Ardunino Astronomical Pond Pump Controller with Frost Protection Update.

Now that we've actually had some cold weather in the UK, I've noticed a couple of minor issues with the controller.

Very occasionally, I've come down on a cold morning to find the controller hung up. I've traced this down to the request loop. When the temp falls too low, the temp sensor can't get the data out in time, and hangs the sketch up. I've slowed the loop down so the temperature is only requested once a minute.

This has also had two beneficial by-products :

1) The time display used to skip a second every now and again whilst the temperature was being requested.
2) The controller does not now repeatedly bounce on and off when the temp is hovering around 1 °C

Sketch follows:

// Dawn & Dusk controller with frost protection.
// 5th December 2014. Modified 28th Dec
// (C) A.G.Doswell 2014
//
// Date and time functions using a DS1307 RTC connected via I2C and Wire lib
//
// Designed to control a relay connected to pin A3. Pin goes low during daylight hours and high during night. Relay uses active low, so is
// "On" during the day. This is connected to the fountain pump in my garden.
//
// Time is set using a rotary encoder with integral push button. The Encoder is connected to interrupt pins D2 & D3 (and GND), 
// and the push button to pin analogue 0 (and GND)
// The RTC is connections are: Analogue pin 4 to SDA. Connect analogue pin 5 to SCL.
// A 2 x 16 LCD display is connected as follows (NOTE. This is NOT conventional, as interrupt pins are required for the encoder)
//  Arduino LCD  
//  D4      DB7
//  D5      DB6
//  D6      DB5
//  D7      DB4
//  D12     RS
//  D13     E
// 
// In this revision, there is a Dallas 18B20 Temperature sensor connected to pin 8, enabling frost protection. This is pulled up to +5volts via a 470K resistor.
//
// Use: Pressing and holding the button will enter the clock set mode (on release of the button). Clock is set using the rotary encoder. 
// The clock must be set to UTC.
// Pressing and releasing the button quickly will display the current sun rise and sun set times. Pressing the button again will enter the mode select menu. 
// Modes are AUTO: On when the sun rises, off when it sets.
//           ON: Permanently ON
//           OFF: Permanently OFF (Who'd have guessed it?)
//
// Change the LATTITUDE and LONGITUDE constant to your location.
// Use the address finder from http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html to find the address of your temperature sensor and enter it where required in DeviceAddress.
// 28th Dec 2014 - Slowed the rate at which the temperature is requested down to once per minute. It has improved the clock display, and solved an issue whereby the temp sensor wasn't always ready to send data, and hung up.
// 
// Be sure to visit my website at http://andydoz.blogspot.com

#include <Wire.h>
#include "RTClib.h" // from https://github.com/adafruit/RTClib
#include <LiquidCrystal.h>
#include <Encoder.h> // from http://www.pjrc.com/teensy/td_libs_Encoder.html
#include <TimeLord.h> // from http://swfltek.com/arduino/timelord.html. When adding it to your IDE, rename the file, removing the "-depreciated" 
#include <OneWire.h> // from http://playground.arduino.cc/Learning/OneWire
#include <DallasTemperature.h> // from http://www.hacktronics.com/code/DallasTemperature.zip. When adding this to your IDE, ensure the .h and .cpp files are in the top directory of the library.


#define ONE_WIRE_BUS 8 // Data wire from temp sensor is plugged into pin 8 on the Arduino
OneWire oneWire(ONE_WIRE_BUS); // Setup a oneWire instance to communicate with any OneWire devices
DeviceAddress outsideThermometer = { 0x28, 0x1A, 0x1A, 0x3E, 0x06, 0x00, 0x00,0xC7 }; // use the address finder from http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html to find the address of your device.
RTC_DS1307 RTC; // Tells the RTC library that we're using a DS1307 RTC
Encoder knob(2, 3); //encoder connected to pins 2 and 3 (and ground)
LiquidCrystal lcd(12, 13, 7, 6, 5, 4); // I used an odd pin combination because I need pin 2 and 3 for the interrupts.
//the variables provide the holding values for the set clock routine
int setyeartemp; 
int setmonthtemp;
int setdaytemp;
int sethourstemp;
int setminstemp;
int setsecs = 0;
int maxday; // maximum number of days in the given month
int TimeMins = 0; // number of seconds since midnight
int TimerMode = 2; //mode 0=Off 1=On 2=Auto
int TimeOut = 10;
int TimeOutCounter;

// These variables are for the push button routine
int buttonstate = 0; //flag to see if the button has been pressed, used internal on the subroutine only
int pushlengthset = 3000; // value for a long push in mS
int pushlength = pushlengthset; // set default pushlength
int pushstart = 0;// sets default push value for the button going low
int pushstop = 0;// sets the default value for when the button goes back high

int knobval; // value for the rotation of the knob
boolean buttonflag = false; // default value for the button flag
float tempC; // Temperature


const int TIMEZONE = 0; //UTC
const float LATITUDE = 51.89, LONGITUDE = -2.04; // set YOUR position here 
int Sunrise, Sunset; //sunrise and sunset expressed as minute of day (0-1439)
TimeLord myLord; // TimeLord Object, Global variable
byte sunTime[]  = {0, 0, 0, 1, 1, 13}; // 17 Oct 2013
int SunriseHour, SunriseMin, SunsetHour, SunsetMin; //Variables used to make a decent display of our sunset and sunrise time.
DallasTemperature sensors(&oneWire); // Pass our oneWire reference to Dallas Temperature.

void setup () {
    //Serial.begin(57600); //start debug serial interface
    Wire.begin(); //start I2C interface
    RTC.begin(); //start RTC interface
    lcd.begin(16,2); //Start LCD (defined as 16 x 2 characters)
    lcd.clear(); 
    pinMode(A0,INPUT);//push button on encoder connected to A0 (and GND)
    digitalWrite(A0,HIGH); //Pull A0 high
    pinMode(A3,OUTPUT); //Relay connected to A3
    digitalWrite (A3, HIGH); //sets relay off (default condition)
    sensors.begin();
    sensors.setResolution(outsideThermometer, 12); // set the resolution to 12 bits (why not?!)
    
