Experiment: Using Voltage Divider in Analog-to-Digital Conversion (ADC)

This experiment demonstrates how a voltage divider can be used in an ADC circuit to scale down an input voltage so it is compatible with the ADC input range, enabling accurate voltage measurement.

Objective

To learn how a voltage divider can adjust an analog signal to match the input range of an ADC for accurate digital conversion.

Materials

Circuit Diagram

Connect the circuit as shown in the diagram below. The voltage divider scales down the input voltage before it reaches the ADC pin on the microcontroller.

Circuit diagram for using a voltage divider in ADC

Theory

An ADC typically has a limited input range (e.g., 0-5V or 0-3.3V). Using a voltage divider, we can scale down higher input voltages to fall within this range. The output voltage from the divider is given by:

V_out = V_in * (R2 / (R1 + R2))

This equation helps us select resistor values so the maximum expected input voltage is safely within the ADC's range.

Procedure

  1. Connect the positive terminal of your input voltage source (or potentiometer) to one end of resistor R1.
  2. Connect the junction between R1 and R2 to the ADC input pin on your microcontroller.
  3. Connect the other end of R2 to ground.
  4. Power on the circuit and apply different input voltages using the potentiometer or variable source.
  5. Use your microcontroller to read the ADC values and monitor the digital output, which corresponds to the scaled-down voltage from the divider.

Observations

Record the applied input voltage and the corresponding ADC output value. Observe how the voltage divider brings the input voltage within the ADC’s range, and compare the readings with calculated values based on the resistor ratio.

Conclusion

This experiment shows that a voltage divider allows for the safe and accurate conversion of higher input voltages by adjusting them to the ADC's input range. This approach is valuable for measuring analog signals that exceed the ADC’s native voltage range.