Wiring extra thermistors?

janjoh

I am looking at the schematic, trying to figure out where to stick a few extra thermistors for display only (Stepper motor temperatures in enclosed electronic bay).

Now the bay is ventilated, but since I have the machine open for some other tinkering, I figured "Why not"?

For thermistor 0-2 there is a 4k7 pullup to ADVref. Is that something I need to include, or can i just connect the thermistor between ADVREF and THERMISTOR3-6?

Basically, what is the proper way to connect an extra standard thermistor?

droftarts

@janjoh basically, you need to replicate the voltage divider circuit on the other thermistor connecters, ie add a 4K7 resistor to ADVREF (pin 41 on the expansion header). Configuration is the same as other thermistors.

Ian

janjoh

@droftarts Thank you.

So, that begs the question, what design choice excluded the resistors from the extra connectors?

Is it because "Well, technically the pins can be used for anything, we've just labelled them as thermistors." alternatively "It saves €0.05 per manufactured unit"."

or is it something else I am missing?

(Not criticism (i certainly have a few resistors around here somewhere.. or everywhere... Just curiosity.)

droftarts

@janjoh damned if we did (someone would want to use them for something else), damned if we don’t (“I need more thermistors!!!!”). Also probably makes DueX connection harder. I don’t know, those decisions were made many years ago! (At least 8, possibly more.)

Ian

janjoh

@droftarts Yeah, that makes perfect sense, and it was my first though. But I figured that it was worth to aske

Thank you. You have been most kind and helpful!