    //Checks to see if the RTC is runnning, and if not, sets the time to the time this sketch was compiled.
    if (! RTC.isrunning()) {
    RTC.adjust(DateTime(__DATE__, __TIME__));
  }
 
 
    //Timelord initialisation
    myLord.TimeZone(TIMEZONE * 60);
    myLord.Position(LATITUDE, LONGITUDE);
    CalcSun ();
}
           
void printTemperature(DeviceAddress deviceAddress)
{
  lcd.setCursor (9,1);
  tempC = sensors.getTempC(deviceAddress);
  if (tempC == -127.00) {
    lcd.print("Err");
  } else {
    
    lcd.print(tempC);
    lcd.print((char)0xDF);
    lcd.print("C ");
   
  }
}


void loop () {
    

  
    DateTime now = RTC.now(); //get time from RTC
    //Display current time
    lcd.setCursor (0,0);
    lcd.print(now.day(), DEC);
    lcd.print('/');
    lcd.print(now.month());
    lcd.print('/');
    lcd.print(now.year(), DEC);
    lcd.print(" ");
    lcd.setCursor (0,1);
    lcd.print(now.hour(), DEC);
    lcd.print(':');
    if (now.minute() <10) 
      {
        lcd.print("0");
      }
    lcd.print(now.minute(), DEC);
    lcd.print(':');
    if (now.second() <10) 
      {
        lcd.print("0");
      }
    lcd.print(now.second());
    lcd.print(" ");
    
    //current time in minutes since midnight (used to check against sunrise/sunset easily)
    TimeMins = (now.hour() * 60) + now.minute();
   
    
    //Get and display temp every minute
    if (now.second() == 10) {
      sensors.requestTemperatures(); // Request temperature
      printTemperature(outsideThermometer); // display on lcd.
    }
    
    // Calculate sun times once a day at a minute past midnight
    if (TimeMins == 1) {
      CalcSun ();
    }
    if (TimerMode ==2) {
      if (TimeMins >= Sunrise && TimeMins <=Sunset-1 && tempC>=2) { //If it's after sunrise and before sunset, and it's not frozen, switch our relay on
          digitalWrite (A3, LOW);
          lcd.setCursor (13,0);
          lcd.print ("On ");
        }
        else {  //otherwise switch it off
          digitalWrite (A3, HIGH);
          lcd.setCursor (13,0);
          lcd.print ("Off");
        }
      }
       if (TimerMode ==0) {
         digitalWrite (A3, HIGH);
         lcd.setCursor (13,0);
         lcd.print ("Off");
       }
     
       if (TimerMode ==1) {
         digitalWrite (A3, LOW);
         lcd.setCursor (13,0);
         lcd.print ("On ");
       }
       

    
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    delay (10);
    
    if (pushlength <pushlengthset) {
      lcd.clear ();
      ShortPush ();   
      lcd.clear ();
    }
    
       
       //This runs the setclock routine if the knob is pushed for a long time
       if (pushlength >pushlengthset) {
         lcd.clear();
         DateTime now = RTC.now();
         setyeartemp=now.year(),DEC;
         setmonthtemp=now.month(),DEC;
         setdaytemp=now.day(),DEC;
         sethourstemp=now.hour(),DEC;
         setminstemp=now.minute(),DEC;
         setclock();
         pushlength = pushlengthset;
       };
}

//sets the clock
void setclock (){
   setyear ();
   lcd.clear ();
   setmonth ();
   lcd.clear ();
   setday ();
   lcd.clear ();
   sethours ();
   lcd.clear ();
   setmins ();
   lcd.clear();
   RTC.adjust(DateTime(setyeartemp,setmonthtemp,setdaytemp,sethourstemp,setminstemp,setsecs)); //set the DS1307 RTC
   CalcSun (); //refresh the sunrise and sunset times
   delay (1000);
   
}

// subroutine to return the length of the button push.
int getpushlength () {
  buttonstate = digitalRead(A0);  
       if(buttonstate == LOW && buttonflag==false) {     
              pushstart = millis();
              buttonflag = true;
          };
          
       if (buttonstate == HIGH && buttonflag==true) {
         pushstop = millis ();
         pushlength = pushstop - pushstart;
         buttonflag = false;
       };
       return pushlength;
}
// The following subroutines set the individual clock parameters
int setyear () {
   lcd.setCursor (0,0);
    lcd.print ("Set Year");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return setyeartemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) { //bit of software de-bounce
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    setyeartemp=setyeartemp + knobval;
    if (setyeartemp < 2014) { //Year can't be older than currently, it's not a time machine.
      setyeartemp = 2014;
    }
    lcd.print (setyeartemp);
    lcd.print("  "); 
    setyear();
}
  
int setmonth () {

   lcd.setCursor (0,0);
    lcd.print ("Set Month");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return setmonthtemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    setmonthtemp=setmonthtemp + knobval;
    if (setmonthtemp < 1) {// month must be between 1 and 12
      setmonthtemp = 1;
    }
    if (setmonthtemp > 12) {
      setmonthtemp=12;
    }
    lcd.print (setmonthtemp);
    lcd.print("  "); 
    setmonth();
}

int setday () {
  if (setmonthtemp == 4 || setmonthtemp == 5 || setmonthtemp == 9 || setmonthtemp == 11) { //30 days hath September, April June and November
    maxday = 30;
  }
  else {
  maxday = 31; //... all the others have 31
  }
  if (setmonthtemp ==2 && setyeartemp % 4 ==0) { //... Except February alone, and that has 28 days clear, and 29 in a leap year.
    maxday = 29;
  }
  if (setmonthtemp ==2 && setyeartemp % 4 !=0) {
    maxday = 28;
  }
  
