New Circuits Page 253
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When the ignition switch is on, relay K1 is energized continuously, and the headlights can be turned on. Turning off the ignition turns on timer IC1,which keeps IC1 energized for a time determined by Rl and CI. With the values shown approximately a 1 minute....
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It is sometimes necessary to retrieve data at power-up in the same way that they were at the last power-down, so that the product wakes up in the state it had before shutdown or to retrieve some measurement. One approach is to save critical variables into....
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Figure 1 presents an alternative to the typical boost power regulator. A buck-converter IC, IC1, generates the higher voltage that the white-light LED needs. An internal buck power stage connects between VIN and PGND, sourcing current to output Pin L. This....
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This circuit operates two LED strips in pulsing mode, i.e. one LED strip goes from off state, lights up gradually, then dims gradually, etc. while the other LED strip does the contrary.
Each strip can be made up from 2 to 5 LEDs at 9V supply. The two....
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This Is a capacitor power supply. This is a very small currents of energy-effective, because it has very little loss, much smaller than the miniature transformer. Capacitor impedance is inversely proportional to frequency. This is a great disadvantage when....
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This electronic level uses two LED indicators instead of an air bubble. If the surface is tilted to the right, one LED lights; if it's tilted to the left, the other LED lights. When the surface is level, both LEDs light. It uses two unidirectional mercury....
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The schematic is very simple and includes, in addition to Nutchip, with its three driving transistor and LED, the radio receiver. The data come from the OUT pin of the receiver and enter the pin REMOTE remote control. The RESET pin connected to an external....
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The world is full of xtal oscillators twiddled by digital designers lacking in the analog design knowledge necessary. Just look at all the PC real time clocks that lags or leads by several minutes per day. And they eat backup batteries too! IC`s with pins....
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This circuit adds a power down function to analog I/O ports (for example, the AD7769 and AD7774). Moreover, the diodes ordinarily needed to protect the devices against power-supply missequencing can be
eliminated Bringing the power down control high....
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What got me interested in building these diminutive devices is the S3FM connector assembly made by Switchcraft. The S3FM is simply a 3.5-inch tube fitted with a male XLR at one end and a female at the other, with enough room in the middle to build a mike....
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When the touch plate is contacted by a large object (human body, etc.), stray 60-?? pickup is rectified by D1 and D2, and produces a negative voltage across R2-C2 and the gate of Q 1. Q1 cuts off, causes Q2 to conduct, and the output goes low. ..
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Osmond PCB is a flexible tool for designing printed circuit boards. It runs on Macintosh. Its many features include: * Virtually unlimited board sizes * Virtually unlimited number of board layers * Virtually unlimited number of parts....
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This is my second-generation guitar reverb circuit. The fidelity is much improved over the earlier design, it is suitable for use as a front-end to a guitar amplifier. This circuit features clipping indicators on the preamp and reverb recovery stages,....
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This oscillator circuit includes a quartz crystal that has a nominal resonant frequency of 262,144 Hz and is cut in the orientation that gives a large linear coefficient of frequency variation with the temperature. In this type of circuit, the oscillation....
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The piezo speaker, MICl, picks up the incoming ultrasonic signal and feeds it to the base of Ql. The two-transistor booster amplifier, Ql and Q2, raises the signal to a level that is sufficient to drive one input of this most unusual mixer circuit.....
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In video systems it is frequently necessary to remove the
sync pulse from a video signal, while passing the active
video information. A familiar application for this is the scrambling
of premium channels by cable operators so that they
may only be viewed....
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Finally I was able to control an LCD Hitachi display and a 12-key matrix keypad with only one 16F84 or 16F628. In a near future, I will be able to control a full QUERTY-type keyboard and a LCD display. The biggest improvement on this projects was the....
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This Power amplifier is equiped with a bipolar transistor,the famous MRF317. As lots of FM amplifier application ,the power transistor is in a C class bias. All the impedance networks (Input & Output) have been determined by using the software: Mimp.EXE. A 9....
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Lithium Ion batteries pack a lot of power by weight compared to other types. There are 2 things that need to be handled differently than nicad on NiMH. They cannot be used as a direct substitute (even if they look like other AA's) since they run at about....
