Server Room Environmental Monitoring – Part 2
[This post should have been published 2 years ago… oops]
In an earlier post I began working on a Server Room Environmental Monitoring based on an Arduino.
This project was started just for fun- I wanted to learn more about micro controllers (specifically the arduino platform), and partially because I didn’t have room in my technology budget at work to do it the “right way” (not even sure what way that is for a small business…netbotz?). I wanted to improve on my original idea by having it accessible remotely via my network. Thus we end up with our first semi-finished prototype:
This device monitors the temperature and ambient light readings and displays the values on an LCD and displays them in a browser windows rendered in html. I have the 2nd iteration pretty much completed, just working through some of the programming issues. [At the time] I wanted to expand the sensors to include multiple i2c temperature sensors, and possibly make the LCD display wireless via Xbee. Later posts will show I ended up using a Nanode with Grove sensors [but I digress as this is documenting the original build.]
Arduino Duemilanove (ATMEL 328p)
DFRobot Ethernet Shield DFR0110, Powered by a Wiznet W5100
Sparkfun Protoboard (v2)
TEMT6000 Ambient Light Sensor by Vishay via the Sparkfun Breakout Board
JK Device HD44780 Compatable 2 x 16 Char LCD display
Sparkfun SerLCD I2C backpack
Adafruit Arduino enclosure
I had to add the Xbee out of necessity (I had them from another project, but when I burned out the FTDI chip on the Arduino I had no way of programming it, but it turned out being rather convenient!)
Two Xbee with a chip based 1mw antenna.
Xbee Explorer Regulated
Xbee Explorer USB
Generic PIR Sensor module from ebay – looks very similar to this.
I have most of the code working. I made the code available as a download. It includes the two libraries for the I2C Serial LCD backpack controls and the LibTemperature library for the I2c temperature module:
Arduino_Environmental_Monitoring_Webserver [this is a .zip file]
The code is also available here in plaintext [here]
This is how it works:
pull in the libraries for all the different modules
set up the variables to store numbers
some code to control the LCD
Set the pins for the LCD and for the LED
Setup the MAC and IP for the Ethernet Shield
read the sensors and store the values to the variables
convert the C temperature to F and store to a different variable.
Print the values to the display
Send the values inside HTML to the browser
Send the browser a command to refresh every X seconds.
When using my Arduino for another project I was testing a large number of SMT led’s all at once, pulling a decent amount of current through the 3.3v regulator, far exceeding the 50Ma spec of the L.D.O inside the FTDI. I inadvertently short circuited or over drive the 3.3v line , burning out the FTDI USB to RS232 chip on the board. I ended up utilizing two Xbee modules and connecting one to the TX /RX lines for serial connection. This worked out great, because It forced me to get the Xbee working! I now have 2 Xbee units paired for serial communications.
There were some small issues with the Ethernet Shield. #1. The pin map on this particular model uses (Arduino) pins A4 and A5 to access the SD card, which I am currently using for my I2C temperature sensor communication. There were also issues with the bottom of my proto-shield hitting the ethernet plug and grounding out, so I extended the pins the quick and dirty way by extending it with pin headers.
The enclosure from Adafruit fit great, but the end plate did not work with the Ethernet shield. I had to discard the plate for the connectors.
Dirty Coding Schemes:
I was getting some odd looking numbers on the LCD screen when testing it in a variety of light and temperature ranges. The number would “print” to the screen, and when it poured over to the 3rd digit, that digit would stay on the screen, regardless of what was being written to the block immediately to the left.
I didn’t bother figuring out how to erase data or clear the screen between refreshes, so in my code I had it over-write 4 blank spaces, then go back to the beginning and write the data value. probably a very dirty way of clearing that part of the screen.
the arduino code strings together the HTML and streams it to your browser. there is a small snippet of meta html HTTP-EQUIV “REFRESH” that tells your browser to refresh every few seconds to see the new values gathered in the loop code.
[Hard Coded IP Address]
Unfortunately, I found that the DHCP library did not work so well for me. I decided to hard-code my device. this has certain advantages, but makes it less portable. Not everyone uses a class B /16 subnet at home.