SERVO_SENSED_HEATER_PROTECTOR

Published:2009/7/7 23:03:00 Author:May | From:SeekIC

This circuit responds quickly enough to prevent damage from most overloads. C1's input is connected to the output of the LT10ss servo circuit. If the LT1088 circuit's output exceeds the threshold at C1's other input, C1 trips, discharging the 2-μF capacitor. This causes C2's output to become low, energize the relay, and break the heater circuit. The 560-KΩ resistor provides a long recharge for the capacitor, preventing chattering action. This arrangement's speed of response is limited by the rms circuit's slew rate, about 0.2 V/ms. For reasonable overloads, the LT1088's temperature increases about 1°C/ms. A 10-V LT1088 output step takes 50 ms, causing a temperature rise of about 50°C.



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