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Magnolia Village is a new residential development which sprung up the last few years in Paulesti, Romania. Three years ago this was only a crop field. Today 25 houses are ready and 10 more under construction. Electricity and gas was brought from far away. Sewer and water were provided on site.
WATER SUPPLYFor the water supply, a well was dug at 120m. A Wilo pump was submersed at 60m and water was stored in a 200 m.c. tank.
From the tank, a pair of Wilo pumps are pushing water into the distribution pipes for the first 1, 000 inhabitants.
One pump is active at any time, and the second one is for backup. If the active pump fails, the backup pump takes over. Once a week the two pumps are switched, to age equally. This seemed to be the perfect task for a Raspberry Pi aided by a MEGA-IO Card.
An industrial panel was used to house all the components. The MEGA-IO card (1) piggy-backed on Raspberry Pi was installed using a DIN-Rail adapter. A Break-out card (2) was added to connect the MEGA-IO Terminals. A rack-mount, industrial power supply (3), provides 12V for the external relays, and a rack-mount 5V power supply (4) powers Raspberry Pi and MEGA-IO.
The programmable timer (5), the time-delay relay (6) and the relay (7) switch the pumps once a week. The task could have been given to the Raspberry Pi software, but we prefered to handle it in hardware. However, any remote operator can trigger a pump switch manually from the browser. The heavy duty power swithing is handled by the power relay (9)
Each of the three pumps has two output signals: ON and FAIL. The signals are routed through the terminal block (10) to the relays (8). The Normal Open output of the relays drive the opto-isolated inputs of the MEGA-IO card.
BROWSER INTERFACEThe default http page of the Raspberry Pi web server displays the status of the three pumps, and a button for switching pumps 1 and 2. In this start-up screen all pumps are off.
The active pump cycles on and off automatically, to maintain the preset pressure in the distribution pipes. The pump status is shown immediately in the browser:
Pressing the arrows image shuts down the active pump and starts up the backup. The change can also be forced once a week by the timer. The browser images change accordingly.
In a pump fails, the error signal triggers a change in the browser image, and can also be used to send an email or a text message to the operator.
The submersible pump is controlled by the level indicator in the storage tank. When the water level falls bellow the preset limit, the pump turns on.
Raspberry Pi runs the Raspbian operating system and the MEGA-IO command line software downloaded from GitHub. The browser software consists of the entry page, index.html, which displays the static images and calls every second get_pump_status.cgi. This file reads the opto-coupled inputs of the MEGA-IO card and reports back to the browser, which decides what images to display based on the current pump status. When the user presses the circular arrows image, the browser calls switch_pump.cgi. This file turns on Relay#1 on the MEGA-IO card, and 1 second later turns it off. The pulse is detected by the hardware, which turns off the active pump and turns on the back-up.
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