What the 940 nm wavelength and side-view package mean for your sensor design
The ELM-4002: Its side-view orientation and through-hole radial package let the emitter sit flush against a PCB edge or inside a housing wall, directing the beam laterally across a sensing gap — common in encoder wheels, paper-edge detection, and slot-type photomicrosensors. The typical forward voltage of 1.2 V means a standard 5 V logic supply can drive it through a current-limiting resistor without a separate LED driver, though the actual forward current must be set by the resistor value — the datasheet's absolute-maximum rating governs the limit.