I've been looking at the thermistor inputs, in particular the fixed resistor in the voltage divider. I notice that the Duet hardware uses a 1k resistor here for both heat bed and extruder, not sure how this was chosen. 4.7k is ok for a heat bed with best response around 100 deg. According to my calculations 220R is about the best value for the range 160 - 300 degrees suitable for extruders. The E96 (1%) value is 221R.
Therefore I suggest we specify 4.7k for the heatbed and 221R for the extruders.
I'd also like to update the schematic with the new thermistor protection circuit, do we have a good idea what this should be?
Therefore I suggest we specify 4.7k for the heatbed and 221R for the extruders.
I'd also like to update the schematic with the new thermistor protection circuit, do we have a good idea what this should be?