This is an electronic monitor which displays the measured value through a series of LEDs.
The IC itself is the temperature sensor. It can be attached easily to heatsinks, power supplies and the likes to monitor the temperature.
When the temperature exceeds the maximum level, the green LED (D1) goes off and the red one (D2) lights up. The maximum temperature (threshold level)
can be set through P1 between -1 and 100°C. The LED is a two-color type.
If you use the thermonitor to control external devices like for example automatically switching on an air blower to cool down a heatsink,
you have to use the current amplifier shown in diagram 35.1.
This circuit boosts the trigger current coming from the pin no. 4 of UC3730 whenever the threshold
temperature is exceeded. The boosted current closes the relay which in turn activates whatever external device is connected to it. Figure 35.2 shows the external wirings
of the circuit's application as an automatic air blower control. The current amplifier uses the power supply of the thermonitor. This simplifies the integration of the two circuits.
Parts Placement Layout
External Wiring Layout
Electronic Circuits volume 1.0 - Circuit Nr. 35
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.