New Circuits Page 226
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The circuit is a modified Colpitts oscillator, tuned with MV209 varactor diodes. The resonating inductor and the drain choke are selected by a rotary switch. 1N5711 Schottky diode, D, clamps the maximum positive voltage on the gate of oscillator FET, Q1 to....
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This buffer amplifier"s overall harmonic dis tortion is a low 0.01 % or less at 3-V rms output into a 500-fl load with no overall feedback. The LT1010CT offers a 100 V/p.s slew rate, a 20 MHz video bandwidth, and 100 mA of output. A pair of JFETs, ]1....
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Here is a simple yet very useful circuit which can be used to eavesdrop on a telephone conversation. The circuit can also be used as a wireless telephone amplifier.
One important feature of this circuit is that the circuit derives its power directly from....
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VUTRAX (pronounced View-Tracks) is the major professional Electronics schematic and PCB (Printed circuit board) design package in the UK. The product was the first EDA package offered for personal computers, having a pedigree back to 1981 when it was created....
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The circuit automatically turns on when the car is turned off. It gives you a variable time to get out and lock..
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The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840. The IRF series of power transistors are available in various voltage and power ratings. A single IRF840 can handle maximum power output of 125 watts. Since these....
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The circuit has a built-in, self-arming feature. The driver turns off the ignition, presses the arm button on theComputalarm, and leaves the car. Within 20 seconds, the alarm arms itself—all automatically! The circuit will then detect the opening of any....
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Using the versatile L200 voltage regulator, this power supply has independent voltage and current limits. The mains transformer has a 12volt, 2 amp rated secondary, the primary winding should equal the electricity supply in your country, which is 240V here....
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A bridge circuit is used to produce a signal from the output of vacuum sensor IC1. IC2b provides about a 0.2 V offset ..
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A common method of transforming the output current of a photodiode into a voltage signal, paralleling the photodiode with a high-value load resistor, produces a nonlinear response. Also the combination of the load"s transresistance, Rr. and the....
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The thermistor used has a resistance of 15k at 25 degrees and 45k at 0 degrees Celsius. A suitable bead type thermistor can be found in the Maplin catalogue. The 100k pot allows this circuit to trigger over a wide range of temperatures. If using a different....
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This Antenna is most widely used all over the world. For example, when you see a police car it has a transmitter with Ground Pole Antenna The body of car serves as ground). It accepts load from 50 ohm source and has larger power output than Half-Wave Dipole....
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The capacitor-diode output circuit is used here as a polarity converter to generate a - 5 volt supply from +15 volts. This circuit is useful for an output current of up to 20 mA with no additional boost transistors required. Since the output transistors are....
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The expander to complement the compressor is shown. An external op amp is used for high slew rate. Both the compressor and expander have unity gain levels of 0 dB. Trim networks are shown for distortion (THD) and de shift. The distortion trim should be....
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Two dual-biquad filter chips and some external components form a multipurpose filter to reconstru..
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The inexpensive 7404 hex-inverter has enough amplification to handle a wide range of transducers. Closing the key completes the battery circuit and applies four to five volts to the 7404. Bias for the first two inverter amps (Ula and Ulb) comes from the two....
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The output-pulse width from the circuit is a linear function of the input pulse"s height. You can set the circuit"s input threshold to discriminate against low-level pulses, while fixed components limit the circuit"s maximum output -pulse width. With a....
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This audio processor is based on the Signc tics/Philips TDA3810N stereo, spatial, pseudo-stereo processor, IC. This processor uses a Philips TDA3810IC device, and it functions as an expander, pseudo stereo processor, and audio enhancer. ..
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The circuit is designed to provide protection to a DIY switching power supply for car amplifiers by shutting down under any or all of the three modes of protection (over voltage, under voltage and over temperature) with minimal components...
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ICl is connected in the astable mode, driving RLA, C3, Dl, and D2 prevent spikes from the relay coil and the wiper motor from triggering ICl. VR2 is adjusted to give the minimum delay time required. VR1 is the main delay control and pro vides a range of from....
