This kit uses ultrasonic waves to detect movement in an area, then triggers a relay.
It has delay on and delay off included in the circuit.
Technical specifications:
- Frequency Range: 40kHz adjustable
- Detection Range 1 - 15 feet (adjustable)
- Relay Output: NO, COM, NC (Form C) 3A max.
- Power Requirement: 12VDC
- Consumption: 37mA.(stand by), 80mA.(working)
- Delay on : 10 sec.
- Delay off : adjustable 10 seconds to 1 minute
- Detect range : 1 to 5 m.
- PCB dimensions : 2.60 x 3.19 inches.

How it works:
This circuit can be divided in to two parts. Transmitter and Receiver.
The transmitter consists of IC3/2 and IC3/3 (frequency generator 40kHz) using R22, R23, C16 and VR4.
VR4 is used to adjust the frequency (40kHz).
This frequency will be fed to amplifier circuit which inverts the phase of the output.

The receiver section and control.
Any reflected sound is detected by the ultrasonic receiver.
The signal is then amplified by IC4, TR2 and IC2/1.
VR2 and VR3 are used to adjust the sensitivity of detector.
The sound is amplified and fed to the comparator circuit (IC2/2 and IC2/3) which detects positive and negative pulses.
If IC2/2 or IC2/3 detects any pulse, the output goes high. As long as the input remains stable the output goes low.(D6 or D7).
The signal is fed to pin 5 of IC2/4 (comparator circuit) which compares the signal between pin 5 and pin 6. C5 (delay off time).
If the voltage at pin 5 is more than pin 6, the output at pin 7 will go high and drive TR1.
IC3/4 is configured as delay on 10 seconds which depends on R3 and C3 (time delay).

You can have a load through the relay of 10Amps at 120vAC, 5Amps at 220vAC.

Circuit Connection