Phidgets Smart Sprinkler Controller with iOS - Part 1

• SBC3003 - Phidget SBC4
• Phidget relays - depending on the number of zones you want to connect
• Power supply to turn on solenoids

If you do not have a sprinkler system in place, you will also need to buy a solenoid valve. Something similar to this should do.

Libraries and Drivers

This project assumes that you are somewhat familiar with the basic operation of Phidgets (i.e. attaching and opening devices, reading data, etc). If this is your first time building a Phidgets project with iOS or a Phidget SBC, please refer to the iOS page or SBC page for instructions on how to set up your environment and get started.

Overview

Step 1: Server Configuration

Step 2: iOS app

When the user selects the "Sync to System" button, the following code will be executed:

	
-(void)syncSettings:(NSNotification *)notification{
    PhidgetReturnCode result = 0;
	//get properties that the user has set and that have been stored in NSUserDefaults
    NSString  *duration = [[NSUserDefaults standardUserDefaults] objectForKey:@"duration"];
    NSString  *startHour = [[NSUserDefaults standardUserDefaults] objectForKey:@"startHour"];
    NSString  *startMinute = [[NSUserDefaults standardUserDefaults] objectForKey:@"startMinute"];
    NSString  *isMinutes = [[NSUserDefaults standardUserDefaults] boolForKey:@"isMinutes"] == true ? @"1" : @"0";

	//Apply new settings to the PhidgetDictionary, let user know if something has gone wrong
    result = PhidgetDictionary_set(ch, "duration", [duration cStringUsingEncoding:NSASCIIStringEncoding]);
    if(result != EPHIDGET_OK){
        [[NSNotificationCenter defaultCenter] postNotificationName:@"syncUnsuccessful" object:nil];
    }
    result = PhidgetDictionary_set(ch, "startHour", [startHour cStringUsingEncoding:NSASCIIStringEncoding]);
    if(result != EPHIDGET_OK){
        [[NSNotificationCenter defaultCenter] postNotificationName:@"syncUnsuccessful" object:nil];
    }
    result = PhidgetDictionary_set(ch, "startMinute", [startMinute cStringUsingEncoding:NSASCIIStringEncoding]);
    if(result != EPHIDGET_OK){
        [[NSNotificationCenter defaultCenter] postNotificationName:@"syncUnsuccessful" object:nil];
    }
    result = PhidgetDictionary_set(ch, "isMinutes", [isMinutes cStringUsingEncoding:NSASCIIStringEncoding]);
    if(result != EPHIDGET_OK){
        [[NSNotificationCenter defaultCenter] postNotificationName:@"syncUnsuccessful" object:nil];
    }
    [[NSNotificationCenter defaultCenter] postNotificationName:@"syncSuccessful" object:nil];
}

Step 3: Program on SBC

For this project, the code that runs on the Phidget SBC is written in C, but can easily be ported to your preferred language.

Note: you should create a project on the SBC that looks like this:

Note: After some minor changes to main.c (serial numbers), and after downloading curl, you can compile the program like so:

Accessing weather data

The first step to creating a smart sprinkler system is accessing weather data. Fortunately, there are many resources available for obtaining weather forecasts. We ended up using OpenWeatherMap which provides free access to weather forecasts in over 200,000 cities. Weather data is available in multiple formats including:

• JSON
• XML
• HTML

For this project, we used JSON along with the jsmn JSON parser for C. We made a request using curl with the following URL:

http://api.openweathermap.org/data/2.5/weather?q=Calgary&APPID=YOUR_APP_ID&units=metric

In order to get an APPID you must sign up for a free account at OpenWeatherMap.

You can see an example of the returned JSON below.

				
{"coord":{"lon":-114.09,"lat":51.05},"weather":[{"id":804,"main":"Clouds","description":"overcast clouds","icon":"04d"}],"base":"stations","main":{"temp":5,"pressure":1015,"humidity":44,"temp_min":5,"temp_max":5},"visibility":64372,"wind":{"speed":7.2,"deg":150},"clouds":{"all":90},"dt":1489788000,"sys":{"type":1,"id":3145,"message":0.005,"country":"CA","sunrise":1489758162,"sunset":1489801605},"id":5913490,"name":"Calgary","cod":200}

Creating PhidgetDictionary and PhidgetDigitalOutput

We want to be able to access the PhidgetDictionary that is running on our server, so we need to create and configure a PhidgetDictionary in our C program. We also need to be able to control Phidget relays, therefore we will create one or more (depending on the number of zones) PhidgetDigitalOutputs.
Note the use of PhidgetDictionary_setOnUpdateHandler(dict, onDictionaryUpdate, NULL). This will allow our program to be notified when the user changes a setting via the iOS app.

	
PhidgetDictionaryHandle dict;
PhidgetDigitalOutputHandle digout;
PhidgetReturnCode result;
...		
//Create and init dictionary
result = PhidgetDictionary_create(&dict);
if(result != EPHIDGET_OK){
	Phidget_log(PHIDGET_LOG_ERROR,"failed to create dictionary\n");
	return 1;
}
result = Phidget_setDeviceSerialNumber((PhidgetHandle)dict, DICTIONARY_SERIAL_NUM);
if(result != EPHIDGET_OK){
	Phidget_log(PHIDGET_LOG_ERROR,"failed to set dictionary serial number\n");
	return 1;
}
result = PhidgetDictionary_setOnUpdateHandler(dict, onDictionaryUpdate, NULL);
if (result != EPHIDGET_OK) {
	Phidget_log(PHIDGET_LOG_ERROR,"failed to set dictionary update handler\n");
	return 1;
}

//Create and init digital output
result = PhidgetDigitalOutput_create(&digout);
if (result != EPHIDGET_OK) {
	Phidget_log(PHIDGET_LOG_ERROR,"failed to create digital output\n");
	return 1;
}

result = Phidget_setDeviceSerialNumber((PhidgetHandle)digout, DIGITALOUTPUT_SERIAL_NUM);
if (result != EPHIDGET_OK) {
	Phidget_log(PHIDGET_LOG_ERROR,"failed to set digital output serial number\n");
	return 1;
}

result = Phidget_setHubPort((PhidgetHandle)digout, 0);
if (result != EPHIDGET_OK) {
	Phidget_log(PHIDGET_LOG_ERROR,"failed to set digital output hub port\n");
	return 1;
}
result = Phidget_setIsHubPortDevice((PhidgetHandle)digout, 1);
if (result != EPHIDGET_OK) {
	Phidget_log(PHIDGET_LOG_ERROR,"failed to set digital output hub port device\n");
	return 1;
}

//Open Phidgets
result = Phidget_openWaitForAttachment((PhidgetHandle)dict, 2000);
if(result != EPHIDGET_OK){
	Phidget_log(PHIDGET_LOG_ERROR,"Exiting program, dictionary did not connect\n");
	return 1;
}
result = Phidget_openWaitForAttachment((PhidgetHandle)digout, 2000);
if (result != EPHIDGET_OK) {
	Phidget_log(PHIDGET_LOG_ERROR,"Exiting program, digital output did not connect\n");
	return 1;
}

Watering your Lawn

Now that everything is in place, we should create the main loop in the C program that will decide whether or not to turn on the water.

	
struct Weather {
	int id;
	char name[100];
	char main[100];
	char description[100];
	double temp;
};

struct UserSettings {
	int startHour;
	int startMinute;
	int duration;
};
...
int counter = 180; //get weather and update dictionary immediately
char temp[6];
struct UserSettings userSettings;
struct Weather weather;
time_t rawtime;
time_t startTime;
struct tm * timeinfo;	
...	
while (1) {
	time(&rawtime);
	timeinfo = localtime(&rawtime);

	if (counter++ == 180) { //every 15 minutes (except when watering)
		PhidgetLog_log(PHIDGET_LOG_INFO, "Getting weather information");
		counter = 0;
		updateWeather(); //gets new JSON packet, parses, and fills updates Weather struct
		updateDictionary(dict); //updates PhidgetDictionary with new id, forecast, and temperature
	}

	//dictionaryUpdate is set in the DictionaryUpdate event handler, lets us know if the user has changed anything
	if (dictionaryUpdate) {
		PhidgetLog_log(PHIDGET_LOG_INFO, "Updating dictionary");
		dictionaryUpdate = 0;
		PhidgetDictionary_get(dict, "startHour", temp, 6);
		userSettings.startHour = strtol(temp, NULL, 0);
		PhidgetDictionary_get(dict, "startMinute", temp, 6);
		userSettings.startMinute = strtol(temp, NULL, 0);
		PhidgetDictionary_get(dict, "duration", temp, 6);
		userSettings.duration = strtol(temp, NULL, 0);
	}

	time(&startTime);
	if (timeinfo->tm_hour == userSettings.startHour && timeinfo->tm_min == userSettings.startMinute) {
		if (isBadWeather(weather.id) == 0){
			time_t currentTime;
			PhidgetLog_log(PHIDGET_LOG_INFO, "Water turned on");
			PhidgetDigitalOutput_setState(digout, 1); //turn on water
			do {
				sleep(5);
				time(¤tTime);
			} while(difftime(currentTime,startTime) < (userSettings.duration * 60.0));
			PhidgetLog_log(PHIDGET_LOG_INFO, "Water turned off");
			PhidgetDigitalOutput_setState(digout, 0); //turn off water
		}
		else{
			PhidgetLog_log(PHIDGET_LOG_INFO, "Not watering due to poor weather conditions");
		}
	}
	else {
		sleep(5);
	}
}	

The code above is still quite simple and is not yet as 'smart' as it should be, however, it is a good start.
Here is a small breakdown of the loop:

• If it has been 15 minutes, update weather
• If dictionary has been updated, update userSettings struct
• If current time is equal to set watering time, begin watering
• Check if the weather is "bad". Weather codes
• If weather is good, set state of PhidgetDigitalOutput to 1 and water for selected duration.

Checking the Weather codes is an easy way to decide whether to water or not. The weather id is divided into multiple groups. For example, id values of 2xx indicate a thunderstorm, this would qualify as "bad weather" and prevent watering.

Conclusion

So far we have a system that will turn on the water when you want, for as long as you want, and it will also check for weather. Overall, we have accomplished the goal of creating a smart sprinkler system, however, a lot can be done to improve this. Here are some ideas for next time:

• Incorporate flow meter to track water usage/cost. This can be stored on the SBC and brought out to users via the iOS app.
• Don't water every day. Let user decide which days of the week to water on.
• Allow user to have unique settings for each zone.
• Make C program smarter. Take future/previous forecasts into account, not just current weather.
• Improve iOS app look by including themes for different weather forecasts.

These are just some ideas, if you have any you would like to share, let us know!