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Total harmonic distortion (THD) measurements are one of the most commonly quoted in audio. Contrary to belief in some circles, these can be very useful if performed properly, and reveal much about the overall performance of an amplifier.
There are a....
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This system will alert you or anyone chosen by automatically dialing a programmed phone number. This is accomplished by monitoring an open- loop or closed-loop sensor switch located in the protected area. Mien the sensor detects a problem (such as a....
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RS-232 is the most common serial interface in the PC world. Most RS-232 interfaces communicate with the receiver at a fixed transmission rate, such as 9600 baud. But what happens if the transmitter operates with different transmission rates? Different....
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The yellow LEDs are on a small PCB, which are easy to remove. On the PCB there is 3 yellow
LEDs and 4 diodes. Pictures of the PCB can be seen here : Top-side - Bottom-side.
The schematic is as follows : You now remove the 3 LEDs and the 3 normal diodes....
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I have seen these devices advertised in magazines, they sell for around £40-£50 and use radio to transmit between receiver and transmitter. This version costs under £5 to make and uses a cable connection between receiver and transmitter. For example, if you....
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When a remote control signal is received, the energy stored in C2 drives the emitter diode. At the same time, Q1 switches on briefly to allow the battery to recharge C2. The green LED shows that the circuit is transmitting; and the yellow LED confirms that....
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A talking compass is made up using a Hall-effect direction sensor (MODI) and an ISD1016 analog audio storage device. It is possible to program eight two-second announcements, for each of the eight main compass directions. The Talking Compass is comprised of....
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The composite input signal is preamplified by transistor Ql and is then coupled to the high-pass filter composed of C3, C4, R6, and R7. The filtered audio is then passed to IC1, an MC1310P "Coilless Stereo Demodulator." That IC is normally used to demodulate....
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This is a circuit for alternative sources selection. It combines mechanical selection using a rotating switch S1, the electronic drive of the relays RL 1-10 and also the optical indication of the selection by the Display DSP1. The function is based on the....
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Readback data is applied directly to the input of the first NE592. This amplifier functions as a wide-band ac coupled amplifier with a gain of 100. By direct coupling of the readback head to the amplifier, no matched terminating resistors are required and....
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PLL (Ul) is set with R2 to desired tone frequency. LED lights to indicate lock-up of PLL. Reduce signal level (Rl) and readjust R2 to assure lock-up. Delay is selected from counter U3 output. Circuits latches (turns on Q1 to allow audio to speaker) when....
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This is a 3U rack unit with standard mains power supply. It provides audio routing and speed control for two domestic three-head cassette tape machines such that they can be used to create authentic 1960s style tape flanging effects. The tape machines link....
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This is an oscillator sync circuit that gives the kind of effect you find on old analogue synths. Oscillator synchronisation is performed by using one oscillator to reset another. In this instance the guitar signal is used to reset an oscillator running at a....
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A small signal amplifier, perhaps of the type to follow the previous buffer amplifier. We will assume we are buffering and amplifying our signal from the voltage controlled oscillator tutorial. In those examples we were generating and buffering 1.8 to 2.0....
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The input audio signal is fed to pin 3 of Ul, an LM386 low-voltage amplifier, via C3 and Rl. Potentiometer Rl sets the drive or volume level. Ul, which serves as a driver stage, can be set for a gain of from 20 to 200. The output of Ul at pin 5 is fed to....
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This circuit will generate a smaller DC output voltage from a larger DC input voltage.It is quick and simple to make and by changing the value of the zener diode, the circuit can be universally adapted to provide other output voltages.The circuit and all....
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I use a RealTimeClock Maxim DS1305. The RTC backup power is a supercapacitor (0,22F). I test it for 4 weeks, works fine. For this reason it don't have the capability to change the time, but you can do small-corrections. Once you push the button, the seconds....
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If you are searching for the 8255 datasheet, click here. Another project describing the 8255 interface to PC is here...
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The following circuit are provded here to give your idea how the overvoltage protecton circuits really work and how you can easily add some protection to your circuits. To make theose circuit really effective need careful component choosing and good....
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A simple SWR meter first needs a calibration to Uv = 100 % (forward power). When switching over to Ur (reflected power) the SWR is indicated. This procedure has to be repeated every time a change is made to the transmit power, antenna tuner or frequency etc.....
