AXRT-24E Incremental Rotary Encoder

Description

The AXRT-24E is a 24 PPR mechanical incremental rotary encoder with an integrated push-to-select switch. It generates quadrature (90° phase-shifted) pulses on channels A and B, allowing host logic to determine both position and rotational direction from a single interrupt source.

Output lines use open-collector (NPN) topology. Internal pull-up resistors are not provided; connect 10 kΩ resistors from OUT_A, OUT_B, and SW to VCC, or enable MCU internal pull-ups. The integrated switch activates on axial shaft depression and is rated for 50 mA at 12 V.

Note: Compatible with 3.3 V and 5 V logic without level-shifting. Most MCU internal pull-ups (20–50 kΩ) are adequate for hand-operated encoders at typical rotation speeds.

Parameter	Min	Typ	Max	Unit
Supply voltage (VCC)	3.0	3.3 / 5.0	5.5	V
Quiescent current	—	0.4	1.0	mA
Output sink current (OUT_A/B)	—	—	10	mA
Output low voltage (V_OL)	—	0.1	0.4	V
Output rise/fall time	—	2	5	µs
Switch rating	—	—	50 mA @ 12 V	—
Switch contact resistance	—	100	500	mΩ
Switch bounce time	—	3	8	ms

Mechanical Specifications

Parameter	Value	Unit
Pulses per revolution	24	PPR
Detents per revolution	24	—
Mechanical life (rotation)	50,000	cycles
Switch actuation force	6 typ, 8 max	N
Switch mechanical life	30,000	cycles
Shaft diameter	6 (D-cut)	mm
Shaft height above housing	20	mm
Body dimensions (L×W×H)	12 × 12 × 7	mm
Pin pitch	2.54	mm
Operating temperature	−30 to +85	°C
Storage temperature	−40 to +100	°C
Weight	2.1	g

Pin Configuration

Pin diagram: 5-pin through-hole footprint, top view — pins 1–5 left to right, 2.54 mm pitch, with body outline and shaft centre marked

Pin	Symbol	Type	Description
1	GND	Power	Common ground reference
2	VCC	Power	Supply voltage, 3.3 V – 5 V
3	OUT_A	Output	Phase A — quadrature channel A
4	OUT_B	Output	Phase B — quadrature channel B, 90° offset
5	SW	Output	Push switch, active low — requires pull-up

Quadrature Output Sequence

Step	A	B	Direction note
0	0	0	CW: 0 → 1 → 2 → 3 → 0
1	1	0	CCW: 0 → 3 → 2 → 1 → 0
2	1	1	—
3	0	1	—

Integration Examples

Arduino (C++)

const byte PIN_A  = 2;   // interrupt-capable pin
const byte PIN_B  = 3;   // interrupt-capable pin
const byte PIN_SW = 4;

volatile int32_t position = 0;
volatile bool    pressed  = false;

void onEdge() {
  bool a = digitalRead(PIN_A);
  bool b = digitalRead(PIN_B);
  position += (a ^ b) ? -1 : 1;
}

void onPress() { pressed = true; }

void setup() {
  pinMode(PIN_A,  INPUT_PULLUP);
  pinMode(PIN_B,  INPUT_PULLUP);
  pinMode(PIN_SW, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(PIN_A),  onEdge,  CHANGE);
  attachInterrupt(digitalPinToInterrupt(PIN_B),  onEdge,  CHANGE);
  attachInterrupt(digitalPinToInterrupt(PIN_SW), onPress, FALLING);
  Serial.begin(115200);
}

void loop() {
  if (pressed) {
    Serial.println("switch pressed");
    pressed = false;
  }
  Serial.println(position);
  delay(50);
}

MicroPython (Raspberry Pi Pico)

from machine import Pin
from time import sleep_ms

pin_a  = Pin(2, Pin.IN, Pin.PULL_UP)
pin_b  = Pin(3, Pin.IN, Pin.PULL_UP)
pin_sw = Pin(4, Pin.IN, Pin.PULL_UP)

position = 0
last_a   = pin_a.value()

while True:
    a = pin_a.value()
    if a != last_a:
        b = pin_b.value()
        position += 1 if a != b else -1
        last_a = a
        print(f"pos={position}")
    if not pin_sw.value():
        print(f"switch pressed, pos={position}")
        sleep_ms(20)  # debounce
    sleep_ms(1)

Tip: For interrupt-driven reading, attach to CHANGE edges on both A and B for full 4× resolution (96 counts/revolution). For hand-operated use, polling at ≥ 1 kHz is sufficient — practical max rotation is ≈ 5 RPS.

AXRT-24E