“Reuse, Reduce, Recycle”
was the general topic for this semesters Sketching with Hardware course, so first of all, we needed something to work with. It was pretty clear that it would be most fun to take an old thing – whatever it would be – and make it behave in an unusual way. Luckily, we found this at a flea market:
It says oscilloscope on it and was once used in medicine for graphing the human pulse. The oscilloscope consists of two main parts, the left side holding a revolving paper roll, a spring and mechanics to move the paper stripe.
On the right side, we find two moving arms with small containers for ink at their ends. Each is mounted onto a box that contains an axis which turns in response to small changes in pressure. Tubes connect the box to a cuff and a switch allows the user to select into which box the air flows.
What did we make out of it?
“Gameboy 0.5 beta” – our idea of how gaming might have looked 100 years ago. We built an arcade game for the advanced. You don’t play one level, you play two. At the same time. With a joystick. The two needles are arranged vertically, so the game is split into an upper level and a lower level. The upper level is always the same, collect the golden coins by going over them and loose one each time you crash into a wall. The y-axis if the joystick directly maps to the position of the needle.
For the lower level, we offer two modes, one of them is basically the same as on the top, so we use the x-axis of the joystick to set the distance between the needles. The second one is inspired by jump and run games, you try to avoid running into boxes by jumping. Once you have jumped, you need to wait until you touch the ground before you can jump again. After completing the level, unfortunately you need to count the score yourself. Which is easy because you left an ink line, see?
How does it work?
Let us first say what we did not change: We saw the beautiful mechanics that power the paper roll and quickly decided to leave that complete part untouched. We replaced the original black cover with a transparent one so you can see the wheels turning while playing.
Apart from that though, we changed most parts. All the tubes had to go and the mechanics in the pressure-sensitive boxes were replaced by servo motors. These
enable us to directly control where the needles point. An arduino receives the input from the joystick and translates it into angles for the servos,
depending on the mode. The mode can be changed with the knob that originally directed the air flow (POS. 1 or POS. 2).
Another thing we changed are the needles. Since we could not find ink that worked with the original ones (picture above), we use the tips of edding rollers that are attached to laser-cut arrows.
This is how the components are put together. The weird thing in the bottom right corner is the joystick ;).
How do we get the joystick input values? – We use an old joystick that has a GamePort-plug, so the arduino 5V is on pin 1, pins 3 and 6 are both wired through a potentiometer in the joystick. The arduinos analog inputs can now measure the incoming voltages for both x- and y-axis. Our code automatically calibrates the center position – the specification says the resistance should vary between 0 and 100000 Ohms but of course, that is not even close to reality.
Where does the power come from? – The arduino delivers enough power to run the servos and the LED. A hole in the box can be used for a USB plug, but we have a 9V battery connector inside as well.
How are the servos held in the boxes? – Mostly glue and some paper to keep the right distance.
How are the servos connected to the axes? – Again, glue. Actually, we broke the original axes and mounts, so we use parts of an old umbrella instead. The moving arms are held by magnets. That allows us to remove them whenever they run out of ink.
How much does it cost? – The oscillograph was 4€, the joystick 0,5€. All other material was already present. We were, however, quite lucky with the oscillograph, there is one on ebay for 60€ at the moment.
If you want to play yourself, you will be able to do so at the Media Informatics Open Lab Day this fall. If you only want to see it in action, check out the video!