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White noise (the sound you hear when a TV is tuned to a non-existent station) has a frequency characteristic which raises the power level by 3dB with each increasing octave, and is not suitable for response testing (and will probably blow your tweeters as....
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It can be helpful to rapidly and easily determine the polarity (npn or pnp) and function of a transistor. The pocket-transistor tester in Figure 1 is ideal for quickly testing without regard to such parameters as gain and frequency response. You connect the....
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A recent Design Idea prompted me to offer the simpler solution that I used in a recent project (Reference 1). We needed a momentary power switch with processor supervision. This supervision would allow the processor to delay a power-down request from a press....
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This circuit is a simple adapter for PC parallel port to think that there is a printer connected to computer. This adapter is useful for testing printing speed with different software and as a part of your own designs.
You can use this circuit to connect....
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This is the timekeeping test circuit. It includes a one-transistor circuit to switch in the 5V power supply when present and drop back to the 3v battery the rest of the time. That loop of blue wire-wrapping wire is a lariat used to quickly and easily pull....
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The circuit employs a 100 ohm isolation resistor which enables the amplifier to drive capacitive loads exceeding 500 pF; the resistor effectively isolates the high frequency feedback from the load and stabilizes the circuit..
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This circuit uses a low-cost feedback scheme in which the dc voltage developed from the primary-side control winding is sensed by the UC1842 error amplifier. Load regulation is therefore dependent on the jcoupling between secondary and control windings, and....
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PCB is an interactive printed circuit board editor for the X11 window system. PCB includes a rats nest feature, design rule checking, and can provide industry standard RS-274-X (Gerber), NC drill, and centroid data (X-Y data) output for use in the board....
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The space-age sound device uses a 556 dual-times IC to produce a phasor sound. That IC is actually two 555 timer ICs in one 14-pin package, as shown in the schematic. Each timer inside the 556 is connected iri an astable multivibrator mode. The first timer....
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The design uses tactile sense (or rather, neural sense) to reveal the contents of a box. The box contains 4 shapes, as in a child`s shape sorter. The conjurer asks a person to secretly remove from the box any shape or shapes of his or her choosing, then to....
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The PIC Microchip Processor must be programmed before it will function as a Volt & Amp meter. There are many internet sites and PIC programmers that you can use. I used a Microchip MPLAB ICD 2 during the project. You might need to made changes to the circuit....
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Twenty-five musical keys and 25 LEDs are provided to denote F to F" with half notes in between. Memory can store a played tune. There are ten preprogrammed tunes (each has an average of 55 note s) masked in the chip. Any tune can be recalled by depressing....
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Large LCD devices of 1 or more exhibit a large driving capacitance to the driver circuits. To solve this problem, the drive circuit shown (see the figure) introduces a buffer amplifier for each of the three common lines. Each amplifier can be programmed....
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This circuit will produce over +10 dBm in the 1800-3 000-MHz range. Drive power is 7 dBm in the 900-to-l 500-MHz r..
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Integrated circuit Ul (an NE602 double-balanced mixer) is a combination oscillator and frequency mixer. Signals from the antenna input (at Jl) are fed through dc-blocking capacitor C1 to the RF-gain control, Rl, and fed to the input of Ul at pins 1 and 2.....
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Controlling the output voltage from a regulator can be made variable in three ways:-
1. Using a fixed reference zener diode to increase the output by the value of the zener
2. A variable resistor for variable output, note that a voltage less than the....
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This is a very useful project for anyone working in electronics. It is a versatile power supply that will solve most of the supply problems arising in the everyday work of any electronics work shop. It covers a wide range of voltages being continuously....
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This is a power generating method from sunlight.This method of power generation is simple and is taken from natural resource. This need only maximum sunlight to generate power. This project helps for power generation by setting the equipment to get maximum....
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model airplanes, boats, cars and use of ignition of glow plugs for their miniature (O. Bcc to 15cc) internal combustion engines. These engines happen with the heavy batteries on board, HT coil, and "condenser" spark required for ignition classic, while....
