Project # 02    
P I R Motion Detector (I)
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A completed detector 


 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

Related links :
Read this excellent documentation on infrared & pyroelectric sensor and motion detector  (PDF)

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)
PIR-Det1sch.jpg (382218 bytes)
Click on picture to view the schematic
PIR-DET-1-partsLayOut.JPG (480770 bytes)
Click on picture to view parts layout & values
Download  pcb artwork in pdf format

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

  -- 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 / 16V min.
  • C2 -- 100 uF / 10V min.
  • C3 -- 47 uF   / 10V min.
  • C4 -- 47 uF   / 10V min.
  • C6 -- 100 uF  / 10V min.
  • C9 -- 47 uF   / 10V min.
  • C10-- 47 uF  / 10V min.
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.     
(* tracing paper is the type of translucent  paper used by architect for drawing plans. It's much cheaper than OHP transparency)