Mitocondrion Mark 4.1 Build: Main PCB

I’m working away on the next version of the Mitocondrion. In an effort not to do everything myself, the next version uses assorted bits and bobs from others but everything comes together and gets wired up by the one main board. This holds the Arduino, the big DC-DC converter that powers the LED strips, the little DC-DC converter that powers everything else, the status indicators, the motion sensor board, the battery monitoring, the extra memory, and the audio analyser. It also joins together the two battery packs, the LED strips, the power, programming, and reset connectors, and the microphone. It’s busy.

So, here’s the board being made, from design, through masking, etching, building and testing the step-down power converter, and then once that was checked and working, populating the rest.

Clickable for even bigger

The status LEDs are the smallest things I’ve ever soldered, 1.6 mm long and 0.5 mm wide. It was a mission to get five of them in place, even getting them out of the packaging without losing them was a mission. Admittedly, there’s supposed to be six of them. One is now on the floor somewhere. Can you spot the missing LED? Hell, can you spot the five LEDs in the picture?

So it’s built, but mostly not tested yet. As I mentioned, it does a lot of different things.

16 thoughts on “Mitocondrion Mark 4.1 Build: Main PCB

  1. Yup, persulphate, plastic tubs in the kitchen sink.

    I’m only producing one-offs at this stage, so a soldering iron works just fine. Doing it that way also lets me complete parts the hardest parts of the board and test them before doing all the rest, which gets important when this board holds over NS$300 worth of bits and I really don’t want to have to bin it.

    I try to avoid getting too tiny – it can be done but the failure rate just goes way up. 1206 packages is what I aim for, but side-emitting LEDs seem to only come in annoyingly-small sizes.

    What you making these days?

    1. Very cool man, I’ve never etched a board – let a lone a two sided board. We’re making analog synth stuff (, so I had a few batches of boards done through one of the companies in China for pretty damn cheap: about $20 per board (16″ x 5″). If the quantities get bigger I’m hoping I can afford to use a Canadian PCB place though.

      That’s about all I’m making right now. My current little project is restoring an old Beaver table saw. You’d like it I’m sure, belt driven cast with cast iron wings. Both the saw and the motor were made only a few hundred KM from here! I’ll be sure to post some pics on when it’s finished!


    2. Hint on soldering smd: solder on one land, then scoot the component into the molten solder. It’ll stick and be less likely to tombstone.
      When you’re soldering 0805 or smaller, you can nudge it over using the solder wire, and if you hold it for a moment the terminal opposite of the soldering iron will solder down to its respective pad, from heat transmitted via the part. (If the pad’s small. I always do solid ground planes, and it’d never solder to that, but if I’m soldering on the ground plane side it’ll solder down to a small pad on the other side.)

      1. I’ve managed decent results with the following technique:

        1) Tin both pads
        2) Wick the excess solder off one pad
        3) Using tweezers, place the part across the two pads. The end on the unwicked pad will be standing proud of the board because of the big lump of solder on that pad. Hold the part in place by pushing down on the part with a tiny screwdriver.
        4) Touch the iron to the unwicked pad – the big lump of solder melts and the part will sit down onto the board, holding it in place
        5) Solder the other end.

        No tombstoning and the part is held at all times.

    1. Yup, a Nano. Is suitably dinky and will fit into a one-inch tube while leaving space for everything else that needs to fit into the one-inch tube.

  2. None of those circuit board patterns are anything I’m familiar with anymore (which I hope suggests new!exciting!lights), but that second one would make an awesome rug. Just saying

        1. All the components are on the top side and most of those are surface mount, rather than having pins that go through the board. Hence the bottom side is mostly wiring.

          1. I actually meant the board itself (as in, all its iterations appear less cluttered than the previous one – despite there being seemingly more components.

            I guess I was trying to compliment your design skills.

          2. Ah yeah. It’s less cluttered, coz a) it’s not trying to do too much itself, it’s mostly just holding other bits that do stuff, and b) it’s much larger, 250 mm long rather than 140 mm, so there’s more room to spread stuff out.

            The new structure for the Mark 4.1 uses much more of the space inside the tube, rather than just being a single layer of boards from end to end like the Mark 3.5. Thus there’s room to divide up functions and overlap sub-assemblies, rather than making everything as tiny as possible to give more room for LEDs.

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