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A monolithic 555-type timer is the heart of this simple automobile voltage regulator. When the timer is off so that its output at pin 3 is low, the power Darlington transistor pair is off. If battery voltage becomes too low, less than 14.4 V in this case,....
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At the heart of the CD4-MX is an astable multivibrator, built around Q1 and Q2, that feeds step-up transformer Tl. The output of 1 is rectified by D3 to D6 and used to charge capacitor C4. When the points close, a small voltage is fed to the gate of SCR1,....
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C1 is a charge pump capacitor*. This works voltage doubler. When TxD is negative voltage, C1 is charged through D7 from GND. If TxD carries out turn-on, since it will become positive voltage, the voltage charged in C1 is raised. The created high voltage is....
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This method is capable of measuring phase between 0 to ±180°. The generated square waves A and are fed to a D flip-flop which gives an output C equal to logic 1 when input 1 leads input 2 and equal to logic 0 in case of lagging. When C = logic 0, the....
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An electrical signal taken from the low tension side of the distributor is converted into a voltage proportional to engine rpm and this voltage is displayed on a meter calibrated accordingly. The 555 timer IC is used as a monostable which, in effect,....
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This circuit measures capacitance by the time it takes an unknown capacitor to reach 6.32 V (10 V 63% or 1RC time const..
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By using Fujitsu (Japan) "IR-Commander" or "Crossam2+ ( Japan ) ", you get high reliability computerized home control environment. IR Commander is a multi-function adapter that supported IrDA / ASK / 24 feet 360 degree TV-Remote. Crossam2+ is the remotes....
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I built this cable for my Casio QV-200 digital camera, it should work for many Casio models. It`s basically a inverting buffer/converter to/from RS-232 voltage levels from/to CMOS levels. Why Casio didn`t put this inside the camera like everyone else does is....
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Current-limit switches are virtually ubiquitous in system controls. They provide a safe means for regulating the current delivered to a load circuit. The switches allow the load current to increase to a programmed limit but no higher. This application note....
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In a CCD (charge-coupled device), packets of charges shift across the array. The transistor array, also called a bucket-brigade shift register, receives drive from a dual-phase clock signal. Dual-phase clock signals comprise two synchronized clock signals....
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Many applications require control signals that have phase shifts with reference to an input signal. Circuit accepts a sine, square, or triangular wave as an input reference signal and produces square-wave outputs with 0", 90", 180", and 270" phase shifts....
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The composite lowpass filter uses interior constant-k full sections terminated by m-derived half-sections.The design technique is also applicable to highpass and wideband filters (references 3 and 4). Figure 1 shows a schematic of the composite lowpass....
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This electronic project stereo amp is based on the STK415-090-E class H audio power amplifier hybrid IC that features a built-in power supply switching circuit. This STK415-090-E class H audio power amplifier provides high efficiency audio power....
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You'll find here few ASCII schematics for Heath and Marantz tube crossovers. They were given in L'Audiophile No 11 old sery July 1979. In the same paper there is another tube crossover designed by Gerard Chretien now at the head of Focal i'll try to....
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In this project, you will make a simple low-power broadcast-type circuit, using a crystal oscillator integrated circuit and an a collector modulated AM oscillator. You can connect the circuit to the an amplified microphone (no amplified microphone has a to....
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his month I am making 3 different types of siren circuits based on the 555 timer. The first circuit simulates the siren of a British police car. It uses two 555 timers in the circuit. The 555 on the right is wired as an alarm tone generator and the second....
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Referring to the simplified schematic in A, the AFG is made up of 10 relatively simple circuit elements. ICl-c and ICl-d arc configured as unity-gain noninverting buffer amplifiers. The summing (L+R) amplifier, IC2-c, combines equal amounts of the left and....
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I just finished a half duplex serial asynchronous link from a simple PIC circuit to the RCX. It is able to receive codes from the RCX (or Lego RCX remote control) store them in RAM & EEPROM and transmit any IR op-code to the RCX in turn. Included in the....
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In this open-loop design, the detector diode is Dl, and a level shifting or compensating diode is D2. Load resistor RL is connected to -5 V, and an identical bias resistor RL is connected to -5 V, and identical bias resistor RB is used to bias the....
