Bed Heat Control and the M300

UPDATE - Bed Heat Controls shipped after March 2017 (black PCB) are compatible with the M300 without use of an extra cable or pin swapping.

Bed Heat Controls shipped before April 2017 (green PCB) are compatible with the M300, but require a small adapter cable or swapping of two connector pins in order to work. We designed the PCB for the bed heat switch so that the thermistor polarity is preserved, i.e. Pin1 of one connector goes to Pin1 of the other connector:

PCB polarity


Unfortunately our cable supplier made the cables so that Pin 1 at one end goes to Pin 2 at the other, and vice-versa (probably because it was easier for them to make them this way).

IMG 1106

Pin 1 is red wire at one end, but black wire at the other end.


With the M200, the polarity reversal is unimportant, because the bed thermistor is a non-polarized floating circuit element. In the M300, however the cable polarity must be correct, probably due to the thermistor being grounded rather than floating.


To switch the polarity back to M300 compatibility, we can simply add an extra male-female cable so that Pin 1 at the end of the female cable connects to Pin 1 of the male header on the PCB, or we can simply swap the wire crimps at one of the female connectors. As of November 14, 2016 customers can specify M300 compatibility when ordering the ZTC-200 kit from our web store.

IMG 1109

Adding an extra M-F cable moves red back to Pin 1 again.


At some point in the future, we will modify the PCB to take into account the cable polarity reversal so that the extra cable will not be needed.


© Z-Temp™ 2016                              "Zortrax", "Z-Suite”, “M200”, and “M300" are trademarks of Zortrax Sp, Olsztyn, Poland