   lcd.setCursor (0,0);
    lcd.print ("Set Day");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return setdaytemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    setdaytemp=setdaytemp+ knobval;
    if (setdaytemp < 1) {
      setdaytemp = 1;
    }
    if (setdaytemp > maxday) {
      setdaytemp = maxday;
    }
    lcd.print (setdaytemp);
    lcd.print("  "); 
    setday();
}

int sethours () {
    lcd.setCursor (0,0);
    lcd.print ("Set Hours");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return sethourstemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    sethourstemp=sethourstemp + knobval;
    if (sethourstemp < 1) {
      sethourstemp = 1;
    }
    if (sethourstemp > 23) {
      sethourstemp=23;
    }
    lcd.print (sethourstemp);
    lcd.print("  "); 
    sethours();
}

int setmins () {

   lcd.setCursor (0,0);
    lcd.print ("Set Mins");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return setminstemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    setminstemp=setminstemp + knobval;
    if (setminstemp < 0) {
      setminstemp = 0;
    }
    if (setminstemp > 59) {
      setminstemp=59;
    }
    lcd.print (setminstemp);
    lcd.print("  "); 
    setmins();
}

int setmode () { //Sets the mode of the timer. Auto, On or Off

    lcd.setCursor (0,0);
    lcd.print ("Set Mode");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return TimerMode;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    TimerMode=TimerMode + knobval;
    if (TimerMode < 0) {
      TimerMode = 0;
    }
    if (TimerMode > 2) {
      TimerMode=2;
    }
    if (TimerMode == 0) {
    lcd.print("Off");
    lcd.print("  "); 
    }
    if (TimerMode == 1) {
    lcd.print("On");
    lcd.print("  "); 
    }
    if (TimerMode == 2) {
    lcd.print("Auto");
    lcd.print("  "); 
    }
    setmode ();
}

int CalcSun () { //Calculates the Sunrise and Sunset times
    DateTime now = RTC.now();
    sunTime[3] = now.day(); // Give Timelord the current date
    sunTime[4] = now.month();
    sunTime[5] = now.year();
    myLord.SunRise(sunTime); // Computes Sun Rise.
    Sunrise = sunTime[2] * 60 + sunTime[1]; // Sunrise returned in minutes past midnight
    SunriseHour = sunTime[2];
    SunriseMin = sunTime [1];
    sunTime[3] = now.day(); // Uses the Time library to give Timelord the current date
    sunTime[4] = now.month();
    sunTime[5] = now.year();
    myLord.SunSet(sunTime); // Computes Sun Set.
    Sunset = sunTime[2] * 60 + sunTime[1]; // Sunset returned in minutes past midnight
    SunsetHour = sunTime[2];
    SunsetMin = sunTime [1];
}

void ShortPush () {
  //This displays the calculated sunrise and sunset times when the knob is pushed for a short time.
for (long Counter = 0; Counter < 604 ; Counter ++) { //returns to the main loop if it's been run 604 times 
                                                     //(don't ask me why I've set 604,it seemed like a good number)
  lcd.setCursor (0,0);
  lcd.print ("Sunrise ");
  lcd.print (SunriseHour);
  lcd.print (":");
  if (SunriseMin <10) 
     {
     lcd.print("0");
     }
  lcd.print (SunriseMin);
  lcd.setCursor (0,1);
  lcd.print ("Sunset ");
  lcd.print (SunsetHour);
  lcd.print (":"); 
    if (SunsetMin <10) 
     {
     lcd.print("0");
     }
  lcd.print (SunsetMin);        

    
  //If the knob is pushed again, enter the mode set menu
  pushlength = pushlengthset;
  pushlength = getpushlength ();
  if (pushlength != pushlengthset) {
    lcd.clear ();
    TimerMode = setmode ();

  }
  
}



}
  
 

Dehumidifer data rate.

Since slowing down the frequency of transmission from the controller in the attic, it has become apparent how many transmissions were being lost, either to the data logging receiver or the remote display. Looking back over historical data, the lost in % of expected transmission is much the same as now, just that there are now fewer!

To try and minimise the loss of transmissions, I spent a little time messing with the location of the transmitter and receivers. I also used my scanner tuned to 433.920 MHz to measure the signal strength. It appears everything is little "on the limit".

To try and improve the link margin, I dropped the data rate to a very pedestrian 75 BPS. This didn't really help much. I've got the link to the data logging PC pretty much 100% now, which is good, but the remote display is a little further away, so it does drop the odd message or two, so I've added a timer into the remote receiver sketch, so if a message falls overdue, "O/D" is written to the top right of the display instead of "On" or "off". At least I then know if the data is current or not.

Here's the sketch:

// Receiver Sketch for Dehumidifier controller project
// Written by A.G.Doswell 23 May 2014, modified 18 Dec 2014
// LCD is a Hitachi HD44780 or compatible, attached thus:
// LCD RS pin to digital pin 12
// LCD Enable pin to digital pin 11
// LCD D4 pin to digital pin 5
// LCD D5 pin to digital pin 4
// LCD D6 pin to digital pin 3
// LCD D7 pin to digital pin 2
// RW to GND
// V0 Held high (this may or may not work with your LCD, usual practice is to connect this to a 10K pot between +5 and GND)
// Receiver connected to pin 9


