My thesis, the Abacusynth, is a synthesizer inspired by an abacus.
I began with some scrap wood connected by a steel rod, and I used small breadboards mounted with rubber bands to hold the sensors in place. I was using a time-of-flight sensor to measure distance and a breakbeam IR sensor to measure rotation.
Designing the Enclosure
I sketched out what I wanted the final enclosure to look like. Initially I wanted knobs on both sides, one to control the waveform, and one to control the volume. This changed pretty quickly, since that added a lot of complexity. I opted for rotary encoders with push buttons so that I could combine multiple controls in a single knob.
The first thing to do was to design the walls that hold the sensors and rods. I started with a cardboard rectangle with holes for the sensors: the distance sensor on top and the break-beam on the bottom.
Once that was working a moved on to wood. The inner section would be removable, since it would not need any electronics — it would just hold the rods and spinners.
I used 1/2” standoffs to connect the inner and outer sections. The PCB boards fit pretty snugly inside.
With the prototype working, I designed the final enclosure in Vectorworks. It consisted of multiple layers of wood that would stack to create the hollow walls.
The walls would be connected by 1/2” square dowels that I would cut by hand. They would fit within the square cutouts on the inner layer. The base would be 1/2” plywood, also cut by hand. I created a 3d render to make sure everything fit together.
I then arranged the panels for laser cutting. The inner wall sections would be made up of two 1/4” (really 0.2”) pieces and one 1/8” (really 0.12”) to add up to just over 1/2”, and the outer panels are all on on 1/8” wood.
Time to cut! I started with cardboard to make sure the design worked.
The one mistake I noticed with the cardboard prototype is that I had reversed the PCBs in the design — the holes for the encoders were closer to the back than the front. Switching this allowed the PCBs to fit and also made the design better by allowing more room for the cables and the interactive pieces to be closer to the user.
Adding the Electronics
I could now add the electronics and see if everything worked. For more details on this, see the PCB development post.
Testing the electronics: Distance, rotation, and encoder
Testing with two rods
Final Wooden Version
Now that I was confident in the design, it was time to cut the wood. I taped over it to minimize burn marks.
The plastic standoffs fit into hexagonal holes in the inner walls, so that the outer walls could both screw in to the same hole.
Drilling it all Together
The inner walls are screwed to the base and the 1/2” dowel support rods. These screws are covered up by the outer wall.
Moving/Spinning is much more firm than with the cardboard prototype
One quirk of the design is that the shaft collars holding the rods in place make it a bit difficult to remove the inner section. I had to cut out a slot in the top and glue it to the inner piece so that you could slide out the entire section.
Removing the inner section
I sanded the visible edges that were burnt during the laser cutting process. This revealed the wood grain and made the surface smooth to the touch.
Testing the build
All four rods working!
Testing with the speaker mounted
The final step was to build knobs for the four encoders on the left wall. I started by just sanding a piece of wood to get a feel for the size.
I then used a drill bit to cut out cylindrical pieces. These were much cleaner and felt/looked nicer, however I needed a connection piece to hold firmly on to the potentiometer.
For the final design, I 3d printed an insert and laser cut circular layers of wood.
Finishing and Painting
It was now time to take everything apart so that I could finish the wood and paint the knobs and spinners.
I used a clear spray-on lacquer for the wood, since I wanted to retain its bright natural color.
I first sprayed multiple layers on to the disassembled pieces.
I then partially assembled it and added another few coats. I taped off the inner sections that I did not want finished (not pictured).
I primed the spinners and knobs in white to prepare them for acrylic paint.
After everything dried, I added the electronics back in and miraculously everything worked.
I painted each pair of sliders and knobs a different color. I didn’t really plan out the pallette in advance, but wanted something playful.
And here are some nicer photos of the final product!