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This humidity detector circuit diagram is very simple and uses few components and can be used for activation of an electronic devices when the detector senses a certain humidity. The sensor is constructed from two pieces of copper placed at a short distance of each other. when the electrical resistance of copper conductors drops below a certain value, Schmit trigger built using transistors T1 and T2 switch. Bistable multi-vibrator is flip through C1, so that at point B there is a low voltage (relay triggers). Relay is activated when the resistor R6 is connected to point B but the point A. The circuit has a low and requires a 5 volt DC power supply.

Temperature and humidity sensors used are SHT75. This sensor is a chip that can measure temperature and humidity as well. The use of these sensors with consideration of its small size and reliability. The output of this sensor has the form of digital data in the chip because it has been there for a 14bit ADC. Temperature measurement range between -40-123,8 º C and humidity between 0-100% Rh. Measurement accuracy reaches ± 0.3 per increase of 25 º C for temperature and ± 1.8% RH for humidity. Temperature and humidity sensor The default measurement resolution of this sensor is 14 bits to 12 bits and temperature sensors for humidity sensors, can also use only 12 bit resolution and 8 bits.