Regulator for charging phone from dynamo

[BTP]

Hi folks,

Slightly geeky question this one...

Anybody designed and built their own regulator so as to use a SON/Shimano dynamo to charge a USB device or NiMh batteries.

I am planning to put one together, and reasoned that a switch-mode regulator would be the most efficient way of accessing the necessary voltage. Anyone willing to share what they have done so far?

Many thanks in advance.

Tony

[pete75]

http://www.instructables.com/id/bicycle ... regulator/

[steveo_mcg]

A cheap diode bridge rectifier and some thing to clamp the voltage to 5v is all you really need. Though you'd be better off charging 4aa nimh and then using that to charge your phone as nimh chemistry is more tolerant of stop start charging. You'll also want a way of shunting the current away from the batteries once they are fully charged to avoid cooking them. They'll have a pretty tough life in a set up like this so what ever you do make sure you can change them out after a year or so as their capacity will drop off.

[RJC]

If you have a small lightweight mobile mains adapter that is rated 100-240V you might find it will cope with the lower voltage from a hub dynamo.
This will probably only work when the lights are off so you get more volts out of the dynamo. If have heard of folk using mobile phone adapters on electric bikes
and the voltages from these batteries are not usually 100V.

A bulkier adapter which is 240V only probably has a transformer inside and wouldn't work.

[[XAP]Bob]

http://www.brocott.co.uk/electronic-dev ... 763g9e6rn5

At £24 is seems too good to be true - but of course it doesn't have a cache battery system, so the component prices don't need to be high.


I've thought about putting a rectifier, super-capcitor and minty-boost style circuit together to power, well anything...

[steveo_mcg]

That looks pretty good for touring where you mightn't stop for a couple hours at a time; using it in the city would do your phone no favours, the stop start nature of the charge would likely kill your battery in short order.

[hufty]

I use a Nokia DC14: donate the supplied dynamo to charity, chop the end off one of the wires, put a usb female connector on then away you go. This chap has done a website about it: http://toddlerontour.com/universal-usb-bicycle-charger-nokia-dc-14-conversion/ which gives you the idea. Have to say I crimped rather than soldered, and also I think you should join white and green together (D+/D-) for devices that like to know that they're connected to a charger not a computer.

[graymee]

If you have a small lightweight mobile mains adapter that is rated 100-240V you might find it will cope with the lower voltage from a hub dynamo.
This will probably only work when the lights are off so you get more volts out of the dynamo. If have heard of folk using mobile phone adapters on electric bikes
and the voltages from these batteries are not usually 100V.

A bulkier adapter which is 240V only probably has a transformer inside and wouldn't work.

Not sure what RJC is suggesting here, a dynamo only pushes out 6V or 12V not the 100v minimum the mains adaptor requires.

I built a circuit that produces a stabilised 5V DC from the 6V AC produced by the dynamo. I used a W005 bridge rectifier and LM2940 voltage stabiliser from Maplin, coupled with a couple of capacitors for smoothing and a bit of circuit board it cost less than a tenner. I used a USB extension lead with the male plug cut off to supply the voltage via the USB female socket.

Not sure about charging batteries, NiMH batteries need a bit more in the way of current regulatory circuitry I believe. There's also the voltage problem as you need more than the rated voltage to charge them as far as I know. Rechargeables are rated at 1.2 V so 4 in series (4.8 V) would, I believe, charge from a 6V supply but would be pushed to supply the 5V (+ or - 0.25 V) required for the USB. Five rechargeable cells in series would supply 6V but getting a holder to hold 5 wired in series might be problematic and I'm not sure a 6V dynamo would supply enough voltage to charge them.

I could send you a link to the data sheet for the voltage regulator if you require, that shows the very basic circuit and the required capacitors.

[steveo_mcg]

To my knowledge the voltage rating on a dynamo is only nominal, it is a current device which tries to produce 500ma at all times the voltage is a function of your speed. The reason they are rated at 6v is because that is the voltage of the bulb traditionally used. Theoretically, unloaded, a dynamo could produce a couple of hundred volts, why you don't put a capacitor in the circuit with out something to discharge it.

NIMH batteries are very easy to charge, give them some power and they store some of it. To get them fully charged you'd need about 1.5v per cell, if you put 4 in series with your dynamo it'll put out more or less the correct voltage. When the total voltage reaches ~5.5v (4*1.4v) or the cells get warm disconnect them.

