The PCB was etched using our currently favoured method: coat the copper board with Halford Matt Acrylic car paint, allow to dry (we did use a hot air gun to speed this up, but it can cause the copper board to curl a little bit) then laser the PCB design onto the paint. A few minutes in the heated bubble-etching tank, and our PCB is good to go.
Another visit to the laser cutter and our top layer of mdf was ready.
A perfect match! The holes in the top layer will hold M4 washers, which in turn connect the two halves of each button contact. We were just about to drill and glue the whole thing together when someone pointed out a problem, which meant making another PCB.
On our first PCB, the "filled pour" plane (the copper between the tracks and traces) meant that any washer over two contacts would also connect to any other washer on the same plane - basically all our washers would be electrically connected together! So it was time to knock out another PCB - this time with the copper fill removed from around the contact pads (in the fullness of time, when these are produced with a solder mask, only the contacts will be exposed, but for our prototype, we need to remove all the extra copper from around the pads).
With the new PCB in place, it was time to fit it all together and see how it looked.
The extra slots in the mdf are where through-hol components are to be mounted on the underside and soldered to our exposed copper surface. These slots allow the mdf to sit flat against the PCB, even though there are rows of solder joints on the "top" side of the board.
Unlike when trying to pull a playing piece down onto a fixed steel disc, allowing the washer to float and using the magnet to pull the washer up works through very thick material even when one of the "weaker" 1m thick magnets are used:
Next will be the printed playing surface for this corridor section, then to hook it up to a computer and see if it actually works! Because this new method means we don't need super-strong magnets and large steel discs, we can even use some thicker material for the printed top surface: some 350gsm photo quality card, laminated in 45 micron gloss film might look very nice. Maybe it's time to call in a few favours from Nick at customstuff.co.uk....