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12th JC: Multiple Sensors


Sunday, 24.4.2016

When there was one cache left to be built, we decided to design the „Questionnaire“, because that should be not so difficult. What a mistake! We learnd such a lot about digital and analog buttons. The first ones you bought were crap. But at the end the cache was built.

Now the caches for the 2016 geotrail are complete, but this is the next one. „Multiple“ sensors have been also on your wish list. 

This is the concept:

After the welcome screens the cacher has to activate 5 different sensors:

  • pushing a button long enough but not too long. The display is only telling too short, too long or perfect done.
  • making noise by knocking on the cache
  • flashing with a torch into the right hole
  • placing a magnet onto a certain area of the cache (with right polarity)
  • spinning the cache around all his three axis with a minimum speed


The biggest callenge was the last one. I bought a 3-axis-gyro breakout with a buit-in temperature sensor. 

71QjmgO02yL. SL1500


This temperature sensor is used for a joke on one of the welcome screens only:

vlcsnap-2016-04-24-08h49m56s228


Back to the sensor. My first idea was that the cacher will have to turn the cache upside down. But the sensor gave very strange output: When turning it, signals were given, but when lying upside down, the signals were the same as with the initial position. Also values for acceleartion given bny the sensor. So I used them, but also strange: When I started moving there was a signal, during the movement not but at the end again…

How blonde (=stupid) I have been!!! Accelaration isn’t speed. So when starting the moving, there’s acceleration, but not when moving with the same speed. At the end of the moving it’s negative acceleration. The same is with the gyro. It’s showing the speed of turning around an axis. So the cache became what it is: At the end the cacher has to spin the cache around its 3 axis with minimum speed.

Here’s a movie of the prototype (as ever: by clicking on the YouTube icon you can watch in 1080p:



You can pick the full sketch here


Stay tuned! 

Blog will be continued… 



©  Olaf Goette 2008 - 2018