#include <VirtualWire.h>
#include <VirtualWire_Config.h>
#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

int TX_ID =10;
int Temp;
int Humidity;
int Dew;
boolean Output;
unsigned long timer = 0;
unsigned long timer2;



void setup() {
              lcd.begin (16, 2);
              // Virtualwire setup
              vw_set_tx_pin(10); // Even though it's not used, we'll define it so the default doesn't interfere with the LCD library.
              vw_set_rx_pin(9); // RX pin set to pin 9
              vw_setup(75); //sets virtualwire for a tx rate of 75 bits per second, nice and slow! 
              vw_rx_start();     
              }  
void loop()
{
typedef struct rxRemoteData //Defines the received data, this is the same as the TX struct
{
int    TX_ID; 
int    Temp;   
int    Humidity;
int    Dew;
boolean Output;
};

struct rxRemoteData receivedData;
uint8_t rcvdSize = sizeof(receivedData);
timer2 = millis(); // capture current time
if (timer2 > timer+200000) { //if it's more than 200 seconds since the last time a message was received write O/D to the display (overdue)
  lcd.setCursor (13,0);
       lcd.print ("O/D");
}

if (vw_get_message((uint8_t *)&receivedData, &rcvdSize)) 
{
  if (receivedData.TX_ID == 10)     { //Only if the TX_ID=10 do we process the data.
    lcd.setCursor(13,0);
    lcd.print (" Rx");
    delay (100);
    int TX_ID = receivedData.TX_ID;
    int Temp = receivedData.Temp;
    int Humidity = receivedData.Humidity;
    int Dew = receivedData.Dew;
    boolean Output = receivedData.Output;
    
        
      // writes the received data to the LCD
  lcd.clear ();
  lcd.print("Humidity:");
  lcd.print(Humidity);
  lcd.print("%");
  lcd.setCursor(0, 1);
  lcd.print(Temp);
  lcd.print((char)0xDF);
  lcd.print("C");
  lcd.setCursor(6, 1);
  lcd.print("Dew:");
  lcd.print(Dew);
  lcd.print((char)0xDF);
  lcd.print("C");
  
  if (Output == true) {
      lcd.setCursor (13,0);
      lcd.print (" On");
    
  }
     else {
       lcd.setCursor (13,0);
       lcd.print ("off");

           }
  
      } 
timer = millis(); // reset timer
  }
}

// End of file

**STOP PRESS!!!

Range has continued to be poor. So I revisited the remote receiver hardware. In my haste to get it running there was only the very minor decouling of the PSU on the Arduino pro mini board itself. I've added a 10uF cap to the power supply input to the receiver module and 100uF on the output of the 5V regulator. Range is now MUCH improved. 

A sad end ... and a new beginning.

Ladies and gentlemen, please. A moment of silence for the workshop's Weller TCP soldering iron.

Since 1995, it has provided many hours of soldering. Repaired countless electronic circuits. Outlasted two marriages. Been a loyal friend. Last month saw the need for a new tip. But, alas, the old one had seized into the element's housing. After a liberal soaking in Plus-gas (other penetrating oils are available), freezing & heating,  the element failed to recover from the procedure.

Thankfully, a new element was just a day away (Here eBay is not your friend. Elements on eBay were very expensive. I got mine from RS Components)

The iron-y (ouch!) is that you need a soldering iron to fit it. Anyway, I have several irons, but none so good as the venerable Weller!

Here's to the next 19 years of service!!

NAD 310 repair.

This nice little 90's amp found it's way to me with the comment ...

"Just needs a squirt of switch cleaner, one of the volume controls doesn't work"

Sadly not.... and I can see marks on the PCB where someone had been liberally spraying the stuff at the poor innocent volume control!

What happens is the joints break up between the volume pots and the PCB... leading to an intermittent or non-existent connection.

A quick solder up of these joints provides a long lasting repair.... if only it was a quick job. Most amplifiers of this design require a considerable amount of disassembly to get to the joints. Joints to and from the phono connectors on back panels present a similar problem.

Just to show you how long this sort of thing takes, here's a time-lapse video I made (and I wanted an excuse to try some sort of overhead camera thing!). This repair took an hour!


... still better than a "soundbar" or other hideous self contained speaker.

Arduino Dehumidifier Controller Failure, and Upgrade!

The dehumidifier controller has been performing faultlessly throughout the summer months. And I've done the geeky thing and plotted the data out on a month by month basis. Humidity has been relatively steady...

Every month has seen the odd un-explainable spike, but other than that it's all been good.

Now the weather has gone colder, I'm a bit concerned about the state of things up there in the attic, but have been keeping an eye on it, and it's been dry, until last week, when there was signs of condensation. I started to contemplate moving the switch point in the sketch to bring the dehumidifier on a little earlier, especially as the actual roof will be cooler than the surrounding air. And also maybe a loop which runs the dehumidifier for an hour every now-and-again, just to make sure it's still working OK (it didn't run for months during the summer).

Also, one months data is 3GB ! Which takes Open Office Calc a little while to plot (like hours), so I thought about slowing the transmission rate down again. Anyway, most of this was a little way down the list of things to do... until Monday, when the kitchen display shows the following....

Now, it's a few degrees above freezing outside, and there's no way it's a balmy 60 in my attic, unless it's on fire.

I go into the attic and reset the box. Nope, same lies there.

I bring the box downstairs and do a few checks. 5v is nice and steady. I re-load the sketch and libraries. No, still the same. I load a simple test sketch provided with the library, and the same lies are repeated via the serial monitor.

So, it's most likely the DHT11 itself has a screw-loose, and has fond memories for hot summer's days!

I think this is a good opportunity to re-engineer the sketch slightly, and have a play with oh-so-very nice DHT22.



Now the DHT22 (A.K.A. RHT03 or  AM2302) has almost the same form factor as the DHT11, is catered for by our library, has the same pinouts, and has better accuracy and does a wider range of temperature (goes negative too) and humidity. It's a little bit more expensive.

