The Mini Differential IR height sensing board for 3D printers provides the following features:

• A differential modulated IR height sensor. The sensor detects the target height by looking for the reflected light from two separate LEDs to be equal. The two LEDs are positioned such that they reflect light into the sensor at slightly different heights. This allows the sensor to be used most any bed surfaces.
• A high degree of immunity from sunlight, incandescent artificial light, and other background sources of IR.
• Unlike capacitive and inductive sensors, the sensor measures the height to the top surface of a glass bed, not the distance to a backing plate.
• A red LED indicates when the head is at or below target height.
• Small size, ideal for use where space is restricted, such as under the effector of a delta printer. The version 1.1 board is 24mm wide but just 18mm high, small enough to fit below the heatsink of a genuine E3Dv6 hot end.
• Automatic selection of a 4-level analog output for printer electronics that support it (e.g Duet), or a digital output for other printer electronics.