

[rpvanpatt]

 ..i'm new to all this so dont mind the question... could it be possible to put a capacitor in front of all the leds?  and maybe with a switch, so that you could turn them all on and off with out any blinking?  thanks

[The Insignificant User]

http://www.instructables.com/id/Contactless-dynamo-bike-wheel-lights/
It's by the same author as this instructable. The circuit diagram is similar enough to what is happening here for you to get some idea as to what's going on. If you need a place to get capacitors/LED's, try Jameco.com. It's a pretty good site if you want low prices and fast delivery.

[iceng]

It is a nice generator but those magnets are powerful enough to grab street metallic scraps and possibly jam the wheel.

[f22archrer]

can i use the part of motors on which the wiring is done ??? as i fail to find myself a relay coil

[joel26]

Doesn't the magnetic field slow the bike down?

[kikiclint]

it will slightly, but generally only the amount by which it is giving you power. Unless you have wierd stuff happening with eddy currents or ferromagnetic materials pulling on it.

[xsmurf]

"only the amount by which it is giving you power" To put that in perspective, 3 leds at roughly 3V and 25mA so 3x0.025x3= 0.225W (no loss I'm aware) of power consumed. Considering a cyclist might put out 300W of power (total ball park, I'm aware), that would be a reduction of power of 0.075% way way under anything noticeable to the rider.

[james.mcglashan]

how mant volts does this make: 1 relay, 1 magnet, i want to do the relays and magnets so i can hopefuly get enough power to power my little list i want to first put power in 10 very good capastor then through regulators to do theese things, and power 8 usb divices (usb battery charger, mp3/4, mobile, camra and other divices), and power my lights, will this work with how many relays and how many magnets to get the wanted power

[kikiclint]

that will depend on the relay and the proximity and speed of the magnet passing. I was able to get 5 volts ac off of one of my coils.

[midnightsky]

 coils aka relays you can find anywhere like auto zone to walmart lol homedepot  most gate openers whill have relays in them find an gate or a door company they will have tons of old gate sys boards andold relays that i am sure they will give up for free or a cheap price hehehe
mid

[rpvanpatt]

how bout in any other typical household electronics, can you find one in anything else?

[kikiclint]

All electronics that have power switching are going to have relays. If you look for dead microwaves, they will have some in them. Other places I have found them are in large power filters for computers. 12 volt relays work good if you get the magnets to pass close to them.

[jules15]

if your computer is old, it might have a modem in it still.  Theres a 5 volt surface mounted relay. But BE CAREFUL taking it off.

[midnightsky]

http://www.gatehousesupplies.com/SearchResults.asp?Search=relays
go here and you can find them once you got the name of the relay you can find for cheaper

[rpvanpatt]

 thanks...but i have no idea, which one would I use for this?

[cdcobre]

this guy really helps in youtube
search for how to wind copper coils tightly for wind turbine stators part 1

thanks mignightsky and rpvapatt you help me not to spend a lot in just test for my project.

[rpvanpatt]

 how much voltage is put out by the coil/magnets?

[rpvanpatt]

 could you charge a battery with this as well?  I would love to use this idea instead of a motor to generate power to charge batterys, which then will power other things

[mheffner]

 There is a plus to using the hard drive magnets in this situation. They have both a north and south on each side, thus each time the magnet passes you're giving it the polarity change needed.

[fireraisr]

And for the people that lurk on instructables or are just low on time, the commercial version www.reelight.com/Default.aspx 

[elenzil]

thanks for the link. i saw someone riding with what look like those a while ago; pretty sweet.

[ensoarts]

Can you give us any more information on where to get coils like this?
I can try my local parts shop (all electronics) but im not sure exactly what id be looking for.

[neuro98]

Awesome! I've been pondering ways to make a contactless generator for my bike, but haven't made lots of progress since I'm not electrotech savvy. I'm going to try this method. My idea also involves a photodetector to switch current generated during daytime into Li-ion battery storage. What other types of coils can one use beside relays (I haven't found so many of those laying around anymore these days).

[heiwlee]

To put magnets on a bike wheel, it is better to make it round and flat, put a flat base material, put magnets N-S-N-S.. with a back steel plate, otherwise it may touch the coil easily.

see video   http://www.wired.com/gadgetlab/2009/10/magnet-powered-bike-lamps-light-up-the-night/

[buzzsterbrown]

Just made one on my bike, used an old hard drive disk as a sort of rotor to mount the magnet on and it works fine. Thanks!

[sushiman1841]

whats a telephone central station?

[danhorton]

a nifty idea. efficiency can be improved. the heart of a generator is making and breaking a strong magnetic field within the coil. the magnetic path should be between N and S poles of the magnet . pole face gaps must be minimal. consider a mag steel plate supporting alternating N and S poles and use a U shaped mag steel core between them