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H Bridge Circuit
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4 Band Resistor
5 Band resistor
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Bike Guard Alarm Circuit
This Simple circuit can be used to Guard your bike from theft. It gives a loud alarm tone if somebody tries to start the bike. The alarm disables only when the hide switch S2 is opened. The circuit has little component count and can be easily fixed in the bike. Working of the circuit is simple. The alarm generator buzzer or Horn is activated by an
Temperature Monitor with Alarm
This temperature monitor alarm circuit continuosly monitors the room temperature and beeps when the temperature drops below 20 degrees centigrade. This capability to constantly monitor the room temperature can help lower your air-conditioning costs by reminding you to turn off your airconditioner. An optical display like a thermometer has a limite
Tilt Sensor Alarm Circuit
Ultra simple circuit of the tilt sensor alarm presented here can be fabricated using readily available inexpensive components. The circuit is a true transistor based design. Home made Tilt sensor for this circuit is an ordinary little glass/plastic bottle with two metal needles inserted through its cap, and a small quantity of water inside....
PC Watcher | Turn On and youll hear the Alarm
This little PC Watcher circuit will help you to prevent unauthorised access to your personal computer. After construction on a small piece of veroborad, en..
Pressure Sensor Alarm Circuit Schematic
The simple pressure sensor alarm is built around a couple of readily available cheap components. Working of this circuit is straight forward and self-explanatory. When the circuit is powered by a 9V compact battery, the active piezo-sounder at the output of IC1 starts beeping for a short time and then goes into idle state. Whenever, the pressure...
Wire Break Sensor Alarm Circuit Schematic
Circuit of a loop sensor based simple security alarm is described here. The sensor loop is nothing but a short length of thin enamelled copper wire, which..
Door Ajar Alarm Circuit
Ever accidentally left your front door ajar and had a pet escape Here is a smart solution to this problem. The circuit is fairly simple but a great example of using a tiny circuit to get the job done. All you need is a CD4011 IC plus a handful of components. In this door ajar alarm/beeper circuit, a bar magnet-reed switch combination is used as t
Invisible Infrared Alarm Circuit
This circuit uses invisible infrared light to detect the movement of people through the door. A short beep will be generated when the infrared beam breaks
Remote Controlled Alarm circuit
A very interesting remote controlled alarm circuit using TSOP1736. Routing of an electric cable to attach a calling bell switch near the bed of an old age/patient is not a good idea. Here is an ultra simple battery operated remote controlled alarm to help old age members/patients in bed, especially at home/hospital. Any tv/video infrared remote co
High Temperature Alarm Circuit
The high temperature alarm will beep and LED blinks when the temperature of the device increases abnormally. This simple over heat alarm is to monitor heat..
Power Resumption Alarm circuit
Here is a simple power resumption alarm circuit that can be fixed inside the switch box itself. It gives beeps when the power resumes after a power failure..
Light Fence Security Alarm Circuit Schematic
A simple light fence security beeper is presented here. This circuit can be used as a door alarm, gate alarm, pathway alarm, etc. Any 12 Volt dc power supply can power the whole circuit. Working of this circuit is straight forward. In standby mode photo transistor T1 receives light from the green LED (D1) and T1 conducts to disable the gated...
Clock Alarm Light Switch Circuit
Here is an ultra simple automatic light switch circuit for bedrooms. After construction, connect the input terminals of this circuit in parallel to the int..
Light Alarm Circuit with LDR
This musical light alarm circuit is very simple, uses only 7 components, a LDR and a 3. 6 V battery or 3 x 1. 2 volts rechargeable batteries. The well-known UM66 is used as the sound generator and will give a pleasent wake up alarm. As you probably know the LDR is a light dependent resistor. Normally the resistance of an LDR is very high, sometimes
Overheat Detector Alarm Switch
The circuit is a precision integrated temperature sensor type LM35 (IC1), which provides an accurately linear and directly proportional output in mV, over the zero to +155 degrees C temperature range. This can be used as part of fire smoke detectors but do not use it as a home fire alarm system. Here the output of the LM35 is applied to the...
Bicycle Anti-Theft Alarm Project
I hate to suggest the specific application `bicycle` because it may be use to protect many items from theft. This anti-theft alarm project is built around..
