Click on picture to enlarge
A completed detector

ABOUT THIS PROJECT

This project demonstrates how pyroelectric IR sensor can be applied in the detection of moving object. Passive IR detector does not emits any IR light by itself. It is triggered by the variation of IR light that comes from warm & moving objects such as human body. Dogs, cats & other household pets have smaller bodies & do not radiate sufficiently strong IR to trigger the detector. Therefore it is pretty well immune to false alarm caused by pets.

Customized pcb with good ground & power routing is strictly necessary for the construction of this project due to the high gain of the two op-amps IC1-A and IC1-B. We tested the circuit on breadboard but the operation was rather unstable. The circuit performs much better on pcb

NOTE : When power is first applied to the circuit, the red LED will light up for a few seconds (circuit is temporarily disabled). This is due to the imbalance of the biasing voltages caused by the charging of large electrolytic caps., C4, C9, C10. After these caps have been fully charged to the required voltages, the LED should be normally off. LED flashes (& transistor Q2 turns ON) when there is a large object moving in front of the detector Output : The output stage is an open-collector NPN transistor driven by the monostable (IC2-A). It can handle small loads such as a buzzer or miniature relay. (see schematic for details) (Buzzer & relay are not included in the components package. They have to be purchased separately if needed) Circuit Operation : (please read the above-mentioned pdf document)
Click on picture to view the schematic	Click on picture to view parts layout & values

PARTS LIST
(the following components will be included in the package unless otherwise stated)

Pyroelectric IR Sensor -- RE200B
Fresnel Lens -- 8002/1

IC1 : LM324 quad op-amps
IC2 : 4013 CMOS dual D-flip flop
IC3 : 78L08 +8V 100mA voltage regulator IC

LED -- 3mm red LED

Q1 -- General purpose NPN transistor ( CS9013, 2N3904,etc with E-B-C pin-out)
Q2 -- General purpose NPN transistor (e.g.: C1815, C945, etc with E-C-B pin-out)

D1 -- 1N400x silicon diode (x = 2,3,... or 7)
D2, D3 -- 1N4148 switching diodes ( or 1SS133)

ZD --- Zener diode, 13V, 400mW

Preset (trim pot) : 470K or 500K
(Sensitivity adjust)

Resistor : ( 1/4W or 1/6W)

R1 -- 33 Ω
R2 -- 1K
R3 -- 3.3K
R4 -- 10K
R5 -- 680 Ω
R6 -- 100K
R7 -- 120K

R8 -- 56K
R9 -- 56K
R10 - 47K
R11 - 470K
R12 - 10K
R13 - 2.2M
R14 - 10K
R15 - 47K

Electrolytic capacitors :

C1 -- 470 uF
C2 -- 100 uF
C3 -- 47 uF
C4 -- 47 uF
C6 -- 100 uF
C9 -- 47 uF
C10-- 47 uF

Ceramic capacitors :

C5 -- 0.1 uF (#104 or 100n)
C7 -- 0.022 uF (#223 or 22n)
C8 -- 0.01 uF (#103 or 10n)
C11-- 0.01 uF (#103 or 10n)

Miscellaneous items :
14-pin socket -- x 2 pcs
Buzzer & relay not included

Download PCB artwork for this project (pdf)
IMPORTANT note on printing the artwork : Open the pdf file with Acrobat Reader. Use a laser printer to print the artwork on tracing paper * in true size (i.e., : do not enlarge or shrink the artwork). The printed artwork can be used for direct exposure with UV sensitized pcb such as the Kinsten PP-1530.