Well, this weekend I actually had some time to sit down and do some long awaited project work. I'm working on doing some PLC (Programmable Logic Controller) stuff for my two 120 gallon tanks downstairs in the living room. It involves a lot of wiring and planning, so I thought that I'd take another small PLC that I had at my disposal and set up a prototype for my tank in the bedroom which is my 20L tank.
The first thing that I had to do was come up with an enclosure for them. I wanted something plastic, because it's much easier to work with. I started with the square box, but figured it would be too small for that I wanted to do. I could have jammed it all in that box, but I have some future expansion plans and using the two boxes allows for that expansion if I ever get around to it.
To explain the fist picture, it's the two enclosures mounted together and with the tops off. The Sola device is the power supply. It provides me with all of the 24V DC that I can shake a stick at. That powers not only the PLC (mounted above it in this picture) but all of my relays too. I think the PLC will handle switching 120V AC, but I figured that I leave the control side of things at 24V to make myself feel better. It was way more work, but for a prototype, I figured it was worth it. On the left of the powersupply and PLC (at least in this picture) is the little 24V power distribution center that I made with some terminal blocks.
Moving to the right in the picture is the smaller slave box that houses the relays and all of the 120V AC stuff. Again, I made a distribution block with some terminal blocks.
This is a closer shot of the AC box. All of the red wires are 24V control wires leading to the PLC. The PLC determines which output (10 total) will energize which relay. All of that is determined by programming it with some software, which I did the other day. When the PLC energizes and output, the relay closes and passes 120V from the distribution block to the corresponding outlet.
The last picture is of everything assembled and the covers on. I put 4 switches on the cover, and each switch controls an outlet. There's also a constant on set of outlets on the side, just because I had extra stuff lying around.
As far as "well that sure looks nifty, but what does it do?" Here goes:
Lets name the outlets for the sake of making things easy. 4 pairs of outlets, pair on being 1 & 2 (1 on top) pair 2 being 3 & 4, etc...
Outlet 1 is programmed for my actinic lights. At 2:00PM the PLC switches that outlet on and the actinics come on. They run until 10:00PM. Switch 2 is the for daylight bulbs. They come on at 2:30PM and switch off at 9:30PM. Outlet 3 is for the auto top-off. In the picture above, you can see a small gray wire. That goes to the float-switch. When the swich is low, the PLC turns on outlet 3 powering a pump that pumps RO/DI water into the tank until the float switch says that it's not thirsty any more. I also too this opportunity to paint the snail guard black. It was annoying me white.
Ok, outlet 4. Constant on right now. If I get bold, it will eventually control the heater via a thermocouple module for temp control. Right now the heater is just operating on it's own.
Outlets 5, 6, 7 and 8 are controlled by the 4 switches in the cover. 5 & 6 are my SEIO 620 and another pump for water flow, and 7 & 8 are for the two refugiums that I have on the tank.
Seeing as 74% of you won't even read this far, I'll just stop for now.
My PLC tank automation thread
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