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Sir backporch . . . . . .
The following minor changes willl have the water sensing portion operating as before, and not have it being overly sensitive when using a constant 12VDCV on the unit.
Of the 3 marked in resistors, (being on the other side of the board), the middle left two are associated with your piezos oscillator circuitry.
The very top left is supplying voltage to your sensor element .
If you take a #11 Exacto knife and open the Cu foil at the BLUE mark up gap, it then opens the 12V supply line to insert a 330 ohm dropping resistor.
If the holes are drilled and the resistor is mounted on the components side, you can then then scrape a ring around the holes foil side and solder in the resistor with about 1/4 in lead feed thru
lesd length on both leads.
That then permits the zener diodes cathode lead to be ring wrapped around the left of those resistor leads, then its other lead gets ring wrapped around the other existing lead shown to get to ground..
A .01 ceramic capacitor is connected around the Zener for any suppression of random shot noise created.
This change then lets your circuitry use 12V for the piezo and relay drive, but keeps a regulated 9 Vdc on your water sense circuitry.
Photo Markup:
73's de Edd
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