Wednesday, September 4, 2019

Integrating the Ideas from a High-Tech, Luxury, Cruise, Ship into your Home



Maybe you didn’t get to take a luxury cruise vacation this summer.  But, that doesn’t mean you can’t incorporate some of the same high-tech, luxury features available on a cruise ship into your home.  I had the opportunity to tour the Viking Sun; an only two year old cruise ship that incorporates many high tech features. 

Unlike the 5000+ passenger, behemoth, cruise ships, the Viking Sun only carries 930 passengers plus crew.   To give you a better picture of the ship it has:

  • Two Pools
  • Six Dining Options including outdoor dining around the main pool
  • Five Bars

While a typical homeowner isn’t going to replicate these amenities in their own home there are many things that the Viking Sun offers passengers that can be replicated in a home.

Stateroom

The typical stateroom on the Viking Sun is a model for a high tech master bedroom in any home. 

  1. King sized bed
  2. Small Refrigerator for snacks and a mini bar.
  3. Nespresso coffee maker
  4. Sitting area with chairs and a small table
  5. Glass enclosed shower
  6. Heated Bathroom Floor
  7. Anti-fog bathroom mirror
  8. 42” flat screen TV
  9. Motorized drapes with both a sheer privacy drape and a blackout drape
  10. Sliding doors that provide access to a private balcony that includes chairs and a table
  11. Motion activated lighting in the closet
  12. Bedside switches for controlling the room lights
  13. Night stands beside the bed that include storage, outlets, and USB charging ports
  14. Viking is experimenting with the use of a touch panel at the entry to the stateroom with, for example, options for setting scenes that combing lighting with the position of the motorized drapes

There is nothing in the above list that couldn’t be retrofit into a home as part of a remodel. And, in many cases, an extensive remodel isn’t even required. 

The TV in each stateroom is used for both entertainment and an information hub.  A guest can view a calendar of events, ship tracker that shows the location of the ship and that path it has taken, view of an outside camera that faces the front of the ship, weather forecasts, and much more.  Control4 has included the ability to use a TV as an interface to their home automation system and many of these features could be replicated if a homeowner chooses Control4 as the platform for their smart home. 

Health

The potential spread of illness in a cruise ship is a key concern.  The Viking Sun includes many features to keep passengers healthy while they are on board.

First there are hand cleaning stations scattered throughout the ship.  While most of these simply spray sanitizer on a person’s hands, at the entry to the ships main buffet style restaurant there is a complete hand washing station with sinks, soap, and towels. 

The ships crew tries to make sure that all the passengers stay hydrated.  Water is served to passengers in the restaurants, there are water decanters in each stateroom that are refilled every day, and bottled water is offered to anyone leaving the ship on an excursion.

Finally, the ship includes a very well appointed gym that is open to all passengers.  The gym includes elliptical cross trainers, treadmills, exercise bikes, a rowing machine, dumbbells, equipment for palates, and even Technogym Kinesis Personal Heritage machines. 

While the Technogym Kinesis machines may be out of reach for most homeowners, a simple home gym that provides for both aerobic, core, and strength training is affordable. 

Hand cleaning, to minimize the spread of illnesses among family members, simply requires making this a priority.  Between the kitchen and bathrooms there are typically plenty of hand washing stations available.  Placing hand sanitizers at convenient locations around a home can further reduce the spread of illness. 

Finally, hiding a mini-fridge full of water bottles wherever the family typically exits the house can make it easy for people to grab a bottle when they leave the home and help everyone stay hydrated.

Security

Security is taken seriously on the Viking Sun.  Every passenger is issued a personalized card that incorporates a near field communication (NFC) chip.  This is used to:

  • Check each passenger on/off the ship so the crew knows if anyone is missing when the ship is going to leave a port
  • As a room key

In addition, passengers are treated to airport style security any time they board the ship.  Any items being carried are placed on a conveyor belt and run through an x-ray machine.  Then, each passenger must pass through a metal detector.  There are also security cameras in public areas of the ship that are monitored 24 hours a day by the ship’s security staff.

Finally, while the Viking Sun doesn’t include the latest in IoT video doorbells, each room does include a doorbell and “peep hole” so a passenger can see who is asking for entry into their stateroom.  Staterooms also include a smoke detector, emergency lighting, and fire suppression.

Asking visitors to your home to submit to metal detectors and the x-raying of their personal articles might be considered excessiveJ.  However, including security cameras in, and around, your home that can be viewed remotely on your smart phone has been embraced by many homeowners.  Further, enabling location services on each family member’s smart phones allows them to find each other in, for example, a time of emergency. 

Outdoor Recreation

In addition to the two pools, the Viking Sun includes a sun deck with a variety of outdoor games.  These include:

  • Shuffle Board
  • Ping-Pong
  • Bocce
  • Putting Greens
  • Lawn Bowling

Any of these could be implemented in a backyard.

Other Amenities

The Viking Sun offers a number of other amenities that a homeowner might consider for their own home.

  1. Sitting areas are scattered throughout the ship.  These areas offer people a place to:
    1. Relax
    2. Read (a selection of books are available at each sitting area)
    3. Play games.  Scrabble and jigsaw puzzles are placed in some sitting areas
    4. Play video games.  Some sitting areas include a table with a built in video game machine
  2. Seamless Wi-Fi is available throughout the ship
  3. The Viking Sun is appointed with artwork throughout the ship.  A small audio device used for excursions can be used to take an audio tour of the artwork.  A homeowner that collects art could create a tour of their own art collection using Alexa Blueprints.
  4. Theater.  The theater on the Viking Sun is used for a variety of presentations and movies. 

The Viking Sun provides an incredible collection of luxury, and hi-tech, amenities for its passengers.  But, that doesn’t mean that any homeowner couldn’t replicate a significant number of these amenities in their own home.

Thursday, August 22, 2019

Helpful Home vs Smart Home: What You Need to Know

My latest blog post, “Helpful Home vs Smart Home: What You Need to Know” was originally published by the good folks at Residential Tech Today Magazine on their web site here:


Below is a copy of the article.

In a recent conversation with Forbes, Rishi Chandra, Vice President of Product and General Manager at Google Nest, defined a subtle, but important change in terminology. 

