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RO Water Controller - Relay Board <<< Previous Next >>>

Image 1

This board consists of 5 relays, three of which are 12 volts to switch the solenoids valves and the other two are 240 volts to switch the heater and Top Up pump.

The mains electricity (Live) is first connected to a on-off switch in the case and then onto this board. On the board the Live of the mains is split three ways, each with it's own fuse. Two of branches are then connected to the 240V relays and the third is then connected to the transformer.

Components in the controller i.e. transistors and IC chips should be protected from a brief high voltage spike produced when the relay coil is switched off. So each relay has a protection diode fitted across the relay coil to provide this protection. Please note that the diodes have been purposely fitted in reverse.

 

Relay Circuit

On the connector X1 all odd pins are positive and the even pins are negative (ground). These are connected to the main board. My initial design was for seperate negative wires for each relay, this is pointless, so when I came to construct the board I just had one negative (ground) from the main board. I then just daisy chained the others together. X2-4 is connected to the 12V positive supply on the power supply board, X2-1, X2-2, X2-3 are connected to sockets mounted in the case. One for each solenoid valve.

Image 2

Image 3

The Eagle board schematic can be download by clicking here and the PCB board layout can be downloaded by clicking here. (Please note that you will need the Eagle software to read these files)

 

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