This instructable shows you how to easily build a water proof housing for your mobile phone.
Trying to use my mobile phone as a navigation and tracking device during a bicycle tour forced me to look for a proper dock to mount it on the handlebar of my bike. I am using a HTC desire Z. This mobile has a keyboard that can be folded underneath the display. It's an android phone where many mapping and navigation apps exist on the market.
After a long search I realized that there is no dock available that fits my needs;
1. Waterproof even during heavy rainfall
2. Securely mountable on the handlebar, stay there also during accidents
3. Easy mounting of the phone
4. Access to screen (touch display) and keyboard druing the travel
As there where not much time left until our easter tour I had to find a quick, simple and easy solution.
Step 1: Parts Needed
The expensive part you need is a box that is designed to keep your food fresh.
I recommend using a good quality box like the emsa clip & close. The box can easily be open and closed with clips. The box is made of strong but flexible platics and uses a rubber ring to ensure that it is sealed tightly wen closed.
Besides the box you need some wire strap, a block of styrofoam and the following tools;
- some sharp knife, I used a scalpel
- a ruler
- a marker pen
- a hot wire styrofoam cutter
i build the hit wire styrofoam cutter myself, using a power supply a big resistor and a wire mounted on a holder. The restor is used to adjust the current that flows through the cutting wire and thus regulate the heat that the wire produces.
Step 2: The Idea ...
... was to put the mobile phone into a box that was sealed. The box should be mounted tight to the handlebar. While mounting it on the handlebar I should be able to see the navigation screen during the travel. While the mobile was mounted inside the box I should still be able to use the keyboard and even the touchscreen. It would also be nice to use the mobile for some hours without the need to save battery power.
1. First I tried to use the dynamo of the bike to charge the mobile phone while traveling. After some experimenting with charger electronics and reading a lot of information on the internet I realized that it does not make sense to charge the mobile while cycling. The energy generated by the dynamo is simply not enough to load a mobile phone. It takes you about 2 hours of constant cycling with a speed above 20km per hour to fully charge the battery. The voltage generated by the dynamo is not constant, therefore modern charger elecronics will not work. Those chargers are designed to work with a constant input voltage over some some time. If the voltage constantly changes and falls below the minimum voltage needed, these chargers will start loading cycles over and over again. Using constant current chargers may work, but it is not a good idea to charge a battery and discharge in setady alteration. It simply destroys the battery. You will get the most out of your battery if you fuly load it in one single cycle and then discharge it to about 20% in one single cycle.
2. I totally dropped the idea of the charger, even when I did some test cycling with a dynamo optimized charger (using a shunt regulator). I even made some experiements with a small lead acid battery. Those batteries can be charged with changing voltages without loosing capacity. But to fully charge this battery I would have to constantly ride my bike for nearly 20 hours (6V, 4.5 Ah capacity).
3. I simply bought a bigger battery for my phone on Dealextreme http://www.dealextreme.com/p/3-7v-3500mah-high-capacity-battery-pack-with-back-cover-for-htc-desire-z-55616 . This battery got twice as much capacity than the original one. The battery comes with a special back cover. The back sticks out somehat but the battery is really great. It extends the usage cycle of the mobile phone significantly.
4. The touch screen should be useable. In the first step I liked to cut a window into the box and glue a foil on the back. The foil should seal the window but still keep the touchscreen usable, because the foils is much thinner than the plastic body of the box. I found out that it is not easy to find a foil that is thin and strong enought to be used for some time. I used different foils but found most of them lasting just for one day. After some experiemting I decided to use plastic bags made to put food into the refridgeraor. I cut the bags into pieces and simply clamped them with the top of the plastic box. This way I was able to replace broken foils with new ones easily.
Step 3: Preparing the Box
I started with the styrofoam block. Styrofoam can be cut into nearly any shape using a hot wire. I build the hot wire cutter myself some time ago. it is made of;
- a steel wire
- some flexible copper wire (speaker cable)
- a glass fibre stick
- some tape
- a power supply, 10A, 12V
- a resistor with tabs, 3.5 Ohms 20W
The glass fibre stick keeps the steel wire tight. By pressing the fibre stick I am able to form the cutting wire and cut holes into the styrofoam.
Next I cut the window into the top cover of the plastic box using the scalpel. The window is cut in a way that allows it to reach the whole screen and even the keyboard. It is not cut too wide to press the mobile phone into the styrofoam block.
Step 4: Mounting
I used two wire straps to mount the box to the handlebar of my bike. To do this I cut four smale holes into the bottom of the box and pushed the wire straps through them. To make it fit better I added some plasic foam. The box is fixed tight but still can be adjusted to get the best viewing angle during traveling.
Step 5: Does It Work ?
I used this construction during our "Tour de Ahr" at spring time 2011. We traveled for one week. Most of the daily tours where short (about 2-3 hours) because we traveled with some small children. One tour was about 6 hours. The battery did not last for the whole day tour. From my experiment I still owned the lead acid battery. I fully loaded it before we began our tour. During a rest I used this battery to charge the battery of my mobile phone. Just to be save I also had the original battery of the mobile phone with me.
The system recorded the tracks during the complete tour. I used it for navigation too. Only once the application died and I lost some meters of tracking. I am very pleased with using Velox and RMaps, both available on the Android market. The big plus of RMaps is that I could use the Opencylemap and German Outdoor Maps at the same time. On high zoom levels the Outdoor map is used and I can see enarly every detail of the region. Otherwise the Opencylemap is used where I imported the Ahr-Radweg track before starting our travel.
The box itself was wonderful. I drove through heavy rain, having a water puddle swapping on the top of the box and the foil. The mobile stayed dry. I used it wor navigation during the rainfall controling it with the touch screen. I swapped foils three times during our 5 days travel.
The box is still (now is Oct 2011) mounted on my bike. I use id regularly when traveling.
During our tour my friends iPhone completely drowned and was not operating anymore ... he simply tried to use a standard iPhone holder.
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