Infrared Alarm Barrier Circuit
This infrared alarm barrier can be used to detect persons passing through doorways, corridors and small gates. The transmitter emits a beam of infrared light which is invisible to the human eye. The buzzer at the output of the receiver is activated when the light beam is interrupted by a person passing through it. The transmitter and receiver circ
Smoke Alarm Circuit
The original smoke alarm circuit has some problems and has left some hobbyists and students disappointed. Rather than to attempt to solve its many problems, I have created an update that uses the venerable LM741 op amp. It is simpler, more conventional, easier to understand and has much better battery life. The photo-interrupter is simply an opti
Shadow Sensor Alarm
Shadow sensors are widely used to detect the movement of a person in a confined area. Many circuits published earlier have a serious drawback that only one..
Arduino Panic Alarm Project
Here is the circuit of an Arduino-based Panic Alarm! The wiring is very simple so that even a novice can construct this interesting circuit without any difficulty. Arduino is a family of microcontrollers (tiny computers) and a software creation environment (Arduino IDE) that makes it easy for you to create programs (called sketches) that can inter
PIC Based Security Alarm Project
Crime in general is still on the rise, and having a security alarm installed is no longer a perquisite of the wealthy! Here is a simple and compact securit..
Theft preventer alarm
This circuit utilising a 555 timer IC can be used as an alarm system to prevent the theft of your luggage, burglars breaking into your house etc. The alarms goes ON when a thin wire, usually as thin as a hair is broken. The circuit is straightforward. It uses a 555 IC wired as an astable multivibrator to produce a tone of frequency of about 1kHz w
Door Knob alarm
Digital IC, Door Knob alarm Here is circuit if you want an alarm to be sounded when somebody touches some thing. If any body touches say, the door handle, buzzer inside rings. But..
IC 555 Light Alarm
IC 555, Light Alarm (Sun Up Alarm) , This circuit designed to sound a loud alarm at the break of the dawn especially for those wh cannot wake up even with an alarm clock. Circuit can be modifi..
Locker Guard Locker Security Alarm Circuit Anti Theft
Locker Guard Circuit Diagram. This tiny circuit can protect your Locker or Almirah from a burglary. If the locker opens in the armed state, the circuit generates a loud police siren to thwart the attempt of burglary
Personal Alarm Circuit Diagram. If you feel threatened or need an urgent support in a crowd, use this alarm to catch the attention of others
Simple Door Alarm Project
Simple Burglar Alarm / Door Alarm Circuit Diagram. You can use this Simple project to protect the door or Window. It gives a loud beep and switch on the room light when an intruder attempts to breaks the door lock
Car alarm circuit
A car alarm in its simplest form, needs to be nothing but one or more sensors connected to some sort of siren. The very simplest alarm would have a switch on the driver`s door, and it would be wired so that if someone opened the door the siren would start wailing. Real world alarms have typically more sensors and controls. The center of the...
This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays. It`s designed to be used with the usual types of normally-closed input devices such as - magnetic-reed contacts - micro switches - foil tape - and PIRs. It has an extremely small standby current - making it ideal for battery-powered operation.
The first circuit was designed for the situation where a hijacker forces the driver from the vehicle. If a door is opened while the ignition is switched on - the circuit will trip. After a few minutes delay - when the thief is at a safe distance - the alarm will sound and the engine will fail. Before fitting this or any other engine cut-out to you
Modular Burglar Alarm
This circuit features automatic Exit and Entry delays and a timed Bell Cut-off. It has provision for both normally-closed and normally-open contacts, and a 24-hour Personal Attack/Tamper zone. It is connected permanently to the 12-volt supply and its operation is "enabled" by opening SW1. By using the expansion modules, you can add as many zones a
Motorcycle Alarm Number 2
This circuit features an intermittent siren output and automatic reset. It can be operated manually using a key-switch or a hidden switch; but it can also be wired to set itself automatically when you turn-off the ignition. By adding external relays you can immobilize the bike, flash the lights etc. Ron has used my Any number of normally-open swit
Surveillance Bug Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
Digital Signal Integrity
Interconnection and Timing of Digital Circuits
CMOS Circuits Tutorial