PIR Motion Sensor and Schematic Diagram

Introduction

The objective of this project is to use inexpensive PIR sensor to detect if a human has moved. To build this project I use a PIC18F25K20 microcontroller to detect if the sensor had change state and it will emit a sound from the speaker or piezo, the MCU also detect the voltage of the battery in the startup, the algorithm it´s very simple it use an interrupt on change to detect the change on the PIR sensor.

PIR Sensor

PIR sensors allows you to sense motion, almost always used to detect whether a human has moved in or out of the sensors range. They are small, inexpensive, low-power, easy to use and don't wear out. For that reason they are commonly found in appliances and gadgets used in homes or businesses. PIRs are basically made of a pyroelectric sensor, which can detect levels of infrared radiation. Everything emits some low level radiation, and the hotter something is, the more radiation is emitted. The sensor in a motion detector is actually split in two halves. The reason for that is that we are looking to detect motion (change) not average IR levels. The two halves are wired up so that they cancel each other out. If one half sees more or less IR radiation than the other, the output will swing high or low.

Schematic

 Part List

Power Supply


I use a 9V battery and it´s connect to a switch and as a voltage regulator I use an L317T and it will have an output of 3,3V to make that possible I use two resistors R1 and R2 to set the output, i use this equations to calculate R1 and I set R2 to 240 ohms:

POR (Power on reset)

I had to add a RC delay on VPP pin because when I switch on/off the circuit there was a voltage drop because the PIR Sensor and that would generate an unknown state when the MCU was restarted to solve that I add a RC delay, you can use this equations to calculate the delay

Speaker or Piezo

I use an 8 ohm speaker but you can use a piezo, i use a transistor BC338 (Q1) because the sound wasn´t too loud and should be able to ear that from a different division, with that transistor i get a HFE = 35. You can calculate ic with this equation.

PIR Sensor

This PIR Sensor works with only 3.3V like the MCU so it´s connect to the output of LM317T it can be connect to a voltage of 8V to 24V, because I use a 9V battery and if the battery gets lower than 8V the PIR sensor won’t work that is why I connect the output of LM317T. The Vout of the sensor it is connected to PORTB.0 and when it occurs a change it will cause an interrupt I use a pull down resistor to make sure the PORTB.0 it is in a low state. The sensor takes 10 to 12 seconds to cause another interrupt and the range is between 2m and 3m. There are the graphs of this sensor and the delays.

Algorithm

At startup both LEDs are on and then it will test the battery if is good Led1(Green) will switch on/off three times, if battery it is low Led2(Blue) will switch on/off three times, next it will put the Led1(Green) on, if PORTB.0 doesn´t change state the circuit will remain the same until a change happen and when a change happen it means the sensor detects some movement and a interrupt will occur and Led1 will be turn off and Led2 will be on and a sound will be generate during 5 seconds and then Led2 will switch off and return to the main routine.
Download Source Code in hex

source : http://www.electronics-lab.com/projects/sensors/007/index.html

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How do motion sensing lights and burglar alarms work?

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How To Build a Laser Security System

Got a mystery to solve? Somebody’s been making off with your stuff, and you don’t have a clue who it is, do you? Here’s your chance to catch them in the act.

To make a laser security system you will need:

    A laser pointer
    Some Duct tape
    A few small mirrors
    An L.M.741 microchip
    A 220-ohm resistor
    A photocell
    An inexpensive digital camera
    An extra small screwdriver
    A wire coat hanger
    Some thin, insulated wire
    A printed circuit board
    A 9 volt battery
    A 9 volt battery clip
    Soldering equipment
    A pair of wire cutters
    A soap caddy with drainage holes
    A voltage relay

Step 1
Build the circuit

Build the circuit. Center the microchip on the circuit board. Pop in the voltage regulator. Connect the battery clip leads to the regulator. Run 2 more leads out from the regulator. Pop in the resistor and the photo cell. Link the chip to the photo cell. Pop in the relay. Link the chip to it as well. Link the other side of the relay to "power."

Step 2
Disassemble camera

Disassemble the digital camera so you can access the board connected to the camera’s trigger button.

Tip
You may have to remove the camera’s board to get a good solder point on the terminal.

Step 3
Solder wires to terminals

Look for the two tiny terminals that lead to the trigger button. Solder wires to each of these terminals and feed them through the trigger button hole.

Step 4
Reassemble the camera

Reassemble the camera. If you can’t get it back together easily, use duct tape to keep it closed. Just don’t tape over the lens.

Step 5
Position circuit inside soap caddy

Position the circuit inside the soap caddy so the photocell is exposed behind one of the holes.

Step 6
Connect battery to circuit

Connect the battery to the circuit, and use tape to secure the whole assemblage inside the box.

Step 7
Attach wires to voltage relay

Slip the two wires coming from the camera through another hole, and attach them to either side of the voltage relay.

Step 8
Cut & tape coat hangers

Cut the coat hanger into several pieces. Tape one piece to the laser pointer and the others to the back of the mirrors.

Step 9
Place camera

Place the camera in an inconspicuous location with the lens pointing at the object you want to protect and secure it in place.

Step 10
Position laser pointer

Position the laser pointer in another inconspicuous place and secure it too.

Step 11
Place mirrors

Place the mirrors to create a perimeter around the object you’re protecting, adjusting them until the laser hits the photocell.

Step 12
Test the system

Now break the beam to test the system… And get ready to confront the perpetrator with your irrefutable evidence.

Fact

The term LASER is really an acronym for Light Amplification by Stimulated Emission of Radiation.

source :  http://www.howcast.com/videos/2947-How-To-Build-a-Laser-Security-System

Related post :
Car Alarm System

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Car Alarm System

Project Summary

The project is almost acceptable of a car alarm system, which could be completed with a transmitter and receiver.
Project Description

This project is practical, and the hex file, it can get. Button switch to disable the system. Button to open the door for when the driver enters the cars, and system deactivates the trigger button, if starter switch is closed, the device is completely passive. In this mode, only open or close doors button can be used.

proteus 7.8 or 7.9

Project Files

File Name	File Size
hex	14.43 KB

 source : http://www.eeweb.com/project/abba_ba/car-alarm-system

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