Top Circuits Page 186
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This is a very good integrated circuit. There is no need for any external glue logic to drive the circuit, there is only 2 pins to drive the motor, one for controlling the direction and the other to trigger the stepping pulses. It provides a very compact....
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This is a simple servo tester which will comprehensively test the capabilities of almost any modern servo. It has two pushbuttons, CENTRE and SWEEP and a potentiometer which works as follows:..
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This project uses an LM3915 bar-graph IC driving two sets of ten LEDs for a 30dB range. The circuit is unique because it has an additional range of 20dB provided by an automatic gain control to allow it to be very sensitive to low sound levels but it....
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This circuit is intended as a reliable replacement to thermally-activated switches used for Christmas tree lamp-flashing. The device formed by Q1, Q2 and related resistors triggers the SCR. Timing is provided by R1, R2 & C1. To change flashing frequency....
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This circuit has been designed to provide a clearly visible light, formed by 13 high efficiency flashing LEDs arranged in a pseudo-rotating order. Due to low voltage, low drain battery operation and small size, the device is suitable for mounting on bicycles....
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This circuit is intended to let the user turn off a lamp by means of a switch placed far from bed, allowing him enough time to lie down before the lamp really switches off. Due to the low current drawing, the circuit can be supplied from 220Vac mains without....
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The basic circuit illuminates up to ten LEDs in sequence, following the rhythm of music or speech picked-up by a small microphone. The expanded version can drive up to ten strips, formed by up to five LEDs each, at 9V supply. IC1A amplifies about 100 times....
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The purpose of this circuit was to create a ring in which LEDs or Lamps illuminate sequentially. Its main feature is a high versatility: you can build a loop containing any number of LEDs or Lamps, as each illuminating device has its own small circuit. The....
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This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc. ). The whole thing is very easy to build....
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This simple pulse width modulation DC motor control eliminates these problems. It controls the motor speed by driving the motor with short pulses. Thesepulses vary in duration to change the speed of the motor. The longer the pulses, the faster the motor....
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The circuit is very simple and inexpensive. This is good thing because most commercial stepper motor controller ICs are quite expensive. This circuit is built from standard components and can easily be adapted to be controlled by a computer. If you use cheap....
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This simple circuit drives 6 LEDs in `Knightrider scanner mode`. Power consumption depends mainly on the type of LEDs used if you use a 7555 (555 CMOS version)...
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The 555 Ic is wired as an astable and the frequency is constant and independent of the duty cycle, as the total resistance (R charge + R discharge, notice the diode) is constant and equal to 22Kohm (givin a frequency of about 1Khz, notice the hum). When the....
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high quality amplifier for headphones electronics project. no need for preamplifier. circuit diagram....
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From 230 V AC a DC supply of + 5 V is obtained. The power supply is given to the other blocks. The pulse generator at a particular frequency generates the clock pulses. The clock pulses are counted by a counter and gives output after every 10 pulses. The....
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Certain part of this circuit is directly connected to AC mains. Therefore, do not touch whilst in operation. Disclaimer Please take the greatest of care in handling AC mains supply while constructing this project. If you have no knowledge of mains wiring or....
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The circuit is built around two 555 timer ICs. U1 and U2. U1 is wired as a variable duty cycle oscillator with a constant time period of around 0. 1 second. Duty cycle can be varied from 0 to 100 per cent by R4 potentiometer. The output of U1 (pin 3) is....
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The under/over voltage protection circuit with time delay presented here is a low cost and reliable circuit for protecting such equipments from damages....
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There are a number of npn transistors that will oscillate in the audio range when reverse biased. Minimum supply voltage is 7V for low power transistors such as BC109, BC238 and 2N2222A, it becomes 12V for medium power transistors such as BD139 and is 16V....
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This circuit generates a good 1KHz sinewave using the inverted Wien bridge configuration (C1-R3 & C2-R4). Features a variable output, low distortion and low output impedance in order to obtain good overload capability. A small filament lamp ensures a stable....
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This circuit is intended to provide good square waves converting a sine wave picked-up from an existing generator. Its major feature consists in the fact that no power-source is needed: thus it can be simply connected between a sine wave generator and the....
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The purpose of this circuit is that of power a lamp or other apparatus for a given time (30 minutes in this case), and then to turn it off. It`s useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep.....
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This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a question, or to move a piece etc. In this view it`s a modern substitute for the old sandglass. Useful also for....
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This circuit was developed since a number of visitors of this website requested a timer capable of emitting a beep after one, two, three minutes and so on, for jogging purposes. As shown in the Circuit diagram, SW1 is a 1 pole 9 ways Rotary Switch. Setting....
