I was building my extruder and thinking about the standard pinout idea brought up on this forum earlier. I liked the idea of DB9 until I actually prototyped a board with the connector on it and stuck it on my extruder, it is pretty big and clunky when you actually look at it and doesn't have enough wires. I think I am going to go with a different plan.
I was going to use a 2x7 shrouded IDC connector to allow a single (cheap and easy to make!) ribbon cable to be used between the extruder and the main board. My plan was to create a small board that took the 2x7 and broke it out into screw terminals, this board would be mounted directly on the extruder and the hot end and stepper would be attached via the screw terminals. This means you can quickly unhook the whole extruder, but also detach the hot end or stepper if needed.
The pinout I was going to use is
1,2 - heater A
3,4 - heater B
5 - stepper A
6 - stepper B
7 - stepper C
8 - stepper D
9 - +12V (misc power)
10 - GND (for misc power and grounding extruder head)
11 - thermister A
12 - thermister B
13 - expansion A
14 - expansion B
notes:
- IDC pins can take 1amp each continuous, so the ganged heater pins will be more than enough for the PWMed heater current.
- thermister has its own cables, and is separated from the high noise cables by a ground and power line
- 2x6 header can be used if you don't want expansion ports with the same PCB since they are at the end.
- the connector is printable: [
www.thingiverse.com]
- a retaining bracket is also printable to avoid the cable coming loose
- the connector is fully enclosed and impossible to insert backwards.
- the same breakout PCB can be used at the other end to connect the signals to the motherboard.
What do people think? I was going to design a PCB and get a few made if people are interested.
As an alternate design, I can combine one of the heater pins with +12V and add 2 ground pins, but the power budget would be trickier to figure out as expansions would be fighting with the heater and moving from a MOSFET drain to say a relay for the heater would be problematic. keeping the signals separate seems more future proof.
