RPM Sensor with LCD

Using Arduino Displays
1

Hello, I have been trying like mad to get this RPM Hall Sensor to LCD working. I belong to GTBA and found this schematic and code on there, but for the life of me, I cannot get it working. If anybody could shed some light, I would be very grateful. Here is the code:

Code:

//--------------------------------------------------------------
//
// Interrupt driven sketch to measure RPM,
// it expects a suitable signal on pin digital 2 / external int0
// Display is via LCD.
//
//--------------------------------------------------------------

/* LCD 1 GND - ground

  • LCD 2 Vcc - +5v
  • LCD 4 RS pin - digital pin 52
  • LCD 6 Enable pin - digital pin 30
  • LCD 7 D0 pin - digital pin 28
  • LCD 8 D1 pin - digital pin 26
  • LCD 9 D2 pin - digital pin 24
  • LCD 10 D3 pin - digital pin 22
  • LCD 11 D4 pin - digital pin 23
  • LCD 12 D5 pin - digital pin 25
  • LCD 13 D6 pin - digital pin 27
  • LCD 14 D7 pin - digital pin 29

*pin 2 interupt
*pin 43 to flash lcd when magnet sensed
*/

#include <LiquidCrystal.h>

LiquidCrystal lcd(32, 30, 28, 26, 24, 22, 23, 25, 27, 29); //8 bit mode

volatile word rpmcount;
unsigned long rpm;
unsigned long timeold;
long rpmdetect; //time of last revo signl;
int rpmmin; //min rpm to be detected, bellow this rpm=0

void setup()
{
lcd.begin(20,4);
lcd.clear();
pinMode(43 ,OUTPUT); // revo led, high=revo detect
attachInterrupt(0, rpm_fun, RISING); //enable int pin2

rpmcount = 0;
rpm = 0;
rpmmin = 800;
timeold = 0;
rpmdetect = 0;
}

void loop()
{
lcd.setCursor(0,0);
lcd.print("RPM: ");

if (timeold==0)
{
lcd.setCursor(5,0);
lcd.print(rpm);
}

if (analogRead(2)>500) ///turn off led when not sensed
digitalWrite(43, HIGH); //rev sensor detect
else
digitalWrite(43, LOW); //rev sensor not detected

if (rpmcount >= 100) //Update RPM every 100 counts, increase this for better RPM resolution decrease for faster update
{

rpm = 1000000*60/(micros() - timeold)*rpmcount;
timeold = micros();
rpmcount = 0;

if (rpm > rpmmin)
{
lcd.setCursor(5,0);
lcd.print(" ");
lcd.setCursor(5,0);
lcd.print(rpm);
}
}

if (((millis() - rpmdetect) >500) && (rpm>0)) //if no revolution deteced in 1/2 sec set rpm=0
{
rpm=0;

lcd.setCursor(5,0);
lcd.print(" ");
lcd.setCursor(5,0);
lcd.print(rpm);
}
}

void rpm_fun()
{
rpmcount++; //Each rotation, this interrupt function is run
rpmdetect=millis();
digitalWrite(43,HIGH);

}

Thanks a bunch,

John

P.S. If you need anything else, please let me know.

tach schem.jpg
tach schem.jpg1182×516 66.7 KB

2

I think I got it working. I used the LCD sketch in the example library and slowly added his code. Now for the most part, it works. At least the screen says RPM: now. I just need to wait for the proper hall effect sensor to come and I can get going. I do urge others to try this and get it working, it is like nothing that I've seen on the internet and is a great way to measure RPM.

John