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Dew sensor principle Commentary

2014-11-15 19:57  
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This article is exposed sensor principle explanation. By convention, in order to better grasp the principles you are, we recommend you to combine text read schematics. This circuit is essentially a switching circuit by the help of a popular dual op amp IC  LM358N  configured here as a comparator. (Note that only one half of the IC used here.) Under normal circumstances, the dew sensor resistance is low (about 1 kohm), so the voltage at its non-inverting terminal (pin 3) is lower than, at its inverting input (pin 2) terminals. The corresponding output of the comparator (the pin 1) is the corresponding low and therefore did not occur in the circuit. When the humidity exceeds 80%, the sensor resistance increases rapidly. Therefore, the non-inverting pin becomes more positive than the inverting pin. This drives the output of IC1 to a high level. Therefore, LED optocoupler and other internal full of vitality. While providing a visual indication, LED1, such as optocouplers can appropriate any electronic device on the interface switching purposes. Circuit by the diode D2, resistors R5 and R6 and capacitor C1 form a low-voltage, low-current power supply device. This simple requirement arrangements exclude large and expensive step-down transformer. If you are a first reading on this principle, we recommend that you carefully read several times in order to better fully grasp this simple but effective circuit.

Dew sensor

Dew sensor

VN:D [1.6.9_936]


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