Today we finally began growing our plants. Because we are starting out with seeds, we decided to germinant extra seeds, hoping half of them will grow. We wrapped six lettuce seeds and six radish seeds into a wet paper towel and put the paper towel in an open zip seal bag (Joe Steinmacher)
While Joe was starting our (hopefully) plants, we set the water pumps in place and hooked up the tubing and ball valve. Mark and I secured the ball valve and tubing to the side of the grow bed. We removed the aeration pump because the ebb and flow cycle should introduce oxygen into the water as it drains through the grow bed and is returned (via the Bell Siphon) to the aquarium. In reference to our necessary bacteria, while securing the pumps in the tank bottom I noticed a fine sludge had begun to form. Good news for us; the fish byproduct is what ultimately feeds the plants. We must note that the control system for the pumps is not installed at this time as we are still awaiting sensors (coming from China). To make the pump operate, we simply wired the leads through the Normally-Closed side of one of the control relays.
We metered the pump flow using the ball valve and measured the time it takes to move approximately ten fluid ounces from the aquarium to the grow bed. Ideally we should see about ten ounces every sixty seconds. We were able to meter the flow to about fifty seconds per ten ounces. At this point it appears to be a small trickle. While it seems slow, we must keep in mind that we need to move approximately two gallons of aquarium water up to the grow bed over a thirty minute span, followed by immediate draining. When the grow bed reached it’s drain point, we soon discovered that in-flow in the siphon was too little and that a vacuum wasn’t being created to initiate the siphon. The overflow was merely matching the pump flow. For the time being we decided to open the ball valve to 100% and to ignore the timed ebb-an-flow cycle because there aren’t any seeds in the grow bed.
The next step in getting our system up and running was to finish the bell siphon and box system which will become our grow tray. We decided to use a homemade bell siphon to drain our ebb and flow system because it is cheap, easy, and reliable; it relies on gravity and has no moving parts so there is very little chance for mechanical breakdown. The picture shown below is our bell siphon. The valve itself is a system of two pipes that work together to siphon the water out of the tank at a predetermined level and stop the siphoning at another predetermined level. After the group installed the valve, we filled the box with clay spheres (Hydroton) which we will use for our growing medium.
In order to germinate seeds soon, we need to be sure that we have a healthy growing environment for both our fish and plants. To do this, we needed to decide what plants to grow based on the knowledge that our fish tank should be between 60ºF and 70ºF and have a pH between 6.5 and 7.5. Also included in our research was what plants grow well together; in other words what plants are companion plants. Companion plants are different species of plants that produce a chemical or nutrient byproduct that is advantageous to other plants. Finally we had to consider what plants can reasonably grow to harvest by the end of the semester (this criterion made us hesitant about fruiting plants). With all of these factors taken into account, we decided to grow Lettuce and Radishes. These are fast growing, resilient, companion plants.
Finally, we ended the day by testing the chemistry of our fish tank. It turned out that the pH of our tank was a little high, around 8.5. I added about 10-12mL of pH down which rapidly dropped the pH to 6.5. Word of wisdom to anyone else that wants to use it: use it sparingly. A little goes a long way.
In a previous post (Proof of Concept: Automated Pump Control ) we discussed how a pair of aquarium pumps are to be used to move the water in our ebb-and-flow Aquaponics system. This week more components arrived including our temperature sensors and a relay board. The proof of concept for the pump control worked well so it was time to add in the relay board. Initially, all that was done was to hook up the control side of the relay (the coil) in series with an LED to ensure that each relay was working properly. The next step was to attach a load, a Red LED in this case, to the controlled side of the relay. The logic is quite simple, when the DPST switch is in position 1, the first relay coil is energized (Green LED is ON) and the action of the relay is to close its NORMALLY OPEN contacts, thus lighting the Red LED. When the DPST switch is moved to position 2, the first relay is de-energized (both its Green and Red LED’s are turned OFF), and the second relay is turned ON, demonstrated by the second Green and Red LED’s being ON as well.
It stands to reason that we cannot have a person standing by the Aquarium at all times, waiting for a pump to fail (when it may work fine the entire time.) The next part of our control system design involves removing our simple “spoof” switch and replacing it with some form of sensor that detects when a given pump is operating. As I said, ultimately there will be an in-line flow sensor attached to each pump that will provide a signal that correlates to how much water is moving through it. All we will have to do is determine a minimum threshold and enter that into the program. If the flow sensor signal falls BELOW the minimum threshold, the Arduino controller will assume that the pump has failed and will place the second pump in operation, looking for a proper signal from its flow sensor. It is important to note that we could do this with a flow switch instead of a dynamic sensor, but, in the event we decide to do something that requires input based on AMOUNT of water flow, we would need a sensor. Might as well start there. If we determine that a switch is more effective, we can always add it later and it will require a minimum amount of program re-writing.
