Top Circuits Page 167
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This project was a sort of challenge: designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality. The Power Amplifier section employs only three transistors and a handful of resistors and....
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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....
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A typical specification can range from a low of 36V to a high of 72- with a 48-V nominal. In some designs, transients in excess of 100V need to be considered. Most of these designs will require input to output isolation of up to 1500V. Output voltages are....
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Up Alarm can be used to provide a audible alarm for when the sun comes up or it can be used in a dark area and detect when a light comes on. It can also be used to detect a light b..
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Today i want to share with you all my water sensor. This is my second successful project when i started with electronic hobby. This circuit is useful for your plant. How it`s work simple. It will beeping when your plant soil is dry and stop when it detect....
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This Simple Portable FM transmitter includes a limiter, a microphone amplifier and a PLL digital tuning. All the components are placed on one circuit board. The RF power is switchable between 1 W (HI) and 0, 2 W (LO). The schematic diagram is split into 3....
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This is the circuit diagram of linear FM Booster / RF amplifier based 2N4427 Philips transistor. The RF Amplifier is for boosting small fm transmitters and bugs. It use two Philips 2N4427 and its power is about 1Watt. At the output you can drive any linear....
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An 30 Watt audio amplifier circuit with TDA2040 shown here. TDA2040 is class AB amplifier monolithic integrated audio Pentawatt available in the package. The IC has a low harmonic distortion, cross low over the distortion and has a built in short circuit....
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This is a 5W -150MHz RF amplifier circuit. It applies the MRF123 TMOSFET. The MRF123 is a very high gain FET which potentially unstable at both VHF and UHF frequencies, so the 68 Ohm input loading resistor has been used to enhance the stability. This RF....
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Here is the circuit diagram of simple and easy subwoofer filter which will be operated from a 12V DC supply. Such a circuit is incredibly helpful in Car subwoofer applications. The circuit is nothing however a low pass filter whose pass frequency will be....
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Its a high quality FM receiver circuit based on IC CXA1019. CXA1019 is a monolithic silicon bipolar radio FM / AM receiver IC for Sony. Built in circuitry within the CXA1019 includes RF amplifier, mixer, oscillator, amplifier, quadrature detection circuit,....
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The image below shows a Block diagram of the entire mixer that includes four Input Amplifier Modules followed by four in-out switchable Tone management Modules, one stereo Line input, four mono Main Faders, one stereo dual-ganged Main Fader, four Pan-Pots, a....
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The circuit diagram shown here is a simple circuit DC power delay, which is based on an SCR (Silicon-Controlled Rectifier). This circuit is very useful and can be used in many applications. The operation of this circuit is very simple. When input power is....
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If you wish to use a double power supply but don`t have a center trapped transformer you can use an electronic circuit in the following configuration. This electronic circuit uses a second rectifier bridge coupled with secondary coil of the transformer using....
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This FM wireless microphone is easy to build and has a large benefit of transmission (about 300 meters, while outdoor). Regardless of its small component count and 3V operating voltage that will easily penetrate the excess of some floors of an apartment....
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No DIY espionage kit is complete without a long-distance listening device, and no DIY long distance listening device is complete unless it uses a sweet laser in some form or fashion. If you agree with that statement, then you`re in luck, because the....
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This metal detector using CS209A made by Cherry Semiconductor. The CS209A is a bipolar monolithic integrated circuit for use in metal detection / proximity sensing applications. The CS209A metal detector IC has two on-chip regulators current, the oscillator....
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Remote control circuit consists of two parts, one is the transmitter and the other is the receiver. A simple schematic diagram of the remote control. IC transmitter transmitter circuit is controlled by NE555. Receiver circuit works by the frequency of the....
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The Passive Aircraft Receiver is basically an amplified "crystal radio" designed to receive nearby AM aircraft transmissions. The "passive" design uses no oscillators or other RF circuitry capable of interfering with aircraft communications so it should be....
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Here is a solar charger circuit to charge Lead Acid or Ni-Cd batteries using solar energy. The circuit harvests solar energy to charge a 6 volt 4. 5 Ah rechargeable battery for various applications. The charger has Voltage and Current regulation and Over....
