There are 98 circuit schematics available in this category. Click here for all circuit diagrams. The Last circuit was added on Saturday, January 28, 2023.Please note some adblockers will suppress the schematics as well as the advertisement so please disable if the schematic list is empty.

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CircuitCategoryDate AddedOK?Votes 
Digital combination lock using pair of CD4013 CMOS chipsAlarmsSep 23, 2024Status-4 vote up vote down
Transistor delay circuits to detect if a door is open for a long periodAlarmsJun 24, 2024Status2 vote up vote down
Sensitive Optical Burglar AlarmAlarmsOct 25, 2024Status-3 vote up vote down
Sound operated music bell using 555 timerAlarmsDec 07, 2024Status-1 vote up vote down
Motorcycle AlarmAlarmsJul 05, 2024Status2 vote up vote down
Car Alarm and ImmobilizerAlarmsJul 05, 2024Status-1 vote up vote down
Car Hijack AlarmAlarmsJul 05, 2024Status-1 vote up vote down
Motorcycle Alarm Number 2AlarmsJul 05, 2024Status1 vote up vote down
Motorcycle Alarm Number 3AlarmsJul 05, 2024Status-4 vote up vote down
Motorcycle Alarm Number 4AlarmsJul 05, 2024Status-3 vote up vote down
Motorcycle Alarm Number 5 & 6AlarmsJul 05, 2024Status1 vote up vote down
Auto Burglar AlarmAlarmsJul 05, 2024Status0 vote up vote down
Fridge door AlarmAlarmsJun 26, 2024Status-1 vote up vote down
Emergency Light & AlarmAlarmsJun 26, 2024Status1 vote up vote down
Door Alarm circuit diagramAlarmsJun 26, 2024Status0 vote up vote down
Everything-that-moves alarm works by inducing eddy currents in living beingsAlarmsJun 26, 2024Status-1 vote up vote down
Electronic locker digital combination lock circuit diagramAlarmsJun 26, 2024Status-2 vote up vote down
Gate alarmAlarmsJun 26, 2024Status-3 vote up vote down
Circuit diagram for 5 Zone Alarm SystemAlarmsJun 26, 2024Status-3 vote up vote down
Miniature Loop AlarmAlarmsJun 26, 2024Status3 vote up vote down
Modular Burglar AlarmAlarmsJun 26, 2024Status-1 vote up vote down
Water Activated AlarmAlarmsJun 26, 2024Status-2 vote up vote down
Enhanced 5 Digit Alarm KeypadAlarmsJun 26, 2024Status-1 vote up vote down
Enhanced 4 Digit Alarm KeypadAlarmsJun 26, 2024Status-1 vote up vote down
Automatic Intruder AlarmAlarmsJun 26, 2024Status0 vote up vote down
Single Zone CMOS AlarmAlarmsJun 26, 2024Status-2 vote up vote down
Travel Touch AlarmAlarmsJun 26, 2024Status0 vote up vote down
Sun - Up Alarm that provides an audible alarm when the sun comes up or a dark area is illuminatedAlarms Status-2 vote up vote down
Doorbell for the DeafAlarms Status-4 vote up vote down
4 Photo-Detector circuit with delayed release and bipolar outputAlarmsAug 18, 2024Status-1 vote up vote down
Electronic door codelock (PIC16F84)AlarmsMar 23, 2024Status-1 vote up vote down
Circuit diagram for basic alarm with delayed triggerAlarmsFeb 09, 2025Status-1 vote up vote down
Wireless alarm FM transmitter moduleAlarmsFeb 09, 2025Status0 vote up vote down
Fuse or line monitor that will check the status of up to six fuses including a PCB layoutAlarmsFeb 20, 2025Status-1 vote up vote down
Ultrasonic remote control & alarm systemAlarmsAug 12, 2024Status-2 vote up vote down
Wire Loop Alarm using 4001UBE Quad NOR GateAlarmsSep 01, 2024Status-1 vote up vote down
Digital Keypad Combination LockAlarmsSep 01, 2024Status-2 vote up vote down
Transistor based single zone intruder alarmAlarms Status-1 vote up vote down
CMOS single zone intruder alarmAlarms Status-1 vote up vote down
Automatic Intruder Alarm - a simple single-zone burglar alarm circuit based on a 4011 quad NAND gateAlarms Status-1 vote up vote down
Door knob alarm (PDF)AlarmsJan 26, 2025Status-1 vote up vote down
Water seepage alarm (PDF)AlarmsJan 26, 2025Status-1 vote up vote down
Micro-power over temperature alarm (PDF)AlarmsJan 26, 2025Status-2 vote up vote down
Frost alarmAlarmsFeb 21, 2025Status-1 vote up vote down
Ultrasonic radar alarmAlarmsFeb 21, 2025Status-1 vote up vote down
LPG leakage alarm using SEN-1327 gas sensor module (detects 4 other dangerous gases)AlarmsJul 17, 2024Status-2 vote up vote down
5 Zone Alarm Circuit circuit diagramAlarms Status-1 vote up vote down
