Interface board for the DS1603NF ultrasonic liquid sensor. Powers the sensor and provides a 20mA constant current 2Hz flashing output for the cathode of an indicator LED. A pushbutton switch in the 12V supply interrupts power, which reboots the sensor and tests the flasher circuit.

Wiring: From the main bus, connect a fused wire to one side of the switch, and to the anode (+, long leg) of the indicator LED. Connect the other switch terminal to the “12V” pad, connect panel ground to the “GND” pad, and connect the cathode (-, short leg) of the indicator LED to the “LED” pad. An LED current-limiting resistor is not needed.

BILL OF MATERIALS:
C1-C3: Vishay K104K15X7RF5TL2 0.1uF 50V X7R Radial Ceramic Capacitor
C4-C5: TDK Corp. FG14X7R1E475KRT06 4.7uF 25V X7R Radial Ceramic Capacitor
D1: Cree, Inc. C503B-RAN-CA0C0AA2 Clear Red LED, 5mm, 2.1V, 20mA, 22,450mcd
J1: JST S4B-XH-A-1(LF)(SN) 4-Position 2.5mm Right Angle Shrouded Header
Q1: Microchip VP2106N3-G 60V 250mA P-Channel MOSFET, TO-92-3
R1-R3: Stackpole RNMF14FTC47K0 47k-Ohm 1/4W 1% Axial Resistor
S1: Pushbutton Switch, Latching Type (Installer’s Choice)
U1: Texas Instruments SE555P Single Timer/Oscillator IC, 8-DIP
U2: Microchip CL520N3-G 20mA Linear LED Driver IC, TO-92-3