I also decide to decrease the transmission rate to one every 198 seconds, and to bring the dehumidifier on when the dew point is within 10 degrees of the temperature. Also, regardless of temperature or humidity, the dehumidifer is run once every 259,200 seconds (or 3 days) just to keep the dehumidifier running and humidity low.

 Sensible figures now...

... and negative if it gets cold up there!









Here's the sketch:

// Wireless dehumidifier Controller
// 
// Copyright Andy Doswell 24th May 2014 modified Dec 2014
// PURPOSE: DHT22 sensor with LCD Display and output for controlling dehumidifier.
// Data send via virtualwire and 433MHZ link to remote display
// Dehumidifier is controlled by a relay attached to pin 7, defined in rlyPin.
// DHT22 sensor is connected to 8, as defined in #define
// LCD is a Hitachi HD44780 or compatible, attached thus:
// LCD RS pin to digital pin 12
// LCD Enable pin to digital pin 11
// LCD D4 pin to digital pin 5
// LCD D5 pin to digital pin 4
// LCD D6 pin to digital pin 3
// LCD D7 pin to digital pin 2
// RW to GND
// V0 Held high (this may or may not work with your LCD, usual practice is to connect this to a 10K pot between +5 and GND)
// TX connected to pin 10
// Modified to transmit every 198 seconds, and to switch dehumidifier on when Dewpoint is within 10 Degrees of actual temperature
// Also brings dehumidifer on every 3 days regardless of temperature or humidity.
// You'll need the wonderful dht library by Rob Tillaart from here : https://github.com/RobTillaart/Arduino/tree/master/libraries/DHTlib 
// and the equally wonderful Virtualwire library from here :https://www.pjrc.com/teensy/td_libs_VirtualWire.html


// reference: http://en.wikipedia.org/wiki/Dew_point
double dewPointFast(double celsius, double humidity)
{
 double a = 17.271;
 double b = 237.7;
 double temp = (a * celsius) / (b + celsius) + log(humidity*0.01);
 double Td = (b * temp) / (a - temp);
 return Td;
}

#include <VirtualWire.h>
#include <VirtualWire_Config.h>

#include <dht.h>


dht DHT;

#define DHT22_PIN 8

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

// define constants & global variables
const int rlyPin = 7; //defines pin the relay is connected to. relay is active low
const int TimerLength = 1800;// number of seconds in an hour / 2 - this sets the minimum time the dehumidifier will remain on for.
int Timer = 0; //timer is off to start
boolean DewFlag = false; // This is the dew flag. Off as default.
boolean OutputStatus = false; //Output status is off as default
int chk;
int Temp;
int Dew;
int Humidity;
int DewTrip;
float Timer2 = 0;


// Data structure set up for Transmission

struct TXData
{
  int TX_ID;
  int Temp;
  int Humidity;
  int Dew;
  boolean Output;
};
  

void setup()
{
  lcd.begin(16, 2); // defines the LCD as a 16 x 2
  pinMode (rlyPin, OUTPUT); // sets our relay pin
  digitalWrite (rlyPin, HIGH); // sets the relay off for default condition.
  
  // Virtualwire setup
  vw_set_tx_pin(10); // TX pin set to 10
  vw_set_rx_pin(9); // RX pin set to a spare pin, even though we don't use it. If left as default it interferes with LCD operation.
  vw_setup(300); //sets virtualwire for a tx rate of 300 bits per second
  

}

void loop()
{
  for(int i = 0; i < 100 ; i++) { //transmit only every 99 loops (198 seconds)
    chk = DHT.read22(DHT22_PIN); // these 4 lines get data from the sensor
    Dew = dewPointFast(DHT.temperature, DHT.humidity);
    Temp = (DHT.temperature);
    Humidity = (DHT.humidity);
    DewTrip= Dew + 10; // Brings the dehumidifier on 5 deg C before the dew point. 
  
    // writes information about the system to the LCD
    lcd.clear ();
    lcd.print("Humidity:");
    lcd.print(Humidity);
    lcd.print("%");
    lcd.setCursor(0, 1);
    lcd.print(Temp);
    lcd.print((char)0xDF);
    lcd.print("C");
    lcd.setCursor(6, 1);
    lcd.print("Dew:");
    lcd.print(Dew);
    lcd.print((char)0xDF);
    lcd.print("C");
   
  // Dew detect loop. If the dewTrip point is reached, start the timer running and set the Dew flag
    if ( Temp <= DewTrip || Timer2 == 129600 ) {
      DewFlag = true;
      Timer = 1;    
      Timer2 = 0;   
    } 
    else {
      DewFlag = false;
    }

  
    if (Timer >= TimerLength and DewFlag == false) { // If the timer has expired and there's no dew, switch the dehumidifier off.
      Timer = 0;
      digitalWrite (rlyPin, HIGH);
   
    }

    if (Timer !=0) {                // If the timer is running, switch the dehumidifier on , and write On to the lcd.
      digitalWrite (rlyPin, LOW);
      lcd.setCursor (13,0);
      lcd.print (" On");
      OutputStatus = true;
      Timer++;
    }
  
    else {
      lcd.setCursor (13,0);
      lcd.print ("off");
      OutputStatus = false;
    }
  
 delay (2000);
 Timer2 ++;
  }
  


  
struct TXData payload; //Loads the Data struct with the payload data
lcd.clear ();
lcd.print ("Transmitting");
  
payload.TX_ID=10;
payload.Temp = Temp;
payload.Humidity = Humidity;
payload.Dew = Dew;
payload.Output = OutputStatus;
vw_send((uint8_t *)&payload, sizeof(payload)); //Transmits the struct
vw_wait_tx(); //waits for the TX to complete

}  
  

Arduino astronomical clock pond pump controller (now with added frost protection)

Time to revisit a project from August...

It's December, the weather forecast for this weekend looks cold.

"What happens if the pond freezes"? asks the wife.

