■ PHOTO 3
end of each wire and tin.
One end of the twisted pair has
ring tongue connectors soldered to
them. These connectors are mounted
to the probe assembly with two 4-40
1/4” long screws and two 4-40 nuts.
The other end of the twisted pair is
connected to terminals P1 and P2 of
TB1 on the circuit board.
that they are separated by 1/8” at the
tips. Next, make the cable that goes
from TB1 to the probe
assembly as follows. Cut
two lengths of wire long
enough to reach the case
containing the circuit board
from the probe assembly.
Once these wires are cut,
twist them together with a
variable speed drill until they
have about eight turns per inch. Then,
strip about 1/2” of insulation from the
Testing and Assembly
Connect the unit to the 12V wall
transformer. Then check the voltage
between U1 pin 8 and U1 pin 1. The
meter should read between 12 VDC
and 18 VDC. If this reading is zero,
check for proper installation of D1
and J1. When the voltage checks out,
install U1 in its socket. Verify that the
wires from the probe assembly are
connected to P1 and P2. Then place
the probe tips into water. The piezo
alarm should sound. If the piezo is
silent, flip the switch S1. If the alarm is
still silent, check the installation of Q1,
Q2, and Q3.
Once the alarm is working
properly, mount the circuit board, J1,
S1, and PZ1 in an appropriately sized
case. Orient the switch S1 so that the
piezo alarm is enabled when S1 is in
the 12:00 position. Drill holes in the
case to route the wires from TB1, TB2,
PZ1, and the lantern battery. Also drill
a hole to mount J1.
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Verify that the probe wires are
connected to TB1. The TB2 terminal
block is connected in series with the
pump motor and the power source for
the pump motor. The relay contact
rating is 10A at 120 VAC. Once all of
the necessary connections have been
made, attach the lid to the case. When
mounting the water detection alarm,
care must be taken to install the unit, as
well as the wall transformer in a place
high above the expected flood level.
The probe assembly should be placed
such that the probe tips are exposed to
water when flooding occurs. A 3/16”
mounting hole on the probe assembly
makes it easy to install. NV
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44 May 2007