@dc42 Thanks, yes I can code to ignore messages that aren't conforming to a format that I'm expecting, and actually I've now just increased the buffer so it will slurp in the longer message (and then ignore it). I was just hoping there was maybe an easy way to avoid the message in the first place.
Also, I might want to send GCode back the other way in due course (I'm just starting to play with that option), so I probably wouldn't want to preclude that.
@Merlin246 An SSR will work fine in PWM mode - just set the PWM frequency to 10 Hz (which used to be the default frequency for bed heaters). I'm not an expert but I think you'll find that a solid state relay is probably a triac in any case, or at least a variant thereof. Probably best to make sure that the SSR is a zero crossing type. My own 800W mains powered bed has been running in PWM mode via an SSR for about 5 years without any issues.
@jay_s_uk Thanks. I ended up connecting it via OUT 4 instead, though, since at the time of posting I didn't realize those ports can be set to 12 volts or 24 volts just by moving the jumper on the three pins above OUT 4 and OUT 7 (to the right, in this case). Big dumb oversight on my end, but I've never used jumpers before. Hopefully this helps someone else who's as clueless as me.
The temperature is a little noisy as @dc42 suggested, it wanders +- 1 or 2 deg .
Does it happen with the bed rotating? Slip rings tend to produce noise too, so in many occasions a single signal is transmitted by two or more slip rings in parallel. That way the noise is cancelled out.
Hi @o_lampe, the slip ring sends CAN and 240v to the SammyC21 and heater so this shouldn't be an issue. I'm just testing at the moment however and the slip ring isn't being used yet.
@skrotz They were sadistic. Black = 24v, Dark grey = ground, light grey = tach, and white = pwm control. PWM needs to be inverted. Hooking up 24v and ground to an always on fan port and control to fan2 ground works fine. It puts out a ton of air, but the shroud spreads it out less than I expected.
I haven't confirmed tach as working but seems likely it would, although I'm not sure it's useful.