Source: Arduino tutorial example.
Understanding the technical limitations and requirements of the FC-51 is crucial for optimal performance. Specification Operating Voltage 3.0V – 6.0V DC (5V recommended) Detection Range (Adjustable) ktechnics.com/product/ir-infrared-sensorfc-51/ Detection Angle 35∘35 raised to the composed with power Current Consumption fc 51 ir sensor datasheet hot
If the sensor was wired backward even for a few seconds, the LM393 IC might already be fried. Disconnect the sensor completely from your circuit. Set your multimeter to continuity mode. Probe between the sensor's VCC and GND pins. Source: Arduino tutorial example
Cheap manufacturing can sometimes result in solder bridges that short out the board straight out of the package. Alternatively, if the sensor was previously exposed to a voltage spike, the internal current-limiting resistors for the IR transmitter LED may have failed, allowing unrestricted current to melt the components. Step-by-Step Troubleshooting Checklist Disconnect the sensor completely from your circuit
The LM393 comparator compares the intensity of the received light with a threshold set by the potentiometer.
(e.g., your hand, a piece of cardboard, or the object your project will detect) at the desired maximum distance.
❌ Digital output only – cannot measure exact distance ❌ Susceptible to ambient IR (sunlight, incandescent light) ❌ Detection distance varies with target reflectivity ❌ May require physical LED alignment for maximum range