I finally get around to buying seeds and gain a much better understanding of how the 4 channel relay works on the DC and AC side of the circuit.  It continues to amaze me how much great learning material is on the Internet.  It’s time to get the Leaf Spa going, so I also list what I see as left to do.

Buying Seeds

It’s past time for me to order seeds.  I start the seeds in my seed starter set up.  Once they get big enough, I will transplant them into the Leaf Spa.   I’m starting to order my seeds from the Territorial Seed Company.  I am ordering from this company because they are known to have good seeds, are family owned, and are located fairly close to my family in Oregon.  Here’s what I ordered:















Sweet Basil




Since I use basil at least twice a day, I’m going to try another variety:



Genovese-type Basil






















I use a mixture of stevia leaves and extract.







Seeds are ordered!

More on Relay ON/OFF

WhyCatYesterday I noted the relay turned ON when the pin = LOW.  Prior to this, the relay turned on when the pin = HIGH.  So why am I getting so confused???  Geez…i get so clueless…so let me take a step back and look at the schematic for the relay:Pasted Image 2 2 17 8 36 AMOh- that makes more sense.  When the Arduino pin is set to LOW, the current flows through the DC circuit since now there is a GND for the current to go from the 5V+ to GND.  The current drives the optocoupler’s light on which activates the AC circuit.  

One more thing about the DC circuit. Dejan Nedelkvski did a great job in his Youtube video pointing out an issue with not having a separate 5V drive the relay in his video.  If I was the kind of person that was extremely risk adverse, I would follow his recommendation.  For now, I will use the Arduino’s 5V to power the relay.

Now over to the AC circuit…this explanation by MKme Lag helped me:


When the AC’s circuit is activated, the armature connects the COM contact with the NO contact.  When the AC circuit is not on, the armature drifts to the NC contact.  Which means given the wiring I did (AC power on COM,  AC wire controlled by DC wired to NO terminal), when current runs through the DC circuit by setting the Arduino pin to LOW (forming a GND), the COM and NO are in contact – completing the AC circuit and turning the light on.

I now have a more intuitive feel for how the 4 channel relay actually works. I reflected on what I learned in my SimpleRelayTest.ino Arduino sketch for this test.

What’s Left To Do

While I wait for the seeds…and then wait for the seeds to grow a bit (should have planned this part better 🙂 ).  I’ll finish up the Leaf Spa:

  • Repair any plumbing piece that leaks when the pump is on.
  • Make an enclosure for the Arduino + Shields.
  • Code and test reading the sensors, adjusting the CO2, and logging readings to an SD card.
  • Evaluate the data written to the SD card and figure out the best (at least short term) use for the data.
  • Drill holes on shelves where cables need to snake through.
  • Put the back and sides on the Base.
  • Mount the Relay box to the Base.
  • Plug everything in and do some test runs that pump water through the Base, control the lights and CO2, and monitor temperature, humidity, and CO2.
  • Iterate the above until everything is working and ready for the plants.