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Many times we needed a stabilized, together regulated power supply and high relatively output voltage. These specifications him it cover our circuit. It `s a circuit that can give in his exit + 40V until + 60V 3A, with simultaneous stabilization. The....
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In spite of the improvement of communication link and despite all progress in advanced communication technologies, there are still very few functioning commercial wireless monitoring systems, which are most off-line, and there are still a number of issues to....
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This circuit is intended to control a heating system or central heating plan, keeping constant indoor temperature in spite of wide range changes in the outdoor one. Two sensors are needed: one placed outdoors, in order to sense the external temperature; the....
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The microcontroller is able to make about 7000 complete line-following decisions per second, which is almost 7 decisions per millimeter when the robot is going full speed. By upping the clock, unrolling loops, and removing my wireless debugging and....
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When the 14B-12B pair opens, 12B is connected to Al's summing point via 13B. The sensor now discharges into the summing point through the 1 µ capacitor. Since the charge voltage is fixed, the average current into the summing point is determined by the....
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This circuit controls resistive and inductive loads up to 2,500W. Its main functional device is an integrated phase control circuit - Siemens TLE3103. It contains its own power supply, a zero voltage crossing detector circuit and a logic driver. An....
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This circuit operates like the one shown in Fig, 57-4, The only differences are that the field is placed across the rectified supply and the armature is placed in the SCR bridge. Thus the field current is unidirectionali)ut armature current is reversible;....
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The RF oscillator using the inverter N2 and 10.7Mhz ceramic filter is driving the parallel combination of N4 to N6 through N3.Since these inverters are in parallel the output impedance will be low so that it can directly drive an aerial of 1/4th wavelength.....
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The 2N4416 JFET will provide noise figures of less than 3 dB and power gain of greater than 20 dB. The JFET's outstanding low crossmodulation and low intermodulation distortion provides an ideal characteristic for an input stage. The output feeds into an....
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Low power dc to dc converter obtained by adding a flyback circuit to a square wave oscillator. Operating frequency is 20 kHz to minimize the size of LI and C2. Regulation is achieved by zener diode D2..
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In the circuit exist a simple power amplifier 60W in the 8 ohm and 80W in the 4 ohm, with components that sure exist in big quantities. It can be used in home cinema systems or in other uses. With the TR1 we regulate the DC voltage in the output of....
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Right- and left-channel signals pass through 1 C4-a and -b buffer amps into active crossover IG5; low frequencies are sent to the IC6-c mixer, and middle and high frequencies are sent to the analog delay lines of 1C1 and 1C2. That output passes through....
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The car alarm here is a simple circuit with basic characteristics that cover all entrances at the car that has switches (doors etc).With one switch (arm-switch) the circuit waits for the sensor-switches to open and to activate it. So the horn with 1 sec....
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After attempting to use this reportedly "pretty good" microphone in a variety of situations with some "pretty bad" results, I dissected the power supply and found the same audio transformer that`s in their 180-in-one project kits! This DAT-Heads Digest....
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One LED monitors three levels: 50, 70 & 85 dB
Useful to detect too noisy environments. 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....
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Many people favor different light and temperature settings for different rooms depending upon their mood or whether they are working or relaxing. The circuit in Figure 1 controls the intensity of the artificial light in a room and monitors the temperature of....
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The circuit requires only one power-switching device, and you can use an analog or a digital signal to drive the switching device. The circuit also requires only a few components: a diode, a switching transistor or a MOSFET, an inductor or a transformer, and....
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Built around an Intersil 7216 frequency-counter IC, this counter has a basic range of 10 MHz, a 100-MHz prescaler, and an..
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Figure 1 shows a complete circuit for an emergency lamp that operates from a 12V automotive battery. The xenon flash tube requires a 250V-dc anode voltage and a 4-kV trigger pulse. To generate the 250V dc, IC1, a switching regulator controller, and T1, a....
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This PSU has been especially designed for current-hungry ham radio transceivers. It delivers safely around 20Amps at 13.8V. For lower currents, a separate current limiting output, capable of 15ma up to a total of 20A has been added...
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This page features basic, visible light photo-detector circuits that can be used to detect trains. These methods would normally be used with the photo sensor mounted between the rails...
