Hi everyone,
Being the way I am, I get VERY frustrated when I'm forced to pay much more for an item than what I know it's worth, and in our hobby this is usually the case when one visits a petshop/LFS.
Like most serious hobbyists, I've had the need to monitor the most important tank parameters electronically, and to capture the data on my computer for further analyses and record keeping - I've just never been happy to pay upwards of R10 000.00 for a hobby-grade "tank computer".
Well, I've recently found a solution - use industrial-grade controllers, available locally , and even cheaper than the flimsy hobby-grade "computers"... in fact, use the VERY SAME controllers used by some of our public aquaria. These controllers not only monitor the required parameters, they can also control them by switching relays. They are much more rugged, can be mounted up to 1.4km away from the tank, can be bought in 230V AC or 24V DC configuration, can be programmed to trip alarms, and can send the data to your computer using the industrial standard RS485 protocol, where it is recorded in Microsoft Excel or ASCII text format by the software supplied free with each unit. The units are daisy-chained from one to the next, and the connection to the PC is with a simple UTP network cable.
Here is a photo of my current 3-controller setup, consisting of a pH, temperature and ORP controller - I will be adding a conductivity controller at a later stage.
One of the nice things about these controllers is that they are completely modular - by simply changing some software settings (and the probe, of course...) one can change the unit from a pH controller to a temperature-, ORP-, or conductivity controller, and if something packs up, one simply replaces the broken module, power supply, etc. and NOT the entire "computer". Also, should something be damaged, it will not affect the other controllers.
While I was busy installing these controllers, I also decided to tidy up my light controllers (also rugged industrial units, as can be seen at the bottom of the following photo), and to install them and the temperature controller's relays in an IP65 rated waterproof switch box.
To me, one of the nicest "features" of using these controllers is the fact that I can generate a graphical picture of the tank parameters. As can be seen from the following Excel graph, the controllers also allow for a MUCH more precise control on variables, such as temperature. The first few days show the tank temperature swing before the controller was activated (only using it as a measuring instrument during that time...). At the time, the tank was heated by 3 Jaeger heaters, totalling 700W, and cooled by a Hailea 500 chiller. The data recorded during the next two weeks showed clearly that the overnight temperature drop was still a bit low, and this prompted me to add a fourth Jaeger heater (of 200W), effectively reducing the temperature swing by 0.4 degrees.
Last weekend I made a small adjustment to the controller's parameters, and the results of the past week clearly show a further 0.3 degree reduction in the maximum temperature swing (this time improving the control of the chiller...).
So, by simply adding the controller and one additional heater, I've reduced the tank's temperature swing from about 2.4 degrees (25.3 - 27.7) to only 0.8 degrees (25.6 - 26.4)
I have not yet started "playing" with the pH and ORP controllers, but hope to achieve similar improvements on these parameter swings during the next few months...
Hennie
Being the way I am, I get VERY frustrated when I'm forced to pay much more for an item than what I know it's worth, and in our hobby this is usually the case when one visits a petshop/LFS.
Like most serious hobbyists, I've had the need to monitor the most important tank parameters electronically, and to capture the data on my computer for further analyses and record keeping - I've just never been happy to pay upwards of R10 000.00 for a hobby-grade "tank computer".
Well, I've recently found a solution - use industrial-grade controllers, available locally , and even cheaper than the flimsy hobby-grade "computers"... in fact, use the VERY SAME controllers used by some of our public aquaria. These controllers not only monitor the required parameters, they can also control them by switching relays. They are much more rugged, can be mounted up to 1.4km away from the tank, can be bought in 230V AC or 24V DC configuration, can be programmed to trip alarms, and can send the data to your computer using the industrial standard RS485 protocol, where it is recorded in Microsoft Excel or ASCII text format by the software supplied free with each unit. The units are daisy-chained from one to the next, and the connection to the PC is with a simple UTP network cable.
Here is a photo of my current 3-controller setup, consisting of a pH, temperature and ORP controller - I will be adding a conductivity controller at a later stage.
One of the nice things about these controllers is that they are completely modular - by simply changing some software settings (and the probe, of course...) one can change the unit from a pH controller to a temperature-, ORP-, or conductivity controller, and if something packs up, one simply replaces the broken module, power supply, etc. and NOT the entire "computer". Also, should something be damaged, it will not affect the other controllers.
While I was busy installing these controllers, I also decided to tidy up my light controllers (also rugged industrial units, as can be seen at the bottom of the following photo), and to install them and the temperature controller's relays in an IP65 rated waterproof switch box.
To me, one of the nicest "features" of using these controllers is the fact that I can generate a graphical picture of the tank parameters. As can be seen from the following Excel graph, the controllers also allow for a MUCH more precise control on variables, such as temperature. The first few days show the tank temperature swing before the controller was activated (only using it as a measuring instrument during that time...). At the time, the tank was heated by 3 Jaeger heaters, totalling 700W, and cooled by a Hailea 500 chiller. The data recorded during the next two weeks showed clearly that the overnight temperature drop was still a bit low, and this prompted me to add a fourth Jaeger heater (of 200W), effectively reducing the temperature swing by 0.4 degrees.
Last weekend I made a small adjustment to the controller's parameters, and the results of the past week clearly show a further 0.3 degree reduction in the maximum temperature swing (this time improving the control of the chiller...).
So, by simply adding the controller and one additional heater, I've reduced the tank's temperature swing from about 2.4 degrees (25.3 - 27.7) to only 0.8 degrees (25.6 - 26.4)
I have not yet started "playing" with the pH and ORP controllers, but hope to achieve similar improvements on these parameter swings during the next few months...
Hennie
Freedom of speech and all that 
The actual controllers also vary in price by the number of functions required, and the size of the controllers, so I will "quote" on what I bought, and then elaborate a bit...