Ugh! I hadn't though of that when I originally came up with the pond pump controller.

In my installation it will be the weir that freezes first, the pump will probably be OK, but empty the pond as the weir will spill over where it's not wanted... so what we need is temperature protection.

Now we've looked at measuring temperature and humidity before here, but this time we need to be measuring low temperatures. Now the DHT11 is a fine device, but it won't go negative, so is unsuitable.

Enter the Maxim (formerly Dallas) DS18B20 IC. Looks like a small transistor (TO-92) package when naked. Find the data here.

Terrific little guy, communicates on a one-wire interface, and is dirt cheap.

I chose an encapsulated temperature probe type from eBay, change from £2!

Superb.

First problem is it doesn't say which wires are which. Mine came with red, green and yellow wires.

Red is +5V Yellow is GND and Green is data.

Marvellous, sealed and a lead long enough to go out through the hole in the wall.

Now we'll need a couple of libraries, and the lovely people at hacktonics have produced a great guide, which I suggest you take a few minutes to read.  http://www.hacktronics.com/Tutorials/arduino-digital-temperature-sensor-tutorial.html

OK, so we'll cobble up our sensor to a spare Arduino, data to pin 3, and a 4.7 Kohm pull up from there to +5 volts.

We'll need to find out the address for our sensor. The beauty of this system is we can hang many sensors off our one wire. We only need one, but we'll still need to find it's address.

Go here: http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.htm and get the one wire library, the dallas library and the address finder sketch. Load the whole shebang into the IDE. I had issues getting the DallasTemperature library to install. Just make sure the .h and .cpp files are in the top directory, and not hidden one down, otherwise the IDE won't find them.

Once you've got that running, open a serial monitor, and the sketch should provide you with the address. In my example it was 0x28, 0x1A, 0x1A, 0x3E, 0x06, 0x00, 0x00,0xC7 write your address down, as you'll need to enter it into the sketch.

Load up the sketch from below, and wire your sensor to +5v and GND, but this time the pull up and data wire to pin 8 (we used pin 3 for the encoder)

I've moved the display around a bit to accommodate temperature display, and there's a minor change to the way the screen is refreshed after returning from a subroutine, to prevent old data being retained on the display. Of course now the output will only be on when the sun's up AND it's not freezing!

Here's the sketch....

// Dawn & Dusk controller with frost protection.
// 5th December 2014.
// (C) A.G.Doswell 2014
//
// Date and time functions using a DS1307 RTC connected via I2C and Wire lib
//
// Designed to control a relay connected to pin A3. Pin goes low during daylight hours and high during night. Relay uses active low, so is
// "On" during the day. This is connected to the fountain pump in my garden.
//
// Time is set using a rotary encoder with integral push button. The Encoder is connected to interrupt pins D2 & D3 (and GND), 
// and the push button to pin analogue 0 (and GND)
// The RTC is connections are: Analogue pin 4 to SDA. Connect analogue pin 5 to SCL.
// A 2 x 16 LCD display is connected as follows (NOTE. This is NOT conventional, as interrupt pins are required for the encoder)
//  Arduino LCD  
//  D4      DB7
//  D5      DB6
//  D6      DB5
//  D7      DB4
//  D12     RS
//  D13     E
// 
// In this revision, there is a Dallas 18B20 Temperature sensor connected to pin 8, enabling frost protection. This is pulled up to +5volts via a 470K resistor.
//
// Use: Pressing and holding the button will enter the clock set mode (on release of the button). Clock is set using the rotary encoder. 
// The clock must be set to UTC.
// Pressing and releasing the button quickly will display the current sun rise and sun set times. Pressing the button again will enter the mode select menu. 
// Modes are AUTO: On when the sun rises, off when it sets.
//           ON: Permanently ON
//           OFF: Permanently OFF (Who'd have guessed it?)
//
// Change the LATTITUDE and LONGITUDE constant to your location.
// Use the address finder from http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html to find the address of your temperature sensor and enter it where required in DeviceAddress.
// 
// Be sure to visit my website at http://andydoz.blogspot.com

#include <Wire.h>
#include "RTClib.h" // from https://github.com/adafruit/RTClib
#include <LiquidCrystal.h>
#include <Encoder.h> // from http://www.pjrc.com/teensy/td_libs_Encoder.html
#include <TimeLord.h> // from http://swfltek.com/arduino/timelord.html. When adding it to your IDE, rename the file, removing the "-depreciated" 
#include <OneWire.h> // from http://playground.arduino.cc/Learning/OneWire
#include <DallasTemperature.h> // from http://www.hacktronics.com/code/DallasTemperature.zip. When adding this to your IDE, ensure the .h and .cpp files are in the top directory of the library.


#define ONE_WIRE_BUS 8 // Data wire from temp sensor is plugged into pin 8 on the Arduino
OneWire oneWire(ONE_WIRE_BUS); // Setup a oneWire instance to communicate with any OneWire devices
DeviceAddress outsideThermometer = { 0x28, 0x1A, 0x1A, 0x3E, 0x06, 0x00, 0x00,0xC7 }; // use the address finder from http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html to find the address of your device.
RTC_DS1307 RTC; // Tells the RTC library that we're using a DS1307 RTC
Encoder knob(2, 3); //encoder connected to pins 2 and 3 (and ground)
LiquidCrystal lcd(12, 13, 7, 6, 5, 4); // I used an odd pin combination because I need pin 2 and 3 for the interrupts.
//the variables provide the holding values for the set clock routine
int setyeartemp; 
int setmonthtemp;
int setdaytemp;
int sethourstemp;
int setminstemp;
int setsecs = 0;
int maxday; // maximum number of days in the given month
int TimeMins; // number of seconds since midnight
int TimerMode = 2; //mode 0=Off 1=On 2=Auto
int TimeOut = 10;
int TimeOutCounter;

