Audio Schematic Frost Detector Temperature Sensor

Posted on Feb 6, 2014

To apperceive whether it is freezing you alone charge to admeasurement the temperature. This has to be done accurately, of course, and accordingly we charge to accept a temperature sensor that we accept some aplomb in. The best has afresh been fabricated for a blazon that we accept already acclimated in abounding antecedent Elektor circuits, the L

Audio Schematic Frost Detector Temperature Sensor
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M35CZ (-40 to 110 °C). This sensor is not big-ticket and generates an achievement voltage that is proportional to the temperature in degrees Celsius (10 mV/ °C). An LM35 is commonly powered from a single-ended ability accumulation and 0 °C corresponds to an achievement voltage of 0 V. It is accordingly not accessible to admeasurement abrogating temperatures with an LM35 in the accepted appliance circuit. It is about accessible to admeasurement abrogating temperatures if its achievement is affiliated to a abrogating accumulation voltage via a resistor. There needs to be a accepted of 50 A through this resistor (R2 in the schematic). We alone charge to ascertain the freezing point with this circuit. That is why there is a comparator afterwards the temperature sensor, which turns an LED on if the temperature has alone beneath 0 °C during the advance of the night. To ensure that the comparator operates appropriately it is all-important that the altitude amount can become hardly added abrogating with account to the input. To break this problem, a diode (D1) has been affiliated in alternation with the arena affiliation of the LM35. The voltage bead beyond D1 (because of the baby accepted through the LM35 this is alone 0. 47 V) acts as `negative` ability supply. Since the non-inverting ascribe of comparatorIC2 is affiliated via R3 to the anode of D1 it functions as the 0 °C-reference akin for the comparator. The comparator is a...

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