As I move forward in planning out this tank, I keep running up against limitations with the available control systems available to our hobby (Apex / Profilux). I started a thread over on the GHL sub-forum to figure out if my idea would work through a Profilux, but the gurus couldn’t confirm or deny the control capabilities. And since the tank inhabitants will be entirely reliant of hardware keeping water in the display, I must minimize the risk of failure as much as possible.
@theatrus recommended building my own controller to facilitate this uniquely challenging application, which seems to me the best option. I’ve developed a few solutions for smaller tank with Arduino, but the development time and stability leads me to struggle with moving forward. Then it hit me! This is an automation project at its finest! Why not use a controller designed for automation?? It can interface everything I need: 4-20ma input/output, 0-10v input/output, inputs for switches/floats, and outputs for solenoids/relays/lights/pumps...the options are nearly endless. And, most PLC’s these days have a built in function for PID loop control, precisely the function I need to control the modulating valve and keep water at a consistent level.
Crazy? Overkill? Yes. But using a PLC will be much easier to program and offer a higher degree of confidence in operational stability. Not to mention, most systems are extremely versatile and modular. I don’t have much experience in using PLC’s, but it shouldn’t be too difficult. Certainly much less difficult than building a Arduino/Pi controller from scratch. Cost wise, several options are available with pricing comparable to a well equipped Apex/GHL setup.
AutomationDirect.com has several low cost PLC options targeted towards small projects. Click, Productivity Series, and Do-More BRX are a few options. Since I’m looking at this as an investment, I’ll likely go with the Productivity1000 or Productivity2000 so expansion down the line is available. These come with free software and a month of free training.
I’ve already ordered a modulating ball valve actuator and will handle water level sensing with a 40-300mm ultrasonic sensor from AutomationDirect.com. Most likely, I’ll also use these sensors for ATO reservoir and dosing reservoirs as they will provide my PLC with level which can be converted to volume with included software.
The P2000 PLC system has a built in OLED which can give status feedback about what’s happening with the system, but for ease of use one of these HMI’s will be added down the line.
More to come! Still deciding on dosing pump motors and ph/orp/conductivity probe integration. If anyone has experience in the PLC automation world, your input would be greatly appreciated!