Trying to run on a 6 cylinder

[cpatersontn]

Mick,
Thanks for posting this project. We're looking forward to getting this running on our race car. We have a 1991 BMW 325i running the 6 cylinder engine. We've built the board as you specified and uploaded a modified version of your code. We are pulling the tach signal from the ECU wire that feeds the factory in-dash tach. The factory tach is working fine so we know it's getting good signal. The engine is firing 3X per revolution so we are assuming the frequency (at a given rpm) is (RPM/60)*3. We are testing at lower RPMs (don't want to upset the neighbors with rev'ing it to redline :)) so we calculated the lower RPMs between 1500 and 3100 (75Hz-155Hz). It idles at 800 RPM.

Once we start the car, the start-up sequence works and they flash one by one and then go off. However, regardless of how high we rev it, nothing else lights up. It's like it does the start-up sequence then somewhere it gets hung-up on lighting the LEDs (0,0,0). Stumped.

Here's the modified code:

//Shift Light V1.5

#include <Adafruit_NeoPixel.h>

#define PIN 6 //LED Data Pin
#define NUMPIXELS 16 //number of leds connected
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

//Calculate the frequency of the tacho signal you are using and adjust the following values accordingly
//example: for a standard tacho signal on a 4 cylinder engine the frequeny is equal to the RPM divided by 30
const unsigned int onFrequency = 20; //startup sequence, value represents engine speed higher than cranking and lower than idle
const unsigned int minFrequency = 75; // minimum frequency to begin turning on LEDs
const unsigned int maxFrequency = 155; // maximum frequency in normal range, after this value shift flash will occur
const unsigned int shiftFrequency = 165; // frequency range from max to shift when shifting should happen, after this value overrev flash will occur

//Set the color for each LED in the neo pixel strip
//Colors are set using an RGB value ranging from (0,0,0) to (255,255,255)
const uint32_t tachColor[NUMPIXELS] = {
Adafruit_NeoPixel::Color(0, 120, 0),//green
Adafruit_NeoPixel::Color(0, 120, 0),
Adafruit_NeoPixel::Color(0, 120, 0),
Adafruit_NeoPixel::Color(15, 105, 0),
Adafruit_NeoPixel::Color(30, 90, 0),
Adafruit_NeoPixel::Color(45, 75, 0),
Adafruit_NeoPixel::Color(60, 60, 0),//orange
Adafruit_NeoPixel::Color(75, 45, 0),
Adafruit_NeoPixel::Color(90, 30, 0),
Adafruit_NeoPixel::Color(105, 15, 0),
Adafruit_NeoPixel::Color(120, 0, 0),//red
Adafruit_NeoPixel::Color(0, 0, 120),//blue
Adafruit_NeoPixel::Color(0, 0, 120),
Adafruit_NeoPixel::Color(0, 0, 120),
Adafruit_NeoPixel::Color(0, 0, 120),
Adafruit_NeoPixel::Color(0, 0, 120),
};

//Set the frequency when each LED should turn on
//First LED turns on at minFrequency
const unsigned int lightShiftFreq[NUMPIXELS] = {
minFrequency,
80,
85,
90,
95,
100,
105,
110,
115,
120,
125,
130,
135,
140,
145,
150,
};

bool hasStartupSequenceRun = false; // only run startup sequence one time
const byte tachPin = 2;
unsigned long igfreq;

void setup() {
pixels.begin(); // This initializes the NeoPixel library.
}

void loop() {

float ighigh, iglow;
unsigned long igcal1, igcal2;

//measure period of tach signal
ighigh = pulseIn(tachPin, HIGH);
iglow = pulseIn(tachPin, LOW);

igcal1 = 1000 / ((ighigh / 1000) + (iglow / 1000));

//do it again
ighigh = pulseIn(tachPin, HIGH);
iglow = pulseIn(tachPin, LOW);

igcal2 = 1000 / ((ighigh / 1000) + (iglow / 1000));

//to filter out some noise, we only consider our measurement valid if they are similar in value, we accept the average.
if ((igcal1 - igcal2) < 8) {
igfreq = (igcal1 + igcal2) / 2;
}

if (hasStartupSequenceRun == false) {
if (igfreq > onFrequency) {
//run start sequence
//LEDs will light up, flash and light out upon starting the engine.
for ( int i = 0; i < NUMPIXELS; ++i) {
pixels.setPixelColor(i, tachColor[i]);
pixels.show();
delay(50);
}
for(int a=0; a<10; a++) {
pixels.fill(pixels.Color(0, 0, 120));
pixels.show();
delay(20);
pixels.fill(pixels.Color(0, 0, 0));
pixels.show();
delay(20);
}
for ( int i = 0; i < NUMPIXELS; ++i) {
pixels.setPixelColor(i, tachColor[i]);
pixels.show();
}
for ( int i = NUMPIXELS-1; i >= 0; --i) {
pixels.setPixelColor(i, pixels.Color(0, 0, 0));
pixels.show();
delay(50);
}
hasStartupSequenceRun = true;
pixels.fill(pixels.Color(0, 0, 0));
pixels.show();
}
if (igfreq < onFrequency) {
//resets hasStartupSequenceRun to false if engine stops but Arduino remains powered,
//startupsequence will rerun upon restarting the engine
hasStartupSequenceRun = false;
}
}

if (igfreq < maxFrequency) {

// normal operating range
for ( int i = 0; i < NUMPIXELS; ++i) {
  if (igfreq > lightShiftFreq[i]) {
    pixels.setPixelColor(i, tachColor[i]);
  }
  else {
    pixels.setPixelColor(i, pixels.Color(0, 0, 0));
  }
}
pixels.show();

