Below is an approach that uses external circuitry controlled by the EZ-B v4’s digital outputs rather than trying to switch the power rails directly through a motor driver like the L298. Digital I/O pins (or PWM signals) aren’t intended to source or switch power for sensors directly-they’re best used to trigger a correctly designed power switching circuit.

Below are two recommended options:

1. Use a MOSFET or Transistor-Based Switch

Concept:
Use a transistor or MOSFET circuit (often in a high-side configuration) to select between two voltage supplies-one regulated to 3.3V and the other to 5V. The digital output from the EZ-B v4 will control the MOSFET’s gate, effectively switching the sensor’s power supply.

Key Points:

• High-Side vs. Low-Side Switching: For powering a sensor, high-side switching (switching the positive rail) is generally preferred. You can use a P-channel MOSFET arranged so that when the digital control is activated, the sensor sees either the 3.3V or 5V rail.
• Use Separate Regulators: Ensure you have a clean 3.3V source and a reliable 5V source available; the circuit will select between these based on the digital signal.
• Current Requirements: Since your sensor draws less than 50mA, choose a MOSFET that has a low on-resistance to maintain voltage levels under load.

Basic Circuit Overview:

            5V ---+                      
                  |                      
            +-----+-----+                
            |           |                
         [Diode]     [Diode]              
            |           |                
         3.3V ---+-----+--- Sensor +---- GND
                    |  
          (Controlled switch/multiplexer triggered by a digital out)

Note: This diagram is conceptual. In practice, you might build two circuits-one that connects the sensor to 5V and one that connects to 3.3V-and then use a single MOSFET (or two MOSFETs arranged appropriately) to select the correct rail. There are several online references for "MOSFET high-side switch" circuits that you can adapt for dual-voltage selection.

2. Use a Dual-Supply Power Multiplexing IC

Concept:
A specialized power multiplexer IC or analog switch can select between two power inputs according to a digital control signal. Some chips are designed to automatically or via a control pin choose between two rails.

Key Points:

• Consistency: These devices have specifications that ensure the voltage doesn’t droop or bounce when switching, which is critical for sensor accuracy.
• Ease-of-Integration: Many power multiplexer ICs are designed for low-current applications (perfect for your <50mA sensor) and include built-in protection features.

Example Products:
While I can’t list every manufacturer’s products, you might look on electronics supplier sites for parts labeled as "power multiplexer" or "power supply selector" for low-current applications. Check datasheets to ensure the switching speed and voltage characteristics match your needs.

A Few Considerations

• Digital Control Logic:
  You can tie one of the EZ-B v4’s digital outputs to the MOSFET gate or the control pin of a multiplexer IC. In your ARC project, you might use a simple script to set a digital line high or low depending on the mode. For example:

  // Pseudocode example (JavaScript)
  // Set the sensor power rail mode: "REFLECTOR" for 3.3V and "OBJECT" for 5V
  if(getVar("$SensorMode") == "REFLECTOR"){
      // Set digital pin "d5" high to select 3.3V (for example)
      setDigitalPin(d5, 1);
  } else {
      // Set digital pin "d5" low to select 5V
      setDigitalPin(d5, 0);
  }
  
  // Then add delays as necessary for the sensor to stabilize.
  sleep(100);  // pause for 100ms
  

• Testing and Validation:
  Before connecting the sensor, test the switching circuit with a multimeter to ensure that you’re getting stable and correct voltage levels on the sensor’s power input.

• External Modules:
  If you’re not comfortable building the circuit from scratch, consider looking for pre-built modules or development boards that handle low-power multiplexing. Once selected, you’d hook the control pin to the EZ-B v4 digital output.

Conclusion

Using an external MOSFET/transistor circuit or a dedicated power multiplexer IC is the preferred method for switching between 3.3V and 5V for your Sharp IR sensor. This setup is much more reliable than attempting to route power directly through a motor driver output (such as the L298), and it lets you maintain consistent voltage levels that the sensor requires for accurate reflector detection.

Do you have experience with building custom circuits, or would you like additional details on a specific circuit schematic? Let me know if you need further guidance or a more detailed circuit diagram!