| Feature | FC-51 (IR) | PIR (Passive IR) | |--------|-----------|------------------| | Detection | Short range, precise | Wide angle, up to 7m | | Sensitivity to small objects | Yes (finger, card) | No (needs body heat) | | Works in complete darkness | Yes (active IR) | Yes (thermal) | | Best for | Gesture, proximity, line | Occupancy, intruder alerts |
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 fc 51 ir sensor datasheet hot