Documentation

// PD Decoy Output Voltage Monitor for Arduino
// Voltage divider sized for 20V max: VBUS -- 1M -- A0 -- 100k -- GND
// Max ADC voltage: 20 * (100 / 1100) = 1.82V (safely under 5V)

const int adcPin = A0;
const float dividerRatio = (1000.0 + 100.0) / 100.0;  // = 11.0
const float vRef = 5.0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  int raw = analogRead(adcPin);
  float vAdc = (raw / 1023.0) * vRef;
  float vOut = vAdc * dividerRatio;

  Serial.print("Output: ");
  Serial.print(vOut, 2);
  Serial.println(" V");

  // Identify which PD profile is active
  if      (vOut > 18.5) Serial.println("  Profile: 20V");
  else if (vOut > 13.5) Serial.println("  Profile: 15V");
  else if (vOut > 10.5) Serial.println("  Profile: 12V");
  else if (vOut >  7.5) Serial.println("  Profile: 9V");
  else if (vOut >  4.0) Serial.println("  Profile: 5V");
  else                  Serial.println("  Profile: none / disconnected");

  delay(1000);
}

// ESP32 PD Decoy monitor with relay cutoff
// VBUS -- 1M -- GPIO34 -- 100k -- GND (20V max -- 1.82V at ADC)
// Relay on GPIO25 opens load if voltage exceeds expected setting

const int adcPin = 34;
const int relayPin = 25;
const float dividerRatio = 11.0;
const float vRef = 3.3;
const float expectedV = 12.0;     // We set DIP for 12V
const float toleranceV = 2.0;     // +/- 2V tolerance

void setup() {
  Serial.begin(115200);
  pinMode(relayPin, OUTPUT);
  digitalWrite(relayPin, LOW);
  analogReadResolution(12);
}

void loop() {
  int raw = analogRead(adcPin);
  float vOut = (raw / 4095.0) * vRef * dividerRatio;

  if (vOut > expectedV + toleranceV) {
    digitalWrite(relayPin, HIGH);   // Open relay -- disconnect load
    Serial.printf("FAULT %.2f V (expected %.0f) -- relay opened\n", vOut, expectedV);
  } else {
    digitalWrite(relayPin, LOW);
    Serial.printf("Output: %.2f V (OK)\n", vOut);
  }
  delay(1000);
}

# Pico PD Decoy voltage monitor
# VBUS -- 1M -- GP26 (ADC0) -- 100k -- GND

from machine import ADC
import time

adc = ADC(0)
divider_ratio = 11.0
v_ref = 3.3

while True:
    raw = adc.read_u16()
    v_adc = (raw / 65535) * v_ref
    v_out = v_adc * divider_ratio

    if v_out > 18.5:   profile = "20V"
    elif v_out > 13.5: profile = "15V"
    elif v_out > 10.5: profile = "12V"
    elif v_out >  7.5: profile = "9V"
    elif v_out >  4.0: profile = "5V"
    else:              profile = "none"

    print("Output: {:.2f} V ({})".format(v_out, profile))
    time.sleep(1)