Bicycle light, usb-charger help

barughy · Mar 5, 2011

Hello,
I have a bicycle dynamo (40% efficeiency, 6v/3w) that I want to charge my bike lights (which is a converted 12v Remington electric shaver, with rechargable batteries - powered by 3 LEDs in parallel)
The voltage going to the LED's is 4.8v, if I've used the multimeter correctly.

I also have a car USB charger with built built-in fuse protection, it converts 12-24v to a 5v charge, which I want to use to power my phone. I'm not sure if it will be able to using a bicycle dynamo.

I dont know much about electronics and what I do know I've learnt myself over the last few days. I'd be grateful if I could get some advice on what what I need to make it all come together and not blow my face off, wreck my phone, or cause a problem with the batteries.

So do I need to build a regulator and if so, how would I go about doing that?
The LEDs work fine and haven't blown (yet) but I'm not confident I have the right voltage going through them (it seems high) so what resistor would you suggest?

If I've missed out any glaring issues you think I should resolve as well then please dont be shy in elightening me.

Thanks.

ezzzekiel · Mar 6, 2011

the only glaring issue i can see that you have missed is "HALFORDS" who sell everything you require.

barughy · Mar 6, 2011

ezzzekiel said:
the only glaring issue i can see that you have missed is "HALFORDS" who sell everything you require.

It's part or a project that I have to complete for an apprenticeship application. Cheers for the comment, really made posting the question worth my while.

telectrix · Mar 6, 2011

a simple way would be to put a 4.8v zener diode across the 5v output. each LED requires 2v across it, so if in series you would need 6v, or in parallel, 2v. if you know the current drwan by the LEDs. you can nwork out a resistor value using ohms law.

grantr37 · Mar 7, 2011

You want to charge battery lights and a mobile while cycling during daylight? is the Dynamo an AC or DC one? theres extra things that you can do as well such as using small flexible solar cells on parts of the frame, or fitting a moving coil system onto the back shocks with a light spring that makes the magnet bounce up and down when you go over bumps.....same as a shake charge torch....PM me with what you want to build and how much you want to spend on the components, I will try to help you out with drawings and ideas,etc...as well as a parts list to fit your requirements...
You can either design a PCB and get it ordered off the internet where somebody will print, etch and drill it for you and you just solder on the components, or you can use Vero Board...

malcolmsanford · Mar 7, 2011

barughy said:
Hello,
I have a bicycle dynamo (40% efficeiency, 6v/3w) that I want to charge my bike lights (which is a converted 12v Remington electric shaver, with rechargable batteries - powered by 3 LEDs in parallel)
The voltage going to the LED's is 4.8v, if I've used the multimeter correctly.

I also have a car USB charger with built built-in fuse protection, it converts 12-24v to a 5v charge, which I want to use to power my phone. I'm not sure if it will be able to using a bicycle dynamo.

I dont know much about electronics and what I do know I've learnt myself over the last few days. I'd be grateful if I could get some advice on what what I need to make it all come together and not blow my face off, wreck my phone, or cause a problem with the batteries.

So do I need to build a regulator and if so, how would I go about doing that?
The LEDs work fine and haven't blown (yet) but I'm not confident I have the right voltage going through them (it seems high) so what resistor would you suggest?

If I've missed out any glaring issues you think I should resolve as well then please dont be shy in elightening me.

Thanks.

barughy said:
It's part or a project that I have to complete for an apprenticeship application. Cheers for the comment, really made posting the question worth my while.

I'm not prone to being critical but I think your answer to ezzzekiel was perhaps not called for. I think he would have given a much better and more concise answer, as he usually does, if in your first post you had suggested this was for a project rather that what I expect he thought, as I did when I read it, that is was some kind of Heath Robinson type DIY.

Think the majority of guys on here, will always try to help rather than not, but what he did was the blind obvious, you can get what your asking for at Halfords, if you had mentioned the project for training it may have been a lot more precise.