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A JFET transistor-is used as a high-to-low impedance converter and signal mixer. Input impedance is approximately 50.0 kQ but it can be increased by increasing R5 to R8 as high as 10 . Output is about 2 kQ, but it can be increased or decreased by changing....
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This is a slightly revised version of the 6-transistor H-bridge designed by Mark Tilden and found on the BEAM Tek website (now only available via archive).
I encourage anyone interested in H-bridges to read Mark's article, as it gives an excellent....
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Power op amps provide accurate speed control for dc motors. The circuit provides bidirectional speed control. The amplifiers' push-pull configuration ensures a full rail-to-rail voltage swing (minus the output stages' saturation drops) across the motor in....
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An inexpensive electronic thermometer is capable of measuring temperatures over a range of from -30°F to +120°F. A diode-connected 2N3904 transistor used as the temperature sensor forms a voltage divider with Rl. As temperature increases, the voltage drop....
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The supply of circuit becomes from a AC line in the J1. This voltage can be from a separate transformer 2X12V (the prices of materials that I give it is for 2X12V AC), from existing coil 12V in their M/T of power amplifier or if it cannot become somebody....
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The uWatch comes as a kit of parts. All of the electronic SMD parts on the PCB are pre-assembled. The uWatch is normally in sleep mode and powers down the LCD to save battery power. (approx 3mA LCD on, and 15uA LCD off) To switch the uWatch on press either....
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The modified inverting amplifier uses an active clamp to limit the output swing with precision. Allowance must be made for the V8E of the transistors. The swing is limited by the base-emitter breakdown of the transistors. ..
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The circuit uses two gates of a 7400 IC cross-connected to form an astable multivibrator driven by the 1-pulse per second output of the digital clock IC. The hee-haw circuit has a low frequency astable modulator added to make a self-contained European-type....
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A pair of non-zenered MOSPOWER transistors, a pair of LEDs and a simple RC circuit make an easy sequential flasher with almost "unlimited sequencing time—from momentary to several seconds. The infinite input resistance of the MOSFET gate allows for very....
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The amplifier in Figure 1 originally served as the photomultiplier preamplifier in a Doppler system intended for eventual operation in the Martian atmosphere. The design is based on a switchable array of six Maxim MAX4258 dual-channel video....
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Based on Valvo FD-1A module, TBA120, and MC1310. Operation of the receiver is based on the phase locked loop principle. The FD-1A contains an RF amplifier, oscillator and mixer (made with BF324, BF451 and BF324 transistors, respectively). Tuning is performed....
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Using the circuit of 40-metre band direct-conversion receiver descr- ibed here, one can listen to amateur radio QSO signals in CW as well as in SSB mode in the 40-metre band. The circuit makes use of three n-channel FETs (BFW10). The first FET (T1) performs....
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Once again my collection of projects creation has been interrupted by another necessity. Patrick and other people have asked me for a circuit of a VHF power amplifier. These circuits are my "standard" building blocks that can be used to amplify RF power....
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The circuit uses a thermistor and three sections of a LM3900 quad op amp IC. When the temperature drops to 36°F the LED indicator flashes about once each second. The flashing rate increases as temperature drops to 32°F when the LED remains on. Amplifier I....
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This simple circuit generates narrow pulses at about 700-800Hz frequency. The pulses, containing harmonics up to the MHz region, can be injected into audio or radio-frequency stages of amplifiers, receivers and the like for testing purposes. A high-pitched....
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The display shows each increment. By using mode 2, external debouncing of the gate switch is unnecessary, provided the switch bounce is less than 35ms. The 3 V lithium battery can be replaced without disturbing operation if a suitable capacitor is connected....
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This circuit produces a symmetrical waveform when dividing by either 2 or 3. The Divide Select input controls the ..
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A school drama needed lamps that automatically turned on and off when spot lights did the same. Lamp switching had to be wireless, durable, dependable, simple and inexpensive. With stage and spot lights off, very little light falls on the CdS photocell, so....
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The circuit comprises simply the PWM source, capacitor C, and resistors RD and RW. For CMOS circuits, you calculate the open-circuit output voltage as VCONT=D½§VDD, where VCONT is the control circuit`s output voltage, D is the PWM duty cycle, and VDD is....
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The LED with integrated flasher is connected in series with the base-emitter junction of transistor Tl. Thus, the l..
