**First things first. I would like to thank Ant_Turbo for all the help with working some of the bugs out to make it easier on everyone when building this little project**

Things you’ll need
- Arduino Uno Here
- (optional) Arduino l2c LCD Screen Here
- 4.7k ohm resistor $1
- 3.3k ohm resistor $1
- USB Car Charger (5v 1amp) $1-$5
- Dorman 800-082 3/8” quick fuel connects
- Flex Fuel Sensor Pigtail
**Library's needed to program the code**
LCD library Drop these into your arduino library. make sure arduino is not open when you do!


Evoscan
Adding request 83 with (5/256)*(x) will display voltage giving the ability to have automatic map switching


Wiring Credit to @ant_turbo for the pic! thanks!


Here is where i mounted my LCD. Had to trim slightly to get it to fit, but im very happy with it.





Code

/************************************************** *****
This program will sample a 50-150hz signal depending on ethanol
content, and output a 0-5V signal via PWM.
The LCD will display ethanol content, hz input, mv output, fuel temp
************************************************** ******/

// include the library code:
#include <Wire.h>
#include <LCD.h>
#include <LiquidCrystal_I2C.h>

#define I2C_ADDR 0x27 // <<- Add your address here.
#define Rs_pin 0
#define Rw_pin 1
#define En_pin 2
#define BACKLIGHT_PIN 3
#define D4_pin 4
#define D5_pin 5
#define D6_pin 6
#define D7_pin 7

LiquidCrystal_I2C lcd(0x27,En_pin,Rw_pin,Rs_pin,D4_pin,D5_pin,D6_pin ,D7_pin);

int inpPin = 8; //define input pin to 8
int outPin = 11; //define PWM output, possible pins with LCD and 32khz freq. are 3 and 11 (UNO)

//Define global variables
volatile uint16_t revTick; //Ticks per revolution
uint16_t pwm_output = 0; //integer for storing PWM value (0-255 value)
int HZ; //unsigned 16bit integer for storing HZ input
int ethanol = 0; //Store ethanol percentage here
float expectedv; //store expected voltage here - range for typical GM sensors is usually 0.5-4.5v
uint16_t voltage = 0; //Store display millivoltage here (0-5000)
int duty; //Duty cycle (0.0-100.0)
float period; //Store period time here (eg.0.0025 s)
float temperature = 0; //Store fuel temperature here
int fahr = 0;
int cels = 0;
static long highTime = 0;
static long lowTime = 0;
static long tempPulse;

void setupTimer() // setup timer1
{
TCCR1A = 0; // normal mode
TCCR1B = 132; // (10000100) Falling edge trigger, Timer = CPU Clock/256, noise cancellation on
TCCR1C = 0; // normal mode
TIMSK1 = 33; // (00100001) Input capture and overflow interupts enabled
TCNT1 = 0; // start from 0
}

ISR(TIMER1_CAPT_vect) // PULSE DETECTED! (interrupt automatically triggered, not called by main program)
{
revTick = ICR1; // save duration of last revolution
TCNT1 = 0; // restart timer for next revolution
}

ISR(TIMER1_OVF_vect) // counter overflow/timeout
{ revTick = 0; } // Ticks per second = 0


void setup()
{
Serial.begin(9600);
pinMode(inpPin,INPUT);
setPwmFrequency(outPin,1); //Modify frequency on PWM output
setupTimer();
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
lcd.setBacklightPin(3,POSITIVE);
lcd.setBacklight(HIGH);
// Initial screen formatting
lcd.setCursor(1, 0);
lcd.print("Ethanol: %");
lcd.setCursor(0, 1);
lcd.print(" Hz F");
}

void loop()
{
getfueltemp(inpPin); //read fuel temp from input duty cycle

if (revTick > 0) // Avoid dividing by zero, sample in the HZ
{HZ = 62200 / revTick;} // 3456000ticks per minute, 57600 per second
else
{HZ = 0;} //needs real sensor test to determine correct tickrate

//calculate ethanol percentage
if (HZ > 50) // Avoid dividing by zero
{ethanol = (HZ-50);}
else
{ethanol = 0;}

if (ethanol > 99) // Avoid overflow in PWM
{ethanol = 99;}

expectedv = ((((HZ-50.0)*0.01)*4)+0.5);
//Screen calculations
pwm_output = 1.11 * (255 * (expectedv/5.0)); //calculate output PWM for NEMU

lcd.setCursor(12, 0);
lcd.print(ethanol);

lcd.setCursor(2, 1);
lcd.print(HZ);

lcd.setCursor(12, 1);
lcd.print(fahr); //Use this for celsius

//PWM output
analogWrite(outPin, pwm_output); //write the PWM value to output pin

delay(1000); //make screen more easily readable by not updating it too often

Serial.println(ethanol);
Serial.println(pwm_output);
Serial.println(expectedv);
Serial.println(HZ);
delay(1000);