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Most of the beginners in digital electronics assume that the hanging input is a logic 0. Then, that`s a misconception. They are neutral state which can be a logic 0 or a logic 1. This will bring chaos on your circuit operation. As you can see, in each case....
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In designing logic circuit, it is sometimes necessary to compare values of two digital data. In this case, creating your own magnitude comparator can cause you more logic IC and can consume more time and money. This magnitude comparator IC might help you. It....
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In most digital electronics projects that uses different kinds of switches, switch bounces are commonly encountered. These are extra glitches after the real switch operation. These are tiny pulses that affect the actual operation of the circuit like....
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This circuit is a real gem! Easy to make and more sensitive than many commercial devices available. It`s based around an LF351 low-noise operational amplifier and a 1mF choke acting as the sensor. Unlike most other simple EMF detectors, this one has a meter....
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One of the most useful gadgets a video enthusiast can have is a low-power TV Transmitter. Such a device can transmit a signal from a VCR to any TV in a home or backyard. Imagine the convenience of being able to sit by the pool watching your favorite movie on....
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This security system is very important for any kinds of home, office, factor. there has a circuit diagram its simple and easy to build. Any one can do it. It`s a low cost circuit diagram. Many security systems use a closed loop of wires and switches arranged....
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This design fulfills these requirements by means of a variable gain microphone preamplifier built around IC1A, a variable steep Wien-bridge pass-band filter centered at about 1KHz provided by IC1B and an audio amplifier chip (IC2) driving the loudspeaker. 1)....
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For making use of this facility, the calling subscriber is required to initially dial the normal phone number of the called subscriber. When the call is established, no ring-back tone is heard by the calling party. The calling subscriber has then to press....
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Notes: The frequency of the transmitter lies within VHF and VLF range on the TV channel, however this circuit has not been tested at UHF frequencies. The modulated sound signal contains 5. 5 -6MHz by tuning C5. Sound modulation is FM and is compatible with....
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This Circuit needs a adapted 10V-DC advanced end able of bartering 2 Amps. Starts the allegation aeon at 240mA and at abounding allegation switches automatically to a float action (trickle charge) of 12mA. The capacitors are the bowl 50V (or better) type.....
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Figure 1 shows the 10. 58 to 10. 74 MHz VFO oscillator circuit. Yes, this is the same circuit that was presented last, but I`ve re-designed to show the Colpitts oscillator more clearly. "L" is approximately 1. 5 uh, 19 becomes a core T50-6 (yellow). The....
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This 220 Volt disco lamp circuit is not a voice switch (VOX), because this circuit is too dumb to differentiate between musical sound and human voice. This is more of a voice-activated sound activated. An interesting application is to control the lighting in....
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This preamplifier was designed to cope with CD players, tuners, tape recorders etc. , providing an ac voltage gain of 4, in order to drive less sensitive power amplifiers. As modern Hi-Fi home equipment is frequently fitted with small loudspeaker cabinets,....
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This circuit uses just two CMOS IC`s, a 4011 quad 2 input NAND gate, and a 4020 14-stage ripple binary counter. At switch on R2 and C2 provide a brief reset pulse, which will ensure the output pin Q1 of the 4020 is high. Gates U1 and U2 form a simple astable....
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A simple astable timer made with the 555, the mark (on) and space (off) values may be setindependently. The timing chain consists of resistors Ra, Rb and capacitor Ct. The capacitor, Ct charges via Ra which is in series with the 1N4148 diode. The discharge....
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The metal detector shown here may well represent a new genre. At any rate, after some exposure, it is regarded as such by those who have seen it. It is based on a standard transformer coupled oscillator(TCO) - hence the name Coil Coupled Operation (CCO)....
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Using a dual polariity power supply (+-5V works fine) will cure most clipping problems. You will have to check the data sheet for the correct pins to connect your voltages. ..
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This circuit uses a conventional spring loaded mouse trap, available from hardware stores. However when a mouse is caught, the circuit triggers and transmits an interrupted tone on the commercial FM band to a nearby radio receiver. This circuit is a small....