// These variables are for the push button routine
int buttonstate = 0; //flag to see if the button has been pressed, used internal on the subroutine only
int pushlengthset = 3000; // value for a long push in mS
int pushlength = pushlengthset; // set default pushlength
int pushstart = 0;// sets default push value for the button going low
int pushstop = 0;// sets the default value for when the button goes back high

int knobval; // value for the rotation of the knob
boolean buttonflag = false; // default value for the button flag
float tempC; // Temperature


const int TIMEZONE = 0; //UTC
const float LATITUDE = 51.89, LONGITUDE = -2.04; // set YOUR position here 
int Sunrise, Sunset; //sunrise and sunset expressed as minute of day (0-1439)
TimeLord myLord; // TimeLord Object, Global variable
byte sunTime[]  = {0, 0, 0, 1, 1, 13}; // 17 Oct 2013
int SunriseHour, SunriseMin, SunsetHour, SunsetMin; //Variables used to make a decent display of our sunset and sunrise time.
DallasTemperature sensors(&oneWire); // Pass our oneWire reference to Dallas Temperature.

void setup () {
    //Serial.begin(57600); //start debug serial interface
    Wire.begin(); //start I2C interface
    RTC.begin(); //start RTC interface
    lcd.begin(16,2); //Start LCD (defined as 16 x 2 characters)
    lcd.clear(); 
    pinMode(A0,INPUT);//push button on encoder connected to A0 (and GND)
    digitalWrite(A0,HIGH); //Pull A0 high
    pinMode(A3,OUTPUT); //Relay connected to A3
    digitalWrite (A3, HIGH); //sets relay off (default condition)
    sensors.begin();
    sensors.setResolution(outsideThermometer, 12); // set the resolution to 12 bits (why not?!)
    
    //Checks to see if the RTC is runnning, and if not, sets the time to the time this sketch was compiled.
    if (! RTC.isrunning()) {
    RTC.adjust(DateTime(__DATE__, __TIME__));
  }
 
 
    //Timelord initialisation
    myLord.TimeZone(TIMEZONE * 60);
    myLord.Position(LATITUDE, LONGITUDE);
    CalcSun ();
}
           
void printTemperature(DeviceAddress deviceAddress)
{
  lcd.setCursor (9,1);
  tempC = sensors.getTempC(deviceAddress);
  if (tempC == -127.00) {
    Serial.print("Err");
  } else {
    
    lcd.print(tempC);
    lcd.print((char)0xDF);
    lcd.print("C ");
   
  }
}

void loop () {
    sensors.requestTemperatures(); // Request temperature
    printTemperature(outsideThermometer); // display on lcd.
    DateTime now = RTC.now(); //get time from RTC
    //Display current time
    lcd.setCursor (0,0);
    lcd.print(now.day(), DEC);
    lcd.print('/');
    lcd.print(now.month());
    lcd.print('/');
    lcd.print(now.year(), DEC);
    lcd.print(" ");
    lcd.setCursor (0,1);
    lcd.print(now.hour(), DEC);
    lcd.print(':');
    if (now.minute() <10) 
      {
        lcd.print("0");
      }
    lcd.print(now.minute(), DEC);
    lcd.print(':');
    if (now.second() <10) 
      {
        lcd.print("0");
      }
    lcd.print(now.second());
    lcd.print(" ");
    
    //current time in minutes since midnight (used to check against sunrise/sunset easily)
    TimeMins = (now.hour() * 60) + now.minute();
    
    // Calculate sun times once a day at a minute past midnight
    if (TimeMins == 1) {
      CalcSun ();
    }
    if (TimerMode ==2) {
      if (TimeMins >= Sunrise && TimeMins <=Sunset-1 && tempC>=1) { //If it's after sunrise and before sunset, and it's not frozen, switch our relay on
          digitalWrite (A3, LOW);
          lcd.setCursor (13,0);
          lcd.print ("On ");
        }
        else {  //otherwise switch it off
          digitalWrite (A3, HIGH);
          lcd.setCursor (13,0);
          lcd.print ("Off");
        }
      }
       if (TimerMode ==0) {
         digitalWrite (A3, HIGH);
         lcd.setCursor (13,0);
         lcd.print ("Off");
       }
     
       if (TimerMode ==1) {
         digitalWrite (A3, LOW);
         lcd.setCursor (13,0);
         lcd.print ("On ");
       }
       
       sensors.requestTemperatures(); // Request temperature
       printTemperature(outsideThermometer); // display on lcd.
    
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    delay (10);
    
    if (pushlength <pushlengthset) {
      lcd.clear ();
      ShortPush ();   
      lcd.clear ();
    }
    
       
       //This runs the setclock routine if the knob is pushed for a long time
       if (pushlength >pushlengthset) {
         lcd.clear();
         DateTime now = RTC.now();
         setyeartemp=now.year(),DEC;
         setmonthtemp=now.month(),DEC;
         setdaytemp=now.day(),DEC;
         sethourstemp=now.hour(),DEC;
         setminstemp=now.minute(),DEC;
         setclock();
         pushlength = pushlengthset;
       };
}

//sets the clock
void setclock (){
   setyear ();
   lcd.clear ();
   setmonth ();
   lcd.clear ();
   setday ();
   lcd.clear ();
   sethours ();
   lcd.clear ();
   setmins ();
   lcd.clear();
   RTC.adjust(DateTime(setyeartemp,setmonthtemp,setdaytemp,sethourstemp,setminstemp,setsecs)); //set the DS1307 RTC
   CalcSun (); //refresh the sunrise and sunset times
   delay (1000);
   