}

void getfueltemp(int inpPin) { //read fuel temp

tempPulse = pulseIn(inpPin, LOW, 25000); // Measure the low pulse time (timeout after 25ms if no pulse is detected)
if (tempPulse > 0) { // If we get a pulse then update the temperature measurement
lowTime = tempPulse;
float celsius = ((41.25 * (float(lowTime) / 1000)) - 81.25); // Calculate temp in celsius from lowTime pulse
float fahrenheit = ((celsius * 1.8) + 32); // Convert to fahrenheit
temperature = fahrenheit; // Update temperature with specified unit
}
}

duty = ((100*(highTime/(double (lowTime+highTime))))); //Calculate duty cycle (integer extra decimal)
float T = (float(1.0/float(HZ))); //Calculate total period time
float period = float(100-duty)*T; //Calculate the active period time (100-duty)*T
float temp2 = float(10) * float(period); //Convert ms to whole number
temperature = ((40.25 * temp2)-81.25); //Calculate temperature for display (1ms = -40, 5ms = 80)
int cels = int(temperature);
cels = cels*0.1;
float fahrtemp = ((temperature*1.8)+32);
fahr = fahrtemp*0.1;

}

void setPwmFrequency(int pin, int divisor) { //This code snippet raises the timers linked to the PWM outputs
byte mode; //This way the PWM frequency can be raised or lowered. Prescaler of 1 sets PWM output to 32KHz (pin 3, 11)
if(pin == 5 || pin == 6 || pin == 9 || pin == 10) {
switch(divisor) {
case 1: mode = 0x01; break;
case 8: mode = 0x02; break;
case 64: mode = 0x03; break;
case 256: mode = 0x04; break;
case 1024: mode = 0x05; break;
default: return;
}
if(pin == 5 || pin == 6) {
TCCR0B = TCCR0B & 0b11111000 | mode;
} else {
TCCR1B = TCCR1B & 0b11111000 | mode;
}
} else if(pin == 3 || pin == 11) {
switch(divisor) {
case 1: mode = 0x01; break;
case 8: mode = 0x02; break;
case 32: mode = 0x03; break;
case 64: mode = 0x04; break;
case 128: mode = 0x05; break;
case 256: mode = 0x06; break;
case 1024: mode = 0x7; break;
default: return;
}
TCCR2B = TCCR2B & 0b11111000 | mode;
}
}



I have modified my own code for a lcd screen output. If you would like the code to have a 16x2 display, please let me know.

 

Thanks for you contribution. Can you post a picture of the finished project so we can see how you packaged the Arduino and LCD display?

 

*updated

 

Dang, I love you people.
What are the chances we could find a 52mm gauge for the output?

 

you could. could use a 1.5" rbg screen and put it in a gauge. Which was honestly what i was going to work on next

 

That's friggin sweet, well done! Might have to give this a shot at some point. But of course until I go with a true flex fuel setup Im still testing my fuel prior. Still a slick gauge love the DIY aspect and the cleanliness of it all.

 

Awesome job!

 

If you need help, feel free to shoot me a PM.

 

Something I found
https://forums.adafruit.com/viewtopic.php?f=47&t=67958
https://forum.arduino.cc/index.php?topic=308808.0

Not sure if it will make someones life easier, haha.

 

i came across that last night too. i saw people asking him if he wanted to sell them. but never saw any kind of responce

 

Where along the fuel line did you find it most convenient to put the ethanol sensor?

 

I put mine in the return line and mounted it on the firewall. It works perfectly in this position.

 

So where exactly does the pink line go to?

Also, how does the lcd get wired in to the whole scenario?

 

it CAN be wired into ADC input for automatic map switching, just depends if you want to use that or not.

the lcd depends on what kind you want you use.
This is the lcd i used, its the easiest to wire. Here

 

Wow I have been looking into doing my own content display recently and I'm glad that I stumbled upon this post. Thanks a lot I will be looking into this once I go FF with my aem infinity. Is that flex fuel sensor that you have linked on amazon the same one/place that you purchased yours?