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[on:]

Hi all!

I've got a project that I'm working on and wondered if the people of this forum could shed some light.

I basically want to open the vent on a greenhouse if the temperature reaches a set point. This will drive a bi directional motor. There will be two limit switches to ensure that the vent is completly open.

When the temperature drops back below another set point I would like the motor to drive in the opposite direction closing the vent untill both limit switches are in the oppose state.

I've attached a basic schematic of the system. Any help, guidance or information would be greatly apreciated.

[Reply #1 on:]

can be done relative easily

a starter how to set things up, some functions are incomplete that need still to be re written. (check tutorial section)

Code: ( partial code)

int highLimit = 25;
int lowLimit = 23;

int switchTop = 4;  // pin
int switchBottom = 5; // pin

void setup()
{
  Serial.begin(115200);   // for some feedback
  Serial.println("greenhouse 0.1");
}

void loop()
{
  int val = getTemperature();

  if (val > highLimit )
  {
    do
    {
      motorUP(1); // run motor for one second
    }
    while ( digitalRead(switchTop) == LOW);
  }

  if (val < lowLimit)
  {
    do
    {
      motorDown(1); // run motor down for one second
    }
    while ( digitalRead(switchBottom) == LOW);  // assume HIGH when at the end
  }
}

int getTemperature()
{
  return 10;
}

void motorUP(int t)
{
   delay(t*1000UL);
}

void motorDown(int t)
{
   delay(t*1000UL);
}

[Reply #2 on:]

Thats brilliant. Thanks very much.

All of that can be done with an Uno board?

[Reply #3 on:]

easily.

take care that the motor(s) need a separate power supply (connect GNDs for common reference)
and the motors need a diode against induction...

[Reply #4 on:]

Yeah cheers. Pretty apt with the electronics. Im an instrumentation technician by trade and did an electrical/electronic apprenticeship.

For testing purposes could I not just get a small voltage DC motor that can be supplied via the Arduino?

[Reply #5 on:]

Hi all. Just thought I would give a quick update on this project.

I have myself an Uno and a few components. For the temperature sensor I decided to go with a AD22100STZ. Its quite user friendly, it does all the linearisation on the chip so all I have to use is an equation given by the manufacturer on the data-sheet. I get about 0.2 DegC sensitivity due to the -50 to 150 and 10bit ADC ranges. I have here a quite precise stand alone temperature probe that I am going to carry out some comparison tests with which I will post when I have the results. I may be able to tweak the equation to get better accuracy.

The code is coming along nicely with some variable integer and floats. I am communicating and printing through the serial port. I have some if statements based on my required temperature setpoints which are currently just controlling a digital output which I will soon change to a PWM output to my servomotor which I just need to sort a power supply out for.

Code:

//temperature readout code

int outputpin = 13;
int inputpin = 1;
int inputmemory = 0; //use for the serial read
float tempout = 0;  //use for temperature out
float setpointhigh = 26.00; //high temperature setpoint
float setpointlow = 25.00; //low temperature setpoint

void setup()
{
  Serial.begin(9600);
  pinMode(outputpin, OUTPUT);
}

void loop()

{
  inputmemory = analogRead(inputpin); //read analogue pin on pin 1
 
  tempout = ((inputmemory*(5.0 / 1024))- 1.375) / 0.0225;
 
  Serial.print ("Temperature: ");
  Serial.println(tempout); //print temperature value to serial
 
  Serial.print ("ADC value: ");
  Serial.println(inputmemory); //print ADC value to serial
 
  if (tempout >= setpointhigh) digitalWrite(outputpin, HIGH); //high setpoint
 
  if (tempout <= setpointlow) digitalWrite(outputpin, LOW); //low setpoint
 
  delay(1000); //delay 1 second before next read

}

The forum is rubbish for uploading pictures so I will also be doing a blog over at http://partecsolutions.blogspot.co.uk/ if you want to check that out.

Any constructive criticism would be cool so just drop a message on here!