PROPORTIONAL_CONTROL_FOR_OVEN

Published:2009/7/8 1:32:00 Author:May | From:SeekIC

Thermistor RV1 and resistor-pot combination form voltage divider across 10-V zener, with output applied to UJT. Voltage across capacitor is ramp during positive half-eycles of AC Iine, slope of which is function of temperature and setting of 5K pot, When ramp reaches firing voltage of UJT, it turns on SCR and applies power to load, Negative half of AC input tums off SCR and cycle repeats. When oven temperature is low, SCR fires early in cycle to give more heat. When preset temperature is reached, SCR fires very late in cycle to compensate for heat lost by oven. Designed for 100'F environmental test chamber.-I. Math, Math's Notes, CQ, Sept. 1978, p 63 and 82-83.



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