Arhi has been busy debugging noise from PTC type soldering iron sensors. The problem was the sensor’s sensitivity to the current used as a bias. If the current used is greater or less then 1mA the sensor picks up too much noise.
In the latest revision of the Soldering iron driver both PTC and TC type sensors are supported correctly, and all major noise has been eliminated. The input stages for each sensor are now separated and are selectable through a jumper.
The image above shows the iron’s PTC temperature sensor output compared to the NTC sensor Arhi drilled directly into the tip. This is a much cleaner sensor reading then his previous attempt.
Via the forum.