Arduino anyone?

[Chippie]

Looking for some coding help…

Any knowledgeable folk here?

 

[Stupoty]

Loads of people seem to use them here , whats the thing ?

Stu

 

[Red'n'Black]

I've used the Nano to run several bits of home-made test gear at work. Happy to take a look if you want?

 

[Anguz]

i have used them and done my own code
also been supprised with how well chatgpt can give you a head start on the code

 

[Kram]

I have used them, also was a profesional developer for a good few years. Whats the question or post up the code your having trouble with?

 

[Chippie]

I’m trying to operate a relay, have 2 push buttons and a temp sensor.

Measuring the temp isn’t an issue, neither is operating the relay, however, I can get the 2 push buttons operating as ‘set temperature’ up and down,

But, when I have the temperature at a reading say 22C, if my set
point limits are 10-30 degrees, and have a hysteresis of 10 degrees, if I use the up button, the value scrolls up from the temp reading of 22 to 30…ok fine, if The set point is left at say 28 and I use the down button, the value goes from 28-26-25-24…etc, but when it hits the temp reading it just goes straight to 10…


*/
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(9, 8, 7, 6, 5, 4);


const int RELAY=12; //Lock Relay or motor

//Key connections with arduino
const int up_key=3;
const int down_key=2;

int SetPoint=30;
//=================================================================
// SETUP
//=================================================================
void setup(){

pinMode(RELAY,OUTPUT);
pinMode(up_key,INPUT);
pinMode(down_key,INPUT);

//Pull up for setpoint keys
digitalWrite(up_key,HIGH);
digitalWrite(down_key,HIGH);

// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print("Temp");
lcd.setCursor(0,1); //Move cursor to second Line
lcd.print("Controller");

 

[Chippie]

digitalWrite(RELAY,LOW); //Turn off Relay
delay(2000);
}
//=================================================================
// LOOP
//=================================================================
void loop(){
double Temperature = ((5.0/1024.0) * analogRead(A0)) * 100; //10mV per degree 0.01V/C. Scaling

lcd.setCursor(0,0);
lcd.print("Temperature:"); //Do not display entered keys
lcd.print(Temperature);

//Get user input for setpoints
if(digitalRead(down_key)==LOW)
{
if(SetPoint>0)
{
SetPoint--;
}
}
if(digitalRead(up_key)==LOW)
{
if(SetPoint<150)
{
SetPoint++;
}
}

//Display Set point on LCD
lcd.setCursor(0,1);
lcd.print("Set Point:");
lcd.print(SetPoint);
lcd.print("C ");

//Check Temperature is in limit
if(Temperature > SetPoint)
{
digitalWrite(RELAY,LOW); //Turn off heater

}
else
{
digitalWrite(RELAY,HIGH); //Turn on heater

}

delay(100); //Update at every 100mSeconds
}
//=================================================================

 

[Chippie]

The above code works fine without the hysteresis….

the extra code for that is replaced where necessary by this:


code

//Check Temperature is in limit
if((Temperature -5)> SetPoint)
{
digitalWrite(RELAY,LOW); //Turn off heater
}
if((Temperature +5)< SetPoint) { digitalWrite(RELAY,HIGH); //Turn on heater


//Check Temperature is in limit
if((Temperature -5)> SetPoint)
{
digitalWrite(RELAY,LOW); //Turn off heater


Conversely, if the temp reading is at say 15 degrees, and my set point is at 12, pressing the up set point button, the reading goes 12-13-14- then jumps straight to 30….

Im thinking this might be a switch bounce issue?

 

[ajlelectronics]

Thank you for providing the full code. It looks well-structured and covers the basic functionalities for temperature control using a relay and push buttons. However, there are a few suggestions for improvement:

1. Button Debouncing: To ensure accurate button readings, consider implementing button debouncing. This can be achieved by adding a small delay or using a more advanced debouncing technique.
2. Constants for Pin Definitions: Define constants for pin numbers to enhance code readability and make it easier to update pin configurations if needed.
3. Commenting: Consider adding comments to explain the purpose of different sections of your code. This will make it easier for you and others to understand the code in the future.
4. Temperature Scaling Constants: Instead of hardcoding the scaling factors for temperature readings, consider using constants to make the code more flexible and readable.

 

[ajlelectronics]

Here's a modified version of your code with these suggestions incorporated:


#include <LiquidCrystal.h>

LiquidCrystal lcd(9, 8, 7, 6, 5, 4);

const int RELAY = 12;
const int UP_KEY = 3;
const int DOWN_KEY = 2;

const int MIN_SETPOINT = 0;
const int MAX_SETPOINT = 150;

int SetPoint = 30;

// Constants for temperature scaling
const double VOLTAGE_PER_DEGREE = 5.0 / 1024.0;
const double SCALING_FACTOR = 100.0;

void setup() {
pinMode(RELAY, OUTPUT);
pinMode(UP_KEY, INPUT);
pinMode(DOWN_KEY, INPUT);

