Help a noob

Question

Hi Guys

Please could you perhaps assist with a piece of code.

The basic idea is to have a countdown timer for my sons model rocket. He sets the time by mapping a pot and then "Arms: the system. After doing the checks he then presses a "Launch" button to initiate the countdown timer.

Once the timer reaches "0" it activates a relay and in turn fires the rocket.

I found the below code on the net and modified it with the help of a friend to use a i2c 16x2 LCD display.

I am in no way an expert but having fun learning.

I have 2 x minor issues now.

1st I need to add a decimal point to the countdown seconds (Currently displaying 000 seconds, I would like 00.0)

2nd, the LCD display is flickering. Even more so when the countdown initiates. ( I think this is due to bad coding)

Is anyone able to point me in the right direction and possibly recommend some improvements?

Code below -

#define FuseTIME 1500 //Fuse current duration in milliseconds.

#include <Wire.h>

#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);//change address according to your LCD

#define Fuss 7 //Pin connected to the Fuse relay.

int GoButt = 6; //Pin Connected to the GO button.

int ArmButt = 5; //Pin connected to the ARM button.

#define BuzzPin 4 //Connected to the Speaker.

#define SetPot 0 //Analog Pin connected to the Pot.

void setup(){

lcd.begin();

pinMode(Fuss,OUTPUT);

pinMode(ArmButt, INPUT); // set "ARM" button pin to input

pinMode(GoButt, INPUT); // set "GO" button pin to input

digitalWrite(Fuss,LOW); //OPEN the fuse circuit.

digitalWrite(ArmButt, HIGH); // turn on pullup resistor

digitalWrite(GoButt, HIGH); // turn on pullup resistor

lcd.clear();

lcd.setCursor(4,0);

lcd.print("Rocket");

lcd.setCursor(3,1);

lcd.print("Launcher");

delay(2000);

}

int DownCntr; // down counter (1/10 Secs.)

int Go=0; // Stopped

//================================================================

void loop(){

if(!digitalRead(GoButt)||!digitalRead(ArmButt)){

Go=0; //ABORT!!!

tone(BuzzPin, 440, 1500);

delay(1500);

}

if(Go==0){

WaitARM();

WaitGO();

}

ShowTimer();

if (DownCntr > 50){

if (DownCntr % 10 ==0)tone(BuzzPin, 1000, 50); //Tone every second.

}

else if (DownCntr % 2 ==0)tone(BuzzPin, 1000, 50); //Tone every 1/5 second.

if (DownCntr ==0){

//------------------ ROCKET LAUNCH! --------------------

tone(BuzzPin, 440, FuseTIME); //Launch audible signal

digitalWrite(Fuss,HIGH); //CLOSE the fuse circuit

delay(FuseTIME);

digitalWrite(Fuss,LOW); //OPEN the fuse circuit.

//------------------------------------------------------

Go=0;

}

while (millis()% 100); //Wait until the next 1/10 of second.

delay(50);

DownCntr--;

}

//----------------------------------------

void WaitGO(){

ShowTimer();

while(digitalRead(GoButt));

Go=1;

delay(20);

while(!digitalRead(GoButt)); //Debounce GO button.

}

//------------------------------------------------------

void ReadTimer(){

DownCntr = map(analogRead(SetPot), 0, 1023, 10, 60); // DownCntr = map(analogRead(SetPot), 0, 1023, 5, 60);

DownCntr*=10;

}

//------------------------------------------------------

void ShowTimer(){

String seconds = String (DownCntr, DEC);

while(seconds.length()<3)seconds= "0" + seconds; //format to 3 numbers.

lcd.clear();

lcd.setCursor(1,0);

lcd.print("Launching In");

lcd.setCursor(1,1);

lcd.print(seconds);

lcd.setCursor(5,1);

lcd.print("Seconds");

}

//------------------------------------------------------

void WaitARM(){

while(digitalRead(ArmButt)==1){

ReadTimer();

delay(50);

ReadTimer();

ShowTimer(); //Show Digits.

delay(150);

}

Go=0;

ShowTimer();

tone(BuzzPin, 2000, 150);

delay(200);

tone(BuzzPin, 2000, 150);

delay(200);

tone(BuzzPin, 2000, 150);

delay(20);

while(!digitalRead(ArmButt)); //Debounce ARM button.

}

Andrew J · Accepted Answer

No probs, we all start somewhere and you've clearly had a good go and got it pretty much working. I'm not too clear on what you are trying to achieve with the display of digits: does your value have an implied decimal point or do you want to add a decimal point plus 0. So if your pot gives you a starting value of 199, should that display as 19.9, 19.0 or 199.0? Keeping the code simple and understandable then instead of your line String seconds = String(etc...: Treat 199 as 19.0: Float displayCount = DownCntr / 10; // This will treat the answer as an integer so 199/10 becomes 19.9 but the decimal places will be dropped leaving 19 (I don't think it will round up!). displayCount will h
String seconds = String(displayCount, 1); Treat 199 as 19.9 Float displayCount = DownCntr / 10.0; // This will treat the answer as an integer so 199/10 becomes 19.9 and displayCount will hold 19.9
String seconds = String(displayCount, 1); Treat 199 as 199.0 String seconds = String(DownCntr) + ".0"; // just append the decimal place I think you are trying to achieve a specific display value length of 3: 101, 100, 099, 098, ... 010, 009...000. Adding 2 characters changes this test to < 5 characters as I assume you still want to display 3 significant digits. Can I just add that I haven't been able to try this code but I believe it will work - let me know if it doesn't!! Good luck.

BigG · Answer

LCD flickering is due to using this "lcd.clear();" repeatedly. Don't use after the first clear. For your first line on LCD. Just write once and that's it. Then all you need to do is update second line. To do this you need to create a 16 char buffer and insert your variables then just overwrite the second line with this buffer. No need to clear first.

Andrew J · Answer

Assuming you don't want to actually display 10ths of a second, then you just need to add ".0" to your seconds variable that you output to the LCD. If you do want to display 10ths of a second then you'll need to do a few things: change DownCntr to be a float type - integers can't hold decimal places Decrement DownCntr by 0.1 : instead of DownCntr--, use DownCntr -= -0.1. Why the delay(50) after waiting 100millis? That will probably need to go to keep the down count reasonably accurate. Change the ShowTimer code to use a float format rather than a decimal format when initialising variable seconds - either truncate to 1decimal place or round to 1 decimal place.

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