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RO Water Controller - Drain Timer Board <<< Previous Next >>>

Image 1

This board is fairly simple, it is basically just a series of resistors. There are a couple of connectors either side. Dependent on the position of the rotary switch dictates how many of the resistors are in the series. The more resistance the longer the time interval. The length of time is also dependent on the capacitor on the main board. Since capacitors vary in manufacturer you will need to experiment with different values of resistors to gain a precise time. Although the values I have listed here should give approximately the time specified. Since the project doesn't need precise timing they should be sufficient. The timer chip is located on the main board.

Drain Timer circuit

X1-1 through to X1-12 are connected to the poles on the 12 way rotary switch. The common pole of the rotary switch is connected to X2-2. X2-1 and X2-2 is then connected to X6-1 and X6-2 on the main board.

Image 2

Time Interval:

Rotary Pole
Rotary Pole
5 Seconds
3 Minutes
10 Seconds
4 Minutes
15 Seconds
5 Minutes
30 Seconds
10 Minutes
1 Minute
15 Minutes
2 Minutes
30 Minutes


Image 3

Values of resistors:-

R1 1K R13 15K
R2 1K5 R14 15K
R3 1K R15 15K
R4 1K5 R16 15K
R5 1K R17 15K
R6 1K5 R18 15K
R7 6K8 R19 68K
R8 680ohms R20 82K
R9 15K R21 68K
R10 0K - (Wire) R22 82K
R11 15K R23 56K
R12 15K R24 390K

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


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