Speaking to Forbes Chandri said: “We're intentionally deviating from the word smart home, because we actually think it's the wrong word, we actually do think it's a very tech-oriented way of thinking about the home. No one asked for smartness, for the smart home. That's not an attribute necessarily people care about. What they want is help. Like, we want to go from what a technology does to where it actually provides benefit. And so our mantra for the next five to 10 years is going to be the notion of how we can help deliver the helpful home.” 

In the past I’ve written about the need for integrators to deliver smart home systems that provide their customers with, what I referred to as, “true automation” vs. a system that just provides another way for customers to control the lighting, HVAC, TV, etc. in their home.  Smart speakers and smart phones simply provided another way of turning on a light switch without having to walk across a room.  While this was “cool”, it really didn’t provide a great deal of value to most homeowners. 

Chandra’s comments show that manufacturers are looking to take the next step and move beyond simple control systems.  My expectation is that this change will leverage the power of machine learning, that has drive the voice recognition capabilities of smart speakers, to move beyond the types of automation that integrators have been able to provide today.  For example, an integrator might have programmed a customer’s system to:

  • Turn off lights, TV’s, music, and set back the thermostat to save energy when the home isn’t occupied
  • Restore the thermostat to the normal temperature when people come home
  • Turn on pathway lights when people arrive home at night
  • Turn off the water to the house and sound an alarm when a leak is detected
  • Disable the irrigation system if it rains
  • Turn on an air cleaner if the air quality in a home is poor
  • Remind the homeowner when the clothes dryer finishes drying a load of laundry so they can be removed from the dryer and won’t wrinkle
  • And the list goes on…

A “helpful home” based on machine learning can provide the same functionality, and more.  For example:
 
  • GPS data from the car, or a smart phone, could show that the family had been to the grocery store so instead of a fixed set of pathway lights being turned on when they arrive home; the lights to the kitchen would be lit.
  • The air quality and temperature in a home could be driven by sensors to provide clean air at a temperature that provides the highest degree of comfort.  For, example, the home might detect that exercise equipment in a home gym is being used and lower the temperature to keep the person exercising cool.  On the other hand if someone is lying on a sofa reading a book the temperature might need to be warmer for the person to be comfortable.  Cooking releases VOC’s into the air so an air cleaner could be turned on when the stove is in use.
  • The wake up time of the homeowner’s alarm clock could automatically adjust based on events on their calendar and deadlines defined for items on their “to do” list.
  • Instead of the fixed set back schedule that thermostats offer today the thermostat could:
    • Bring the house up to the normal temperature just before the homeowner morning alarm was scheduled to go off
    • Set back the temperature to the night time setting when people actually went to bed
    • Recognize when guests were over and make adjustments so everyone was comfortable.  For example, during a summer party people frequently move between inside the house and the back yard.  The system could sense that the door to the backyard was opening and closing, letting in air with lots of pollen, and engage the air cleaner. 

While this utopian dream would have sounded like science fiction only a few years ago, I expect we will be seeing many of the above features sooner than we think.  One challenge will be creating a system that can initially be helpful to homeowners and grow even more helpful over time.  Using one of the above examples, the “helpful home” should, after installation of a machine learning system, turn on a default set of pathway lights when the homeowners arrive at night.  Over time the home can then learn more about the homeowners movement habits and make better decisions as to which lights should be lit.  How a machine learning system is provided with default behavior based on a customer’s unique home will be an interesting challenge. 

It should also be noted that this utopian vision also has downsides

Privacy

For a “helpful home” to operate it will require a large number of sensors that monitor the activities of the people in a home.  How this data will be used raises significant privacy issues.  The E.U. is far ahead of the U.S. in laying a foundation of laws to govern personal privacy.  The data collected by a “helpful home” is going to raise the stakes in how data collected, about the way we live our lives, in the privacy of our homes, is used.

Security

In the “helpful homes” more, and more, devices in our homes are going to be interconnected including

  • Light Switches
  • Thermostats
  • Appliances
  • Thermostat
  • Air Quality Monitors
  • Motion Sensors
  • Cameras
  • Health Sensors
  • Irrigation Controllers
  • Water Heaters
  • Audio and Video Equipment (TV’s, etc.)
  • Security System
  • Door locks
  • And More…

Protecting all of this from hackers is going to be a significant challenge.  It would be very annoying for a bored teenager down the street to have fun turning your bedroom lights on, and off, in the middle of the night.  But, it would be a much more significant issue for your thermostat to shut off in the middle of the winter and to have to pay a ransom to regain control of it before your pipes froze/burst, causing thousands of dollars of water damage in your home.  Just as machine learning will help make our homes more “helpful” this same technology needs to be applied to our home networks to detect intrusions and make them more secure. 

Cost

How a system that creates a truly “helpful home” is paid for hasn’t been defined.  Starting with smart speakers, the systems in our homes are relying more, and more, on powerful cloud servers to run them.  The sale of the data collected about us has kept people from having to pay for the cloud services we use today.  Whether this continues in the future, or whether laws that provide privacy are passed, requiring companies to pass the costs to consumers in the form of subscription fees, remains to be seen. 

Summary

Rishi Chandra’s coining of the term “helpful home” is a step in the right direction towards home systems that are focused on customer needs instead of tech innovation.  However, privacy and security safeguards are going to become even more important than they are today for the “helpful home” to be successful.



Thursday, August 8, 2019

Smart Ways to Minimize the Expense of Heating Water in your Home


My latest blog post, “Smart Ways to Minimize the Expense of Heating Water in your Home” was originally published by the good folks at Residential Tech Today Magazine on their web site here:


Below is a copy of the article.

According to the U.S. Department of Energy, the typical American family will spend $2,200 per year on home utility bills and water heating accounts for about 18% of that; or almost $400.  So, reducing the energy used to create hot water in a home along with strategies to reduce overall water usage can save a homeowner a significant amount of money.

There are three aspects to optimizing hot water usage in a home:

  1. How the water is heated
  2. How the water gets to the faucets and fixtures where it will be used
  3. How smart home integrations can help reduce the energy used

Heating Water in a Home

There are two primary types of residential water heaters

  • Tank or Storage Water Heaters
  • Tankless Water Heaters


Storage water heaters are the most popular type of residential water heater.  There are models that heat the water using:

  • Gas
  • Electricity
  • Propane
  • Fuel Oil
  • Heat Pump
  • Solar Energy

A storage water heater heats the water and stores it in a tank so it is ready to use when needed by a family.   While the tanks are insulated, there is still heat lost over time while the water is sitting there waiting to be used.  Then, more energy is required to reheat the water to bring it back up to the desired temperature.

