Posted on Jul 23, 2012 5759
TCA965 window discriminator IC allows the potentiometers RVl and RV2 to set up a window height and window width respectively. Rl and thermistor THl for a potential divider connected across the supply lines. Rl is chosen such that at ambient temperature the voltage at the junction of these two components will be approximately half supply. As the temperature of the sensor changes, the voltage will change. RVl will set the point which corresponds to the center voltage of a window the width of which is set by RV2
The switching points of the JC feature a Schmitt characteristic with low hysteresis. The outputs of ICl indicate whether the input voltage is within the window or outside by virtue of being either too high or too low. The outputs of ICl drive the LEDs via a current limiting resistor.