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.
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.
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Signing UpStep 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.
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.
![Voltage Regulated [5v] Bicycle Dynamo Light & USB Charger](http://www.instructables.com/files/deriv/FKR/TCHO/GSEEJZIP/FKRTCHOGSEEJZIP.SQUARE.jpg)
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Cheers.
-Buy more expensive carbon drill bits.
-Use a cutting oil, and be liberal with it. It will help to cool the bit and keep it from melting and help to clean out the metal bits from the hole.
Cutting oil can be bought in small 8 oz. bottles
-Use a low speed, high speed causes the bit to make small metal bits and can lubricate the drill bit, causing it to ride above the metal you are trying to cut through.
-Drill bits are actually cutting tools, look at one, they normally have two cutting flukes (surfaces). You will know you are using the correct speed when you get a nice ribbon of metal, rather than a lot of small chunks.
-Keep good hard force on the drill, if you don't it will again make small chunks and just float on them above your metal surface.
-For very hard metal, It becomes necessary to start with a smaller pilot hole, and enlarging it drill size by size to your desired hole size.
I don't think these magnets have a very hard metal strap, they are not made for really hard abuse as other metal parts are, so this should not be necessary.
vbnicolau,
I have used the FreeLights and am not impressed with them. They are way too dim. But the idea is good. The paper from the NM students is good information. I like the way you have made use of salvage parts.
I would consider ways to make this all waterproof, as I commute come rain or shine. PVC tubes with caps could be used to house the relays, with a small hole on the bottom side for the wires to come out, sealed with some silicone.
Thanks for sharing this, over all a great idea, and a great presentation here.
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,,,
Thanks
Best of luck.
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.
mid
go here and you can find them once you got the name of the relay you can find for cheaper
this guy really helps in youtube
thanks mignightsky and rpvapatt you help me not to spend a lot in just test for my project.search for how to wind copper coils tightly for wind turbine stators part 1