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This tester is designed to locate stray electromagnetic (EM) fields. It will easily detect both audio and RF signals up to frequencies of around 100kHz. Note, however that this circuit is NOT a metal detector, but will detectmetal wiring if it conducting ac....
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As many or as few channels as are required can be added to the mixer. Do this by just duplicating the input "sections" which are clearly shown on the schematic. One version of this mixer I saw had 25 inputs! ..
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The circuit is a standard RC phase shift oscillator using a single bipolar transistor as the active element. When power is applied regenerative feedback is applied via C2 from collector to base of the transistor. The timing components, R1, R2, C1 and C3....
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The signal sources in the analog output stage of the PC SVGA card see the right impedance - 75 ohms on each line (five resistors), and the input impedances of the transistors are so high that they do not make any significant additional load. The transistors....
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The first thing that you must do, is to measure the end transistors (T3 and T4) amplifying coefficient, the hfe or ². If their disagreement is bigger than 30 %, the amplifier would not give a clear sound. I used MJ3001 and MJ2501 transistors, and this....
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This timer circuit is similar to the 5 to 30 minute timer except that when switch S1 is closed, the on/off actionof the circuit will continue indefinitely until S1 is opened again. A 7555 time and low leakage type capacitor for C1must be used. The 6 way....
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This circuit has an adjustable output timer that will re-trigger at regular intervals. The output period can be anything from a fraction of a second to half-an-hour or more - and it can be made to recur at regular intervals of anything from seconds to days....
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This timer is based on a simple Monostable Circuit. The length of time the relay remains energized - the ON period - is controlled by the values of R3 & C2. And the length of time the relay remains de-energized - the OFF period - is controlled by the values....
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This circuit uses a Cmos 4017 decade counter to create a sequence of four separate events. The number of events in the sequence may be increased to nine or ten. And the length of each event is controlled independently. You`re not limited to a series of -....
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A simple test circuit to fault find audio and radio equipment. Can be used to inject a square wave signal, rich in harmonics, or used with headphones as an audio tracer. A single pole double throw sitch is used to switch between inject and trace modes. The....
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This is a small general purpose audio test set. It comprises a low 0. 3% distortion phase shift oscillator and a level meter. The level meteris set at 100mV FSD and can be used for gain measurements and general testing. Current consumption is just under 4mA.....
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This circuit is a single transistor flyback (Joule Thief) circuit that features a third coil. With it, flash duration and brightness is much enhanced, without resorting to large value capacitors. ..
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Shaping block has the role to provide fixed length impulses (2 mS) at each breaker-points opening. In this way are eliminated the false impulses which appear due contacts vibrations. As shown in drawing, shaped impulse triggers directly the EID and act as....
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Please note that it is illegal to make a physical permanent connection to your telephone linein some countries (this includes the UK and Ireland). If building this circuit it is advisable touse a plugin cord so that the unit can be unplugged should a fault....
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Using the tester is easy, starting with power off, insert a transistor into the test socket. Set S1 for NPN or PNP androtate S3 to the required test position. Rotate VR1 so the desired collector emitter voltage. Pressing S2 now allows the measurement of hFE....
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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.....
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These are two - easy to build - relay-based alarms. You can use them to protect your motorcycle - but they have many more applications. If you use relays with 6-volt coils - they`ll protect your "Classic Bike". Both alarms are very small. The completed....
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This alarm is designed to sound its Siren only once. That is - when the alarm is activated - the Siren will sound for a preset length of time. Then it will switch off and remain off. The alarm will not re-activate. The basic circuit has a single zone with....
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This is a simple transistor-based burglar alarm circuit. Its features include automatic Exit and Entry delays - together with a timed Bell cut-off and Reset. It`s designed to be used with the usual types of normally-closed input devices such as -....
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The electronic circuit is a TV modulator that is really no more than a transmitter. It is a very small transmitter, admittedly, but none the less that is what it is. What does a modulator actually do In general -and this design is no exception to the rule -....
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Q1 and Q2 form an ALL-ON ALL-OFF circuit that in the off state draws no significant current. P1 starts the circuit, the relay is turned on and the two ICs are powered. The lamp is powered by the relay switch, and IC2 is reset with a positive voltage at pin....
