The control system has a PLC (Programmable Logic Controller) at its heart. The board is a SPLat SL88A and has 8 inputs and 8 outputs. Also in the control box are the connections for external cabling as well as a relay to switch the higher current required by the submersible pump. Both the sump and the header tank are fitted with float switches which feed information back to the controller on the state of the fluid level. The controller has two modes of operation, Automatic and Manual. These modes are explained below in the table. The manual mode makes use of Start and Stop buttons on the top of the control box and modes of operation are selected with a two position switch.
| Mode of operation | Mode particulars | Start / Stop particulars |
| Automatic | Runs every hour | Starts with timer inside PLC Stops when sump is empty or header tank is full |
| Manual | Start button starts pump Stop button stops pump |
Starts with timer inside PLC Stops when sump is empty or header tank is full |
The control system and submersible pump power is 12VDC and is supplied from a switch mode power supply in a near by fan ventilated housing. My reason behind using 12VDC is the systems proximity to water (nutrient solution) and the fact that I can replace the switch mode power supply with a 12V battery maintained by solar panels. Below are some pictures of inside the control system and power supply box.
The Software if you are interested is downloadable here. (Download and use at your own risk)
Picture 5 - Inside the control box. PLC and relay on the left and mode switch and rear of start/stop buttons on the right.
Picture 6 - Inside the Power supply box.
More to come soon when I get the time.....
Last updated 02/04/2008
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