According to HomeAdvisor, the average cost of a storage hot water heater is between $762 and $1426; including installation.  And, a storage hot water heater will last between 8 and 12 years.


Tankless water heaters heat the water as it is needed using either gas or electricity.  Hot water is not stored but is delivered, on demand, to the faucets and fixtures in a home.  Because of this, deciding the size of the heater needed for a home is a more complicated process than a tank style heater, which can simply be chosen based on the number of people living in a home. 

Tankless water heaters are sized based on the flow rate to the fixtures, that could be in simultaneous use, the temperature rise required based on the temperature of the water as it enters the home, and the desired temperature of the heated water.  For example, the temperature of water entering a home varies depending on where you live and the time of the year.  In northern parts of the U.S. the water entering a home in the winter can be as low as 40 degrees F and U.S. Department of Energy recommends that homeowners set their hot water heaters to deliver water heated to 120 degrees F.  So, in the northern parts of the country a tankless hot water heater would have to be capable of raising the water temperature by 80 degrees.  On the other hand, the water temperature as it enters a home in southern states can be 50 degrees F; or more. So, a hot water heater with less capacity can be used in the south.

Tankless water heaters are more efficient than their storage water heater counterparts.  According to U.S Department of Energy they can be up to 34% more efficient than a storage hot water heater. They also have an expected lifespan of up to 20 years.  However, according to HomeAdvisor, the average cost of a tankless water heater is $3000 so the purchase cost needs to be balanced with the energy savings and the expected time a family believes they will stay in their home. 

In addition to whole house, tankless, water heaters, there are also smaller units that are installed close to fixtures; such in a cabinet, under a sink.  These smaller units remove the waste of running a faucet until the hot water reaches the fixture from the large, central, hot water heater.  However, while these units are much less expensive than a central hot water heater, they typically require 240 volts so the cost of retrofitting them into a home can be high because, at a minimum, new wiring needs to be run from the circuit breaker panel to the water fixture location.  So while this can be a very efficient way of delivering hot water to a remote location in a home, it is best to include this capability when the home is built instead of retrofitting it later. 

There are so many hot water heaters on the market that it is impossible to try and pick favorites.  Models from Rheem, A.O. Smith, Ecosmart, Rinnai, GE, Stiebel, Bosch, and others are all highly rated.  The choice, especially when choosing a tankless water heater will come down to one that meets your requirements, price, and availability in your area. 

Recirculation Pumps

Recirculation pumps are typically installed in large homes to provide instant access to hot water at fixtures that may be a significant distance from a hot water heater.  If a kitchen sink is 50 feet from the hot water heater, the homeowner is going to pour over a gallon of water down the drain before the hot water from central storage, or tankless, water heater reaches the kitchen sink.  If that happens three times a day, every day of the year, that is a loss of over 1200 gallons of water at that one location in a home.  Some estimates are that a family can waste 12,000 gallons of water a year waiting for hot water.  Instead of dumping the water down the drain a recirculation pump pushes it back through water lines in the home so it isn’t wasted. 

In addition to the convenience a recirculation pump offers, according to statista, a family of four in the U.S. pays over $70 per month for water; and the trend is for costs to continue to rise.  So, an energy efficient recirculation pump can save money.

There are two types of recirculation pumps.  In a full recirculation system an additional water line is added to return water back to the tank style hot water heater from an end point in a hot water line.

The second type of recirculation pump is called a comfort system.  In these systems a one way connection is made between the hot and cold water lines at the far end of the hot water line.  Water that has sat in a hot water line and cooled is pumped into the cold water line until hot water reaches the fixtures where it will be used.   This system eliminates the expense of the separate return line but when a cold water faucet is opened the water will be lukewarm.  If lukewarm water from the cold water tap isn’t acceptable to the person using the water, water will be dumped down the drain and wasted until water of the desired temperature reaches the tap.

The pumps in these recirculation systems vary in their capabilities to minimize the energy they use.  The least energy efficient models simply circulate water 24 hours a day.  The most efficient models include temperature sensors that stop the pump when it has pumped enough so the water at the fixtures is hot and ready for use.  The pump will only start again to circulate the water as the temperature of the water in the hot water line drops below a threshold.  In addition, the best pumps have a built in timer so the pump can be shut off when family members are at work or asleep.  Grundfos, a leader in recirculation pumps, has introduced technology where the pump learns the usage patterns of the homeowners to further reduce energy usage.

While the primary goal of recirculation pumps is to reduce the time people wait for hot water while minimizing the energy required for the added convenience, the Chilipepper CP9000 takes a different approach.  This recirculation pump is designed to be installed by a homeowner, underneath the sink, where hot water is used; such as in the kitchen or bathrooms.  Like other comfort units it pumps water from the hot water line into the cold water line until hot water is available at the tap.  Unlike other recirculation pumps it only does this when the homeowner presses a button on an included, small, remote control.  This greatly reduces the energy wasted by running the pump throughout the day and the energy loss by hot water cooling in the pipes when nobody is using it. 

In addition, the CP9000 includes a contact closure interface so it could be integrated with a smart home processor / hub.  While I haven’t used this particular product, a Wi-Fi Relay/Switch, such as the Sonoff model on Amazon, could be used to control the CP9000 through voice commands.

With the CP9000 the homeowner still has to wait for the hot water to travel from the hot water heater to the faucet but there is no water wasted.  Further, the manufacturer claims that the pump will only use $2 in electricity per year; a minimal cost compared to saving 1,200+ gallons of water.

How a Smart Home Can Help Minimize the Cost of Hot Water

While the number of tankless hot water heaters is growing, storage hot water heaters are still the most common type of water heaters in homes.  The first step to making this type of water heater as energy efficient as possible is to simply add an extra layer of insulation to the outside of the tank.  Energy blankets are readily available at big box home improvement stores and online retailers.  I personally chose the US Energy Nastech model for my own home because of its high insulation value. 

No matter what kind of hot water heater is installed in a home, a second, low tech, improvement that can be made is to insulate the hot water pipes; where they are accessible.  Foam pipe insulation, such as Tubolit SS by Armacell, comes in 6 foot lengths and is easy to install.  If a hot water heater is located in an unheated garage, or the pipes in the home are run through a cool basement, foam insulation can help reduce the loss of heat from the water as it makes its way through the pipes to the fixtures in the home.  If the water that reaches a faucet is hotter, then the amount of it needed when mixed with cold water to create the warm water for washing is reduced; saving money.  It is even possible that after insulating the pipes that the temperature setting for the hot water heater can be reduced; saving even more money. 

