Hardware/LA2

Copied from LA2's OSM Diary

Here's my first attempt at mounting my PDA/GPS (Mio P550) for mapping from my bike. Click on the images for larger versions. The bike shakes a lot, and I don't want to expose the fragile PDA for this.

I went to Biltema to shop the following parts:

• Article 27-953. Bicycle basket, children size, SEK 16.90
• Article 80-406. Lead accumulator 12 volt 2.6 Ah, SEK 89.90
• Article 37-707. Motorcycle battery charger 6/12 volt, SEK 79.90
• Article 80-502. Battery cord 30 cm with lighter outlet, SEK 22.90
• Article 35-758. "Flatstifthylsa" (Female Faston/Blade connectors, Flachsteckerhülse) 4.8 mm, 5 red, 5 black, SEK 11.90

That's a total of SEK 221.50 = EUR 24.60. I also bought 2 metres of black elastic string from a sewing shop.

The PDA is powered with 5 VDC through the USB connector. In theory I could do fine with a 6 volt motorcycle battery, but I already own a power cord that has a lighter plug for 12 volt, so that made the choice easy. I don't know, but I guess the lighter cord uses a linear regulator that burns 7 volts into heat. That's no big deal. This battery weighs 1.08 kg and I could easily carry two of them.

While charging, the battery poles have 14.8 volts, which immediately adjusts to 13.2 volts when the charger is removed. When the PDA is connecte and switched off, it draws 380 mA. When the PDA is turned on with no programs running, it draws only 180 mA. With programs running it draws between 230 and 270 mA. Note that this is PDA+cord at 12 volts. According to the battery's data sheet, it can deliver 260 mA for 10 hours, which is of course exactly 2.6 Ah. The lighter-USB cord on its own without the PDA draws 22 mA (this includes a green LED). At that rate the battery would be drained in some 100 hours or half a week.

The lighter outlet comes with big battery clamps that I don't need. Instead I need something that fits the battery's poles. Instead of the standard dimension 6.3 mm (1/4 inch), these batteries have 4.8 mm male Faston/blade connectors (Flachstecker, flatstift). It turns out there are gold plated females (Flachsteckerhülse, flatstifthylsa) for audio gear.

Here's the battery cord with the new connectors mounted.

And this is how the battery and cord fit in the bottom of the basket under some elastic string. For this first round, I'm not encapsulating the battery.

On top of the battery I intend to mount the PDA in a little box of its own that hangs in a suspension of elastic string. I found this box in my kitchen and made some holes for the cords and strings. When the USB power cord is connected to the short side of the PDA, the unit becomes too long to be mounted in portrait mode in this children sized bicycle basket. However, the PDA easily flips to landscape mode, so that's how I will have to use it.

Here are all the parts, spread over the table.

And the same mounted in the bicycle basket, in a suspension of elastic string. On the top left is the external antenna that I normally put on my car's roof. I discovered it will need some better fastening, perhaps adhesive tape.

Just hang the basket on the bike's handle bar, and off you go. When you park, just lift it off and bring it with you. Nothing is mounted on the bike.