}

// subroutine to return the length of the button push.
int getpushlength () {
  buttonstate = digitalRead(A0);  
       if(buttonstate == LOW && buttonflag==false) {     
              pushstart = millis();
              buttonflag = true;
          };
          
       if (buttonstate == HIGH && buttonflag==true) {
         pushstop = millis ();
         pushlength = pushstop - pushstart;
         buttonflag = false;
       };
       return pushlength;
}
// The following subroutines set the individual clock parameters
int setyear () {
   lcd.setCursor (0,0);
    lcd.print ("Set Year");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return setyeartemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) { //bit of software de-bounce
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    setyeartemp=setyeartemp + knobval;
    if (setyeartemp < 2014) { //Year can't be older than currently, it's not a time machine.
      setyeartemp = 2014;
    }
    lcd.print (setyeartemp);
    lcd.print("  "); 
    setyear();
}
  
int setmonth () {

   lcd.setCursor (0,0);
    lcd.print ("Set Month");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return setmonthtemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    setmonthtemp=setmonthtemp + knobval;
    if (setmonthtemp < 1) {// month must be between 1 and 12
      setmonthtemp = 1;
    }
    if (setmonthtemp > 12) {
      setmonthtemp=12;
    }
    lcd.print (setmonthtemp);
    lcd.print("  "); 
    setmonth();
}

int setday () {
  if (setmonthtemp == 4 || setmonthtemp == 5 || setmonthtemp == 9 || setmonthtemp == 11) { //30 days hath September, April June and November
    maxday = 30;
  }
  else {
  maxday = 31; //... all the others have 31
  }
  if (setmonthtemp ==2 && setyeartemp % 4 ==0) { //... Except February alone, and that has 28 days clear, and 29 in a leap year.
    maxday = 29;
  }
  if (setmonthtemp ==2 && setyeartemp % 4 !=0) {
    maxday = 28;
  }
  
   lcd.setCursor (0,0);
    lcd.print ("Set Day");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return setdaytemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    setdaytemp=setdaytemp+ knobval;
    if (setdaytemp < 1) {
      setdaytemp = 1;
    }
    if (setdaytemp > maxday) {
      setdaytemp = maxday;
    }
    lcd.print (setdaytemp);
    lcd.print("  "); 
    setday();
}

int sethours () {
    lcd.setCursor (0,0);
    lcd.print ("Set Hours");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return sethourstemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    sethourstemp=sethourstemp + knobval;
    if (sethourstemp < 1) {
      sethourstemp = 1;
    }
    if (sethourstemp > 23) {
      sethourstemp=23;
    }
    lcd.print (sethourstemp);
    lcd.print("  "); 
    sethours();
}

int setmins () {

   lcd.setCursor (0,0);
    lcd.print ("Set Mins");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return setminstemp;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    setminstemp=setminstemp + knobval;
    if (setminstemp < 0) {
      setminstemp = 0;
    }
    if (setminstemp > 59) {
      setminstemp=59;
    }
    lcd.print (setminstemp);
    lcd.print("  "); 
    setmins();
}

int setmode () { //Sets the mode of the timer. Auto, On or Off

    lcd.setCursor (0,0);
    lcd.print ("Set Mode");
    pushlength = pushlengthset;
    pushlength = getpushlength ();
    if (pushlength != pushlengthset) {
      return TimerMode;
    }

    lcd.setCursor (0,1);
    knob.write(0);
    delay (50);
    knobval=knob.read();
    if (knobval < -1) {
      knobval = -1;
    }
    if (knobval > 1) {
      knobval = 1;
    }
    TimerMode=TimerMode + knobval;
    if (TimerMode < 0) {
      TimerMode = 0;
    }
    if (TimerMode > 2) {
      TimerMode=2;
    }
    if (TimerMode == 0) {
    lcd.print("Off");
    lcd.print("  "); 
    }
    if (TimerMode == 1) {
    lcd.print("On");
    lcd.print("  "); 
    }
    if (TimerMode == 2) {
    lcd.print("Auto");
    lcd.print("  "); 
    }
    setmode ();
}

int CalcSun () { //Calculates the Sunrise and Sunset times
    DateTime now = RTC.now();
    sunTime[3] = now.day(); // Give Timelord the current date
    sunTime[4] = now.month();
    sunTime[5] = now.year();
    myLord.SunRise(sunTime); // Computes Sun Rise.
    Sunrise = sunTime[2] * 60 + sunTime[1]; // Sunrise returned in minutes past midnight
    SunriseHour = sunTime[2];
    SunriseMin = sunTime [1];
    sunTime[3] = now.day(); // Uses the Time library to give Timelord the current date
    sunTime[4] = now.month();
    sunTime[5] = now.year();
    myLord.SunSet(sunTime); // Computes Sun Set.
    Sunset = sunTime[2] * 60 + sunTime[1]; // Sunset returned in minutes past midnight
    SunsetHour = sunTime[2];
    SunsetMin = sunTime [1];
}

void ShortPush () {
  //This displays the calculated sunrise and sunset times when the knob is pushed for a short time.
for (long Counter = 0; Counter < 604 ; Counter ++) { //returns to the main loop if it's been run 604 times 
                                                     //(don't ask me why I've set 604,it seemed like a good number)
  lcd.setCursor (0,0);
  lcd.print ("Sunrise ");
  lcd.print (SunriseHour);
  lcd.print (":");
  if (SunriseMin <10) 
     {
     lcd.print("0");
     }
  lcd.print (SunriseMin);
  lcd.setCursor (0,1);
  lcd.print ("Sunset ");
  lcd.print (SunsetHour);
  lcd.print (":"); 
    if (SunsetMin <10) 
     {
     lcd.print("0");
     }
  lcd.print (SunsetMin);        

    
  //If the knob is pushed again, enter the mode set menu
  pushlength = pushlengthset;
  pushlength = getpushlength ();
  if (pushlength != pushlengthset) {
    lcd.clear ();
    TimerMode = setmode ();

  }
  
}



}