As I said, it' the very very first prototype. And of course you're right that water would leak inbetween the bar and the tape. But since the button itself is sandwiched between two layers of tape, the electrical contacts shouldn't get wet at all.
Ok, I hadn't realized that it was sandwiched in the middle. I don't think that a bit of water would manage to let enough current through to generate a HIGH so your arduino senses it...
H2O doesn't conduct, but I like to think I'm getting some vital salts when I'm drinking out of the tap, and the salt ions dissociated in the water should conduct pretty well?
Anyways, I just submerged the entire switch in water and it still displayed infinite resistance (as opposed to some M[ch937] when in contact with water), so I declare it watertight Roll Eyes
I will tweak the optics a bit, though.
Yeah it should conduct a bit... Anyway, rain doesn't conduct (or not anywhere near as much) because there aren't all the minerals/salts in it.
I see what you were saying about the positive feedback on a tactile switch which you don't get on a capacitance sensor switch.
I have found another use for capacitance sensing though. If you put a massive resistor in the circuit used for the Capsense stuff then you can sense people over 1m away, this can be altered with different resistors. I used a LDR covered over and sensed my movements towards it from about 1m away from a 5x5cm bit of aluminium foil.
If you had this in your device then you could set it to sound an alarm if someone is really close to it (10cm or so) for a period of time unless something is done to turn it off (key switch etc). This would stop someone stealing it without someone else noticing... You could also sense when you are on the bike to turn on or off the display etc... A few ideas...
The AAA ones have a capacity of 800mAh, AA deliver 2000mAh.
And actually, I'm thinking of using the batteries as the main source of power, and the dynamo as a backup. I haven't really made too many calculations about the power consumption, that will commence when I know what component's I'll be using exactly.
But will Eneloops like the -10°C? The Sparkfun Li Battery seems to be rated for down to -25°C, but surely it's not the best thing to do to it?
I had just presumed that you would be driving your arduino from the dynamo, it would easily provide enough power and wouldn't be as difficult to pedal with as powering a light. I'm guessing that with the stuff you want, the draw will be 100-150mA or something (not including a GPS). The blinkers would obviously take more and the front/rear light, if using a battery for them, would flatten it pretty quickly...
For temp details see:
http://www.eneloop.info/home/performance-details/low-temperature.html
Apparently still high performance at -10°C Just stick them in a bit of foam and they shouldn't get that cold...
Mowcius