This project involves 120VAC Electricity - I've designed and worked on High Voltage Equipment up to 1000VDC 1000A in professional engineering environments. I have a sound understanding of the consequences, and the requirements to do things like this safely.
***Please do not attempt to mimic this project unless you have the requisite skill. I assume no responsibility for bodily injury or damage to property as a result of trying to copy these instructions unsuccessfully.***
The point of this project is to make a "set-it & forget-it" type seed starting box.
To avoid the risk of burning my house down, I'm utilizing Solid State Relays that I Acquired Cheaply second hand.
Lastly a real time clock and LCD were added to the assembly to improve upon the stand-alone capability of the device.
Solid State Relays
Duemilanove in this case
Real Time Clock Module
Spark Fun Real Time Clock Module Based on DS1307
Serial Enabled 16x2 LCD
Spark Fun Serial Enabled LCD
I took a little time off. It's the end of the ski season here, and between skiing with friends, and everything else, I dealt with it as is.
Finally I've gotten back into the coding spirit, and have added a few new features, in addition to new software. For upgrades, I added a Real-Time Clock, and an LCD Screen. Both were from Sparkfun. The real time clock ensures that the time is always correct, regardless of how many times the Arduino is restarted. The LCD screen was serial enabled, and allows me to see the status of the device at all times.
Code is still evolving, version 3 will be out shortly.
I'm still testing my code. I'm discovering that I haven't implemented the alarms for the light correctly, so it never turns off/on properly...
I have installed a small 12V Fan , cutting a hole for it out of the top of the container. I also drilled a corresponding ammount of inlet vent holes at the opposite end of the enclosure.
So long as the lamp is on, the enclosure will always remain fairly warm, and the fan will run intermittently. I've found it take 15-30 seconds for the fan to cool the enclosure from 25C back to 24C. It may take less, eventually I'm going to put a very sensitive temperature sensor at the fan outlet to ensure it shuts off when the exhaust temperature is the at the bottom of the set point.
About saftey: I've set the fault temperature in my code to be 30C. In my experience most wire insulation is good to about 60C. Additionally, the relay is rated for 240VAC at 25A (That's 6000W), and I'm using 120VAC at <=5A (600W.)
I've been struggling through the code. I got it all working finally. It's not perfect, but when theres a fault, it fault's to a safe state. The fault doesn't run as perfectly as I'd like, but that's ok.
Coding is my weak point. As such, when I approach projects as such, I start with the BARE MINIMUM necessary to get the thing to show functionality as quickly as possible.
For initial testing, I am simply running the light in the growing enclosure, and measuring the temperature over time. The program that I wrote spits back over serial, comma separated strings of the temperature readings.
To log the data, I'm using the logging feature of putty, saving the entire session to a .CSV file, while putty simply listens to the arduino at 9600 baud. If you have a computer available, this is about the easiest way to store output from your Arduino.
Take a 20 gallon storage tote. Using hot glue, fit mylar coated bubble wrap around the interior of the enclosure, and the interior of the cover.
Cut insulation carefully to allow container to close easily.
(These are the areas I wing it.) Get a board slightly larger than the footprint of your fluorescent lamp.
Layout your junction boxes approximately how you'd like them to sit.
When the junction box is roughly where you want it, collect a relay, and place it in the bottom of the junction box.
Using self-drilling dry-wall screws, drill through the hole in the heat sink of the relay, through the junction box, and into the wood. Add another screw to prevent the junction box from easily rotating.
Electricity and loose metal fragments are not friends, clean these out of your enclosure as necessary.