Signal integrity of external stepper vs CAN

kuon

I am designing a large machine (1m3) and I will use clearpath motors.

To control them, I have 2 options, one 6 XD mainboard and running the step signal all the way to the motor (about 5meters) or use a mini mainboard and use 1 XD extension boards, one per motor.

The pro of the first option is price and not having to mount 1 board on each motor (with the problem of cooling, protection...). The pro of the second option is signal integrity.

Is the signal integrity issue big enough to justify mouting the board on the motor and use CAN?

dc42

@kuon it's a tough call. Normally I would have suggested driving the motors direct from the 6XD board. However, the Clearpath servos are quite fussy according to the datasheet. With 5m cable length, you may need to add 1K pullup resistors at the Duet end to improve the turn off time of the optocouplers in the Clearpath servos - see the datasheet for details.

The 6XD can achieve significantly higher step rates that the 1XD can. Also, input shaping is not currently supported on the 1XD.

kuon

@dc42 Ok. My other issue is that I have 10 motors (I forgot to mention that). Can a 6XD board be used as a daughter from another one? I can make an intermediate board with pullups.

dc42

@kuon said in Signal integrity of external stepper vs CAN:

Can a 6XD board be used as a daughter from another one?

Yes.

kuon

@dc42 Ok, I'll use two 6XD then.

I am quite confident I am correct, but just to be sure, that's the datasheet you were referring to?

So I need 1k between "5V<->STEP-", "5V<->DIR-" and "5V<->EN-"?

Also, bonus question for temperature sensor. Is it worth it to put a toolboard near the sensors or is a 5m cable fine?

kuon

@dc42 I'm currently going the route of having all the electronic outside the printer, but I am still wondering about temperature sensors. Is 5m cable fine for them or should I use a particular setup? (shielded cable, pt100....)

dc42

@kuon 5m of shielded cable to a PT100 should be ok if you use a 4-wire connection.

kuon

@dc42 Great thanks