Build an iButton electronic lock based around a AT91C2051 microcontroller (includes ASM source code)AlarmsNov 10, 2024Status-1 vote up vote down
Ultrasonic Radar Alarm Circuit DiagramAlarms Status-1 vote up vote down
Home security projectAlarmsNov 17, 2024Status-1 vote up vote down
Touch activated alarm systemAlarmsJan 26, 2025Status-2 vote up vote down
Waterpump Safety Guard for fish pond / fish tankAlarms Status-1 vote up vote down
Wailing alarm sirenAlarms Status-1 vote up vote down
Refrigerator Door AlarmAlarms Status-1 vote up vote down
Rain alarm / rain detectorAlarms Status-1 vote up vote down
Combination Lock (PIC16F84)AlarmsJul 24, 2024Status-2 vote up vote down
Novel BuzzerAlarmsNov 27, 2024Status-1 vote up vote down
Modular Burglar AlarmAlarmsNov 27, 2024Status-2 vote up vote down
Motorcycle alarmAlarmsNov 17, 2024Status0 vote up vote down
Enhanced 5 Digit Alarm KeypadAlarmsNov 27, 2024Status-2 vote up vote down
Enhanced 4 Digit Alarm KeypadAlarmsNov 27, 2024Status-1 vote up vote down
RF AlarmAlarmsNov 27, 2024Status-1 vote up vote down
Single Zone AlarmAlarmsNov 27, 2024Status-1 vote up vote down
Water Activated AlarmAlarmsNov 27, 2024Status1 vote up vote down
Water level alarmAlarmsNov 17, 2024Status-1 vote up vote down
Perimeter monitorAlarmsJan 26, 2025Status-1 vote up vote down
Cold activated switch (frost alarm)AlarmsJan 26, 2025Status-1 vote up vote down
Digital combination lock circuit diagramAlarmsJan 26, 2025Status-1 vote up vote down
Alarm control keypadAlarmsNov 27, 2024Status-1 vote up vote down
A handy 2-Input alarm using the PIC Lick-1 moduleAlarmsJun 28, 2024Status-1 vote up vote down
Anti-Theft Security For Car Audios based on a CMOS NAND chip CD4093AlarmsJul 15, 2024Status-1 vote up vote down
Luggage Security System based on UM3561 melody generator ICAlarmsJul 15, 2024Status0 vote up vote down
General purpose alarm using discrete transistorsAlarmsJul 15, 2024Status-1 vote up vote down
Simple Darkness Activated Alarm using a 555 timerAlarmsJul 15, 2024Status-1 vote up vote down
Circuit diagram for a simple, gated, pulsed alarmAlarmsJul 15, 2024Status-1 vote up vote down
Remote Alarm For Smoke DetectorAlarmsJul 15, 2024Status-1 vote up vote down
Simple 6-Input Alarm that was designed for use in a combined garage and rumpus roomAlarmsJul 15, 2024Status-1 vote up vote down
Night Alert that turns a light on for a short time when a dog is barking to scare off intrudersAlarmsJul 15, 2024Status0 vote up vote down
Simple Knock Alarm With Piezo SensorAlarmsJul 15, 2024Status0 vote up vote down
Smoke Alarm Battery Life ExtenderAlarmsJul 15, 2024Status-1 vote up vote down
Mains Supply Failure AlarmAlarmsJul 15, 2024Status-1 vote up vote down
Water Alarm Circuit DiagramAlarmsJul 15, 2024Status-1 vote up vote down
Midnight Security Light Circuit SchematicAlarmsJul 15, 2024Status-1 vote up vote down
Low Cost Burglar Alarm For BoatsAlarmsJul 15, 2024Status-2 vote up vote down
Water Level Alert - 1.5V battery powered portable unitAlarmsJul 15, 2024Status0 vote up vote down
Fridge Door Alarm Circuit - Beeps if you leave open the door over 20 secondsAlarmsJul 15, 2024Status-1 vote up vote down
Fire Alarm Using ThermistorAlarmsJul 15, 2024Status-1 vote up vote down
Mini Alarm - Suitable for doors & windows, Portable anti-bag-snatching unitAlarmsJul 15, 2024Status-2 vote up vote down
Fridge-Door Open Alarm Circuit ProjectAlarmsJul 30, 2024Status-2 vote up vote down
Fridge Door Alarm Schematic 2nd VersionAlarmsJul 30, 2024Status1 vote up vote down
Microwave Motion DetectorAlarmsSep 07, 2024Status-1 vote up vote down
UHF Movement DetectorAlarmsSep 07, 2024Status-2 vote up vote down
UHF Doppler Motion DetectorAlarmsSep 07, 2024Status-2 vote up vote down
Ultrasonic Proximity DetectorAlarmsSep 07, 2024Status1 vote up vote down
Ultrasonic Radar Alarm CircuitAlarmsSep 07, 2024Status-1 vote up vote down
Gunn diode proximity detectorAlarmsSep 14, 2024Status-1 vote up vote down
Infrared Proiximity Detector using a CA3240AlarmsSep 14, 2024Status-3 vote up vote down
Thermal Proximity Detector using a RPW100AlarmsSep 14, 2024Status0 vote up vote down