I have a replacement 24V/60W desoldering gun I would like to modify for use on my Aoyue Int958A+ soldering station. My 968A+ has a smoke absorber which has enough suction to double as a solder vacuum. Mapping the pins is relatively straightforward.
During my measurements, however, I found the desoldering gun's heat sensor resistance was significantly lower than my soldering iron's (see table below). When I briefly heated the tip of the gun with a torch lighter, I noticed the resistance steadily climb to around 6 ohms. Could this be a thermistor instead of a thermocouple? Also, is it possible to correct the resistance range by adding a ~50 ohm resistor in series with the heat sensor?
Desoldering Gun Pinouts
PIN WIRE PURPOSE
1 Black Heat Sensor
2 Blue Heat Sensor
3 Red Heating Element
4 Red Heating Element
5 White Trigger switch
6 White Trigger switch
7 CENTER Vibration sensor (unused)
Resistance Measurements
Pins 1 & 2 1 to 2 Ω
Pins 4 & 5 1 to 2 Ω
Pin 3 & solder tip Below 2 Ω
Soldering Iron Port Pinouts
PIN WIRE PURPOSE
1 Blue Heating element
2 Green Heating element
3 Yellow Case ground
4 Red Heat Sensor
5 Black Heat Sensor
6 Unused
Resistance Measurements
Pins 1 & 2 2.3 to 3.5 Ω
Pins 4 & 5 43 to 58 Ω
Pin 3 & solder tip Below 2 Ω
Best Answer
Could be either, thermocouples usually put out microvolts. If it's a thermocouple, you'll see the voltage vary by a small amount with temperature.
It's possible to correct for one temperature point with a resistor, but if your adding a resistor to a thermistor, this will shift the entire curve up and will not be equivalent. This will most likely cause problems for the control circuitry, and the temperature display. Your best bet is to find an equivalent temperature sensor and swap it out.