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This circuit uses the versatile MAX038 function generator. Although in this circuit some of the advanced characteristics of this IC are disabled, you can generate Sine, Triangle, Square waves (adjusting A0 and A1 pins see datasheet on if you want other....
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This is a programmable clock timer circuit that uses individual LEDs to indicate hours and minutes. 12 LEDs can be arranged in a circle to represent the 12 hours of a clock face and an additional 12 LEDs can be arranged in an outer circle to indicate 5....
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A photodiode, SFH2030 as an infra red sensor. A MOSFET opamp, CA3140 is used in the differential mode to amplify the pulses of current from the photodiode. LED1 is an ordinary coloured led which will light when IR radiation is being received. The output of....
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This is a simple XTal tester circuit. T1 and XTal have formed an oscillator. C1 and C2 are voltage divider for oscillator. if the XTal is safe, the oscillator will work well and its output voltage will be rectified by C3, C4, D1 and D2, then T2 will run and....
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This simple circuit has helped me out on many occasions. It is able to check transistors, in the circuit, down to 40 ohms across the collector-base or base-emitter junctions. It can also check the output power transistors on amplifier circuits. Circuit....
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Portable Mixer. High-quality modular design. 9V Battery powered - Very low current drawing. Preamp, tone control, mixer - all in one. Electronics project. Circuit diagram. Schematics....
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A simple triangle/squarewave generator using a common 1458 dual op-amp that can be used from very low frequencies to about 10 Khz. The time interval for one half cycle is about R*C and the outputs will supply about 10 milliamps of current. Triangle amplitude....
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This circuit uses an LM11 to form a voltage follower with 1G ohm input resistance built using standard resistor values. With the input disconnected, the input offset voltage is multiplied by the same factor as R2; but the added error is small because the....
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This circuit enables you to test quartz resonators at the range values from 32kHz to 24MHz. Confirmation of good state of quartz resonator is done by diode signalling LED and acoustic signal. Switch S2 enables change of range...
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This circuit is a Logic Probe. It indicates the logic state of the node of any TTL logic circuit. To do that, we have to supply the probe with the same power of the circuit that we want to analyse: same Vcc and same GND. To check the logic level, we must....
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This circuit is a Digital Radar Speedometer. It allows us to evaluate the speed of any object moving, especially cars and other vehicles. The speed is calculated in kilometers per hour (KPH). Its display has three digits. This radar works with the laser....
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A bright lamp flashes in sychrony with the lightning bolts indicating the proximity and intensity of the storm....
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This basic oscillator will detect the Earth magnetic field. The ferrite rod and coil are taken from an old Medium Wave receiver and a small magnet is glued at one end. Tune to a medium wave commercial station until you hear a beat note. Any movement of the....
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The piezoelectric element of a kitchen gas lighter is used in this simple, yet effective seismic detector. The piezo element must be placed vertically, one end solidly to ground. A 2-3 pound weight of fine gravel in a loose package should be placed on top at....
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IC1 is a 555 timer in astable mode, sending approx. 10 ms pulses to decade counter IC2. IC2 is continually reset through R3, until pin 15 is taken low through the "Fire" button. IC2 then sequences through outputs Q1 to Q7, to feed power transistors TR1 to....
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This lovely circuit is a real gem! Easy to assemble 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....
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This is a very straightforward circuit. The first stage acts as a crystal receiver. Use a germanium detector diode (like 1N34, but AA119 is much more common in Europe), a silicon one won`t do. The frequency is determined by L and C. For the FM band and VHF,....
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The Bio-Stimulator provides muscles` stimulation and invigoration but, mainly, it`s an aid in removing cellulitis. Tape the electrodes to the skin at both ends of the chosen muscle and rotate P1 knob slowly until a light itch sensation is perceived. Each....
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The circuit generates this type of Geo-magnetic-fields and lets us perceive them: in this manner our brain is surrounded by an ideal environment for a sound sleep. With SW2 opened (Alternate mode operation) the device operates for the pre-set time, then....
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This unit can be useful as a short-range, single-channel remote-control. When the pushbutton in the transmitter circuit is briefly activated, the LED D1 in the receiver illuminates and an optional beeper or relay can be operated. Circuit operation is based....
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This device produces high voltage pulses discrupting muscles and nervous sYstem, leaving anyone who touches it in a state of menthal confusion. Can be used agains ferocious animals or attackers, BUT REMEMBER, this device may be illegal in your state (for eg....
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This is a fun and non-dangeros project for those people who like to throw projectiles magnetically. It simply works by placing a ferromagnetic projectile at one end of a coil and pulsing some power in it. The trick is to switch off power when the projectile....