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Many people experienced sleeping well in natural surroundings, into a tent or a wooden hut. This fact is due not only to the healthy atmosphere but also from our unconscious ability to perceive natural Earth`s magnetic-fields. The circuit generates this type....
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This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time....
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Pushing on P1 resets IC2 that start oscillating at a frequency fixed by R3 & C1. With values shown, this frequency is around 4Hz. LED D2, driven by IC1A & B, flashing at the same oscillator frequency, will signal proper circuit operation. SW1 selects the....
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Some 20 years ago it was common to see small key-holders emitting an intermittent beep for a couple of seconds after its owner whistled. These devices contained a special purpose IC and therefore were not suited to home construction. The present circuit is....
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This device is a simple timer, allowing to keep on the headlights of your vehicle for about 1min. and 30sec. , e. g. when accessing some dark place, without the necessity of coming back to switch-off the lights. Pushing on P1 allows C1 charging to full 12V....
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Circuit To squeeze even more energy from a alkaline battery cell, this circuit adds two transistors to a circuit similar to the above design to boost the efficiency. A small 1. 5 volt alkaline N cell should flash the LED for a full year. It too uses a....
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You can use any LED you want for D1 - D10, however blue LEDs have a higher voltage requirement so if you want to go blue for a modern look, they may appear more dim then red, yellow or green. By leaving pin 9 of U2 disconnected, the graph will operate in dot....
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This is a very basic circuit for flashing one or more LEDS and also to alternately flash one or more LEDs. It uses a 555 timer setup as an astable multivibrator with a variable frequency. With the preset at its max. the flashing rate of the LED is about 1/2....
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Car Burglar Alarm timer alarm system circuit, model to economize. This circuit convenients for to set up in an automobile. usually switch at set up keep with automobile door will the circuit closes. But in case of car owner opens in and out while note as a....
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This circuit is intended for children fun, and can be installed on bicycles, battery powered cars and motorcycles, but also on models and various games and toys. With SW1 positioned as shown in the circuit diagram, the typical dual-tone sound of Police or....
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Circuit Here is a circuit of a remote control unit which makes use of the radio frequency signals to control various electrical appliances. This remote control unit has 4 channels which can be easily extended to 12. This circuit differs from similar circuits....
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This timer was designed mainly to switch off a portable radio after some time: in this way, one can fall asleep on the sand or on a hammock, resting assured that the receiver will switch off automatically after some time, saving battery costs. R1 and C1....
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This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants` pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is....
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The basic digital circuits are Flip Flop and Counter, both are here. This circuit can be cascaded to make even a 6 digit event counter, even a simple frequency counter can be made. These are best done with microcontrollers today. Then what if you have to....
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Most, if not all, recent cars have an impressive amount of electronics, whether it be ABS brake systems, engine control with injection calculators, airbag activation, or other various functions, called comfort functions. Among them is one which we tend to....
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The quartz clocks which have dominated time-keeping for the past 20 years or so have one problem: their errors, although slight, are cumulative. After running for several months the errors can be significant. Sometimes you can correct these if you can....
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Some cheap car alarms do not have a connection for the central locking system. However, in most it should be possible to find a point in the alarm circuit which is high when the alarm is activated and low when it is off. This signal can then be used to drive....
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For several years now, a rear fog lamp has been mandatory for trailers and caravans in order to improve visibility under foggy conditions. When this fog lamp is switched on, the fog lamp of the pulling vehicle must be switched of to avoid irritating....
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Protect your valuable laptop against theft using this miniature alarm generator. Fixed in-side the laptop case, it will sound a loud alarm when someone tries to take the laptop. This highly sensitive circuit uses a homemade tilt switch to activate the alarm....
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These two headlight reminder circuits are easy to install and operate on the KISS (Keep It Simple Stupid) principle. The simple circuit involves adding just a 12V piezo buzzer between the lights circuit and a door switch. The buzzer sounds if the lights are....
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This circuit could be regarded as a simple alternative to the Sooper Snooper device featured elsewhere in this issue. It is based on the PreChamp preamplifier featured in the July 1994 issue of SILICON CHIP. It can be used to pinpoint or locate sounds coming....