}
else if (igfreq >= maxFrequency && igfreq < shiftFrequency) {
//shift flash
//default color=blue
//to change shift flash color, edit RGB value in following line
pixels.fill(pixels.Color(0, 0, 120));
pixels.show();
delay(20);
pixels.fill(pixels.Color(0, 0, 0));
pixels.show();
delay(20);
}

else if (igfreq >= shiftFrequency) {
//overrev flash
//default color=red
//to change overrev flash color, edit RGB value in following line
pixels.fill(pixels.Color(120, 0, 0));
pixels.show();
delay(20);
pixels.fill(pixels.Color(0, 0, 0));
pixels.show();
delay(20);
}
}

[MickTheMechanic]

If you have an ocsilloscope please check your Signal wire and confirm you have a 12v square wave (I am not familiar with BMW Tacho Signal, it’s possible it’s a 5v Signal).

Does your car have a single coil with a distributor? If so, please try using coil negative.

Report back with results.

[cpatersontn]

We don't have an ocsilloscope. If it's a 5V signal, then what do we need to modify (hardware and software)?

Yes, single coil with distributor. We tried the coil negative and it was very noisy.... LEDs jumped all over the place.

[MickTheMechanic]

If its a 5v signal then you can feed it directly into the arduino, bypassing the transistor. But if its not 5v and you do that, you'll fry your arduino.

Do you maybe have a video showing what it looks like when using coil negative?

[MickTheMechanic]

You could even check with a multimeter, if its a 12v signal you should read about 6v on the signal wire with engine running. If its a 5v signal you should read about 2-3v

[cpatersontn]

Tach signal from ECU is 7.9V (set to DC on multimeter).

Here's the shift light attached to the negative on the coil. It always goes through the start-up sequence then just flashes red at idle as if it's over-reving. Our shiftFrequency is set to 165Hz just for testing but that should equate to 3300rpm if our equation is correct for this 6-cylinder (RPM/60)*3)

Link to video: https://www.facebook.com/chris.paterson.399/videos/10219498587075256/

[MickTheMechanic]

Link doesnt work.

Are you able to test on another car?
Perhaps there is a problem with the circuit.

Have you tried using the original code, unchanged?

[MickTheMechanic]

Tach signal should be fine.
Can you upload photos of your circuit?

[cpatersontn]

Try copying and pasting the linked address instead of clicking on it

Ok on tach signal

We reloaded the original code and it just blinks all red. Unplug the USB from the computer but leave it plugged in to the USB-B port on the PCB. Does that matter?

Can't try it on any other vehicle at this time

Here's pics of the PCB and LED. My first ones I've ever built so definitely can use any pointers or corrections if something doesn't look right

[MickTheMechanic]

I just had a look at the video, the red flashing appears to be the overrev flash.

It would suggest that the frequency’s in the code are set far too low, the frequency at idle is higher than the programmed shift frequency.

To confirm, change the shiftfrequency to something like 1000 and see if anything changes.

Do you only have this problem when using coil negative, or also with the Tacho Signal wire from the dash?

The USB cable doesn’t matter if you have it connected to the car via the 5v reg.

I will take a closer look at the pics tomorrow and see if I can spot anything in regards to the circuitry.

[cpatersontn]

When we run the unmodified program, we have red blinking lights on the negative coil and tach signal

[MickTheMechanic]

I just updated my previous comment

[cpatersontn]

Thanks. We'll try a few experiments and see if changing values higher gives a different response.

In this section of the program, it looks like it is measuring the tach period and then doing some function to scale that number. Why is it dividing everything by 1,000?

//measure period of tach signal
ighigh = pulseIn(tachPin, HIGH);
iglow = pulseIn(tachPin, LOW);

igcal1 = 1000 / ((ighigh / 1000) + (iglow / 1000));

[MickTheMechanic]

Because the pulseIn() doesnt read Hz, rather it measures how many microseconds between pulses. From this we have to calculate Hz.
This code is run twice, both values are compared, and if similar the average of both values is used (helps cut down unwanted noise).

[MickTheMechanic]

Also had a closer look at your board, the circuitry look ok, seems everything is connected in the right spot. Also confirmed by the fact that the start up sequence runs.

[cpatersontn]

Ok, thanks on explaining the pulseIn() code. Would you expect a magnitude difference between different makes/models/# cylinders on the actual time between pulses which would affect the calculated Hz? For instance, your original code has 123Hz @ 3700 RPMs.... would it be unexpected if the Hz calculation for our BMW 6-cylinder is a magnitude different? e.g. 2000 Hz (or higher) @ 3700 RPMs ?