Click on the to get a more detailed picture of a typical
RS-485 Aquatic Monitoring and Control System
System Philosophy:
Automated Aquarium Systems has formed an alliance with one of todays leading suppliers of Data Aquisition and Control Systems, ICP DAS This alliance allows AAS to supply to our customers one of the most powerfull and scalable Aquatic Monitoring and Control Systems available. The Hardware is a network of RS-485 ICP DAS Modules and the Software is our own Windows 95/98/XP Aquatic Monitoring and Control Software DIY ToolPak . Together this combination creates a system that provides an easy to use and affordable solution that is fully scalable from the aquariust with perhaps just one or two aquariums on up to even the most demanding commercial aquariums, fish farms, and breeding facilities alike.
Basic Control Systems:
The concept of a process measurement system is a simple one; measure a process (Sensors do this). Send the measurements back to the controller (Transmitters do this). Calculate the amount of error from a programmed set point (the PC's CPU does this). Command various devices to On/Off, datalog the results, alarm on system faults or out of tolerance readings, and provide a Friendly Graphical User Interface to the operator, and our Aquatic Monitoring and Control Software (AMACS) does all of this and more.
The Measurements (Sensors):
The Users PC gets its input data from process measurement sensors placed in the aquarium water filter's return line and all sensors are connected back to the PC by a serial RS-485 network bus. A sensor is simply a device that generates a known output signal in relation to the process parameter in which the sensor is measuring. For example, in any Aquarium system one of the most important water parameters to measure or to "sense" is pH. To perform a pH measurement the AAS System uses an Industrial Quality pH Sensors manufactured by Hanna Instruments.
Sending the Data (Transmitters):
One complication of many water analysis sensors is that they are only capable of driving their output signals into extremely high impedances, or loads. Because of this reason the data signal is very susceptible to noise and other sources of interference. To solve this problem the Sensor is connected to a device called a Transmitter, and in our pH example this transmitter is the HI8614. This pH Transmitter converts the very sensitive output signals of our sensors into a 4-20 mA Dc current that is directly proportional to pH levels from 0 to 14 as measured by the pH sensor. So why do we choose 4 to 20mA signals? The majority of industrial applications use current loop signals because of their distinct advantages. For instance, 4 to 20mA signals can travel over 1000 feet of wire without degradation. This permits you to install your 7xxx I/O Modules up to 1000 feet away from the sensor's measurement point! Also, 4-20mA signals are extremely immune to noise and to offsets due to ground loops thereby increasing the measurement accuracy and minimizing the measurement errors. Finally, the AAS Control System has an Input Module called the 7018 that can directly accept 4-20mA signals then convert the readings into digital data that is sent over the RS485 bus back to the PC Controller to datalog and use.
The Controller (CPU):
At the heart of any control system is a microcontroller, also known as a Central Processing Unit, or CPU. One of today's most common CPU architecture is known as a Complex Instruction Set Controller, or CISC. A CISC CPU resides in almost every Personal Computer available today. And it is the cost and performance issue that drove AAS to employ this controller architecture in our current system. The PC's CPU is the brain of your system and it is capable of computing millions of instructions per second and of performing many advanced algorithms and functions. With this inexpensive and readily available computational power, the Aquatic Monitoring and Control System has the capability of easily controlling from 1 to 256 networked RS-485 7xxx Modules.
The Outputs (Control Signals):
Now that the controller has the measurement data what's next? Well the AMACS software decides what to do next. The software can be set up by the user to control lights, valves, pumps, solenoids, fans and more. It also datalogs every reading to a user defined file that can be loaded into many popular spreedsheets for data analysis, graphing and trending. Also, the output signals can help control several non real-time critical processes. For example, in keeping with our pH control example, if the controller has determined that the pH level was too high, then the output control signal could energize a solenoid to open a CO2 Gas Supply to inject the CO2 gas into your aquariums water stream in order to lower the pH. This Control Module is the 7042: 13-Channel Output Control Module.
In Summary:
We have just discussed one example of an application for the RS-485 Aquatic Monitoring and Control System. When this hardware system is combined with our AMACS Software the combination of cost, performance, flexability, and power is unsurpassed. In this discussion, we have measured a process, sent these measurements back to the PC, data logged the readings, calculated the deviation errors from a set point, and then output the control signals to adjust the system accordingly. This Process Control Loop is repeated over and over again for each of the many processes that we are able to control and monitor in your Automated Aquatic System. Depending on your hardware configuration you can monitor and/or control many process parameters such as; Temperature, pH, ORP, Conductivity, Flow, Chemical Dosing, Lighting, Water Level, Fans, Chillers, Pumps, Valves and more... all from an easy to use Graphical User Interface(GUI), the Aquatic Monitoring and Control Software & Hardware ToolPak running on your Windows PC.
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