I have an IR emitter and IR receiver set up where I bring four IR emitter/receiver pairs into separate analog inputs. I'm trying to read the voltage change that occurs when an IR receiver is blocked from the emitter. I am using the 3v pin as my reference and am using an adafruit SD card shield for data logging. Here is my problem: when I block one receiver with aluminum foil, all of the receivers report the same voltage change. They each have their own analog input, and the only lines the receivers share is the power and ground. Any ideas on how to resolve this issue?
// A simple data logger for the Arduino analog pins
#include <SPI.h>
#include <SD.h>
#include <Wire.h>
#include "RTClib.h"
// how many milliseconds between grabbing data and logging it. 1000 ms is once a second
#define LOG_INTERVAL 1000 // mills between entries (reduce to take more/faster data)
// how many milliseconds before writing the logged data permanently to disk
// set it to the LOG_INTERVAL to write each time (safest)
// set it to 10*LOG_INTERVAL to write all data every 10 datareads, you could lose up to
// the last 10 reads if power is lost but it uses less power and is much faster!
#define SYNC_INTERVAL 1000 // mills between calls to flush() - to write data to the card
uint32_t syncTime = 0; // time of last sync()
// the digital pins that connect to the LEDs
#define redLEDpin 2
#define greenLEDpin 3
// The analog pins that connect to the sensors
#define vccPin0 0 // analog 0
#define vccPin1 1 // analog 1
#define vccPin2 2 // analog 2
#define vccPin3 3 // analog 3
// Analog Pin 4 is protected // analog 4 (Protected)
// Analog Pin 5 is protected // analog 5 (Protected)
// Digital Pin 10 is protected // digital 10 (Protected)
// Digital Pin 11 is protected // digital 11 (Protected)
// Digital Pin 12 is protected // digital 12 (Protected)
// Digital Pin 13 is protected // digital 13 (Protected)
//#define BANDGAPREF 14 // special indicator that we want to measure the bandgap
#define aref_voltage 5.0 // we tie 3.3V to ARef and measure it with a multimeter!
//#define bandgap_voltage 1.1 // this is not super guaranteed but its not -too- off
// Choose the correct chip to get the time right!
//RTC_DS1307 RTC; // define the Real Time Clock object
RTC_PCF8523 RTC;
// for the data logging shield, we use digital pin 10 for the SD cs line
const int chipSelect = 10;
// the logging file
File logfile;
void error(char *str)
{
Serial.print("error: ");
Serial.println(str);
// red LED indicates error
digitalWrite(redLEDpin, HIGH);
while(1);
}
/*****************************************************
* SETUP
*
****************************************************/
void setup(void)
{
Serial.begin(9600);
Serial.println();
// use debugging LEDs
pinMode(redLEDpin, OUTPUT);
pinMode(greenLEDpin, OUTPUT);
// initialize the SD card
Serial.print("Initializing SD card...");
// make sure that the default chip select pin is set to
// output, even if you don't use it:
pinMode(10, OUTPUT);
// see if the card is present and can be initialized:
if (!SD.begin(chipSelect)) {
error("Card failed, or not present");
}
Serial.println("card initialized.");
// create a new file
char filename[] = "LOGGER00.CSV";
for (uint8_t i = 0; i < 100; i++) {
filename[6] = i/10 + '0';
filename[7] = i%10 + '0';
if (! SD.exists(filename)) {
// only open a new file if it doesn't exist
logfile = SD.open(filename, FILE_WRITE);
break; // leave the loop!
}
}
if (! logfile) {
error("couldnt create file");
}
Serial.print("Logging to: ");
Serial.println(filename);
// connect to RTC
Wire.begin();
if (!RTC.begin()) {
logfile.println("RTC failed");
Serial.println("RTC failed");
}
logfile.println("time, datetime, V1, V2, V3, V4");
Serial.println("time, datetime, V1, V2, V3, V4");
// If you want to set the aref to something other than 5v
//analogReference(EXTERNAL);
}
/*****************************************************
* LOOP
*
****************************************************/
void loop(void)
{
DateTime now; // Creating the DateTime object 'now'
// delay for the amount of time we want between readings
delay((LOG_INTERVAL -1) - (millis() % LOG_INTERVAL));
// turning the green LED ON
digitalWrite(greenLEDpin, HIGH);
// log milliseconds since starting
uint32_t m = millis();
logfile.print(m/1000.0); // milliseconds since start
logfile.print(", ");
Serial.print(m/1000.0); // milliseconds since start
Serial.print(", ");
// fetch the time
now = RTC.now();
// log time
logfile.print(now.month(), DEC);
logfile.print("/");
logfile.print(now.day(), DEC);
logfile.print("/");
logfile.print(now.year(), DEC);
logfile.print(" ");
logfile.print(now.hour(), DEC);
logfile.print(":");
logfile.print(now.minute(), DEC);
logfile.print(":");
logfile.print(now.second(), DEC);
Serial.print(now.month(), DEC);
Serial.print("/");
Serial.print(now.day(), DEC);
Serial.print("/");
Serial.print(now.year(), DEC);
Serial.print(" ");
Serial.print(now.hour(), DEC);
Serial.print(":");
Serial.print(now.minute(), DEC);
Serial.print(":");
Serial.print(now.second(), DEC);
// Pre-reading the analog pins
analogRead(vccPin0); // cage one
analogRead(vccPin1); // cage two
analogRead(vccPin2); // cage three
analogRead(vccPin3); // cage four
delay(10);
// Reading again and storing data in variables
int vcc0Reading = analogRead(vccPin0);
int vcc1Reading = analogRead(vccPin1);
int vcc2Reading = analogRead(vccPin2);
int vcc3Reading = analogRead(vccPin3);
delay(10);
// converting that reading to voltage, for 3.3v arduino use 3.3, for 5.0, use 5.0
float voltage0 = vcc0Reading * aref_voltage / 1024;
float voltage1 = vcc1Reading * aref_voltage / 1024;
float voltage2 = vcc2Reading * aref_voltage / 1024;
float voltage3 = vcc3Reading * aref_voltage / 1024;
logfile.print(", ");
logfile.print(voltage0,4);
logfile.print(", ");
logfile.print(voltage1,4);
logfile.print(", ");
logfile.print(voltage2,4);
logfile.print(", ");
logfile.print(voltage3,4);
logfile.println();
Serial.print(", ");
Serial.print(voltage0,4);
Serial.print(", ");
Serial.print(voltage1,4);
Serial.print(", ");
Serial.print(voltage2,4);
Serial.print(", ");
Serial.print(voltage3,4);
Serial.println();
// Turn the green LED OFF
digitalWrite(greenLEDpin, LOW);
// Now we write data to disk! Don't sync too often - requires 2048 bytes of I/O to SD card
// which uses a bunch of power and takes time
if ((millis() - syncTime) < SYNC_INTERVAL) return;
syncTime = millis();
// blink LED to show we are syncing data to the card & updating FAT!
digitalWrite(redLEDpin, HIGH);
logfile.flush();
digitalWrite(redLEDpin, LOW);
}
