Arduino Servo Read

In this tutorial, you'll learn about Servo Read Returns Wrong Position. We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

Servo.read() returns the last written angle, not the actual physical position.

Quick Fix

Wrong

#include <Servo.h>

Servo myServo;

void setup() {
  myServo.attach(9);
  myServo.write(90);
}

void loop() {
  int pos = myServo.read();
  Serial.println(pos);  // 90 even if blocked
  delay(1000);
}```

Serial: 90 (always the commanded angle, not actual position).

### Right

```cpp
#include <Servo.h>

Servo myServo;

void setup() {
  myServo.attach(9);
  Serial.begin(9600);
  myServo.write(90);
  delay(500);
}

void loop() {
  int commanded = myServo.read();
  int analogPos = analogRead(A0);
  int physicalDeg = map(analogPos, 0, 1023, 0, 180);

  Serial.print("Cmd:");
  Serial.print(commanded);
  Serial.print(" Phys:");
  Serial.println(physicalDeg);
  delay(500);
}```

Cmd:90 Phys:87 Cmd:90 Phys:88 (Small difference due to mechanical tolerance)

## Prevention

Servo.read() returns the last angle passed to write(), NOT the physical position. Standard servos have no position feedback. For closed-loop control, add an external potentiometer or magnetic encoder (AS5600). Use read() only to track what angle was commanded.

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## FAQ

<details style="margin-bottom:12px;border:1px solid #e2e8f0;border-radius:10px;overflow:hidden"><summary style="cursor:pointer;padding:14px 18px;font-weight:600;font-size:1.05rem;background:#f8fafc;border-bottom:1px solid #e2e8f0;color:#1e293b">### Do all servos support read()?</summary><div style="padding:14px 18px;color:#475569;line-height:1.7;background:#fff"><p>read() is a library function that returns the last value written. It works with any servo connected to the library. It does NOT read the actual shaft position.</p>
<h3 id="how-do-i-get-actual-servo-position">How do I get actual servo position?</h3><p>Attach a potentiometer to the output shaft, read with analogRead(), map to degrees. For precision, use AS5600 magnetic encoder over I2C.</p>
<h3 id="can-i-detect-servo-stall">Can I detect servo stall?</h3><p>Not directly. Monitor current with ACS712 sensor -- stall current is 2-5x normal. Or use an encoder to detect when position stops changing.</p>
</div></details>