Burglar/Security Circuits - Sensors and Detectors

12C508 Smart Lock: The base sends a data sequence (the password) which is recognized by the key. The key checks the sequence and -if it recognizes it -sends to the base another data sequence, as an answer to the password. At the Time when the base gets a correct answer (which means that the key has been introduced), the relay is put into action, and it can command a number of consumers.

4 Digit Keypad:

5 Zone Alarm Circuit:

A Basic RF Transmitter for PIR Sensors:

Active IR Motion Detector:

Alarm Control keypad:

Almost Ultrasonic Motion Sensor:

Anti Theft Motorcycle Alarm:

Anti Theft Security for Car Audios:

Automatic Entry Control System:

Combination Lock (PIC16F84):

Combination Lock: This circuit is very basic to build. To open a the lock which is connected to the K1 Load. you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switches are pressed the circuit will reset and you will need to start over. Depending on how you wire the switches, you can use any4 switch combination 

Cut Phone Line Detector #1: Can be used to alarm security system 

Digital Combination Lock:

Digital Entry Lock:

Door/window sensor resists tampering: 01/21/99 EDN-Design Ideas  / PDF contains multiple circuits - scroll to find this circuit

Electronic Card Lock System:

Electronic Door Codelock:

Electronic Lock:

Enhanced Alarm Keypad:

Fridge Door Alarm:

Gate Alarm Circuit:

Home Security Project:

Infrared gate for Door:

Intruder Radio Alert System:

Low Power RFID Transponder:

Luggage Security System:

Miniature Loop Alarm:

Modular Burglar Alarm:

Moisture Alarm:

Motorcycle Alarm:

Novel Buzzer:

Oscillating output improves system security: 02/06/03  EDN-Design Ideas / Many electronic-control systems have digital outputs that use transistors. One method of improving the security in these outputs is to use an oscillating signal to represent a logic-high state instead of a fixed voltage level (Figure 1). This type of signal, a dynamic variable, can drive the circuit shown in Figure 2...

Passive Infrared Pyroelectric Infrared Motion Sensor:

Perimeter Monitor: Using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned, for example, at the bottom of a garden or garage, and used to detect all sound in that area.  The cable can be buried in a hosepipe or duct and is concealed out of sight. The mic is an ordinary dynamic mic insert and should be housed in a waterproof enclosure with the rest of the circuit.  

Personal Silent Alarm System:

PIR Motion Detector:

Proximity Alarm:

Proximity Switch:

Pyroelectric Infrared Motion Sensor:

RF Alarm:

Simple Alarm System:

Simple Electronic Lock Uses Single-Transistor Circuit: 05/26/03 Electronic Design - Ideas for Design / Building on the recent Design Brief theme of one-pin keypads, this design uses only one analog microcontroller (MCU) input to scan numerous keys, plus one resistor per key and another resistor and capacitor. The circuit is simply a crude... 

Single Button Lock Provides High Security: 03/04/99 EDN-Design Ideas  / PDF contains multiple circuits - scroll to find this circuit.

Single Zone Alarm:

TinyTwo Zone Alarm:

Touch Activated Alarm:

Touch Activated Switch:

Toxic Gas Detector:

Ultrasonic Motion Detector:

Ultrasonic Remote Control & Alarm:

Wire Loop Alarm: