... it is night and you're out for finding a special geocache - a night cache. You start when dusk begins and follow a small path through a forest, led by small reflectors at the trees you have to find with your flashlight. Stars and the moon are shining bright above you. The inhabitants of the forest wake up and fill the scene with their sound. Slowly a feeling like being in a horror movie rises up. And you are right in the middle of it.
Most night caches...
... consist of reflectors and UV ink. But if you are the owner and want to present the cachers something unusual, a reactive light is the gadget you are looking for.
... are small electronic circuits with a microcontroller, one (or more) LEDs and a light sensor. At daylight they will fall to sleep and be inactive. But if brightness falls below a threshold, it starts to work. As soon as the light sensor detects a fast change of brightness (a cacher lights it with his flashlight), the LED starts to blink a predefined sequence. This can be just a number of flashes or even morse code with a short message. Triggering the reactive light works over a long distance. Up to 100 m - depending on the flashlight - is no problem. As power consumption is optimized to a very low level, a set of standard batteries (the circuit requires 3 V) lasts for several years.
... contains the circuit board and all components. Just the batteries and the battery holder are not included. None of the components is SMD to make it easy to assemble even for beginners. Most kits contain an already programmed microcontroller.
The circuit board has a size of 15 mm x 28 mm. This small dimensions make it easy to hide the reactive light in a crack, a knothole or a fake birdhouse.
... enables the owner to change the blinking sequence whenever it is necessary. One just need a flashlight and a magnet.
A magnetic switch has to be triggered to start teaching. Then the flashlight is used to define the sequence. The light sensor detects it and the microcontroller stores the sequence in its nonvolatile memory. When the sequence is finished, the teaching has to be terminated by triggering the magnetic switch again. Due to the nonvolatile memory the sequence won't get lost if the power supply is removed.
The sequence may consist of up to 32 bright and 31 dark phases. Each phase may have a duration up to 8 s. It is saved with an accuracy of 0.125 s.
Please notice that not all kits contain the teachmode.
... 400 EUR: You can choose the color of the LED. Possible colors are white, yellow, red, green, blue and violet.
... 550 EUR: The circuit board gets prepared for a second LED. All kits contain two LEDs. When programming the microcontroller on your own, both LEDs can be controlled separately. Already programmed kits will use both LEDs synchronously.
... 800 EUR: Each kit will contains a centrifuge tube that is big enough for the circuit and two AAA-batteries. It can be used as a waterprove case for the reactive light.
Risks and challenges
As long as I won't get lost while caching in the mountains of Saxony, there is no risk at this project. The program and the circuit design is already finished and tested. Just the circuit board has to be produced and the microcontrollers programmed. The first point is a question of money (you'll help me getting it), the second one of time (I'll do the programming on my own). Just in case that hundreds of people want to have a kit, there mey be a small delay.Learn about accountability on Kickstarter
- (30 days)