Introduction: 10€ BICYCLE USB CHARGER

About: I am an 19 years old guy from Germany who love to make things. Later I want to become an Electrical Engineer :-)


in this Instructable I want to show you, how to create your own Bicycle USB charger for a bicycle dynamo for less than 10€.

This summer, I took an bicycle tour with my friend for around two weeks and we had the problem that we don't had access to a power socket to charge our batteries for our GPS devices and smartphones. So I searched for an solution.

The first Idea was to use a solar charger. Solar charger works great when the sun shines, but when it is cloudy they didn't work really well.

The second Idea was to use the hub-dynamo from my bicycle to produce the power for charge my electronic devices. This is the best solution, because I am not limited by the weather and I can even charge my devices at night. However hub-dynamos don't produce a regulated 5V voltage to charge my devices over USB, so I created a simply circuit that will transform the unregulated AC voltage from the dynamo to regulated DC 5V. I tried to build the USB-Charger very professionell and waterproof, so that it will look great on my bicycle.

All in all this charger is an awesome device for Bicycle-Travellers, Geocachers and Camper, who don't had access to an powersocket, but don't want to travel witouth electronic devices.

Specs of the charger:

  • INPUT: 6V 3W hub-dynamo ( Voltages can be higher than 6V when no load is connected to the dynamo !!! )
  • OUTPUT: 5V (max. 700mA) USB regulated voltage
  • charging stars at 10km/h (Megallan Explorist 310 GPS and cheap powerbank succesfully tested)
  • nearly completly hidden in the 1inch steeringrod
  • watertight
  • puffered voltage with additional powerbank
  • overvoltage protection
  • modern design

### If you like my Instructable, please vote for me in the Powersupply Contest and Travel Contest###

Step 1: Fusion 360 File

The USB Charger is completely designed in Fusion 360. Here is an interactive model of the charger:

If you can't see the interactive 3D model above, its probably because
you're not using a WebGL-enabled browser, or you're using the Instructables Mobile app)

All Fusion 360 files can be downloaded at this link: http://a360.co/2qsgFhA

Step 2: Required Parts

Electronic Parts:

Here are all required parts for the USB-Charger. I tried to source all parts as cheap as possible. Often I had to buy more than I need, so you can easily build up to three chargers with this bill of materials.

1xUSB-A plug female
Aliexpress0,64€ (for 5 pieces)
1xStepdownmodule MP1584
1x680µF 25V polarized capacitor
Aliexpress2,40€ (for 20 pieces)
2x220µF 50V polarized capacitor ultra low ESR
1xSurpressordiode 1.5KE22CA Aliexpress1,28€ (for 20 pieces)
Aliexpress0,91€ (for 20 pieces)
1xBimetall switch NC KSD9700 50°C
Aliexpress2,32€ (for 10 pieces)
1x10x7cm PCB single side (enough for 3 chargers)

Mechanical Parts:


Screw M5x50mm DIN912

local hardware store

M5 Hex Nut

local hardware store

3D-Printed Parts:

Please print the parts in a heat resistant material. Otherwise you will have problems on hot summer days with melting parts. You can download the .stl files at the bottom of this step.

### You can purchase all the 3D-Printed Parts on my Website: https://www.vulcaman.de/ ###

QuantityDescriptionHow the Part look like





Etch template:

Here is the etch template for the PCB. I am using the toner transfer method to make my PCB. So you have to print out the attached pdf and transfer it to the PCB. Also this is my first project with Autodesk Eagle so I am giving my best to create this PCB :-) . You can download the .pdf file at the bottom of this step.

QuantityDescriptionHow the Part look like

Etch template.pdf

Step 3: Let's Take a Look at Your Bicycle Wether It Is Compatible With This Charger or Not

  • Hub-dynamo (normal dynamos didn't work so good, because of an bad efficiency)
  • 1 inch steering rod
  • removable Ahead-ring

Here you see an example of a bike which is compatible with this charger:

Step 4: The Circuit

The circuit of the charger contains of three different circuits:

Circuit 1:

The first circuit is an bridge recifer and an voltage doubler refered to Delon. This is the key feature of this chargers, because with the voltage doubler I can charge even at lower speeds >13km/h . Which makes it really comfortable for long distance riding.

Circuit 2:

The second circuit is my overvoltage protection. Here I coupled the bimetal switch with the suppressordiode. If the voltage rises over 22V, the suppressordiode opens and protects my DC-DC coverter from an over voltage. Also the suppressordiode is protected by the bimetall switch. So if the suppressordiode opens and burnes the complete power, it will get hot after some time. To protect the diode from too much heat and an potencial heat damage, the bimetall switch is coupled to the diode. So if the temperature is getting to high ( >50° ), the bimetal switch will cut of the main voltage from the charger.

Circuit 3:

The third circuit contains of a MP1584 DC-DC-Coverter. This coverter will convert the unregulated voltage from 6-22V DC to regulated 5V DC for the USB power . The converter has an efficiency of max. 96%, which is great for this project, because I am trying to build the circuit as efficiency as possible.

