03 Jun

Polargraph/Eggbot/Spherebot Electronics v2.1

I’ve somehow managed to skip from v1 directly to v2.1 with the electronics for my Polargraph.

drv8825_arduino_pro_pcb

With this version i’ve fixed the mistakes and gotchas from v1, rearranged the component layout and changed the Arduino pins used to make routing the PCB easier (no vias!). I’ve also added a connector for an SPI SD card module. I don’t know if I will be able to use the SD card as the current firmware for ATMega328 based Arduinos is pretty much maxed out as it is, but I want to have a go at understanding the firmware and seeing if I can make it any smaller. And if I can then it is better to have a connector on the board ready, than have to add it later.

I also considered adding a connector for an SPI LCD but that would be really optimistic that I can make room for all the required libs.

After blowing up several Arduino nanos that seem to have a problem coping with external power and USB power at the same time, I’ve added a jumper to enable/disable external power to the Arduino. With external power disconnected the Arduino is powered via USB.

Boards are being manufactured by iTead using their great PCB prototyping service.

I’m also working on a better Polargraph gondola that piviots around the pen and has a quick change pen holder so I can easily do colour changes. I’ll post an update when its all done.