post details Humidity-Sensor-89C51-89C52-89S51-89s52-Microcontrollers-Interfacing | Soil-Humidity-Sensor-AT89C51-AT89C52-AT89S51-AT89S52-Microcontrollers
Interfacing Humidity Sensors : 8051 Microcontroller
Interfacing Humidity Sensors Family Models :
Atmel, NXP, Philips, 8051, 8052, 89C51, 89C52, 89S51, 89s52, 89C1051, 89C1051, 89C2051, AT89C4051, AT89S8252,l AT89C1051, AT89C2051, AT89C4051, P89C51RB+, P89C51RC+, P89C51RD+, P89C51RB2Hxx, P89C51RC2Hxx, P89C51RD2Hxx, P89C660, P89C662, P89C664, P89C668, P89C669, P89C51RA2xx, P89C51RB2xx, P89C51RC2xx, P89C51RD2xx, P89C60X2, P89C61X2,P89LV51RB2, P89LV51RC2, P89LV51RD2, P89V51RB2, P89V51RC2, P89V51RD2, P89V660, P89V662, P89V664.
About Humidity Sensors 
Humidity sensor is used to detect the quantity of humidity from the environment. Humidity is measured into percentage and different types of Humidity Sensors are used to measure humidity. With interfacing with microcontrollers it becomes a standalone system to measure the percentage in the environment. Relative humidity/temperature and relative humidity sensors are configured with integrated circuitry to provide on-chip signal conditioning. Absorption-based humidity sensors provide both temperature and %RH (Relative
Humidity) outputs. On-chip signal processing ensures linear voltage output versus %RH. Sensor laser trimming offers +5 %RH accuracy and achieves 2 %RH accuracy with calibration. Packages are chemically resistant and operate in ranges of -40 °C to 85 °C [-40 °F to 185 °F] to accommodate harsh environments. They are following types:
  • Relative Humidity Sensor
  • Digital Humidity Sensor
  • Soil Humidity Sensor
  • Humidity And Temperature Sensor
  • Humidity Sensor Switch
  • Humidity Sensor probe
Applications Of Humidity Sensors 89C51 89C52 89S51 89S52 Microcontrollers
Relative Humidity Sensors are used in every fields. It has lots of importance and plays an important role in measuring Humidity from environment. They are also useful in all applications where humidity compensation is needed. It is used to develop following applications :
  • Office Automation Applications
  • Automotive Cabin Applications
  • Air Control Applications
  • Home Appliances Applications
  • Industrial Process Control Systems & Applications
  • Refrigeration And Cooling Systems & Applications
  • Drying Systems & Applications
  • Meteorology Applications
  • Battery Powered Systems Applications
  • OEM Assemblies and Applications
  • Offical Applications
  Features Of Humidity Sensors
  • Full interchangeability with no calibration required in standard conditions
  • Instantaneous desaturation after long periods in saturation phase
  • Compatible with automatized assembly processes, including wave soldering, reflow and water immersion
  • High reliability and long term stability
  • Patented solid polymer structure
  • Suitable for linear voltage or frequency output circuitry
  • Fast response time
  • Individual marking for compliance to stringent traceability requirements.
 Circuits & Diagrams Interfacing Humidity Sensors 
humidty-sensors-89c51-89c52-microcontrollersThis circuit is the typical astable design for 555.
The HS1100/HS1101, used as variable capacitor, is connected to the TRIG and THRES pin. Pin 7 is used as a short circuit pin for resistor R4. The HS1100/HS1101 equivalent capacitor is charged through R2 and R4 to the threshold voltage (approximately 0.67Vcc) and discharged through R2 only to the trigger level (approximately 0.33Vcc) since R4 is shorten to ground by pin 7.
R1 unbalances the internal temperature compensation scheme of the 555 in order to introduce a temperature coefficient that matches the HS1100/HS1101 temperature coefficient. In all cases, R1 should be a 1% resistor with a maximum of 100ppm coefficient temperature like all other R-C timer resistors. Since 555 internal temperature compensation changes from one trademark to one other, R1 value should be adapted to the specific chip. To keep the nominal frequency of 6660Hz at 55%RH, R2 also needs slight adjustment