Bike mount/charger (DIY)
I use to go on long bicycle trips and thus needed a charger for my mobile phone while on tour - especially because I use the phone as GPS/map (osmAnd).
I found a good DIY charger for a hub dynamo on the site (german only): forumslader.de / 12V-Version-mit-zusaetzlichem-USB.209.0.html (sorry, as new user I'm not allowed to post URLs)
So last year, I built it and mounted it in a waterproof case with an external switch panel with USB connectors.
I used it quite succesfully on a 16days trip around Sweden/Finnland. But some months later on a 1day trip, the micro USB socket of my Samsung Galaxy S+ broke. There was heavy rain on this day (and phone protected quite ok in my bag on the handlebar, but of course there was a general problem with moisture just due to humidity). Anyhow, I think the main reason the micro USB socket was broken, were the permant vibrations when using it on a bike in a handlebar mount. And I also think that vibrations are a general problem for micro USB as long as a cable is plugged in and it will ever be on any device.
So, for my new phone - the Xperia Z, I decided to build a charger using the "dock connector" on the side. This also means that I really don't have to care for rain, even while charging.
Voila, here it is:
So, first I was looking for the electrical characteristics of the dock connector and found them in various threads here on xda-developers.com:
Upper pin: +5V
Lower pin: GND --> This is important: it is also connected to USB GND. So if you ever decide to use a external power supply and USB at the same time, please make sure the "-" of your power supply is grounded or your phone will do.
Charging current: 1,5A-2A
And it is protected against external short-circuit (no current can flow back). This is obvious, otherwise the Xperia Z wouldn't be waterproof.
For the charger this means that you don't have to take care for your phone - only for your charger. In my case, I use a 1A DC/DC converter in my charger that just do not load more than 1A and is short-circuit safe.
- Pogo Pins (e.g. Ingun GKS-113 217 230 R 15 02)*
- One strip of acrylic glass
- stranded wire
- shrinkable tubing
- optional: sponge rubber
* they were available on ebay, but I think there are better ones, e.g. with more force (the value after the R is the force in dN, so in my case it is 1,5N) or smaller but better shaped head. The head in my case is quite large (2,3mm) and close to "too large". I suggest < 2mm.
- Soldering station
- heat gun
- driller (for the suggested pogo pins, use 2.5mm)
- wire cutter
- Cut a strip of acrylic glass (use a cutter, then just break it along the cut line)
- Bend one side approx 90 degrees by heating the acrylic glass with the heat gun and use a corner e.g. on your desk or workbench to bend it around
- measure the distance around your phone (please keep in mind that it must go around your bicycle mount) and mark the bending corner on the acrylic glass strip
- Bend the other side with the heat gun. Try if it fits, if not just heat it up again and adjust the bending.
- Mark the position of the holes for the pogo pins (please again keep in mind that the acrylic glass must go around your bicycle mount)
- Drill the holes. If the pins do not fit, just move the acyrlic glass around the rotating drilling shaft carefully to slightly increase the size of the hole.
- Mount the Pogo Pins
- place the shrinkable tubings on the wires and then solder the wires to the pogo pins
- wait for the pins to cool down and then move the shrinkable tubings above the pin and shrink them with the heat gun. (fast, don't heat up the acrylic glass again).
- if necessary place some sponge rubber into the bending to protect your phone and to absorb some vibrations.
- connect the wire to your 5V power supply.
Additional information about things shown in the pictures:
- GPS software: osmAnd (free, premium 5,99€, OSS, can be installed from source, too).
- Bike mount: from Amazon (Germany), 8,99€: "mumbi Fahrrad Halterung Sony Xperia Z Motorrad Halter / Fahrradhalterung Motorradhalterung"
- Charging electronics: See forumslader.de . There is also a new version that don't need any external switch box and can be installed into the headtube.
- Box for charger electronics: Bopla 63205000 (Reichelt: BOPLA ET-205, 4,95€)
- Buffer batteries: I also connected 10xAA batteries (rechargable) to the charger electronics. (Reichelt: "HALTER 10XUM3QDK", 1,10€) and used shrinkable tubings to make it water-proof. I also have a spare batterie holder, so if necessary I can buy some batteries in the supermarket and charge my phone this way.
- external switch box: I tried to build the switches (high speed/normal / charging on/off), info LEDs and USB connectors in one extra box and to build it quite waterproof to. Waterproof switches are quite large and so is the box. I think I won't use waterproof switches in the future and just place the (then smaller) box into my handlebar bag, when it rains.
- Cabling: This is also work in progress, I should add connectors between the charger box and the battery pack or the external switch box. But waterproof connectors are quite expensive.
I used the charger on some tours and it works fine. In case of heavy vibrations or shocks, the phone sometimes stops charging. This maybe better with stronger pogo pins (5N or 3N instead of 1,5N).
In general, the power of a hub dynomo is not sufficient
to charge a phone when display is on. So switch the display off whenever possible and try to save power as much as possible (flight mode, Stamina Mode).