Weather Monitor-Recorder with LCD Display

A large LCD screen is used to display the results of 3 days logged temperature and barometric pressure by this weather monitor-recorder.

A graph of more than 3 days of atmospheric pressure and outside temperature is being displayed by the device by showing the approaching high and low pressure. The MIN and MAX temperature for the last 3 days will also be shown in order to determine if there is a change temperature due to air mass. It uses a PIC16F876-20/P microcontroller which directly feeds from the output of the DS18S20 high precision digital thermometer with a resolution of 0.5°C. the PIC also performs the driving & scaling of the LCD and the A/D conversions.

The zero of the scale is at 3.8V since the pressure sensor is used at the top of its range. The range between 0-5V can be restored by IC3 and the voltage required by the LCD display will be generated by the MAX868 which is a charge pump voltage quadrupler. No calibration is required since the temperature output of the sensor is a digital signal. The pins of the DS18S20 thermometer can be waterproofed by covering with epoxy.