Well, I have finally found the time to get working on my fish tank controller project again. Having an electronics background, I have always wanted my own fish tank controller and couldn't be bothered to go out and spend the money on a prebuilt system. The idea when I first started on this adventure, was to build the system from scratch. I would design and build the circuit boards, write the embedded software for the controller and come up with some kind of interface that will work on a PC. Other people have done this kind of thing already and although I still plan to in the future, I went with something that required a bit less hardware design to start.
For this project, I decided to use a PLC (Programmable Logic Controller) as the base for the system. The PLC I chose is made by Modicon and has 12 digital outputs (means I can turn 12 devices on and off) and 16 digital inputs (allows me to monitor the status of 16 devices). This PLC also has a number of analog inputs which allow me to monitor things like temperature, PH and ORP which I will be taking advantage of in the future. I have bought a PH probe already and just need to build a quick amplifier circuit to make it compatible with the PLC.
Here is a quick idea of how I connected everything up:
Each digital ouput is connected to a relay. When the output is turned on, the relay attached to that output gets energized. When the type of relay I chose to use gets energized, it means its contacts close, just like a switch being turned on. I wired the line voltage (115VAC) to one side of each relay and then wired one receptacle to the other side. The end result is 12 receptacles that can be turned on and off by the PLC.
The black box with the white dial in the bottom right of the fourth picture is an Intermatic timer. I have wired this into one of the digital inputs so that I will be able to use it later for whatever I want. For example, I could write some logic that uses the timer to shut off my main pump for a certain period of time while my fish eat. The possiblilities are endless. I have a number of float switches that will be connected in to some of the other inputs. In the logic, I will be using these to monitor water levels in the display in the sump. If the water level gets too high in the display, shut off the main pump.. etc. You get the idea.
Obviously I'm not done yet. I managed to get all of what you see here, done in the last couple of days. I was lucky to get the gray box you see for free but it sure made the wiring tight! I managed to make it all fit though. The box didn't come with a lid so I will be cutting a piece of plexiglass to fit over the top. This way, while keeping the salt spray out of the electronics, I will be able to open my stand and check the status of everything.
If I don't feel like looking at the controller itself to see how things are running, all I have to do is turn on my laptop and load up the interface I built in LabView. The picture you see here is what I made a few months back. While I have tested and it works quite well, I will need to change things around a bit. I will post the updates as I make them.
Anyways, I'm not sure if any of this made sense but I just wanted to post what I had so far so that I could add posts here and there as I went along instead of typing out the whole thing in one sitting.
