over the last month I built a reverse geocache that is trackable on geocaching.com, uses nixietubes and looks cool :)
At first I used an lcd display that that seemed a bit boring for what I was planning.
So I bought some IN-12B Nixie tubes with driver ICs from ebay. They where pretty cheap (20$ for 6 tubes, connector pins and ICs) and they have a decimal point. With 3 of these I can display from 10 meters (0,01km) to 999km.
These tubes need 180 Volts so I also got a small DC-DC boost converter. Each tube needs one driver ID that has a 4bit binary input for switching on a number in the tube.
I also need another driver chip for the decimal point (with just two connected inputs) and a signal to switch the nixie powersupply on and off - That makes a total of 15 data pins. Because I wasn't sure that I had enough IO pins left on the arduino I added a 4bit binary counter to the nixie drivers, that reduced the needed IO pins to 9 - I could have reduced that more, but so I have 9 pins left, that's enough for this project.
The finished nixie board:
The back (Yes, next time I will make a real board :) )
The rest ist pretty straightforward, I added a serial GPS module, 2 LEDs and a servo and mounted all of it on a board:
The box for this is a metal box from the french army (medical box). A friend with a CNC lathe made the cuts in the lid.
This is the locking mechanism:
And this is the painted box: The red bars are ikea door handles :)
The GPS-LED blinks while it's trying to get a fix. If it gets one within 3 minutes, the GPS-LED lights solid and it displays the distance or opening 'animation' for 8 seconds and switches off. It it can't get a fix, the Error-LED lights for 8 seconds and it switches off.
The on-off switch is built with a latch relay, so it's really off when not operating.
The box contains 4 D Cells because the tube draw a lot of power.
When someone has opened the box he'll find instructions inside on how to reprogram it via usb and a serial console. I made a special serial dialog to enter new coordinates.