Step 5: Etch the PCB

What you need for this step:



At first you have to print the EtchTemplate.pdf with an laser toner printer to a glossy sheet of paper. In my case it was an electronic catolog. Once the pdf is printed to the catalog, clean your single side PCB with aceton, to make sure that the pcb is free of fingerprints.Then you can start tranfering the Toner with an steam iron. Once transferd you should check, if your toner transfer was succesfull.

Now you can etch the PCB in the etch material of your choice. In my case I am using Sodium.

After some minutes, the PCB is completely etched. Now you can remove the toner with aceton and check that everything is etched fine.

Then you can start drilling the holes for the electronic parts. Here I am using an one milimeter drill.

Now your Board is etched, drilled and ready to assemble.

Also please take a look at this Instructable from which I learned the Toner Transfer.

Step 6: Assemble the PCB

What you need for this step:



Stepdownmodule MP1584 adjusted to 5V DC


680µF 25V polarized capacitor


220µF 50V polarized capacitor ultra low ESR


Surpressordiode 1.5KE22CA




Bimetall switch NC KSD9700 50°C

1xEtched and drilled PCB


isolation tape or heat shrinking tube

At first you start with the small components. Place the four Schottky diodes at the right side of the PCB.

After that you can mount the preadjusted to 5V Stepdownmodule and the 680µF capacitor at the left side of the PCB.

Now the safety switch of the circuit, which prevent an over voltage damage of the stepdown module and the charged devices, will be installed.

If the suppressor diode will get to hot, the bimetal switch will cut of the complete voltage from the charger. For an improved heat conduction, I've added an little pice of metal, which will clip the switch and the diode together.

Once assembled, you can install the diode and the switch to the PCB.

Then you have to attach the two low ESR 220µF capacitors to the PCB.

Finally you can mount two little connectors to the PCB.

Now the PCB is ready for the next step.

The PCB needs to be protected from dust and it needs to be isolated from the steeringwheel. The best solution for this task is a hugh heat shrinking tube with an diameter of 25mm. Sadly I don't had acces to heat shrinking tube in these dimensions, so I had to use isolation tape for my application. Try to stick the isolation tape as tight as possible to the charger.

Step 7: Installation of the Ahead-Ring

What you need for this Step:



USB-A plug female




little wires; lenght about 8cm


XH2.54 2 Pin plug



At first you have to solder the the two wires to the USB-A plug. Isolate it with some heat shrink tube. After that you need to crimp the XH2.54 plug to the wires. For the right orientation of VCC and GND, please refer to the pictures below:

Next you have to insert the pre assembled USB plug to the Ahead.stl 3D-printed part. Once the USB Plug is inside the printed part you take some silicone and glue the USB Plug and the printed part together. I am using silicone, because I want to make sure that my charger is waterproof and protected against dust.

Step 8: Prepare the Ahead-Ring

What you need for this Step:



pre assembled Ahead-Ring from Step 7






Screw M5x50mm DIN912


M5 Hex Nut

At first you have to insert the M5 hex nut to the ClampingRingBottom.stl. After you simply put the ClampingRingBottom.stl inside the ClampingRingTop.stl. The parts are designed for clamping. If the ClampingRingBottom.stl gets pressure in vertical direction, the ClampingRingTop.stl will be spread. Later this feature will hold the Ahead-Ring in place.

Next you need to screw the Clamping-Ring to the Ahead-Ring together by using the M5x50mm screw. Don't screw it to tight. At this time the screw needs to move freely.

Step 9: Adjust the Steering Rod

Now it is time to adjust the steering rod, to make some space for the PCB.

At first you need to remove the Ahead-ring.

As you can see on this picture, the Ahead-ring is screwed to this snap ring. To make some space for the PCB, you have to push the snap ring deeper inside the steering rod.

I am using a metal tube and a hammer to push the snap ring inside the steering rod. You have to push the ring 18cm inside the steering rod.

As you can see the snap ring is deep enough:

Now you can test, If the charger fits inside the steering rod:

So you have prepared the steering rod and you are ready to start with the electrical installation of the charger.

Step 10: Installation of the Charger

What you need for this step:


two pole wire with XH2.54mm plug


pre assembled PCD


pre assembled Ahead-Ring

At first you need to create a connection between your dynamo and your PCB. I made it simple, because I go directly to the two powercables from the dynamo. To create a better look, I wired the cables inside the bicycle lamp together. For that you have to open the lamp and take a look wether there is enough space for a wiring like this.

Now the most of the work is done. You just have to connect the charger to the XH2.54mm plug. Please check the orientation of the charger in the picture below. Otherwise your charger will be damaged.

Then it is time to push the PCB inside the steering rod. Once it is inside, you have to install the Ahead-Ring by simply connecting the XH2.54mm plug from the Ahead-Ring to the PCB.

After that you can push the Ahead-Ring inside the steeringrod. But make sure that the wires are inside the wire-channel (see picture)

Once the Ahead-Ring is in place, you need to take a screwdriver and tighten the screw, until you feel that the Ahead-Ring will not move anymore.