[al_yrpal]

What you need is a diode bridge rectifier (AQ96) to turn the AC to DC, a smoothing capacitor (1000 microFarad) and a voltage rectifier limiter (5V) to prevent overvoltage. I use mine to charge a battery and charge my phone from that. I'll try to sort out a circuit and post it. All the bits from Maplin only cost a couple of £'s

Al

[sbseven]

http://www.brocott.co.uk/electronic-devices/power-modules/bicycle-dynamo-powered-usb-charger-6vac-to-52vdc-p-1017.html?osCsid=v0fes1dkk3fbv3ei763g9e6rn5

At £24 is seems too good to be true - but of course it doesn't have a cache battery system, so the component prices don't need to be high.

Perhaps it is...
http://www.crazyguyonabike.com/reviews/ ... 1&nested=0

[Ribblehead]

If you have a small lightweight mobile mains adapter that is rated 100-240V you might find it will cope with the lower voltage from a hub dynamo.
This will probably only work when the lights are off so you get more volts out of the dynamo. If have heard of folk using mobile phone adapters on electric bikes
and the voltages from these batteries are not usually 100V.

A bulkier adapter which is 240V only probably has a transformer inside and wouldn't work.

Not sure what RJC is suggesting here, a dynamo only pushes out 6V or 12V not the 100v minimum the mains adaptor requires.

I built a circuit that produces a stabilised 5V DC from the 6V AC produced by the dynamo. I used a W005 bridge rectifier and LM2940 voltage stabiliser from Maplin, coupled with a couple of capacitors for smoothing and a bit of circuit board it cost less than a tenner. I used a USB extension lead with the male plug cut off to supply the voltage via the USB female socket.

Not sure about charging batteries, NiMH batteries need a bit more in the way of current regulatory circuitry I believe. There's also the voltage problem as you need more than the rated voltage to charge them as far as I know. Rechargeables are rated at 1.2 V so 4 in series (4.8 V) would, I believe, charge from a 6V supply but would be pushed to supply the 5V (+ or - 0.25 V) required for the USB. Five rechargeable cells in series would supply 6V but getting a holder to hold 5 wired in series might be problematic and I'm not sure a 6V dynamo would supply enough voltage to charge them.

I could send you a link to the data sheet for the voltage regulator if you require, that shows the very basic circuit and the required capacitors.

Most if not all plug-in adaptors are now of switched-mode rather than transformer design. You'd have to find a way of feeding the dynamo output into the circuit in such a way that it was regulated as if it was plugged into 240v. If i remember correctly, the switched-mode circuit consists of a rectifier, smoothing capacitor, HF inverter, HF transformer and smoothing capacitor, there is a feedback to the inverter to give control over the output. It may be easier to just build something with a regulator from Maplin.

[ferrit worrier]

If you have a small lightweight mobile mains adapter that is rated 100-240V you might find it will cope with the lower voltage from a hub dynamo.
This will probably only work when the lights are off so you get more volts out of the dynamo. If have heard of folk using mobile phone adapters on electric bikes
and the voltages from these batteries are not usually 100V.

A bulkier adapter which is 240V only probably has a transformer inside and wouldn't work.

I might be up a gum tree here but mains chargers work off AC dynamo's generate DC and at much lower voltage how that work?

Malc

[RJC]

I was assuming that the switched mode phone adapters rated 100-240V will have some margin so will in practise work with lower voltages. Looking at the data here I overestimated how many volts you would get out of an unloaded hub dynamo, so maybe it wouldn't work.
You could expect to get a few 10's of volts out of unloaded dynamo when going fast, which is something to be aware of if designing your own regulator.

[graymee]

I might be up a gum tree here but mains chargers work off AC dynamo's generate DC and at much lower voltage how that work?

Malc

Up a gum tree? Yes and no. Dynamos are misnamed, bicycle dynamos are in fact alternators and produce ac. Voltage wise they normally produce 6V or occasionally 12V and I don't believe that is sufficient to get a suitable output from a charger designed for mains use even if it is variable input (100 to 240V). The voltage output of a dynamo might rise under no load conditions but as soon as you connect any load, even a very light one, the voltage will drop to around the stated 6V.