I was inspired the other day when I meandered round the internet and I saw a lot of Computer controlled etch a sketches, but not a single etch a sketch controller computer. So I put aside my other projects for a night or two and set about actually making one of these things. I’m quite pleased with the results, but you can take it for a test drive yourself, when NortHACKton go to the UK Maker Faire next month.
The basic construction is an MDF frame, mounted over an LCD monitor. Two water bottle caps act as the knobs for the etch a sketch and the guts of an old roller ball USB mouse have been re purposed to control the PC.
An old mouse already has two sets of rollers, one for left-right and one for up-down. These normally press against the ball to detect the mouse movement. A slotted disk on the roller spins between an LED and opto sensor pair to detect the rotation of the knob. I have extracted these roller and sensor arrangements and put them on the left and right of the screen. The left and right clicks have also been extended and put behind each knob.
I extended the cables from the PCB in the mouse, it’s quick and dirty, I didn’t even common up the ground wires. It works and that’s good enough for a hack right? The tricky bit was aligning the LED with the sensor correctly and was achieved with lots of careful adjustments before glueing each knob section together. Finally a little bit of friction prevent the mouse unclicking, so I wedged a small section of foam into the gap to help it return to the off position.
Higher res photos can be found here and a small sample video should appear below.