Circuit for controlling temperature of electric soldering tool

摘要: In a circuit arrangement for controlling the operating temperature of heating coil an electric soldering iron, resistance variation itself is to be evaluated at lowest possible cost circuitry and doing away with thermocouple sensor that used arranged in region bit or coil, high mechanical cost. To this end, precision resistor inserted TRIAC switching element connected between latter element, which switched open by comparator as function voltage drop lets through only pulses pulse generator required measuring switch-on threshold, synchronized via null detection passage AC voltage. The further compared preset when it reached integration capacitor charged, controls proportion reference on long output exceeds voltage, off lower than case forms time reheating coil.