Hello friends of Kinograph. Here’s the latest on the development of the v2 prototype.

PCBs - mistakes were made

I hired a contractor in late 2019 to help translate all the manual wiring I had done on the Kinograph v2 prototype into a more organized PCB design. In that process, it was suggested by the contractor that we give each board its own MCU and each of those chips would talk to the Arduino through serial communication. The advantage was a truly modular design that would a) allow for any MCU changes anywhere in the future, and b) isolate the concerns of each PCB to only the components directly attached to it.

I’ve come to see this as a mistake. I don’t think this added complexity has any true advantages. The reasons above are mute if you have a single MCU that can do the job. A few thousand dollars later, I’m left with a palm-sized bruise on my head and will soon be redesigning the PCBs myself since I can’t really afford to go back to the contractor again.

If you want to help support this redesign of the PCB (Eagle or Fusion360 skills required) please reach out!

Motors - final decisions

After testing a variety of motors and design strategies I’ve settled on a straightforward application of the permanent magnet motors and a timing belt pulley system. I’ve switched from the hard-to-find T5 pulley/belts to GT2 which is very easy to source thanks to their popularity in small CNC designs. I’ve also cut down the number of parts required for the shaft assemblies after finding some pillow-block bearings that have a built-in set screw.

I’ve also made the shift to 12V for the entire system (from a mix of 24V and 12V) so that power supply will be simplified.

MCU upgrade

Thus far I have been using the Arduino Mega due to its ease of access. But because Kinograph’s main mission is to capture images on fast moving film, I thought we could benefit from a speed upgrade. After looking at the Arduino Due, Teensy 3 and 4, and the Adafruit Grand Central, I’ve decided to try out the Grand Central.

If users can’t get a Grand Central or prefer the Arduino brand, they should be able to easily swap out one for the other (pin differences will be noted in the documentation if there are any). The Teensy’s double-sided design makes it hard to fit into a modular design (or I just don’t know how to do it) .

As always, because the Kinograph is an open-source project, I’d love to hear your thoughts on these choices and encourage you to post a response in the forums.

Next Steps

Mount and test the new motor and shaft design (this weekend)

PCB layout and prototyping (next couple of weeks)

Integration tests of PCBs and motors.