I have been searching for a solution to run small USB chargable devices powered by the dynamo hub of my Surly big dummy bicycle without additional batteries. I was not willing to design a circuit myself and I do not like to blow up the connected device due to unsufficient voltage protection. There are several converters available for charging USB devices as like music players, phones, PDAs or navigation devices on the bicycle. I got me the bike charger from a German distributor and installed it today. In my blog there are some pictures of initial cabling. I still need to attach the PNA to the handlebar (still waiting for some parts) to be able to complete the installation. Basically it appeared to work, when connecting the charger and spinning the wheel. The device should be virtually sufficient to power any USB charged device according to USB spec (5V DC constantly, 500mA at max, even at low speed). The box has got 50g approximately and is quite small, but must not be exposed to rain or humidity. According to manufacturer it will not heat up due to the digital design of the circuit. I am a novice with electronics, so I cannot tell any details, but I will be using it for some bicycle touring within the next time.

This is the circuit I designed and use.

As dynamo voltage output approaches 5 volts the impedance of the Ni-MH batteries becomes so high the dynamo is limited to a maximum of 5.2 volts. This is well within USB voltage requirements and sufficient to recharge the batteries. The batteries also absorb excess current as recharging current protecting the USB device. Batteries must be solder tab type with no possibility of poor or open connections. Open or poor connections would allow unregulated voltage and current which could damage the device plugged into the USB port. Any standard dynamo headlight can be used in place of the duel LED headlight shown in the circuit. In places such as tunnels where you would need your headlight during the day you may switch from the USB circuit to the headlight circuit allowing the batteries to continue to provide limited power to the USB device. It's not possible to completely recharge most USB devices without help from the dynamo. The batteries may be rapid recharged by disconnecting any USB devices from the USB connector. Most AA Ni-MH batteries which are completely discharged may be fully recharged by the dynamo in about 2.5 hours. Your cycle computer trip time can be used to time battery charging. Simply reset it and when it shows 2.5 hours your batteries should be fully recharged. It will automatically start and stop timing as you start and stop moving allowing you take breaks during this time.

There was a sequence of articles in a big German computer magazine where they designed and implemented a circuit as like yours. A nice project, I think. For me, I did not want the extra weight of an additional batterie pack, since the devices I would like to use already have internal batteries that just need to be recharged to stay operational. I may even switch off the connected device every now and then if required for recharging. I wanted a minimal solution to run some navigation device the whole day or week or whatever without using transformer power supply. For sure, the bike charger will not allow operating devices without internal batteries, while your circuit could be used as a power supply in itself, I guess.

There's another design on this forum: https://yacf.co.uk/forum/index.php?topic=6672.0

Dahon have announced a product that would seem to fulfil your requirements. See this link: https://www.dahon.com/news/releases/08272009.htm

Tout Terrain is also releasing a version called the Plug
https://www.tout-terrain.de/2/product....html?start=2#

And Busch and Mueller is also selling a similar device, specifically aimed at charging stuff via usb from the dynamo hub.

Pulled from the other thread --

https://bumm.de/index-e.html?docu/361e.htm
https://www.eurobike-show.de/eb/press...e=detail&lg=en

Thinking about it now, the USB connection makes a ton of sense, as mobile phone manufacturers have recently settled on USB as a power connector standard.

Wow... does that look kludged together to anyone else?

It looks cleaner than the homebrew setups I've seen pictured around here.

It's also got a lot more flexibility than The Plug mentioned a few posts back.

Pedalpower has come out with an AC to DC (5v 600ma) adaptor cable which allows for a direct connection between any dynamo and electronics.

Here's the link for the product, and here's a link to the only review I found. The bottom comment under the review confirms that the cable is able to charge the tester's GPS and battery pack. Very promising.

An implementation as suggested in the link from Celos: bike-mounted-usb-charger
I work with this one myself and it work just great!

https://www.peterwhitecycles.com/ewerk.asp

Hi there,

I've just tried making a USB charger for my dynohub. I'm using a shimano 3N80 hub, 6volts, 3 watts.
I made the exact circuit that N4ZOU designed. It works well to charge my old 1st generation ipod nano but will not charge my 6th generation 120Gig ipod classic.
Can anyone confirm that this circuit will charge the 6th generation 120G ipod classic?

Seems strange to me that it will charge one but not the other.

Please help

No, not in the least. It looks quite well designed and built, actually.

sorry to bump!

This is a really elegant design, and I recently built a similar one (though, without a switch - alligator clips to connect also serve to turn it "off" when I want, and with my lights outside of the DC, running off the hub in parallel. 1/4" fastons with rubber dust covers provide the clipping point. A velcro strap integrated into the charger's housing holds the thing to the fork blades to keep it out of the way. Other notables include a fancy positive-locking usb port, because that sounded like fun, as well as a rubber dust-plug to keep it safe when it's empty. Next time around, I think I'll use a battery holder sized for AA batteries with flip-down tabs to accommodate AAAs - versatility to the max, but I couldn't find one when I was working on this.

I'd also recommend soldering D+ and D- together in order to let the device know that it's just a charger, not a computer.

But my main use case is charging things after I'm done riding - removing the battery pack and powering a device when I leave the bike behind. The thought occurred to me today that there's a potentially dangerous situation - what happens when the AAA batteries are drained? Will they suck the device's batteries dead? Should the circuit include, perhaps, a Zener diode between the AAA and the USB port? I suppose this is the device's responsibility, not the charger's, but.....
thoughts?

Also interesting: when I have both my light and the charger running at the same time, the light is dimmed considerably, maybe to about half the appropriate power, just a point of interest, not a big issue. Son 20 in a 700c wheel with (first generation) E3 lamp and tail light.

well I was lurking around for something like this so that I could charge my Garmin Edge & Nokia for the longer brevets. will be a good thing to tryout for the upcoming 600km brevet.

Could you give a pic of your setup?? & an actual circuit... it's cause I don't understand the part nums or stuff about circuit diagrams. But if you could give a instruction of what to connect where that'll help.

I was thinking... if I could take a Hand Crank charger & simply connect it to the Hub dynamo will that work???

It sounds like a lot of the Mass produced USB charging devices such as the BioLogic and the E-WERK aren't capable of recharging my Iphone 3GS. Has any work been done on this?

Pedalpower+ Super-i-cable: https://www.pedalpower.com.au/page12.html
Regards, Phil

The biologic recharged my Droid x and iPod Touch very well on tour last year.

What exactly are iPhones and iPods so finicky about USB charging? Some manufacturers of these dynamo circuits support them, older ones don't. For something like the circuit above, would any mods be required? Maybe it's as simple as connecting D+ and D- on the USB side?

It seems that the 3gs is worse than most. see Adafruit


I've found shorting D+ to D- to work very well for my iPhone 4.

I purchased the Plug so that I would be able to keep my Android phone charged on multi-day bike rides. There were a couple of challenges with the installation. But once those were sorted out, I have had no other problems with the plug. It is well-made, simple, and (so far) durable.


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