Digital humidity sensor using PIC microcontroller

Digital humidity sensor with LCD display using PIC microcontroller

Digital humidity sensor with LCD display is used to measure relative percentage  of water vapors in air. HS1101 capacitive humidity sensor is interfaced with PIC16F877A microcontroller to measure humidity and LCD is used to display percentage humidity in air.For humans there is certain limit for water vapors presence in air. Above that limit relative humidity may cause problems to human health.Digital humidity sensor using PIC microcontroller

Applications of digital humidity sensors

Humidity sensors have many application in industry and domestic areas. Humidity means presence of water vapors in air. Percentage of water vapors in air should be with in safety limit. Otherwise It have harmful physical and chemical effects on human beings and also in industrial products. Humidity sensors have major applications in agriculture ,chemical, oil, gas and medical industry. For example in agriculture industry humidity sensor is used to measure moisture in fields. There are also many other application of humidity sensor.You can search them om Google.

digital Humidity sensor selection

When you search on Google, you will come across many humidity sensors. All these humidity sensors have their advantage and disadvantage. But I used capacitive HS1101 humidity sensor in this project. What is meant by capacitive humidity sensor? All capactive senors give output in capacitive form.They change their capacitance with respect to change in sensing parameter like in HS1101 sensor sensing parameter is amount of water vapors in air. The reason why I used this humidity sensor?  Because

  • It can be used for highly sensitive applications.
  • less cost
  • easy to interface with microcontroller with small extra circuitry
  • No calibration is required
  • It can be easily used for home appliances and industrial control system.

How to use HS1101 digital humidity sensor

HS1101 is a  capacitive humidity sensor, so it can be used with 555 timer circuit to generate square wave of different frequency. I assume you know about 555 timer IC and its use.

Schematic Digital humidity sensor using PIC microcontroller

humidity sensor circuit with external circuitry

As shown in above figure, variable capacitor is used in place of humidity sensor for simulation purpose. Becuase HS1101 simulation model is not available in Proteus. Above circuit is used as a signal conditioning circuit to convert one form of parameter to its other proportional parameter so that it can be easily interfaced with any digital system or microcontroller. It is not possible for any microcontroller to read change in capacitance directly. That why above circuit is used to convert changing capacitance of HS1101 into sqaure wave whose frequency changed according to change in capacitance .

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