// Pull-up for setpoint keys
digitalWrite(UP_KEY, HIGH);
digitalWrite(DOWN_KEY, HIGH);

lcd.begin(16, 2);
lcd.print("Temp");
lcd.setCursor(0, 1);
lcd.print("Controller");
digitalWrite(RELAY, LOW); // Turn off Relay
delay(2000);
}

void loop() {
double Temperature = readTemperature();
displayTemperature(Temperature);
handleSetPointInput();
displaySetPoint();
controlRelay(Temperature);
delay(100); // Update every 100 milliseconds
}

double readTemperature() {
return (analogRead(A0) * VOLTAGE_PER_DEGREE) * SCALING_FACTOR;
}

void handleSetPointInput() {
if (digitalRead(DOWN_KEY) == LOW && SetPoint > MIN_SETPOINT) {
SetPoint--;
}

if (digitalRead(UP_KEY) == LOW && SetPoint < MAX_SETPOINT) {
SetPoint++;
}
}

void displayTemperature(double temp) {
lcd.setCursor(0, 0);
lcd.print("Temperature:");
lcd.print(temp);
}

void displaySetPoint() {
lcd.setCursor(0, 1);
lcd.print("Set Point:");
lcd.print(SetPoint);
lcd.print("C ");
}

void controlRelay(double temp) {
if (temp > SetPoint) {
digitalWrite(RELAY, LOW); // Turn off heater
} else {
digitalWrite(RELAY, HIGH); // Turn on heater
}
}

 

[ajlelectronics]

That is from ChatGPT, however I have found that you end up going around in circles and it is easier to do it yourself. It did however find a bug in one of mine where I had misspelt a variable name.

 

[Chippie]

AJL, thanks for the code, Ill give it a try....

I've just fired up the Arduino again, I have since found that if the current reading which is 16 C, if I now try to adjust the setpoint, that the fig 22 is significant for some reason....

If the setpoint is 10, winding it up the reading goes straight to 22, then 23-24-25 etc....if I leave it at say 27 and wind it back down it goes 27-26 to 22 then jumps to 10....

 

[Chippie]

Right, compiles the code and downloaded it to my test bed...All good, no errors...

I've amended the code by changing the delay to a longer time (700 ) and changed the upper and lower setpoint limits to 30 and 10...

All working good now...thanks...

But I really need to try and understand what the code is doing/meaning...Im not really a software bod , but I do like building hardware

 

[ajlelectronics]

But I really need to try and understand what the code is doing/meaning...Im not really a software bod , but I do like building hardware

You and me both! However, you can ask Chat GPT to explain any parts that you are unsure of. It's quite good for that sort of thing. https://openai.com/

 

[ajlelectronics]

I've amended the code by changing the delay to a longer time (700 ) and changed the upper and lower setpoint limits to 30 and 10...

If you are using delay(); that will cause you grief. It causes the loop to stop dead at that point and should be replaced with a millis(); routine. Look at the "blink without delay" example code.

 

[Chippie]

Thanks, I'll look into that and see where it leads me....

 

[Red'n'Black]

What @ajlelectronics has said, plus:

Do you know how bad the contact bounce is for the up / down set buttons you're using? 100 ms delay at the end of each loop should be more than adequate, but it would be good to confirm it with a scope. Do you have one?

If I've understood it right, all the phantom button presses occur when the set point crosses the actual temperature, which (presumably) causes the relay to switch? The switching noise from that could well be coupling into the button wiring. Does it still do it if you disconnect the heater?

The way I normally do button debouncing is to sample the pin quite a bit faster, say every 5 ms, and only register a button press if it sees at least (say) five HIGH samples followed by five LOW samples. Adjust as needed depending on how long the contact bounce goes on for on the ones you have. That would also filter out any relay switching noise, if that's what's causing the problem.

Any library functions you call in your loop() will add to the time, so you'll get 100 ms plus however long it spends calling the other functions in the loop. It shouldn't vary much in your case, but if it does matter, you can get much more consistent timing using the millis() or micros() functions as suggested instead of delay().

One of the guys at work wrote some debouncing code using these ideas which seems pretty robust, I'll take a look at it on Monday and post the relevant bits if you're interested.

 

[Kram]

Commenting: Consider adding comments to explain the purpose of different sections of your code. This will make it easier for you and others to understand the code in the future

No! Encapsulate code in well named functions and classes (a bit more advanced for arduino stuff).
Good code should not have any comments.

Cant remember the standard arduino ide is rubbish. The experience is much improved with VS code and the addon for it, name escapes me at the moment.

Visual Studio Code - Code Editing. Redefined

Visual Studio Code is a code editor redefined and optimized for building and debugging modern web and cloud applications. Visual Studio Code is free and available on your favorite platform - Linux, macOS, and Windows.

code.visualstudio.com

 

[ajlelectronics]

No! Encapsulate code in well named functions and classes (a bit more advanced for arduino stuff).
Good code should not have any comments.

Dom't tell me, that was ChatGPT.

 

[Kram]

Dom't tell me, that was ChatGPT.