It doesn’t make sense to heat water in a tank style hot water heater when nobody is home or when a family is sleeping.   Both gas and electric hot water heaters can be integrated with a smart home system to only operate them when hot water might be needed.  For gas operated hot water heaters the Gas Water Heater Timer from American Pacific is easy to install.  It comes with a simple timer but this can easily be replaced by a smart outlet to put your gas hot water heater under control of your smart home processor / hub. 

Similarly, a high voltage electrical switcher, such as this one from Red Coral Technologies, can be retrofit to an electric hot water heater to provide smart home control.  It can be ordered with a variety of different smart light switches built in that provide the smart home integration.  Options include Belkin Wemo, TP-Link Kasa, Leviton Z-Wave, Elgato Eve, and more.   These provide a wide range of integration possibilities including Alexa, Google, Assistant, Apple Homekit, SmartThings, and others.

While this device is advertised as DIY, it requires working with 240 volt wiring so many people may be much more comfortable hiring an electrician for installation.  A shock from 240 volts can be lethal so safety should be a primary concern.

A smart home processor / hub that includes occupancy sensing can turn off the hot water heater when nobody is home and then turn it back on when people return.  With an added insulation blanket there will be minimal loss of water temperature and family members won’t even notice the change.  Further, the hot water heater can be turned off in the evening when the family goes to bed and back on in the morning when people are scheduled to wake up.  If the family uses Alexa devices as alarm clocks, the IFTTT Alexa service includes a trigger for when an Alexa alarm clock “goes off”.  This can be used to turn the hot water heater back on when people get up during work / school days; as wake up times can vary from day to day making a fixed schedule problematic.  A backup trigger that turns the water heater on at a fixed time in the morning can take care of weekends and holidays when an alarm clock isn’t set.

Hot water recirculation pumps can also be integrated with a smart home processor / hub that includes occupancy sensing to minimize the energy used by the pumps and lost through water circulating through the plumbing system.  Powering a recirculation pump through a smart switch, or outlet, allows the pump to be:

  • Turned off when nobody is home
  • Turned off late at night when the family is in bed

Summary

Water is expensive, hot water is even more expensive, and prices are going up.  Saving both water and the energy needed to heat it makes both economic sense and environmental sense.  The changes to a home to minimize the cost of heating water aren’t expensive and, in most cases, can be retrofitted by a homeowner. 


Wednesday, July 24, 2019

Hacking Alexa: How to Better Integrate Amazon Alexa into Your Smart Home

My latest blog post, “Hacking Alexa: How to Better Integrate Amazon Alexa into Your Smart Home” was originally published by the good folks at Residential Tech Today Magazine on their web site here:


Below is a copy of the article.




Amazon Alexa devices, along with Google Assistant, have become a popular addition to the smart home.  The integration of voice commands simply makes the complexities of a smart home much simpler to control.  Unfortunately, both Amazon and Google have limited the integration capabilities of their respective voice assistants; which can be frustrating.

While voice commands can be used to control integrated third party equipment, such as lighting, thermostats, and more, the integration is not a two way street.  There is nothing a third party smart home processor / hub can do to control an Alexa or Google Assistant device.  For example:

  1. Music is playing on Alexa or Google Assistant devices in various rooms of the house.  You set the alarm system in the home, which is integrated with a smart home processor / hub, to away mode.  There is nothing the smart home system can do to turn off the music that is currently playing.  The only way to turn it off is to issue voice commands at each voice assistant device or to use music groups to over-ride the currently playing music and then shut down the music group.  In either case, there is nothing convenient about this process. 

  1. The new Amazon Guard is a nice feature that leverages Alexa devices around the home to listen for the sound of broken glass, smoke detectors, or carbon monoxide detectors.  If an Alexa device detects one of these sounds while the home isn’t occupied then it will send an alert to your phone.  Unfortunately, the only way to enable, or disable, Amazon Guard is with voice commands or through the Alexa app on your smart phone

  1. The new Amazon Alexa feature that allows a user to delete that days voice interactions could automatically be triggered every evening at 11:59 PM. 

  1. There are many events in the home where it would be convenient to play a message on the Alexa, or Google Assistant, devices around a home.  For example, if your garage door was left open for more than five minutes you would like a reminder to close it.  Or, you might have a sensor on your mailbox that detects when the mail has been delivered.  It would be nice to have a message played on the voice assistant devices around the home to let you know when the mail has been delivered.  Unfortunately, neither Amazon nor Google have opened up any ability to automate a message being played on their devices. 

With the above in mind I set out to figure out a way to work around the barrier put in place by Amazon and Google limiting third party control of their voice assistants.  I set out to find a way to work around these problems in my own home where I use Alexa devices for music streaming and to control my Crestron automation system.  My solution cost me a little over $100 and consists of:

  • Arduino Uno Wi-Fi Rev 2 open source, easily programmable, single board computer – $44.48 on Amazon
  • Power Supply for the Arduino Uno – $8.60 on Amazon
  • Parallax EMIC 2 text to speech circuit board – $59.99 on Amazon
  • Breadboard Wires – $6.98 on Amazon
  • Inexpensive set of computer speakers – In my case they were rescued out of a closet but these are readily available on Amazon, eBay, or even at a thrift store if you really want to save money.
  • Small Plastic Project Box – I had one on hand but something like this would also work - $7.99 on Amazon

I then wrote the code for the Arduino board to accept strings sent to it over Wi-Fi using industry standard UDP protocol, send them to the EMIC board for conversion from text to speech, and the verbal commands are played over the cheap computer speakers that are placed next to an Amazon Echo in my home.  The software even does some simplistic encryption of the strings being sent to make it a little harder for someone that gains access to the network to hack this system.  The encryption I used is very simplistic.  If desired, there are plenty of code examples on the Internet of much more complex encryption algorithms that could be ported to this system. 



Wiring is very simple and doesn’t require any soldering.  The power supply for the Arduino simply plugs into the Arduino board.  Similarly, the EMIC 2 board has a 1/8” (3.5mm) audio jack that is compatible with almost any pair of computer speakers.  Finally, there are only 4 wires needed to connect the EMIC 2 board to the Arduino.  These connections are made using the push on terminations of the breadboard wires I’ve specified above.

  1. Make a connection from the pin marked 5V on the Arduino to the pin marked 5V on the EMIC 2
  2. Make a connection from the pin marked GND on the Arduino to the pin marked GND on the EMIC 2
  3. Make a connection from Digital Pin 2 on the Arduino to the pin marked SOUT on the EMIC 2.
  4. Make a connection from Digital Pin 3 on the Arduino to the pin marked SIN on the EMIC 2.

Arduino single board computers are relatively simple to program and all the code for this project, along with the example program I wrote for a Crestron automation processor is available for free download from my GitHub.  While I wrote the example program for a Crestron processor there isn’t any reason it couldn’t be easily ported to another platform.

The free, IDE software for programming the Arduino board can be downloaded from their web site here.  There is also a full tutorial to teach you how to use it here.

To turn off streaming music on all your Alexa devices there is some additional setup required:

  1. On your computer go to the Amazon Music web site here.
  2. Search for “Silent Meditation” and add the album “Silence, Album by Silent Meditation, No Sound Pause Breaks to “My Music”.
  3. On the Alexa app, create a “Speaker Group” named “Everywhere” that contains all your Alexa devices.
  4. The example Crestron program will send the command “Alexa, Play Silence 1 Minute on Everywhere”.  This will cause all the Alexa devices to start playing a one minute track that consists of nothing but silence.  If there is music playing on various echo devices in the home this will interrupt that playback and replace it with the group track that consists of nothing but silence.  Once it is complete there is no music left playing on any Alexa device. 


Shown above is the final assembly of the project.  I took leveraged a small plastic jar to house an Echo Dot, cut a hole in the top, and glued the speaker in place.  The plastic jar allowed me to isolate the sound so it is almost impossible to hear the speaker annunciating the commands to the Echo Dot. 

 Also included in the Crestron example program is an illustration of how a message can be played on all the Alexa devices in a home using the Alexa announcement feature.   The example program instructs the Aruduino/Emic to say “Alexa, Announce Mail Has Arrived”. 

Hopefully, this simple project introduces you to the easy to use Arduino platform and gives you a tool to help break through the barriers that Amazon and Google have put in people’s way that want to truly integrate voice assistants into their smart homes.

Thanks for reading

Wednesday, July 3, 2019

Smart Lawn Mowers: Everything You Need to Know

My latest blog post, “Smart Lawn Mowers: Everything You Need to Know” was originally published by the good folks at Residential Tech Today Magazine on their web site here:


Below is a copy of the article.

According to Pro Landscaper Magazine, people spend almost 2 months of their lives mowing their lawn.   In the past, the only alternative was to hire a professional landscaper.  Now, technology has come to the rescue in the form of robotic lawn mowers. 

There are a wide variety of robot lawn mowers available from well known manufacturers of lawn care equipment including two manufacturers with reputations for high quality products; Husqvarna and Honda. 

As you would expect, robot mowers, that operate unattended, have a wealth of safety features.  First all mowers include collision sensors.  If they bump into an object they will reverse, turn, and proceed in another direction.  Second, unlike a standard mower, the blades of a robot mower are very small and designed to only cut grass.  Further, the blades will automatically stop if the mower is lifted or tilted.  The blades are also recessed, away from the edges of the mower, making it much more difficult to be cut by a blade if someone accidentally sticks their foot underneath the mower while it is running. 

The small, razor sharp blades also contribute to longer battery life; as does the design of the mowing schedule.  A typical homeowner will cut their lawn once a week.  Robot mowers are designed to cut much more frequently.  Cutting more frequently means that each cut has to remove less grass growth.  Anyone who has tried to cut a lawn after missing a week while on vacation has found that the extra long grass requires much more effort to cut.  So, cutting more frequently saves battery life and allows the robot mower to cut more of the lawn between charging cycles

A regular mower, with its large blades, mulches the grass by cutting it multiple times. The large blade first cuts the grass at the selected height.  The shape of the blade creates an air  current that keeps the clipping from immediately falling to the ground and allows each clipping to be cut multiple times.  On the ground these small pieces of grass decompose, and provide nutrients for the lawn. 

Instead of cutting each grass clipping multiple times to create the small pieces of grass that can easily decompose into mulch, robot mowers mulch the grass by cutting the lawn more frequently and only cutting small pieces from the top of the grass.

Robotic mowers also have features to prevent theft.  These range from requiring a pin code to operate the mower to a built in GPS that allows the location of the mower to be tracked. 

Unlike a robot vacuum that can map your room by bumping into or scanning your walls, a robot lawn mower requires a boundary wire to be run around the perimeter of the lawn, flower beds, trees, and any other obstructions.  The mower senses an electronic signal that is sent along the boundary wire and stays within its border.

While it may seem obvious, it is important to note that if a yard is divided into several areas or levels, possibly with a fence or flower bed dividing them, a robot mower will not be able to automatically mow the entire lawn.  However, the software in the mowers allows them to be moved to a secondary area and a manual mowing session started.  But, if the area is too large for the mower to complete before the battery is exhausted, the user will have to carry the mower back to the charging station and then return it to finish mowing after the battery is recharged.  While this does make sense it makes a robot lawn mower less of a time saver for some people.

Husqvarna manufactures a total of eight different robot lawn mowers.  These can be split into two main categories:

  • Mowers with Automower® Connect technology include a cellular radio, GPS navigation, theft tracking, and integration with Amazon Alexa, Google Home, and IFTTT
  •  Mowers with Automower® Connect@Home can be controlled through Bluetooth using a smart phone app

For the purpose of this article I’m going to focus on the five mowers that include Automower® Connect as they provide the opportunity for integration in the smart home.  The primary differences between the Automower® 315X, 430X, 430XH, 450X, and the 450XH are the sizes of the lawn that can be cut by each mower.  The 315X is designed for a lawn of up to .4 acres.  Both the 430X and the 430XH are designed for lawns of .8 acres and, the 430XH allows for higher cutting heights.  Finally, the 450X and 450XH are designed for a lawn of 1.24 acres with the 450XH, again, allowing for higher cutting heights.

For safety, when any of the Automowers® strike an object they will backup, turn, and proceed in another direction.  In addition, the 450X and XH models include ultrasonic sensors and will slow down as they approach an object that blocks the path of the mower.

All of these Husqvarna mowers have a 19 button keypad and LCD display in addition to their ability to be controlled through a smart phone app.  All have an alarm, require a pin code, and include lift/tilt sensors.  All mowers have 18V lithium ion batteries.  But the battery capacity varies by model.  The 315X has a 2.0Ah battery with a 60 minute charging time and a 70 minute run time.  The 430X and XH models have 5.0Ah batteries with a 50 minute charging time and a 145 minute run time.  Finally, the 450X and XH models have 10.0Ah batteries with a 60 minute charge time and a 270 minute run time.

Like other robotic mowers the Husqvarna Automowers® are designed to cut the lawn frequently, removing only a small amount of growth.  The cutting width of the 315X is 8.7” while the other models all have a cutting width of 9.45”.  The 315X can climb an incline of 22 degrees while the other models can climb an incline of 24 degrees.  All the Husqvarna mowers are designed to operate in the rain and in temperatures up to 113 degrees Fahrenheit.  Husqvarna recommends that the mower be taken inside during extreme weather conditions. 

All the Automower® models use three, small, razor sharp blades for cutting the lawn.  The blades will pivot aside if they encounter a hard object.  Blade life is estimated to be around two months for a quarter acre lawn and when dull, the blades can be replaced by the homeowner with just a screwdriver in only a few minutes.

All the Automower® models are quiet.  The sound levels of the various models are as follows

  • 315X   -           60 dB
  • 430X   -           58 dB
  • 430XH-           59 dB
  • 450X   -           59 dB
  • 450XH-           63dB

In comparison, a typical gas powered lawn mower generates 95 dB and even an electric push mower generates 75 dB.

Each mower comes with an operating manual, quick start guide, charging station, power supply, low voltage cord for connecting the charging station to the power supply, plastic screws for securing the charging station to the ground so it can’t shift, three spare sets of mower blades and blade securing screws, wire labels, and a ruler used during the installation of the boundary wire.

Unlike other the mowers from Honda, a separate installation kit that includes boundary wire, staples, and wire connectors must be purchased.  This adds between $100 and $250 to the price of the mower depending on the size of the yard.  The cost of installation must also be considered.  The Husqvarna dealer I spoke to said that professional installation typically costs between $200 and $500; depending on the size and complexity of the yard.  The dealer I spoke to said that while some homeowners do the installation themselves that most opt for having the dealer do the installation for them.

In addition to installing the boundary wire around the lawn, a piece of wire from the reel of boundary wire is run from a connection on the charging station to the boundary wire on the far side of the lawn.  This “guide wire” is used to help the mower efficiently return to the charging base and to guide the mower to areas of the lawn that it otherwise might have difficulty locating as it randomly cuts the lawn.  The 315X’s design allows for a single guide wire, the 430X and 430XH’s design allows for dual guide wires, and the 450X and 450XH’s design allows for three guide wires.  The larger number of guide wires allows for the mower to more efficiently operate in a more complex yard. 

In conjunction with the guide wire the 315X can be programmed for three starting points while the 430 and 450, X and XH models, can be programmed for five.  Starting points allow the mower to more evenly cut the various sections of a yard.  For example, separate starting points can be set for the back yard, front yard, and side yard.  The mower would then rotate between these starting points making sure that each area was completely mowed before moving on to other parts of the yard and possibly needing to recharge.

The Husqvarna dealer I spoke to told me that some customers were very creative in how they ran the guide wires.  Some examples are:

  • Though pet doors installed in fences allowing the mower to travel between areas it otherwise wouldn’t be able to reach
  • Over a bridge the homeowner built across a small stream
  • Between neighbors yards that shared in purchasing the mower

In addition, the Husqvarna mowers make use of their built in GPS to assist with navigation.  This feature primarily adds value in larger yards where the mower gains a better understanding of where it needs to go and where it has already mowed. 

Similar to the Honda mowers, the Automower® models can optionally change to a spiral mowing pattern if the mower encounters an area with thicker grass.  The mower can also be manually moved to a specific location and placed in a spot cutting mode where it also uses this spiral pattern to cut an area that requires special attention.

The Automowers® include a basic weather timer that allows the homeowner to adjust the mowing schedule based on the weather.  There are five different options, from Low- to High+.  During the times where the grass grows rapidly, typically during the spring and fall, the cutting frequency can be raised by setting the weather timer to High, or High+.  During mid-summer, when grass typically doesn’t grow as quickly, the weather time can be changed to Low, or even Low-.

To prevent theft, the mower includes an alarm that sounds if the mower is lifted.  As the mower requires a pin code to operate, even if the mower was taken it would be of no use to the thief.  Further, the mowers are serialized and if a stolen reporting the mower to Husqvarna allows them blacklist the mower so it can’t be paired with the smart phone app for operation. 

The on-board GPS is used for added security in several ways.  First, a geofence around a home can be setup and a notification will be sent to the homeowner’s smart phone in the event that the mower is moved beyond the geofence.  Second, the on board GPS can be used to locate the mower if it is stolen.


Honda manufactures two robotic lawn mowers.  The Miimo HRM310 is for lawns up to .37 acres and the HRM520 is for lawns up to .75 acres.

Like other robotic mowers, the Miimos rely on a boundary wire to keep them within the confines of the homeowner’s lawn and to avoid obstacles; such as trees.  Unlike the Husqvarna mowers, it doesn’t use a guide wire to help the mower return to the base station for recharging or to locate difficult to reach sections of a yard. 

A homeowner can even view how a Honda Miimo mower would work in their yard using a simulator on the Honda Miimo web site. Using the simulator a homeowner can zoom in on a satellite image of their home, lay out the boundary wire around their property, and watch how the Miimo mower would cut the lawn

Unlike the Husqvarna models with Automower® Connect, or Automower® Connect@Home, technology, there is no ability to control the mower with a smart phone app.  Both the HRM310 and HRM520 are controlled through an integrated 18 button keypad and an LCD display.  Both have an identical cutting width; 8.7 inches.  Both have an anti –theft alarm, require a pin code, and include lift/tilt sensors.  

The HRM310 operates on a 22.2V, 1.8Ah lithium ion battery and the HRM520 operates on a 22.2V, 3.6Ah battery.  The larger battery allows the HRM520 to operate for 60 minutes vs. only 30 minutes for the HRM310.  The HRM310 can be recharged in only 30 minutes while it takes a full 60 minute to charge the HRM520.

The mowers come with a transformer, docking station, special screws that secure the docking station to the ground so it won’t shift, a reel of boundary wire that attaches to the docking station, pegs to secure the boundary wire, and a spare set of blades.

