Simon Barker / Mbed 2 deprecated RPMMonitor

Mbed Fan RPM/Speed meter using QTR-1A Reflectance Sensor

Dependencies:   mbed

main.cpp@0:812fda2beeaa, 2013-06-23 (annotated)

Committer:
simonbarker
Date:
Sun Jun 23 10:21:15 2013 +0000
Revision:
0:812fda2beeaa
Commented RPM meter using QTR-1A Reflectance Sensor sensor

Who changed what in which revision?

UserRevisionLine numberNew contents of line
simonbarker 0:812fda2beeaa 1 #include "mbed.h"
simonbarker 0:812fda2beeaa 2
simonbarker 0:812fda2beeaa 3 AnalogIn input(p20);
simonbarker 0:812fda2beeaa 4 DigitalOut led1(LED1);
simonbarker 0:812fda2beeaa 5 Serial pc(USBTX, USBRX); // tx, rx
simonbarker 0:812fda2beeaa 6 Timer t;
simonbarker 0:812fda2beeaa 7
simonbarker 0:812fda2beeaa 8 int main() {
simonbarker 0:812fda2beeaa 9 float sample;
simonbarker 0:812fda2beeaa 10 bool newDetection = true; //need this as multiple reads happen across white spot
simonbarker 0:812fda2beeaa 11 int samples[120]; //higher number = greater accuracy but longer read time
simonbarker 0:812fda2beeaa 12 int sampleCount = 0;
simonbarker 0:812fda2beeaa 13
simonbarker 0:812fda2beeaa 14 pc.printf("Starting:\n\r");
simonbarker 0:812fda2beeaa 15
simonbarker 0:812fda2beeaa 16 //start initial timer
simonbarker 0:812fda2beeaa 17 t.start();
simonbarker 0:812fda2beeaa 18
simonbarker 0:812fda2beeaa 19 while(1) {
simonbarker 0:812fda2beeaa 20 //poll analogue in
simonbarker 0:812fda2beeaa 21 sample = input.read();
simonbarker 0:812fda2beeaa 22 if(sample < 0.1 && newDetection == true){ //tune 0.1 to appropriate level
simonbarker 0:812fda2beeaa 23 //detected white spot so stop timer
simonbarker 0:812fda2beeaa 24 samples[sampleCount] = t.read_us();
simonbarker 0:812fda2beeaa 25 t.reset();
simonbarker 0:812fda2beeaa 26 //reset flag
simonbarker 0:812fda2beeaa 27 newDetection = false;
simonbarker 0:812fda2beeaa 28 sampleCount++;
simonbarker 0:812fda2beeaa 29
simonbarker 0:812fda2beeaa 30 //change for shorter/longer read times - must be less than array length (set in ling 11)
simonbarker 0:812fda2beeaa 31 if(sampleCount == 100){
simonbarker 0:812fda2beeaa 32 //total up time and average across number of readings taken
simonbarker 0:812fda2beeaa 33 int total = 0;
simonbarker 0:812fda2beeaa 34 for(int i = 1; i < 99; i++){ //start at 1 as the first one will be a junk reading
simonbarker 0:812fda2beeaa 35 total += samples[i];
simonbarker 0:812fda2beeaa 36 }
simonbarker 0:812fda2beeaa 37 float ave = total/98;
simonbarker 0:812fda2beeaa 38 float rpm = (1000000/ave)*60; //convert from us to rpm
simonbarker 0:812fda2beeaa 39 pc.printf("RPM = %f\r\n",rpm);
simonbarker 0:812fda2beeaa 40 sampleCount = 0;
simonbarker 0:812fda2beeaa 41 }
simonbarker 0:812fda2beeaa 42 }
simonbarker 0:812fda2beeaa 43 else if(sample > 0.9){ //tune 0.9 to appropriate level
simonbarker 0:812fda2beeaa 44 newDetection = true;
simonbarker 0:812fda2beeaa 45 }
simonbarker 0:812fda2beeaa 46 }
simonbarker 0:812fda2beeaa 47 }