I'm trying to build an infrared tripwire to detect when a HO scale model train passes, using this module:
I have de-soldered the transmitter led and the three pin receiver, and re soldered them to leads. Then I have placed each part (transmitter led and receiver) on separate sides of the track. Last night, I tested the output pin of the module and it always outputs ~0.5 volts, whether the IR led is on or off. I have made sure that the led is focused directly on the receiver, but that doesn't change anything. It doesn't work. It does not detect whether a train or anything else has passed through the beam.
This is my code:
[code]
#include "U8glib.h"
U8GLIB_ST7920_128X64_4X u8g(10);
uint8_t draw_state = 0;
#define SENSOR_DISTANCE 200000 // [um] measured distance between the two IR beams
#define INIT_TRAIN_LENGTH 20 // [cm] New measurement only starts when train fully passed
// Loco Length can be changed via keyboard input
#define SENSOR_L_PIN 6
#define SENSOR_R_PIN 7
byte l_r, state;
byte scale, scale_old;
byte units, units_old = 99; // 0=MPH, 1=km/hr, 99=startup dummy
int train_length, serialread;
unsigned long start_us, stop_us, measured_us, waittime;
float m_per_s;
float km_per_hr;
float mi_per_hr;
void read_write_scale() {
if (Serial.available()) {
serialread = Serial.parseInt();
if (serialread) train_length == serialread;
Serial.print(F("Train length set to: "));
Serial.print(train_length);
Serial.println(F(" cm"));
Serial.println(F("Waiting for train ..."));
Serial.println();
}
scale = 87; // scale HO
if (!digitalRead(14)) scale = 45; // scale O
if (!digitalRead(15)) scale = 76; // scale OO
if (!digitalRead(16)) scale = 120; // scale TT
if (!digitalRead(17)) scale = 160; // scale N
if (scale != scale_old ) {
scale_old = scale;
Serial.print(F("Scale set to: 1/"));
Serial.println(scale);
}
units = digitalRead(8); // 0=MPH, 1=km/hr
if (units != units_old ) {
units_old = units;
Serial.print(F("Units set to: "));
if (units) Serial.println(F("km/hr"));
else Serial.println(F("MPH"));
Serial.println(F("Waiting for train..."));
}
}
void setup() {
pinMode(13, OUTPUT);
pinMode(SENSOR_L_PIN, INPUT_PULLUP);
pinMode(SENSOR_R_PIN, INPUT_PULLUP);
pinMode( 8, INPUT_PULLUP);
pinMode(14, INPUT_PULLUP);
pinMode(15, INPUT_PULLUP);
pinMode(16, INPUT_PULLUP);
pinMode(17, INPUT_PULLUP);
pinMode(18, INPUT_PULLUP);
Serial.begin(9600);
train_length = INIT_TRAIN_LENGTH; // [cm]
Serial.println();
Serial.print(F("Train length is set to "));
Serial.print(train_length);
Serial.println(F(" cm "));
Serial.println(F("For longer trains change this by typing"));
Serial.println(F("in the input field above and hit ENTER"));
// Serial.println(F("For auto measurement with Traincontroller:"));
// Serial.println(F("1: Open TC Speed Profiling Tab"));
// Serial.println(F("2: Start AutoHotKey"));
Serial.println();
read_write_scale();
digitalWrite(13, HIGH); // LED on means ready for measurement
}
void loop() {
read_write_scale();
switch (state) {
case 0: // initial state, ready to start measuring
if (digitalRead(SENSOR_L_PIN)) {
start_us = micros();
l_r = 0;
state = 1;
}
if (digitalRead(SENSOR_R_PIN)) {
start_us = micros();
l_r = 1;
state = 1;
}
break;
case 1: // wait for the other sensor to be triggered
digitalWrite(13, LOW);
if (!l_r) {
Serial.println(F("L >>> R"));
while (!digitalRead(SENSOR_R_PIN)) {} // loop here until sensor R is triggered
}
else {
Serial.println(F("L <<< R"));
while (!digitalRead(SENSOR_L_PIN)) {} // loop here until sensor L is triggered
}
stop_us = micros();
state = 2;
break;
case 2: // calculate and show speed values
measured_us = stop_us - start_us - 10UL; // -10 to compensate for code delay
m_per_s = float(scale) * float(SENSOR_DISTANCE) / float(measured_us);
km_per_hr = 3.6 * m_per_s;
mi_per_hr = 2.23694 * m_per_s;
if (!units) {
Serial.print(mi_per_hr);
Serial.println(F(" MPH"));
}
else {
Serial.print(km_per_hr);
Serial.println(F(" km/hr"));
}
Serial.println();
waittime = (int)(10UL * measured_us * (unsigned long)train_length / (unsigned long)SENSOR_DISTANCE + 1000UL); // [ms]
// measured_us is needed for a move of SENSOR_DISTANCE um
// measured_us * train_length / SENSOR_DISTANCE) time is needed for train_length to pass
Serial.print(F("Wait "));
Serial.print(waittime);
Serial.println(F(" ms"));
// delay(waittime);
digitalWrite(13, HIGH); //Next measurement can start when LED is on
Serial.println(F("Waiting for train..."));
state = 0;
break;
}
}
[/code]
The code and basic idea for this project come from an online tutorial:
