The Compost Professor - A Smart Composting System

6/5/2017 -

I created a simple Alexa skill that tells a user if an item can be composted.... I wanted to extend this functionality into a "bolt on" Alexa skill for the Smart Compost System. The Alexa skill would integrate with the Smart Compost data to tell the user recommendations specific to his/her needed. For example, if the oxygen flow was too high (not enough carbon), then the user would be directed to add items like grass clippings, leaves, newspapers instead of fruit or vegetable scraps.

Video below is a demo of the skill...

You can read more about it (and get the source code) here: https://www.hackster.io/darian-johnson/compost-helper-alexa-skill-51d52e

6/3/2017 -

I am in the process of creating a dashboard for the Compost System. The version is still very much in the early stages, but will share what I have created to date:

• The gauge shows the number of days until the compost is ready (25 days at greater that 110 degrees F).
• The sensor indicators are red, yellow, and green based on the state of the sensor
• The actions panel shows the interpretation of the data, and the actions the user must take. This also has a red, yellow, and green indicator.

The dashboard is written in HTML/Javascript, leveraging:

• Bootstrap
• JustGage.js
• icons from Freepik

The data is stored in a SQLite database. The data is retrieved by making a http call to an php.file (see code in attachments section for details).

Right now, the actions are hard coded into the HTML; I am still in the process of writing the logic for determining when a particular action needs to take place. For example, if the temperature is low, but the ambient temperature is low as well, then we would want to wait 5-10 hours to determine if the temperature rises before asking the user to take more corrective actions (e.g. stirring the compost or adding more nitrogen-rich materials).

June 2 2017 -

I've assembled the sensors and actuators into a bird's nest of wires... but, it works fine for a prototype. The attached video shows how the assembled prototype will work (I wanted to show the components before I added them into the composting soil).

A few notes:

1. I originally planned to use a solenoid and use gravity to water the compost, but ultimately decided on a pump.
2. I have a difficult time calculating % humidity using the moisture sensor (there isn't a great correlation between the voltage out of the sensor to the % wetness of the soil). I'm looking into using a better sensor that (a) outputs % moisture and (b) is more robust (this sensor would only last a few months) [I'll probably use this sensor - https://www.amazon.com/Adafruit-Accessories-Temperature-Moisture-Sensor/dp/B00XW2NXD4]
3. I am using an ultrasonic sensor for the prototype, but plant to switch to a "dumb" float sensor (I don't need to know levels - just dry or not dry]
4. I was originally using Bluetooth LE to send data from Arduino to a Raspberry Pi - but decided to remove that logic and go with LoRa instead. Devices are in the mail now... hope to show that interaction later this month.

Last note - here's a simple process flow that outlines the logic.

5/27/2017 -

I got my first set of sensors in the mail. At a high level, my though process is:

• Temperature sensor to measure compost - healthy compost must reach a temperature of 140 F for 20-25 days
• Moisture sensor - compost should be 40-60% moist
• Methane Sensor - a high PPM reading would indicate that the compost is in an anaerobic cycle (similar to a landfill)

I also have a few actuators

• solenoid valve to support gravity drip of water (if moisture is below 40%)
• servo - to open/close a vent to a perforated pipe embedded in the compost (to support additional oxygen and air flow

Finally, I am using a Arduino 101 as the micro-controller for the sensors and actuators. I will use a Raspberry Pi to persist the data and make it available in a web page. I'll use BLE for communication between to the for the prototype (will need to move to LoRa for the final product.

May 26 -

So, my family composts.... but we do a poor job of it. We rarely turn the compost or water it. We just add compost-able materials and hope everything works out. What we end up with is what you see below (questionable-quality compost at the bottom and rubbish/leaves at the top)

There is a science to composting, and I'm hoping to use sensors to measure gas output, temperature, moisture of the compost. This information would then be used to make recommendations (more brown, less green, more water, turn, etc). I ordered a bunch sensors from Amazon; so I hope to have a very high-level prototype in the next 1-2 weeks.