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Today, almost all computers contain logic blocks for implementing a USB port. A USB port, in practice, is capable of delivering more than 100 mA of continuous current at 5V to the peripherals that are connected to the bus. So a USB port can be used, without....
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I n this circuit, the alarm will be switched on under the following four different conditions: 1. When light falls on LDR1 (at the entry to the premises). 2. When light falling on LDR2 is obstructed. 3. When door switches are opened or a wire is broken. 4.....
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This is basically a flasher circuit modified to turn on and off a bulb instead of a LED. It uses a 555 timer IC working as an astable multivibrator. The flashing rate can be varied from very fast to a maximum of once in 1. 5 sec by varying the preset VR1. ..
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Circuit Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is placed around the inside doorknob of a wood door. Anyone grabbing the knob from the outside is detected....
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Circuit This schematic is the power supply and front-end sections of the field monitor that is discussed in more detail at Electric Field Disturbance Monitor. (this link is off-site) The system can detect human and animal motion by the electric fields they....
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Circuit Pressing a single key on the keypad - will energize the relay. Entering a four-digit code of your choice - will de-energize the relay. The circuit was designed to control the Modular Burglar Alarm System - but it will have other applications. If you....
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This tiny circuit comprising of a single 3 terminal IC UM66 can be built small enough to be placed inside a greeting card and operated off a single 3V flat button cell. There is not much to the circuit. The UM66 is connected to its supply and its output fed....
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This circuit produces a sound similar to the police siren. It makes use of two 555 timer ICs used as astable multivibrators. The frequency is controlled by the pin 5 of the IC. The first IC (left) is wired to work around 1Hz. The 47uF capacitor is charged....
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This Home Alarm System is simple, secure, fast and cheap. It`s only few components with maximum security with Rolling Code TX and Shock Sensor with variable sensitivity. The alarm module can be assembled in only 2 hours and it don`t need manual preset. Home....
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A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of J1, P1, C2, C3 &C4. Connect C9 to the output ground. ..
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The TDA8581(T) from Philips Semiconductors is a 1-watt Bridge Tied Load (BTL) audio power amplifier capable of delivering 1 watt output power into an 8-Wload at THD (total harmonic distortion) of 10% and using a 5V power supply. The schematic shown here....
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Here is the 22 watt stereo audio power amplifier circuit diagram based on TDA1554 and integrated circuit from NXP semiconductors (formerly PHILIPS semiconductors). It is very simple and useful circuit for amplify the stereo signals. The circuit dissipates....
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This design will interest technicians who work on pneumatically operated valves and other 4-20mA current loop controlled devices. Although 4-20mA signal injector/calibrators are available, this one is both cheap to build and easy to operate. When first....
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This design adopts a well established circuit topology for the power amplifier, using a single-rail supply of about 60V and capacitor-coupling for the speaker(s). The advantages for a guitar amplifier are the very simple circuitry, even for comparatively....
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Add a cheap stopwatch to this circuit to produce an accurate reaction timer. The circuit is wired in parallel with the start/stop button in the watch via a 2. 5mm socket, which fits snugly in one corner of the casing. The person conducting the test (the....
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AFX slot car sets are very enjoyable but you can increase the fun with a lap counter. This circuit will count from 00 to 99, with independent counters for each track. The sensing device used is a Hall effect sensor (UGN3503; available from Dick Smith....
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We are surrounded by battery operated equipment of all kinds, and this array is growing still. Manufacturers and designers lean over backwards to make sure that their equipment draws a small current and can thus be operated by a battery. This has its flip....
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Do you drive an older car without an automatic "lights-on" warning circuit If so, you`ve probably accidentally left the lights on and flattened the battery on one or more occasions. This headlights reminder circuit will prevent that. It`s more complicated....
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Although you may well be the proud owner of the very latest NiCd battery charger, you may still come across the odd `incompatible` battery, for example, one having a rare voltage or requiring a much higher charging current than can be supplied by your....
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A number of readers have asked how to tell when the Lead-Acid Battery Zapper has done its job and battery desulphation is complete. In the author`s experience, batteries that are going to respond to this treatment will generally show quite a high peak....