Using the defusable clock for geocaching

[pgielen]

The defusable clock gives me a fantastic idea for a thrilling geocache! But battery life is an issue here, since maintenance should not be a burden. That’s why I’d like to know if it is possible to hack the device for maximum power efficicency.

My idea is to normally turn the display off and use an light sensor to trigger the start button: only if the cache box is opened and light enters the box, the display is turned on and the countdown should start.

After that, it would be nice if defusing the clock not only stops the countdown, but also triggers a solenoid which unlocks a second box with the log roll (if you’re unfamiliar with geochaching, you can find all about it at geocaching.com).

Is this possible with the defusable clock kit? Would it have a significant effect on battery longevity?

Thanks!
Pierre

(sorry for posting in the wrong forum just now)

[Michael]

Yes, keeping the display off would greatly increase the battery life when using a 9V battery. Six C or D cells will run the clock (even with display) for days.

All of the ATmega328’s digital and analog buttons are in use, so you would need to use existing ones (like button or led) to add the new sensor and output.

A photoresistor could be used as a sensor, and it could be installed in place of a button, and software tweaked to read the value as an input. You could control a solenoid using another output (use one of the LED outputs). But keep in mind that a solenoid requires a lot of current, and would need its own beefy power source.
Hope that helps.

[Englishfire]

I’am really interested in that! Any help to get things done?

[Author]

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