For recurring costs and reliability (and probably physical space), the less pins I need to use, the better.
I'm thinking that
- Main tool GND toggle
- Always-connected GND
would cover my use cases, though a 5th one for nozzle/drill bit location sensing, as seen in the video below, would be a cool feature. If there's anything I can do to automate calibration, I'd like to further explore that solution.
I'm thinking that a wireless method such as NFC or IR could be used for controlling non-realtime features, like turning on an LED or fan on the tool that is powered by an on-tool regulator from 24V input. For mechanical actuation, such as the plunger for the chocolate tool, I'm thinking of utilising sensorless homing on the extruder motor to detect end limits. As for something like an inkjet tool, there probably wasn't ever going to be enough pogo pins anyway (the max is 6). Hmmm I wonder if those new CAN bus board things I've been hearing about could present a solution. I feel like that has the potential to drastically increase the per-tool price though. For the spindle, I'm thinking that the motor controller would have to be on the tool.
I'm planning to use the same style pogo connector as MihaiDesigns. I haven't yet been able to confirm that they allow up to 9A of current, but can confirm that they're rated over 1 million cycles.
I'm thinking of using solder cups for connectors on the Slime, but I'm undecided on using solder cups or SMD (essentially just a gold pad) for connectors on the tools; the solder cups are more expensive by about £1.30 and could take up tool space, but be easier to solder, especially when 2 or more wires need to be soldered to a pin. I'm likely to choose solder cups for that reason, as well as consistency.