Using with thercouple in parallel with heater

[jducifuentes]

Hi there, I was looking for a project that can resurrect my old and broken Aoyue 701 desoldering gun. Original heater element has 4 wires (2 for resistor and 2 for thermocouple) but newer replacement comes only with 2 wires so thermocouple is wired in parallel with heater. I also checked that applying heat externally with hot air and measuring mV on wires.

My question/request is if can modify somehow your circuit to use this kind of heating elements.

I tested this heating element with a cheap t12/jbc/936 chinese clone solder board And apparently works but when reaching +-300ºC controller goes crazy and never stabilizies temp.

The approach I think is to make readings between pwm pulses to not get heater voltage over thermocouple.

Thanks in advance!

[sfrwmaker]

Hello!
Usually, the hot iron gun heater is powered by high voltage, i.e. 220 volts or so. I cannot imagine the heater and thermo-couple are connected consequently. The thermo-couple generates a vary small electricity, about several mV. To detect this value you should use some sort of operating amplifier. Then, when power is applied to the heater the controller shoud read 220 volts on op-amp input? I wold advice you to look for another hot air gun handle, for instance 858D or similar. And i have published several soldering/rework projects on hackster.io you can choose some of its.

[jducifuentes]

Hi! thanks for your reply. My equipment is a desoldering suction pump, not 220V involved, heating resistor is around 24V. As I told before I powered it from a t12/jbc/936 clone board and works but didn't stabilizes the temp.