The Creek: Solution Architecture 1.0

In the previous post I introduced my IOT Project for the Elkhorn Creek.  In this post I provide an overview of each of the building blocks in the system.  Currently (because I have some ideas for improvements) there are four major blocks.  Over the next few weeks I will write one or more detailed posts for each of the blocks.

1. Pressure Sensor

The Pressure Sensor is a Measurement Specialties US381-000005-015PG installed into the end of a long PVC pipe.  Inside of the pipe there is a ~150 foot long telephone wire which is attached to the Creek Board.

All of the PVC came from Lowe’s and is glued together with PVC cement.  At the end of the pipe you can see a ball valve.  This valve will allow me to drain out any water that leaks or condenses into the system.  This can absolutely happen and in fact killed an earlier revision of the system.  The sensor itself is screwed into a 4″ clean-out cap.  This will allow me to unscrew the cap and replace the sensor if it is ruined by something.  Also, the cap is fairly thick and allowed for more threads on the sensor to grab into the PVC, which also improves my chances of not needing to replace this $142 sensor.

2. The “Creek Board”

The Creek Board is an Arduino Shield that I designed to replace my prototype bread-board.  The shield contains:

• The 51.1 Ohm Resistor which turns the current loop into a measurable voltage
• A TMP36 Temperature Sensor which I was originally planning to use for temperature compensation.
• Testpoint’s to measure the voltages with a DMM
• Analog low-pass noise filters for the current loop
• A Transient Voltage Supressor Diode to protect the CYPI board from an ESD event.

3. CYPI

I designed CYPI to be a “Cypress” to “Raspberry Pi” bridge.  On the bottom of the board is a connector that is compatible with the Raspberry Pi GPIOs.  On the top of the board are connectors that are compatible with Arduino.  On the board is:

• A Cypress PSoC4200 – CY8C4245AXI-483
• A wall wart barrel power connection
• Voltage regulators that allow the entire system to run off of one wall wart
• A 10-pin ARM Program/Debug header
• A reset switch
• A user LED

4. Raspberry PI

The Raspberry PI is a single board linux computer.

This RPi serves the following tasks

• An I2C Master to read temperature and pressure data from the PSoC4.  This task is performed by a Java program that is triggered once per minute by the Linux crontab
• A MySQL database server to hold the historical data
• A Java program that uses a JDBC connection and JFreeChart to once per minute create a PNG chart of the last 8 hours of data.
• Tomcat with a Java Server Page (JSP) which dynamically creates the website http://www.elkhorn-creek.org