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Last week I picked up Make magazine vol. 26 and found a cool project called the ‘Luna Mod’. It is basically a sound generator/looper based on a picaxe 08M. It has 2 potentiometers, a button and a couple of LEDs to indicate power and tempo. When you press the button it adds a tone to the loop. One of the pots controls the pitch of the tone and the other controls the tempo. In Make the author also builds a wooden box to put it all in but I don’t fancy myself as much of a wood worker so I came up with a somewhat simpler case for it. I am really happy with how the case looks and actually prefer it to the wooden on. Here is how I built it.
The instructions called for a small piece of strip protoboard. Usually I would try an rebuild the schematic in Eagle CAD and design a proper PCB but I couldn’t be bothered this time. The circuit is only small and I liked how it all fit on the board anyway.
After some of the traces had been broken on the back of the PCB. To break the traces I used a drill bit and gave it a couple of turns by hand. This worked really well.
Most of the other components installed. I used a LM7805 regulator because it was what I had handy. The instructions specify a LM78L05 which is physically smaller. I didn’t take a photo of the board with the power, audio and programming jacks and pots installed, but I assure you I did install them.
Next up I built the box for everything. This took a little bot of trial and error. Originally I had planned to use a whole record and melt it over a block of wood or something to form a box in the middle. When I tried this though the record just warped and the box in the middle was more like an unusable lump. Next I tried making a net (just like in primary school) for a box by cutting a record with scissors. I found it really easy to cut the record after heating it up with a hair dryer. It was almost like cutting a thick bit of paper. Once I had my net I heated it up over the stove top and using a metal ruler I bent all the sides in to shape. In the end it was really easy to make a looks awesome. The hole in the middle also made the perfect spot for the on/off switch.
Using a small drill bit I marked out all the holes for the various parts. After I was happy they were all in the right spot I enlarged the ones that needed enlarging.
Most of the parts have screws and nuts so they were really easy to mount. The LEDs just sit in the holes all on their own.
To hold the battery in I got an off cut from the record and melted it in to shape as a holder of sorts. The vinyl has a nice springiness to it so the holder works really well. In the future I would use a proper battery holder but this was all I had on hand. I also glued the battery clip in place.
I used another off cut and a whole bunch of glue to hold the board in place.
After everything was in place I went to put the knobs on the potentiometers and found they were too tight to fit on. Using a large drill but I made the hole bigger until I got the perfect fit. A little bit of hot glue ensured the knobs stayed in place. The stick things on the pots were too long so I just cut them down until the knobs fit on with a millimeter of so of clearance.
Video demo of how it sounds.
I am really happy with how it looks and how everything works. I would change the position of the button to the opposite side though. When you are pressing the button you are usually turning the pitch dial which is a little awkward with the current layout.