PIC 16F88 Digital Thermometer Light Meter and resistance ohm meter

Posted on Feb 5, 2014

My original idea for this project was simply to try and interface the WINTEK WD-C2401P lcd panel to the pic (see my previous post). I figured it would be fun to add a couple of ADC readings to display something useful on the lcd. PORTB on the PIC is used as the data port for the LCD. The Enable, Register Select and Reset are tied to PORTA. Once th

PIC 16F88 Digital Thermometer Light Meter and resistance ohm meter
Click here to download the full size of the above Circuit.

e LCD is initialized, the PIC reads the ADC values from the thermistor, CDS cell and resistor (if connected) via a voltage divider. The voltage divider translates any change in resistance from the sensors into changes in voltage. The Vout is calculated as Vdd*(R2/R2+R1). ) So any change in R1 (the sensor`s resistance) will result in a change in the output voltage. In order to translate this into the ADC value, a 10 bit ADC resolution microcontroller will have 1024 (2 to the power of 10) possible steps. So if the controller is operating on 5V then each step will increment the voltage by 5/1024 =0. 004882813V every increment. So the value in the ADC will be the voltage input at the ADC divided by 0. 004882813. This allows for an accurate calculation of the resistance of the sensor. In order to translate the resistance to useful human readable form, its necessary to calibrate the sensors using real life instruments and extrapolating the values to the resistance offered. Since the display does not have any backlight, an LED is connected to PORTA4 to turn on whenever the light falls below a certain threshold.

Leave Comment

characters left:

Related Circuits

  • New Circuits



    Popular Circuits

    6 Amp Solar Power Center
    5volt power supply
    Lamp Fader schematic
    80 milliwatt Improved 3 Transistor Audio Amp
    Low Voltage High Current Time Delay Circuit
    BQ24020 battery charger
    remote control
    nimh battery problems and cures
    maze robot sensor integration
    sound generator
    high and low voltage cut out with delay and music circuit diagram
    Odd application of neon glow lamps
    CMOS Integrated Switched-Mode Transmitters for Wireless Communication
    ISL81487 5V Half Duplex 5Mbps RS-485/RS-422 Transceiver
    Float Charger For NiMH Cells