GB1076060A - Temperature control circuit for electric soldering irons - Google Patents

Abstract

1,076,060. Temperature control of electric soldering irons. WELLER ELECTRIC CORPORATION. July 6, 1965 [Feb. 9, 1965], No.28691/65. Heading G3R. The heating element 36 of an electric soldering iron is supplied through a step-down transformer 16 and silicon controlled rectifier 29 the conducting periods of which are automatically varied, to maintain constant the temperature of the soldering tip, by a gate control circuit comprising another silicon controlled rectifier 23, a thermistor 28 in thermal communication with the soldering tip and a potentiometer 22 adjustable to obtain a desired tip temperature limited by a resistor 27. With the potentiometer setting at its maximum temperature position, the value of resistor 27 necessary to limit the tip to a desired maximum temperature is determined, the tip temperature being measured with a thermocouple and potentiometer arrangement which is subsequently used to calibrate the control dial of potentiometer 22. System stability is improved by mounting rectifiers 23, 29 in the handle of the iron, Fig. 1 (not shown) with rectifier 29 in heat-dissipating contact with the metal portion thereof. In operation the rectifiers 23, 29 conduct in each appropriate half cycle for a period corresponding to the extent of the deviation of the tip temperature from the desired value.