The DPST switch is set to "spoof" the controller, making itthink that PUMP 1 has failed, and having it mode RELAY 2 ON, shown my the RED / GREEN LED on the right
Now that we have a good basis for controlling our two pumps, we need to build a control circuit that SENSES. Because we didn’t have our flow sensors in-hand, we used a simple potentiometer; a variable resistor to act as our changing sensor value. The Arduino is capable of reading a changing 5VDC signal and converting it to a digital signal, a number from 0 to 1023. We talked about needing a threshold value earlier. For this proof-of concept we chose a value of 500. When the potentiometer is above the “500” threshold, PUMP 1 remains on, additionally, the program was written to print “PUMP 1 ON” and PUMP 2 OFF” on the computer screen. As we turn the knob on the potentiometer, the number the Arduino sees, falls below the 500 mark. The program was written, telling the controller to turn OFF the PUMP 1 relay to turn ON the PUMP 2 relay. Again, in this state, “PUMP 1 FAIL” is printed on the screen along with “PUMP 2 ON”.
If you’ve read this far and have a decent comprehension of what we are trying to do, you may be wondering, “Why does this matter at all?” Redundancy is used throughout our daily lives in our technologically advanced society. If you’ve ever flown on a commercial airliner or been in a building when the power goes out, you have probably experienced this type of electronic control without even knowing it. Aircraft are required to have backup systems for every flight-critical system on board. In some cases it is a manual system the can be used by the pilots, in other cases, a sensor causes a master controller to switch from using a faulty component to using a good one. At times, aside from a light, bell, or annunciation on a screen, the pilot would never know the hand-over even took place. In another example, you have probably seen those large black boxes that computers are plugged into in an office building. These are basically batteries with intelligent control. When the controller senses that there is a power failure in the building, it automatically switches to its internal battery, allowing the computer, etc. to keep operating, al least until someone can shut it down properly. In our Aquaponics system, if the water stops flowing, the plants will soon die. If the water stops flowing, the grow bed, plants, bacteria, and worms can no longer filter the dirty water and the fish will die. For this reason, we need relatively fail-proof system to ensure that both our plants and fish stay happy and healthy.
While we gear up to put our Aquaponics system into full operation, some time needs to be devoted to the development of the automated control and monitor system.
As a brief update we have secured a modest aquarium and have stocked it with six goldfish in order to start the cycling process. Typically it is necessary to place fish in the tank and to wait for the proliferation of certain bacteria. This process can take a bit of time so we opted to remove gravel from the donor’s tank in an effort to “salt” our system with bacteria. We installed an automatic feeder and, until we have the pump system up and running, we installed an air stone for aeration.
Moving on. A logical choice for system automation is to use an Arduino microcontroller. Arduino boards are open-source and there is a plethora of development information available including circuit design and code. Capable of both input and output tasks, the Arduino UNO will likely be used to control the ebb-and-flow pumps, to monitor temperature, and for system redundancy. The idea is to connect a Hall-Effect flow meter in line with each of two submersible pumps. One pump will be on at any given time, should it fail, the back up pump will immediately come online. The plan is to use a flow-meter on each pump to send feedback to the controller, indicating that the pump is…pumping. If the flow-meter attached to the active pump indicates that no water is being pumped, the controller will assume that the given pump has failed and will command the second pump online and will look for a corresponding signal from that flow-meter.
Right LED representing "Pump 2" as ON, switch makes Arduino Controller think "Pump1" has failed
As a proof-of-concept, a simple LED circuit was prototyped. The LED on the left represents “Pump 1” and the LED on the right represents “Pump 2”. The DPST microswitch is our pretend “pump failure” Note that no flow-meters are included as we do not have these on-hand currently. A simple program was written to prove the idea, albeit in a simplified manner.
Now comes the hard part, making a 5VDC microcontroller switch relays that ultimately control a 110VAC aquarium pump, all based off the readings coming from in-line flow meters…
Welcome to Ecolibrium Aquaponics, the new experimental endeavor of Joe Steinmacher, Mark Powell, and Jeffrey Oberholtzer.
Before we begin, let’s take a moment to define Aquaponics and the design challenge we were given; the birthplace of our endeavor…
What is Aquaponics?
Aquaponics is described as: “… the cultivation of fish and plants together in a constructed, re-circulating ecosystem utilizing natural bacterial cycles to convert fish wastes to plant nutrients. This is an environmentally-friendly, natural food growing method that harnesses the best attributes of aquaculture and hydroponics without the need to discard any water or filtrate or add chemical fertilizers.” “Aquaponics is the cultivation of fish and plants together in a constructed, re-circulating ecosystem utilizing natural bacterial cycles to convert fish wastes to plant nutrients. This is an environmentally-friendly, natural food growing method that harnesses the best attributes of aquaculture and hydroponics without the need to discard any water or filtrate or add chemical fertilizers.” (Aquaponics Gardening Community, 2014)
What is the Design Problem?
Design, Build, Test, and Troubleshoot a small-scale, self-contained aquaponic gardening system using available resources and components, keeping space and cost requirements to a minimum. Include active or passive automatic monitor and control systems to augment the aquaponic garden’s life-cycling.
What are the Constraints?
Plants must be harvest-ready by the close of the Academic Semester
System must be contained in a 12 cubic-inch space, expandable to a larger size if authorized
System Cost should be kept below $45.00
System should be capable of growing three different types of plants
Stay Tuned and Follow Along as we create our Aquaponics System ! More to follow soon!