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Infra-red Light Barrier Using 555 – Circuit Schematic
Infra-red Light Barrier Using 555
This is a short-range light barrier for use as an intruder alarm in doorposts, etc. The 555 in the transmitter (Figure 1) oscillates at about 4.5 kHz, sup.....
High Low Voltage Cutout Without Timer – Circuit Schematic
High Low Voltage Cutout Without Timer
This inexpensive circuit can be connected to an air-conditioner/fridge or to any other sophisticated electrical appliance for its protection. Generally, c.....
Fridge Door Alarm Schematic 2nd Version – Circuit Schematic
Fridge Door Alarm Schematic 2nd Version
The main purpose of this design was to obviate a small defect of the very popular Fridge Door Alarm circuit, available on this website since 1999 and built by a...
Fridge Door Alarm Circuit – Circuit Schematic
Fridge Door Alarm Circuit
Beeps if you leave open the door over 20 seconds This circuit, enclosed into a small box, is placed in the fridge near the lamp (if any) or the opening. W.....
Fire Alarm Using Thermistor – Circuit Schematic
Fire Alarm Using Thermistor
Small and simple unit, Can be used for Home-Security purpose In this fire alarm circuit, a Thermistor works as the heat sensor. When temperature increases.....
Emergency Light and Alarm – Circuit Schematic
Emergency Light and Alarm
This circuit is permanently plugged into a mains socket and NI-CD batteries are trickle-charged. When a power outage occurs, the lamp automatically illuminates....
DTMF Proximity Detector – Circuit Schematic
DTMF Proximity Detector
A DTMF-based IR transmitter and receiver pair can be used to realize a proximity detector. The circuit presented here enables you to detect any object capable o...
Drinking Water Alarm – Circuit Schematic
Drinking Water Alarm
The State Jal Boards supply water for limited duration in a day. Time of water supply is decided by the management and the public does not know the same ...
Doorbell MemoryCircuit – Circuit Schematic
Doorbell MemoryCircuit
If you re expecting an important visitor but you just have to step out for a moment, an electronic doorbell memory can come in handy so you can see whethe.....
Doorbell Cascade – Circuit Schematic
Doorbell Cascade
Sometimes you have to do it the hard way, even if doing it the easy way is an option. That is the case here. The intention is to add a second doorbell in.....
Dark Detector – Circuit Schematic
Dark Detector
The dark detector circuit shown here can be used to produce an audible alarm when the light inside a room goes OFF. The circuit is build around timer IC N.....
Clap Sensitive On-Off Relay – Circuit Schematic
Clap Sensitive On-Off Relay
3V Battery operated, Small portable unit This circuit was intended to activate a relay by means of a hand clap. Further claps will turn-off the relay. An.....
Cellular Phone Calling Detector Circuit Schematic – Circuit Schematic
Cellular Phone Calling Detector Circuit Schematic
Flashes a LED when detecting an incoming call, Powered by one 1.5V cell This circuit was designed to detect when a call is incoming in a cellular phone (e.....
Cat and Dog Repeller – Circuit Schematic
Cat and Dog Repeller
Nowadays, just about every house has an outside lamp with a motion sensor. Such a device eliminates the need to feel your way to the front door, and it ap.....
Cat And Dog Repellent – Circuit Schematic
Cat And Dog Repellent
The electronic dog repellent circuit diagram below is a high output ultrasonic transmitter which is primarily intended to act as a dog and cat repeller, w.....
Bell Alarm – Circuit Schematic
Bell Alarm
If you use a lamp with a motion sensor for outdoor lighting, the original electrical switch is actually no longer necessary. If you replace the switch with the ...
Alarm Circuit for Snoring Prevention by 555 Timer – Circuit Schematic
Alarm Circuit for Snoring Prevention by 555 Timer
The circuit was designed to produce a circuit that will alarm a sleeping person to prevent snoring by using a vibrator instead of an audio alert so as not.....
Alarm System for Entrance/Exit Gate – Circuit Schematic
Alarm System for Entrance/Exit Gate
The circuit employs the functions of reed switches to produce a gate alarm that is powered by a universal AC/DC power supply Oscillator an electronic ci.....
Prevent tampering in energy meters – Circuit Schematic
Prevent tampering in energy meters
Consumers have been found manipulating their electric meters, causing them to stop, under-register or even bypassing the meter, effectively using power without ...
Economy Timer 555 IC – Circuit Schematic
Economy Timer 555 IC
This circuit detects when a window is open (it can also be used with a door), indicates that the window is open by means of a red LED or a blinking LED, and emi...