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  • gawley7

MIDI to CV (part two)

This is the second post in my series about building a MIDI to CV box (the first one is here).

A quick reminder of what we are trying to build. A USB-MIDI to CV device to let me computer control my MS-20 via MIDI-CC. I don't need to to provide Gate or CV for note triggering since this is already handled via USB-MIDI by the MS20. So far we picked an Arduino, designed the circuit, wrote the Arduino code and got a prototype up and running on a breadboard. This time we're going to move to a soldered Perf Board, build an enclosure for the device and set up a the necessary bits and pieces in Ableton to make it work.

Moving to a soldered Perf Board was by far the biggest step for me 👨‍🏭. I've not done much soldering so there was a pretty steep learning curve. Some things that I learned along the way.

  • A cheap soldering iron from Amazon is just fine. But make sure you use one of the wedge-shaped tips rather than the pointy tips. It's just much easier to make a good contact with the board and the component.

  • You have to heat the component and board then apply the solder. you can't melt solder and then sort of 'drip' it onto the joint. It won't make a good bond with metal that is not hot.

  • You need to look after your soldering iron tip as a dirty or degraded tip won't transmit heat in the way you need it to. This means using the (included) wire wool to clean it and adding a dab of solder to the tip after you are done with it. If it gets very dirty, use some flux in conjunction with the wire wool to clean it.

  • You can overheat Perf Board and burn out the tracks! Take care. I assume you can also overheat components but I didn't manage to do that.

I found the first 20 minutes of this video from Mylar Melodies really helpful when learning to solder.

Before getting started you want to layout your Perf Board. For this I used a little program called DIYLC. It has some standard components and lets you see physically how the board will look / work. The big green rectangle is the Arduino. You can see the resistors and capacitors forming the low-pass filters and each of the three channels is coloraturas coded. The 3 coloured lines will go to the end of the 3.5mm jacks that I have with a ground line from each of those coming back into the penultimate 'ground' column.

First I placed all of the components in the board, using masking tape to hold them in place. Now I could check that they all fit and trace a few pathways to make sure it looked like right. The eagle-eyed amongst you will notice that I added some extra vertical and horizontal spacing to make the board a less crowded at this stage.

Next it's time to solder. Following all the tips above I soldered the chip (only in the pins that were going to connect to something else), the Ground wire and one of the channels. I also used a drill bit to break the copper conductive rails that ran between the pints on the chip (don't want any randomness short circuits).

The moment of truth.

It works! Okay. Some final soldering and we have our finished board. Now to build an enclosure. For this I just decided to keep it simple. A little 3mm Plywood box. I had thought to do fancy mitre joints and the like, but soon realised that's really overkill for 3mm ply. So, butt joints it is and after getting some spacers and with the judicious use of a bit of glue, we're done. BTW - test on an oscilloscope first. Don't plug half-assed electronics into your fancy synth until you know they are right.)

Finally here it is in place...

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