The final countdown

In Flanders (Belgium) sixth-formers yearly celebrate the last 100 days. This tradition celebrates that high school is almost over, and that freedom is on its way. Students will usually dress up in costumes and party all day and night long. Most school also organise special activities like a breakfast or allow students to decorate the school buildings.

This year I was one of the revelers and since the event is the start of a countdown, I decided to make a big countdown timer to count down to our graduation.


At first I considered using large 7 segment display, but after some consideration I went with a large clock face that counts down from ’100 days’ to ‘we survived!’ (the theme of this year)

The clock face and hand are laser cutted out of 3 mm plywood, and all electronics and servo’s are immediately attached to it. The board consists out of an ATmega8 running the Arduino bootloader and a RTC (ds1307).

Last year I noticed a network switch above the ceiling tiles, so I assumed there must power there. Popping my head through the ceiling confirmed that, so I just went ahead and installed the thing.

It’s easier to ask forgiveness than it is to get permission.

— Grace Hopper —


The software is very simple. It reads out the RTC, calculates the remaining numer of days and then maps those value’s to a position for the servo. The code is embedded after the break.

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Janus, The gatekeeper

Because I was annoyed that every time I came home I had to take out my keys, I wanted to make my front gate keyless. At first I considered options like a keypad or RFID, but those all involved installing extra hardware at the gate and running extra cables.

A couple of years ago I had read about a secret knock lock on hackaday, and I came up with the idea to do something simular, but to replace the knocking with ringing the doorbel. So I looked up the project, and found the source code writen by Steve Hoefer to be almost perfect for what I wanted to do. After a few tweaks I already had a first prototype running.


For the final hardware I used a mehduino, an bare bone arduino clone designed at the bitlair hackerspace that already has some prototyping space around it. Appart for the mehduino, there are only some resistors, diodes, buttons, dip-switches and relays on the board. The board sits between the door unit and the rest of the bell system, and intercepts signals comming from the front unit. It can send two types of signals: open the gate, and ring the bell.


When someone rings the bell, first the entire sequence is record. Once they stoped ringing, the recorded sequence is matched against the prerecorded secret code. If they match the board will open the gate, if they don’t it will ring the bell.
The code can be found on github.

And the project got to hackaday, and gizmodo, and discovery channel :)

Electricty timer at kapot karnaval

For a small and free festival in Ghent (BE) I designed the electronics for an “electricity timer”. This device was made to encourage people to donate to the event, and it’s basically a big timer that you can recharge by inserting coins. When the timer get’s at 10 minutes a blue flashing light goes on, and when it’s at 0 a loud sirene will go off and the music is turned of.

The machine was built around an Arduino that controls a servo that the clock-hand is attached to. When you drop coins into the machine they roll down a shaft, and are detected by an optical interrupt before they drop in a bucket. Every time a coin is detected two minutes are added to the timer.

The code for this project can be found on github
And the project got to hackaday  :D