Walkthrough Metal Detector Based on FG-3+ and Arduino UNO R4 WiFi

1#include <Arduino_LED_Matrix.h>
2
3const int sensorDig = 2;  // Digital pin 2 for sensor input (interrupt pin)
4
5unsigned int updateRate = 100;    // Sensor update rate in ms
6unsigned int measureTime = 100;   // Sensor measure time in ms
7
8volatile unsigned int intEnable = 0;      // Interrupt counter enable flag
9volatile unsigned long sensorDigCnt = 0;  // Count of sensor signal changes
10unsigned long prevMillis = 0;              // For timing updates
11
12float base_line = 0.0;                // Moving average baseline
13const float alpha = 0.1;              // Smoothing factor for baseline
14const float base_line_change = 10.0; // Threshold for significant change
15const int N = 10;                     // Number of samples for peak event duration
16
17int peakSamplesCount = 0;     // Samples counted during peak event
18bool inPeakEvent = false;     // Flag: tracking a peak event?
19float peakValue = 0.0;        // Maximum deviation recorded during peak event
20
21int state = 0;  // State machine variable
22
23// LED matrix setup
24ArduinoLEDMatrix matrix;
25
26const int matrixWidth = 12;
27const int matrixHeight = 8;
28
29// Alert sign bitmap 10x7 pixels (largest fitting design)
30// A large exclamation mark ! with border
31const uint8_t alertWidth = 10;
32const uint8_t alertHeight = 7;
33const uint8_t alertBitmap[alertHeight] = {
34  0b0000110000,  // border top
35  0b0000110000,  // |    !   |
36  0b0000110000,  // |    !   |
37  0b0000110000,  // |    !   |
38  0b0000000000,  // |    !   |
39  0b0000110000,  // |    !   |
40  0b0000110000   // border bottom
41};
42
43uint8_t frame[matrixHeight][matrixWidth];
44
45void clearFrame() {
46  for (int y = 0; y < matrixHeight; y++) {
47    for (int x = 0; x < matrixWidth; x++) {
48      frame[y][x] = 0;
49    }
50  }
51}
52
53void drawAlert(int xPos, int yPos) {
54  clearFrame();
55  for (int row = 0; row < alertHeight; row++) {
56    for (int col = 0; col < alertWidth; col++) {
57      bool pixelOn = alertBitmap[row] & (1 << (alertWidth - 1 - col));
58      int x = xPos + col;
59      int y = yPos + row;
60      if (pixelOn && x >= 0 && x < matrixWidth && y >= 0 && y < matrixHeight) {
61        frame[y][x] = 1;
62      }
63    }
64  }
65  matrix.renderBitmap(frame, matrixHeight, matrixWidth);
66}
67
68void setup() {
69  Serial.begin(115200);
70  pinMode(sensorDig, INPUT);
71  attachInterrupt(digitalPinToInterrupt(sensorDig), sensorDigHandler, RISING);
72
73  matrix.begin();
74  matrix.clear();
75
76  // Initialize baseline with first measurement
77  sensorDigCnt = 0;
78  intEnable = 1;
79  delay(measureTime);
80  intEnable = 0;
81  base_line = sensorDigCnt;
82  Serial.print("Initial baseline: ");
83  Serial.println(base_line);
84
85  prevMillis = millis();
86}
87
88void loop() {
89  unsigned long currMillis = millis();
90
91  switch (state) {
92    case 1:
93      // Update baseline (moving average)
94      base_line = alpha * sensorDigCnt + (1.0 - alpha) * base_line;
95
96      // Calculate deviation from baseline
97      float diff = sensorDigCnt - base_line;
98
99      if (!inPeakEvent) {
100        // Not currently tracking a peak event
101        if (abs(diff) > base_line_change) {
102          inPeakEvent = true;
103          peakSamplesCount = 1;
104          peakValue = diff;
105        }
106      } else {
107        // Tracking peak event
108        peakSamplesCount++;
109        if (abs(diff) > abs(peakValue)) {
110          peakValue = diff;
111        }
112
113        // End peak detection when signal returns near baseline or max samples reached
114        if (abs(diff) <= base_line_change || peakSamplesCount > N) {
115          Serial.print("Peak detected: ");
116          Serial.println(peakValue);
117          inPeakEvent = false;
118          peakSamplesCount = 0;
119          peakValue = 0.0;
120
121          // Display alert sign centered on the matrix
122          drawAlert((matrixWidth - alertWidth) / 2, (matrixHeight - alertHeight) / 2);
123          delay(2000);   // Display alert for 2 seconds
124          matrix.clear();
125        }
126      }
127
128      Serial.print("Sensor= ");
129      Serial.print(sensorDigCnt);
130      Serial.print(" Baseline= ");
131      Serial.println(base_line);
132
133      state = 0;
134      break;
135  }
136
137  if (currMillis - prevMillis >= updateRate) {
138    sensorDigCnt = 0;
139    prevMillis = currMillis;
140    intEnable = 1;
141    delay(measureTime);
142    intEnable = 0;
143    state = 1;
144  }
145}
146
147// Interrupt handler increments counter on rising edge
148void sensorDigHandler() {
149  if (intEnable == 1) {
150    sensorDigCnt++;
151  }
152}