E18-D80NK IR proximity switch

An infrared proximity switch with an NPN open-collector output: it pulls OUT low while something is within its range, 3 to 80 cm.

The E18-D80NK: a threaded plastic barrel with an infrared emitter and receiver in its nose, a range screw and a lamp in its tail, and three wires. Aliases: IR proximity switch, photoelectric switch, E18 sensor.

The beam is modulated and the receiver looks for the modulation, so unlike the FC-51 it is not fooled by room light. Something within its range reflects the beam back and it switches.

Pins

Pin	Wire	What it does
VCC	brown (or red)	5 V, under 25 mA.
GND	blue (or black)	Ground.
OUT	black (or yellow)	NPN open collector: pulled low while something is in range, not driven otherwise.

Wire colors vary between batches; the brown, blue and black set is the industrial convention.

Properties

range is the screw in the tail, 3 to 80 cm by the listings, 40 cm by default, for a white target. pullup adds the 10 k pull-up some batches have inside; it is off by default because the listings tell you to add your own.

While it runs

Drag the target in front of it, 1 to 100 cm (100 is nothing there). The lamp in the tail lights while it detects.

What the model gets right

Open collector. With nothing in front, the output transistor is off and OUT is not driven at all. With no pull-up, digitalRead on it reads noise on a real board. Use INPUT_PULLUP or a 10 k to 5 V, and LOW means something is there. The output sinks up to 100 mA, enough for a small relay.

What it does not model

A dark target, which has to come closer by an amount no listing gives. The beam's angle, the 2 ms response, and the lack of reverse-polarity protection the listings warn about. There is no hysteresis: none is given.

Common mistakes

Reading OUT with pinMode(pin, INPUT) and no resistor. Add the pull-up.

Powering it from 3.3 V. It is a 5 V sensor.

See it in action

KY comparator boards and an IR switch has one on pin 6 with INPUT_PULLUP, printing "something there" while the target is within range. Open it at /templates.

The Object counter with an E18-D80NK counts each object once on an I2C LCD, with a beep.