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A simple and effective receiver for actuating garage doors, alarms, warning systems, etc. The SCR, which has a very low trigger current 30 µ is typical—it requires an input power of only 30 juW to activate the relay. A high Q tuned antenna circuit assures....
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The bug tracer is made up of a simple rf-injector circuit consisting of Ql and Q2, and a pocketsize, AM broadcast receiver. The two-transistor rf-injector circuit supplies a constant rf signal to one end of a cable. Then the AM receiver is used as a....
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Tired of always spending money on flashlight batteries only to have them fail just when you need them? Try this simple circuit out. It would make an excellent science fair project. The white LEDs are quite bright, they provide enough light to illuminate a....
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The temperature sensor U2 needs to be located next to the item being monitored. As the temperature increases the motor duty cycle will increase. D1 and R2 are optical components, they only need to be installed for a visual indication of the current duty....
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Using a charge pump and oscillator, this circuit uses a 7-kHz oscillator. When the clock is high, C and D..
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You'll find that this is a very easy project to build. It will transmit good quality sound in the FM band ( 88 - 108 mhz ). One inportant item is that the IC chip operates on 3 volts DC. The chip will get destroyed if it is operated on any voltage higher....
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A pair of timer IC"s are the heart of a circuit that simulates the warbling bee-haw of a British police siren. One of the 555 timers, U2, is wired as an astable multivibrator operating at about 900 Hz. The other, Ul, operates at approximately 1 Hz. Its....
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Build a Guitar Looper with an Arduino board. Here is how to produce pedalboard for electric guitar. The idea is to connect pedals to the Arduino, and to use them to control a software of sound processing in Pure Data. Here I show you the example of a....
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For those who are still with me, the preamp featured has optional tone and balance controls which may be omitted if desired (although I do not recommend this generally). The input switching may be extended if needed to accommodate more signal sources,....
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A complete AM radio set based on the MK484 IC (formerly ZN414). It uses a PNP transistor and can drive a 150R loudspeaker. Chad has built a complete radio receiver using 1 IC and a single transistor. The IC requires around 1.2 to 1.6V and this is supplied....
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The AM Tuned Radio Frequency (TRF) receiver, has a sensitivity of about 1 m V at tbe input for an audio output of "iz W. Capacitor C22 couples audio signals from the power line to the PC board-it must be rated at 600 Vdc. R8 will cause F1 to blow, if C22....
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This is a circuit thich I originally included in my book, 22 Tested Transistor Projects, published by Babani Press in 1976 (ISBN 0 900162 63 S). It is one I had great fun with. It uses the PUT Complimentary Feedback Pair as a sensitive detector of changing....
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The Keypad must be the kind with a common terminal and a separate connection for each key. On a 12-key pad, look for 13 terminals. The matrix type with 7 terminals will NOT do. The Alarm is set by pressing a single key. Choose the key you want to use and....
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The circuit disconnects the battery from the load when output voltage falls below a preset level. Cl charges through R1 and turns on Q2. Collector current flows through R2 turning Ql on and battery is connected to the load..
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The circuit consists of eight cascaded identical cells, each ccll being a dc-controlled active phase shifter. Because the dc control is common for all shifters, the circuit is adjusted by trirtuiiing RA so that the phase difference between and Vi is zero.....
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This regulator delivers 90% efficiency at 12-V input, 5-V output. It uses an LT1158 and LT1431 by Linear Technology, Inc. High efficiency is obtained by synchronously switching two power MOSFETs in a step-down switching regulator...
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This is a successor of the PIC16C71 4-digit LED f-counter & V-meter. Some hard to find parts used in the previous version, which are out of production for some time, has been omitted. A rather early PIC16C71 has also been replaced by 28-pin device....
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Here`s a simple lie detector that can be built in a few minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as the ones the professionals use, but it works. It works by measuring....
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In many applications, a solenoid driver must first briefly supply a large amount of pull-in cnrrent, which quickly actuates the solenoid. Thereafter, the driver must supply a much lower holding cnrrent to avoid burning the solenoid out. To avoid using the....
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The circuit in Figure 1 eliminates the need for adjustments. The circuit uses dc-coupled feedback to control the current in the output resistor. Hence, the output voltage is predictable and constant...
