How to connect a weak-signal sensor to a Doosan robot via Arduino and Python

thijs · September 2, 2026, 12:16am

Based on contributions by Luke.

Some sensors output a signal too weak for the Doosan controller’s digital input to detect reliably. Routing the sensor through a microcontroller first — which reads the signal, cleans it up, and forwards it over serial — is a workaround that lets you process the signal in Python before acting on it.

What you need

A sensor with a digital output (e.g. a photoelectric sensor)
An Arduino (or similar microcontroller)
A breadboard and jumper wires
A PC running Python with the pyserial package (pip install pyserial)
The sensor’s datasheet, to confirm its required voltage and wiring

Steps

1. Wire the sensor to the Arduino

Connect the sensor’s signal output to a digital input pin on the Arduino.
Use a breadboard to connect the sensor’s V+ and GND.
Check the sensor’s datasheet for the correct supply voltage and wiring before powering it up.

2. Read the digital input on the Arduino

if (digitalRead(SENSOR_PIN) == LOW) {
    count++;
    Serial.print("Count: ");
    Serial.println(count);
}

This checks whether the sensor has triggered, and prints a running count over serial.

3. Connect to the Arduino from Python

import serial

arduino = serial.Serial('COM11', 115200, timeout=1)  # edit the COM port and baud rate to match your setup

4. Read the serial data in Python

if arduino.in_waiting > 0:
    count_value = arduino.readline().decode().strip()
    print("Count from Arduino:", count_value)

This reads a line from the Arduino’s serial output and prints it.

Check: this only prints the count to the terminal. It does not forward the value into the Doosan’s own program — if you need the robot to act on it, you still need to add that link yourself (for example, opening a TCP connection from the robot’s DRL program to the PC, or driving one of the robot’s digital/analog inputs from the microcontroller — see How to connect a Doosan digital I/O port to a microcontroller using a transistor and How to use the analog I/O ports on a Doosan robot).

5. Test in the real environment and eliminate false positives

Sensors can behave differently once installed, depending on lighting, vibration, motion, or electrical noise — test in the actual working environment, not just on the bench:

Run the sensor with the Arduino connected and watch the serial output.
Trigger the sensor intentionally (e.g. place an object in front of it) and confirm the Arduino registers it consistently.
Watch for false triggers — random count increases with no real trigger.

Troubleshooting

Reduce false positives with debounce logic, especially for mechanical switches or IR sensors:

if (digitalRead(SENSOR_PIN) == LOW && millis() - lastTriggerTime > 200) {
    count++;
    lastTriggerTime = millis();
    Serial.println(count);
}

Or require a stable reading over several samples before counting it as a real trigger:

bool stableLow = true;
for (int i = 0; i < 5; i++) {
    if (digitalRead(SENSOR_PIN) != LOW) {
        stableLow = false;
        break;
    }
    delay(2);  // 2ms between checks, 10ms total
}

if (stableLow) {
    count++;
    Serial.print("Count: ");
    Serial.println(count);
}

If false positives persist:

Add a small delay between readings to reduce noise/bounce.
For analog sensors, add a capacitor or a software filter to smooth unstable signals.
Physically isolate the sensor from vibration or electrical noise sources.
Use shielded or twisted-pair cable for longer runs, especially near motors or high-voltage lines.
Double-check the sensor’s voltage/current specs against what the Arduino and the sensor’s own power source actually provide.