Got this soldering iron circuit which I think I can follow as to how the 555 operates when triggered via U2B and the control pot, but its what U2A is sensing via R4 and R11 that is the puzzle ?
Should add that W2 looks like it may have been a trim pot or thermistor /diode at one time and just had a resistor fitted for this lower cost solder station design with no sensor in the solder iron itself.
Should add that W2 looks like it may have been a trim pot or thermistor /diode at one time and just had a resistor fitted for this lower cost solder station design with no sensor in the solder iron itself.
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