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Figure 1 shows the block diagram for the NTE789. The input signal form the detector is amplified by a lowdistortion
preamplifier and simultaneously applied to both signal, generated by a local voltagecontrolled oscillator
(VCO), is counted down by two....
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This circuit uses only one JC, either 1, LM393 dual comparator or 1/z, LM339 quad comparator. RV1 and RV3 set the full scale reference voltage, and RV2 and RV4 set the switching thresholds to a value between 0 V and the full-scale reference. ..
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The detector uses three sections of an L144 and a DC4011 type CMOS NAND gate to make a very low power voltage monitor. If the input voltage, Vin, is above Vhigh or below Vlow, the output will be a logical high. If (and only if) the input is between the....
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Using a 12-bit-resolution analog-to-digital converter (ADC) does not necessarily mean your system will have 12-bit accuracy. Sometimes, much to the surprise and consternation of engineers, a data-acquisition system will exhibit much lower performance than....
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Choosing de rather than ac coupling can reduce much of the noise associated with preamplifiers for a magnetic reading head, particularly in the low frequencies. The LM1897 eliminates the need for the capacitor that usually ac couples the read head to the....
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This amplifier provides 140-W PEP nominal output power when supplied with input levels as low as 3 W. Both input and output transformers have a 4:1 turn ratio and a 16:1 impedance ratio to achieve low input VSWR ..
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A simple but useful circuit for all they have problem with parking car, in spaces without good visibility. The electric circuit appears in picture 1. It is constituted by the IC1 and components round he. When the car bumper touch soft and push lightly the....
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The LED Torch is based on a 7555 timer running in astable mode (do not use an ordinary 555). A white LED (Maplin order code NR73) produces 400 mcd light output, which, when focussed, can illuminate objects at 30 metres. Try Conrad Electronic for what appears....
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This is a description of an experimental AM receiver for VLF. It is crystal controlled to receive 181.818 kHz (more or less) and operates as either a single conversion superhetrodyne or a direct conversion receiver. The bandwidths are expected to be 15 Hz to....
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The first step is to remove the film. Be sure the film is fully wound in. Then use a flat blade screwdriver to pry up the tab at the seam in the middle of the right side of the camera. The right side of the rear panel of the camera should then pop up. You....
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A follow up Mk2 version described by EA`s Jim Rowe in the May/June/July 94
issues of EA improved on the original with calibrated time and vertical
scales, and extra triggering features. This design proved even more popular
than the first, proving that....
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Electromechanical door chimes can enhance your home, but they are vulnerable to costly repair problems. A defective pushbutton switch or a careless visitor can maintain the chime in an energized state for a prolonged period, thereby damaging the chime. The....
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Take care with transmitter circuits. It is illegal in most countries to operate radio transmitters without a license. Although only low power this circuit may be tuned to operate over the range 87-108MHz with a range of 20 or 30 metres...
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Bartels AutoEngineer® (BAE) is a famous EDA/CAE/CAD/CAM software system for schematic capture, printed ciruit board design and IC/ASIC design. Bartels AutoEngineer® software runs under Microsoft Windows, Linux and various X11/Unix systems...
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This is a simple circuit which I built to one of my audio amplifier projects to control the speaker output relay. The purpose of this circuit is to control the relay which turns on the speaker output relay in the audio amplifier. The idea of the circuit is....
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Many record players unfortunately exhibit two undesired side effects: rumble (noise caused by the motor and the turntable) and other low-frequency spurious signals. The active high-pass Chebyshev filter presented here was designed to suppress those noises.....
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The timer includes an oscillator and a counter in an integrated circuit. The timing interval equals the oscillator period multiplied by the number of cycles to be counted. The oscillator frequency depends upon resistor RS and capacitor CX. The number of....
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The Stereo Tape Head Preamplifier kit is based on LA3161 IC from SANYO. Power supply - 9 ~ 12 VDC @ 20 mA. Output power - upto 200 mW. Input Resistance - 100 K? (Typ), Load Resistance - 10 K? (Typ). Low noise, good ripple rejection owing to the on-chip....
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This amplifier is useful for audio and video applications. Gain is set by Rf and the voltage gain of this amplifier ..
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Using two op amps, this circuit produces a full-wave rectified version of the input signal. Op amp IC1 invert..