Experiment: Voltage Divider in Sensor Interfacing

Objective

To learn how to use a voltage divider to scale down sensor output voltage for compatibility with low-voltage microcontrollers or ADCs.

Materials

• Sensor with an analog output (e.g., a temperature sensor or photoresistor)
• 2 x Resistors (values depending on desired voltage division, e.g., 10kΩ and 10kΩ)
• Breadboard
• Jumper wires
• Multimeter
• Microcontroller or ADC module

Circuit Diagram

Connect the circuit as shown in the diagram below. The voltage divider is used to scale down the sensor's output voltage to a safe level for the microcontroller.

Theory

A voltage divider can reduce a higher voltage output from a sensor to a lower voltage compatible with microcontroller ADC inputs. The output voltage of the divider, V_out, is determined by:

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

This equation allows you to select resistor values that scale the sensor output down to the ADC's input range, such as 0-5V or 0-3.3V.

Procedure

1. Connect the sensor's output to one end of resistor R1.
2. Connect the junction between resistors R1 and R2 to the ADC input pin of the microcontroller.
3. Connect the other end of R2 to ground.
4. Power on the sensor and microcontroller, and measure the voltage at the ADC pin. It should be a scaled-down version of the sensor output voltage.
5. Read the ADC values on the microcontroller to observe how the voltage divider allows you to interface with higher voltage signals.

Observations

Record the output voltage from the sensor and the voltage at the ADC input. Note how the ADC input voltage remains within the microcontroller's input range, enabling safe interfacing with the sensor.

Conclusion

This experiment shows how a voltage divider enables safe interfacing with sensors by reducing their output to a compatible voltage level for ADCs. This setup is essential when working with sensors that output a higher voltage than the ADC's maximum input.