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This article has two parts. Part I describes a way to determine the effective average impedance of a pair of mono headphones or a speaker using a device called a FILVORA. This is the optimum resistance with which to drive the headphones or speaker to obtain....
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A circuit that offers visual indication of fluid level in a vessel, with a switchable audible alarm. Example uses would be to monitor the level of water in a bath or cold storage tank. Conductance is the reciprocal of resistance. The conductance of fluids....
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The op amp is alternately an inverter or buffer, under control of the switch polarity. As a buffer, the gai..
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This clock timer uses a PIC16F628 microcontroller to display 3 and 1/2 digit time and control an external load. The clock includes a calendar with leap year and optional daylight savings adjustments. The timer output can be set from 1 to 59 minutes and....
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This is basically a high gain amplifier with feedback that causes the LED to flash at a rate determined by the 10u and 330k resistor. Remove one of the transistors and insert the unknown transistor. When it is NPN with the
pins as shown in the photo, the....
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This application note features 8-, 10-, and 12-bit data
acquisition components in various circuit configurations.
The circuits include battery monitoring, temperature sensing,
isolated serial interfaces, and microprocessor and
microcontroller serial and....
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Microchip Technology (www.microchip.com) offers a family of cooling-fan speed controllers that operate in PWM mode for use with brushless dc fans (Reference 1). To control fan speed using the PWM waveform`s duty cycle, you can use either an external NTC....
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This project is provided as a "prototyping project" as no PC board has been produced. The photographs show the project built on a matrix board using surface-mount components and very fine wire.
The final design will require a double-sided board with....
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When the "ON/OFF" button is pressed once, the equipment goes on and stays on. It goes off when the button is pressed again. The circuit is straight forward. It uses a JK CMOS FlipFlop to with its JK terminals tied high to achieve the toggling action. The....
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The circuit is built around a 555 oscillator (Ul), which is turned on when a trigger is applied by touching the touch ..
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This simple circuit is the electronic version of the combination lock. Using the special purpose LS7220 digital lock IC, the circuit allows a 4 digit combination of your choice to activate a relay for a set period of time. This relay can then be used to....
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Here it is a brand new TX300 FM transmitter. The amplifier has exactly the same architecture as TX500 with the difference that TX300 has only one stage variable VHF amplifier. It is a cute schematic that was made for all of you who wanted something even....
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The main power supply to the system must be a regulated 12 volts DC with a minimum input from the train control AC or DC power supply of 13.5 VAC connected to pos 3 and 4 of the rectifier bridge . The ground bus of the regulated 12 volts supply must be....
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The circuit includes Better channel separation, resulting in an increased stereo effect, as well as reduced noise and hum. This schematic will allow you to cancel or blend left and rigth channels of your stereo. Uses the LM4136 but at the circuit is a 741....
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This circuit uses a sync-generator chip, a counter, and a decoder to detect the horizontal sync pulse that occurs a..
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The schematic shown, does no need any power supply because is a simple low frequency passive filter. It could be usefull if you want to drive an extra subwoofer from your stereo system...
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The major advantage of amplifiers of this type is that the normal static power dissipation is very low, and the overall power-conversion efficiency is high. Unfortunately there are also some inherent disadvantages due to the intrinsic dissimilarity in the....
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Simple add-on module. A simple approach to this problem can be done inserting a circuit in the preamplifier stage, capable of varying automatically the frequency response of the entire audio chain in respect to the position of the control knob, in order to....
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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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The circuit can generate a negative output from a positive supply or a positive output from a negative supply. When the circuit starts up, the substrate diode of the output FET bootstraps the output voltage to the point where synchronous switching takes over...
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When using a regulated supply to reduce a supply voltage there is always the danger of component failure in the supply and consequent damage to the equipment. A fuse will protect when excess current is drawn, but might be too slow to cope with overvoltage....
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If you ever get tired of trying to remember the subtleties of the "carry" status bit every time you want to use the subtract instruction to perform a comparison, the macro in Listing 1 can help. The macro contains all of the nuances, once and forever. The....