Step 11: How to Use the Charger & Troobleshooting


The usage of the charger is realtivly simple. Just connect your device with the USB-Plug inside the Ahead-Ring and your are done.

The charging process will beginn at 10km/h. However a stable charging situation will be reached at 13-15km/h. The current which is available at this situation is around 500-700mA. For charging an powerbank or a GPS device, this is more than enough.

Devices with an power consuption of over 700mA can not directly charged with this charger. For these devices (smartphones, tablets...), I recommend to use an powerbank as a puffer battery for a succesfull charging process.


My charger stops charging after some time of riding. What is the problem?


Because your dynamo produce to much power and your device which you want to charge needs only a piece of the produced power, the voltage will rise and the overvoltage protection of the charger will cut of the complete power from the charger


You need some extra devices, which have to been charged so that the voltage will drop and it will not activate the overvoltage protection. Turn on your Lamp or connect a second or a more power consumable device to the charger. This should solve your problems.

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22 Discussions

Really nice ´ible. Voted!

If anyone need more than 500-700mA there are 2 simple steps to follow:
1. Use step up step down 5V voltage regulator ie. Pololu S9V11F5 or something similar

2. Short pins D+ and D- together (this tells smartphons and other electronics that this is wall charger)

2 replies

Input voltage range of that regulator is way to low. Dynamo will burn it quickly.
You really need regulator which input voltage range is wide enough.. about 6 to 70 volts would work just fine.
Finding that kind regulator is challenging.

Nice instructables and very well documented. One criticism, one suggestion for improvement and one question.

suggestion for improvement: to wrap the PCB with normal tape leaves some "crevices" for humidity to attack the soldering. There is a tape (black) with once in contact with oxygen "melts", and if you wrap your PCM with that you obtain a "cocoon" absolutely water-tight (that tape is just for electrical contacts outdoor)

criticism: why the plastic sold has a seat for a V-shaped bolt and the bolt has a plain head? A V-shaped bolt would make a tight seal against the V-shaped hole in the plastic

question: 500-700 mA seem quite a reasonable current for a smart phone to charge (I personally would be scared to charge mine at higher pace), do you deem that for normal phones a higher current would be required?

Anyway, my heartfelt compliments


2 replies

Thanks for your comment!

Do you have a link for this kind of tape? It sounds really interesting.

Well, the small fillet at the Aheadring.stl is just a design element. If you take a closer look at the plastic part, you will see that the small fillet has no function. Also the plain head bolt sits on an plain surface.

I can only talk about my smartphone, which requires 1,5-2A for fast charging. If the current is under 1A, it takes a lot longer to charge nearly. The charging time nearlygets quadruple. For normal phones I think 500-700mA would be more than enough. However the charging current is different from phone to phone. I would take a look at the original charger of the phone first.

The sticky tape, which undergoes a kind of "rubber vulcanisation" (melts together) is sold as a commodity in every shop of electrical gear, home appliances.Another suggestion came to me: to clip together the thermal switch and suppressor diode you could use also the "cement" used to glue together the heat sink to CPU in powerful computers (which develop a lot of heat). A friend of mine used it with Peltier cells to cool down his beer reactor during hot season with satisfying results. Said "cement" conducts heat very well but NOT electricity (very strange.....)

Really nice!


1 year ago

Great write up, about the best I have seen just for the format, and a brilliant idea.

I have one question / concern though. Looks like the star nut is not used any longer with this setup. Just mentioning here that the star nut is used to preload the headset bearings, which is a bit redundant once the stem is on. However if the stem were to loosen there would be no easy way to reset the preload, and the star nut may also help to keep the bars attached to the bike if the stem were to become loose (sort of a backup).

4 replies

I know. Your are right.

But let me explain why I pushed the starnut down:

At first I don't wanted to push the star nut down, and just screw the AheadRing.stl directly to the star nut. But after etchting and assembling the PCB, I recognized that the 1 inch steering rod on my bicycle had an rejuvenation at the bottom end of round 4mm. This problem was not visible from the outside.

So because I don't want to etch a second PCB, I simply pushed the star nut down.

Ah, I think I see. Was the original plan to install the board through the bottom of the steering tube but due to the narrowness at the bottom (where it connects to the fork), it would not fit?

Yes, that was the original Idea. Yes, the narrowness prevents me to push the pcb from the bottom inside the steering rod. The narrowness was not visible from the outside.

Please take a look at this picture:


Perfect, now I understand 100%, thanks!

Very nice instructable. It remainds me about my Master's thesis. I see, you have found same challenges that makes these kind chargers difficult to build. Riding fast and charged device uses to less power. Voltage produced by dynamo will rise extremely high.

Here is some science about this subject: http://urn.fi/URN:NBN:fi:aalto-201307127181 (sorry, text is only in finnish)

1 reply

Thanks a lot!

Your Master's thesis looks really interesting. Thanks for sharing!

Very nicely detailed instructable. Thanks for sharing!

Very nicely written and an original idea!

Nice and very detailed - you got my vote!