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This is an improved IR remote control extender circuit. It has high noise immunity, is resistant to ambient and reflected light and has an increased range from remote control to the extender circuit of about 7 meters. It should work with any domestic....
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This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electret (ECM) microphone. If an ECM is used then R1 (shown dotted) will need to be included. A suitable value would be between 2. 2k and 10kohms.....
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The hardest part for this circuit was the title. It is quite easy to miss the sound of a doorbell if you are watching TV, this circuit gets round the problem by providing a visual indication, i. e. a lamp. As an alternative, a LED could also be used. You....
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This is a very interesting project with many practical applications in security and alarm systems for homes, shops and cars. It consists of a set of ultrasonic receiver and transmitter which operate at the same frequency. When something moves in the area....
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This circuit indicates audio output power via three LEDs. Nice addon to your amplifier....
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This circuit is intended for precision centigrade temperature measurement, with a transmitter section converting to frequency the sensor`s output voltage proportional to the measured temperature. The output frequency bursts are conveyed into the mains supply....
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This circuit is intended to signal through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electret....
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For proper operation, circuit ground must be connected via a small value, high voltage-rating capacitor to one side of the mains supply socket. The "Live" side is the right one. The purpose of this circuit is to animate shop-windows by means of a capacitive....
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This circuit is useful in liquids level or proximity detection. It operates detecting the distance from the target by reflection of an infra-red beam. It can safely detect the level of a liquid in a tank without any contact with the liquid itself. The....
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This circuit, enclosed in a small plastic box, can be placed into a bag or handbag. A small magnet is placed close to the reed switch and connected to the hand or the clothes of the person carrying the bag by means of a tiny cord. If the bag is snatched....
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This circuit emits a beep and/or illuminates a LED when someone touches the door-handle from outside. The alarm will sound until the circuit will be switched-off....
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Pressing the pushbutton of the transmitter, a sound and/or light alert is activated in the receiver. The system uses no wiring or radio frequencies: the transmitted signal is conveyed into the mains supply line. It can be used at home, in any room from attic....
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This handy little circuit can tell the difference between darkness and light, making it very useful for switching on and off signs, porch lights or other things when it gets dark or light...
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The circuit described here is that of a metal detector. The opera- tion of the circuit is based on superheterodyning principle which is commonly used in superhet receivers. The circuit utilises two RF oscillators. The frequencies of both oscillators are....
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The automatic pump controller eliminates the need for any manual switching of pumps installed for the purpose of pumping water from a reservoir to an overhead tank (refer Fig. 1). It automatically switches on the pump when the water level in the tank falls....
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This circuit is an Electronic Locker. It is controlled by a switches combination (by a code). There is a switch matrix on the door of the locker. This one is a unit of switches connected into 4 arranged of 4 columns for a total of eight terminals. When we....
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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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This is a new design of a tutorial board based on the popular PIC16F84A microcontroller. It features eight single leds, a 7-segment display, an LCD display and five push buttons. It is an ideal solution for the beginner to take his/her first programming....
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On board the AVRs that can be programmed are those in the schematic. For other members of AVR family or the rest programmable ICs that Ponyprog can program, there is the J1 connector (CON10) which allows expanding the programmer`s hardware. See Ponyprog`s....
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The IC produces all the sound effects, the output at Pin 3 being amplified by the transistor. A 64 ohm loudspeaker can be substituted in place of the 56 ohm resistor and 8 ohm loudspeaker. The 2 pole 4 way switch controls the sound effects. Position 1 (as....
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Simple to build, simple to make, nothing too complicated here. However you must use the CMOS type 555 timer designated the 7555, a normal 555 timer will not work here due to the resistor values. Also a low leakage type capacitor must be used for C1, and I....
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A simple astable timer made with the 555, the mark (on) and space (off) values may be set independently. 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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To start in 24 seconds; 24s LOAD SW and Reset SW should be push simultaneously. If not, the count will start in 99. Pulse input can be connected to 555 astable multivibrator but must be calibrated for real time clock. The PAUSE SW must have a Switch....
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Do not use the "on-board" relay to switch mains voltage. The board`s layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage - mount a suitably rated relay somewhere safe -....
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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 detect metal wiring if it conducting ac....
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Using a single 555 Timer IC and a small transformer to generate a high voltage, this circuit will test zener diodes of voltage ratings up to 50VDC. The 555timer is used in the astable mode, the output at pin3 drives a small audio transformer such as the....
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This simple circuit uses a 741 op-amp in differential mode as a continuity tester. The voltage difference between the non-inverting and inverting inputs is amplified by the full open loop gain of the op-amp. Ignore the 470k and the 10k control for the....
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