The Miimos software includes some more advanced mowing options than the Husqvarna mowers.  Homeowners can choose from three different lawn cutting patterns:

  • Random – for cutting large open areas
  • Directional –  more back and forth pattern (typically used by a human cutting a lawn) for obstacle free areas
  • Mixed – for large complex yards

The Miimos seasonal timer offers more ability to adjust cutting to the season that the Husqvarna weather timer.  Through the keypad percentages can be entered for each month.  For example, in May and June a percentage of 100% can be entered and the mowers will cut at their maximum frequency.  In July and August, when temperatures are much hotter and grass doesn’t grow as rapidly, a percentage of 70% could be entered to reduce the cutting frequency.  During the fall, the monthly percentages can again be raised so the mower will again cut at their maximum frequency.

In addition, the Miimos can detect thicker grass areas and they will change to a spiral cutting pattern to cut these areas of the lawn.  They also include a special edge cutting mode for the area bordered by the boundary wire.

Like other robot mowers, the Miimos have three, small, pivoting, razor sharp, cutting blades that require replacement every one to three months.  These blades allow the mowers to operate very quietly.  In normal operation, the mowers only produce 58 db of noise.  In quiet mode, which can be used for operating the mower at night or when homeowners want to enjoy their yard while the mower is operating, the Miimo mowers only produce 55 db.   My experience with the Honda Miimo is that it could easily be scheduled to cut the grass at night and not disrupt anyone’s sleep; even with the windows open.

The Miimo HRM310 can be programmed for 3 starting points while the HRM520 can be programmed for 5 starting points.  Multiple starting points assist the mower in efficiently mowing the yard.  For example, if the yard consists of a front yard, back yard, and 2 side yards, starting points could be assigned to each area.  By then starting the mower in each area it helps assure that each is mowed evenly.  The mower will, eventually find its way to all areas but using multiple starting points makes the process go more efficiently.

It should be noted that Honda requires that the Miimo be professionally installed by a dealer.  At the time of this writing, Honda was offering a $500 credit towards installation with the purchase of a Miimo mower.  When I spoke to a local dealer, their business model was to simply install the mower at no charge to the homeowner and then to apply to Honda for the credit.

Integration
All the Husqvarna models that include Automower® Connect have a built in GPRS cellular radio.  Included with the mower is a 10 year mobile data contract.  This provides connectivity for the smart phone app, Alexa voice control, Google Home voice control, and IFTTT.

Voice commands provide the ability to start the mower, pause the mower, and tell the mower to resume mowing.  In addition you can tell the mower to park (return to its charging base), park until further notice (return to the charging base and ignore scheduled mowing until a command is issued), and request status of the mower.

The IFTTT service is even more full featured.  Similar to voice commands there are actions to start the mower, pause the mower, resume the mower, park the mower until the next scheduled start, and park the mower until further notice.  In addition, there are IFTTT triggers for when the mower starts charging, when the mower has an error, when the mower starts mowing, when the mower has paused, when the mower has stopped, when the mower has parked, when the mower is leaving the charging station, when the mower status has changed, and when the mower is going home.

Unfortunately, the Honda mowers do not offer any integration capabilities.  There is no ability to program, or control, the mower with a smart phone app or through a web service, such as IFTTT.

Grass Growth Model and Scheduling Software

The one common issue I see with all these mowers is with their scheduling software.  None of them is capable of truly taking environmental conditions into account.  The Honda Miimo mowers include a feature that allows you to adjust the schedule by month; taking into account that grass typically grows less in late summer than it does in the spring.  The Husqvarna models include a very basic weather timer that allows a homeowner to manually adjust the schedule themselves as the weather changes.  However, any abnormal weather conditions can cause the mower to cut the grass too often, wasting energy and causing undo wear on the mower; or not mow often enough. 

With that in mind I wrote a scheduling system for a Crestron automation processor that estimates grass growth based on both historical norms and environmental conditions.  The software for this can be found on my GitHub. 

The growth model took several months of research to develop with the help of people in turf grass research from across the country.  A detailed explanation of how the model works, for those interested, is provided below.

The example program I wrote measures how much water has been applied to a lawn through irrigation and rain. It then passes this data to the mower scheduler software that includes the grass growth model.  This is accomplished through integration with a Rachio smart irrigation system controller and through integration with a Weatherflow smart weather station.  The example program also gathers temperature data from the Weatherflow and passes it to the grass growth model.  The software could easily be changed to collect this data from a different smart irrigation controller.  Similarly, the weather data could be collected from a different smart weather station or the Internet.

The software uses this data, along with information on the type of lawn grass, to estimate growth and schedule the mower appropriately. 

The only mowers that the software will currently work with are the Husqvarna mowers with Automower® Connect technology because of their integration capabilities through IFTTT.  However, as new mowers come available, that include either an IFTTT interface or an open API, there is no reason the software couldn’t be modified to work with them.

Parting thoughts

Compared to a common gas or electric push mower, Robot mowers are fairly expensive.  Below is a chart that includes the list prices of each mower and the yard size the mowers are designed for

Mower
Yard Size (acres)
List Price*
Honda Miimo HRM310
.37
$2500
Honda Miimo HRM520
.75
$2800
Husqvarna 315X
.4
$2000
Husqvarna 430X
.8
$2700
Husqvarna 430XH
.8
$2700
Husqvarna 450X
1.24
$3500
Husqvarna 450XH
1.24
$3500
*This is just the price for the mower itself.  In the case of Husqvarna a separate installation kit must also be purchased.  The price also doesn’t include installation.  At the time of this writing Honda is including a $500 credit for professional installation; which is a requirement.  Husqvarna doesn’t require that their mowers be professionally installed but it is highly recommended by the dealer.

All the above mowers, when paired with the lawn size they are designed for, should provide relief to the homeowner from the time required to mow a lawn every week during the summer.  It is important to note that there is still a long list of tasks required to take care of a lawn.  For example, even though a robotic mower, with a properly installed boundary wire, can get closer to obstructions than most riding mowers, for a clean, manicured, lawn a homeowner will still need to use a trimmer to clean up around trees, shrubs, next to fences, etc.  However, the time to perform that task is still significantly less than it would take someone to mow their entire lawn.

