Nuts & Volts - May 2007

■ 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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Use

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