It is also important for potential buyers to recognize that fences and gates will provide additional challenges to using a robotic mower.  All of the above mowers can find their way through gates; but only if they are left open.  Dog owners that allow their pet to roam freely in a fenced back yard will need to make adjustments for a robot mower that needs open access to all parts of a yard.  The scheduling software I wrote includes a trigger to open gates if a motorized system is installed.  However, this adds an additional cost to an already fairly expensive product.   Alternatively, a cutout that allows the mower access through the fence could be made but this may, or may not, work for every pet owner.

Both mowers are capable of operating in the rain.  However, as Honda warns on their web site, “mowing in the rain is not recommended for optimal cut performance”.  Neither the Mimmos nor the Automowers® have a rain sensor to avoid this situation.  Integrating an Automower® with a smart home processor, or hub, through IFTTT could resolve this by triggering the Automower® to return to its charging bay when either rain was detected by a smart weather station or through weather data obtained through the Internet. 

Similarly, there are potential issues if one of these mowers is operating at the same time an irrigation system is active.  Again, the mower may not cut the lawn as well as it would were the grass dry.  Further, if the mower strikes a pop-up spray head it could break it, leading to a significant water leak. 

Finally, even with the security features built into the robotic mowers, they will probably present an inviting target to thieves that don’t recognize that they can’t be used by anyone other than the original owner.  For that reason it is fortunate that the mowers are quiet enough to be run at night.  Scheduling the mower to operate late at night can provide an added degree of security. 

For those left wondering how well these mowers work, all the dealers I spoke to discussed their adoption by professional landscaping companies.  After installing a robotic mower at a client’s home, the landscaping company would only have to dispatch a single person to visit the customer each week instead of a team of workers as the work to trim the edges of the yard, clean up flower beds, etc. could easily be handled by just one person.  This is a significant savings in labor and money.  In fact, one of the dealers talked about a pending order for almost 200 robotic mowers from one landscaping company.

Thanks for reading.

Growth Estimation Model

For those interested in digging into the details, I’m including this section on the model I developed for estimating the growth of turf grass.  This is an integral part of the software I wrote for automating the operation of an Internet connected robot mower using a Crestron automation processor, which can be downloaded from my GitHub.  I’ve included this explanation of the model so anyone with a different automation processor can port this to their programming environment

First I would like to thank Dr. Larry Stowell at PACE Turf, Dr. Paul Brown at University of Arizona Cooperative Extension, and Dr. Thomas Samples at the University Of Tennessee Institute Of Agriculture for their patience and assistance in helping.  The model estimates grass growth based on temperature and water (irrigation + rain).  While fertilizer is a very important factor in estimating grass growth I didn’t see a practical way of asking a homeowner to accurately report the amount of nitrogen, and other nutrients, that were applied to their lawn.  To work around this limitation I simply added an adjustment to the model that allows the homeowner to “tweak” it based on how well it represents the growth rate of their lawn.  For example, if their lawn is well fertilized then they can increase the calculated growth rate for their lawn by increasing the adjustment factor (AF).  Similarly, if they haven’t fertilized their lawn they can simply decrease AF.

The basic equation for grass growth is:

Grass Growth Rate = OSGR * GP * ETP * AF

Where

OSGR = Optimal Species Growth Rate - The growth rate for a given species of grass under optimal conditions
GP = Growth Potential
ETP = Evapotranspiration Potential
AF = Adjustment Factor where the value is greater than 0 and less than or equal to 2.  For example, an AF of 2 will double the rate growth that the model predicts.

The “Optimal Species Growth Rates” for popular species of lawn grasses are as follows:

Grass Species
Growing Season
OSGR in Inches per Day
Fine Fescue
Cool Season
1/8”
Kentucky Bluegrass
Cool Season
3/16”
Tall Fescue
Cool Season
1/4”
Perennial Ryegrass
Cool Season
3/8”
Centipedegrass
Warm Season
1/16”
Zoysia Grass
Warm Season
1/8”
St. Augustine Grass
Warm Season
1/4”
Bermuda grass
Warm Season
3/8”

Growth Potential is defined as follows
GP = e(-½ (((average temperature – optimum growth temperature) / variance) ²))

Where

Optimum Growth Temperature = 67.5 degrees Fahrenheit for cool season grasses and 87.5 degrees Fahrenheit for warm season grasses
Variance = 10 for cool season grasses and 12 for warm season grasses

Before diving into the equation for ETP it is important to understand what evapotranspiration is.  Google’s online dictionary defines evapotranspiration as “the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants”.  It is also important to note that the amount of water required for plant growth, beyond what is defined by evapotranspiration, is negligible and can be ignored. 

In addition, water isn’t applied to a lawn in an orderly manner.  It doesn’t rain every day and local ordinances may specify that irrigation can only be applied to a lawn on a non-daily schedule.  The water a lawn receives through irrigation and rain needs to be measured, accumulated, and removed through evapotranspiration.

The equations to precisely calculate evapotranspiration are quite complex.  Rather than trying to perform these calculations I chose a simpler route and leveraged the power of the Internet.  An online search for evapotranspiration by your location should provide you with historical ET values by month.  These can simply be entered into the software. 

The ET value obtained from the Internet must be multiplied by a crop coefficient (Kc).  For warm season grasses, Kc varies from .6 to .8.  Below .6 the grass is in stress and above .8 there is no increase in benefit to the lawn and you are wasting water.  For cool season grasses the Kc ranges from .8 to .93.  ET * Kc defines the amount of water (in inches) required for grass growth where varying the value Kc defines how lush the lawn will be.

Each day the water in the soil (SW) equals the previous day’s water in the soil plus any rain and irrigation applied during the day.

If SW is greater than or equal to ET * Kc2 then water removed from the soil (WR) = ET * Kc2 and SW = SW – WR.  The assumption here is that the evapotranspiration will remove as much water as available up to Kc2 at which point water beyond that will simply remain in the soil.

If SW is less than ET * Kc2 then WR = SW and SW = 0.

ETP = ((WR / ET) – Kc1) / (Kc2 – Kc1)

Where for warm season grasses Kc1 = .6 and Kc2 = .8.  For cool season grasses Kc1 = .8 and Kc2 = .93.

If ETP is greater than one then ETP is equal to 1.
If ETP is less than zero then ETP is equal to 0.

References
Growth Potential Values for cool season and warm season turf – Paceturf.org –

Converting Reference Evapotranspiration into Turf Water Use – The University of Arizona College of Agriculture and Life Sciences, Cooperative Extension - https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1195.pdf