New Circuits Page 228
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We are OUT OF STOCK on the surplus brushless DC motor we used to build this project, and since it`s surplus we cannot get any more. The resistor and capacitor values listed in the schematic and on the PC board plan depend on using this exact same motor...
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When the current through the load exceeds a level determined by the position of the wiper on the 1k wire-wound pot, this circuit cuts off the load immediately. If S1 is open, the range is approximately 300-650 mA, and 0.8-2A when it is closed. The key....
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There are a number of ways to obtain the low voltages required to run small projects from the wall power outlet. The simplest way is to buy a factory-built molded supply which is designed to plug directly into the wall outlet. Some such supplies have an....
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This regulator is suitable for devices that need up to 1mA. For higher output current, the resistors would have to be scaled down in reverse proportion to the peak current expected. With the resistor values shown, the regulator draws a current of only....
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If you are developing applications for the PIC mcu, and miss debugging tools, or don't have enough I/O pins for a parallel LCD interface in your design, this serial interface can help printing debug messages and/or reduce the pin count. This version uses a....
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This was my second Nixie clock project. I wanted something a little smaller / cheaper / simpler then my rather large B-7971 clock. I will post the design for that one of these days. I was trying to simplify everything. And basically wound up with a one chip....
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The circuit"s threshold is set by resistor R2. When the intensity of the light falling on the LDR is lowered, resistance of ..
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Driving Helium-Neon Lasers can be simplified considerably using This power-supply configuration. When power is applied, the laser doesn`t conduct and the voltage across the 190- resistor is zero. However, a resonant circuit and a voltage tripler then....
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This project is also an essential part of the expandable analyser to be published soon (or perhaps "eventually"), and one meter circuit is used for each frequency band. There are many other uses for a simple LED VU meter. They are ideal as power meters on....
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The remote control receiver is a custom design based on a pre-built 433MHz UHF radio receiver, a decoder chip and a BASIC Stamp. The Stamp is expensive, but easy to work with. The receiver requires 8.5mA, plus 1.5mA for each LED (individual or segment) that....
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As I was developing my IR Extender Circuit, I needed to find a way of measuring the relative intensities of different Infra red light sources. This circuit is the result of my research. I have used a photodiode, SFH2030 as an infra red sensor. A MOSFET....
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The FET input amplifier has fixed bias with source feedback. This provides a very high input impedance with very low capacitance. The FET amplifier drives an emitter follower which, in spite of the fact that it has a low output impedance, feeds a transformer....
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SWR can be adjusted by adjusting the connection point L3 figher or lower...
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This is a simple display controller. It can be controlled with a small microcontroller, such as MCS51, 68HC11, Z80, AVR and others.
Several years ago, I found an article that controlling a TV with only a PIC micorcontroller, and I surprised to it. It is....
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Using a 4060 CMOS binary divider and built-in clock oscillator, a long-duration timer can be made veiy simply. The solid-state relay can be sized for your application, and can be replaced with a mechanical relay if a suitable power supply is available. With....
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This circuit is very basic to build. To open a the lock which is connected to the K1 Load you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switches are pressed the circuit....
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It's a very simple circuit, for the follow-up of baby. It can however be also used for other use, as intercom etc. In the place of M1 we can we use a simple electret mic capsule. The regulation of gain becomes from the R1, whoever can be trimmer or....
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An LCD requires an ac electric field to excite the organic compound in the display. Applying a dc voltage could permanently damage the LCD. The circuit in Figure 1 is a simple configuration to test the performance of an LCD. The circuit produces biphase....
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This Project can be used in home, shops, offices etc. It keeps tracking of both Incoming and Outgoing Calls. It has a built in Caller ID. The incoming and the dialed numbers are displayed on the LCD display. The system will display the numbers over the LCD....
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The High Speed Function Generator was published in the professional electronics section of the Aug 1996 issue of Electronics Australia, and has proven to be extremely popular. The kit is no longer available from any of the kit suppliers...
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Wisp628 is designed to be used as an in-circuit programmer only, hence no socket is provided for the target chip. `Why use such a limited design`, you might ask, `an ex-circuit programmer with a ZIF socket can do the same things and more!` You are partially....
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This circuit employs an adjustable resonant tank circuit which insures operation at the desired crystal overtone. Cl and LI form the resonant tank circuit, which with the values specified as a resonant frequency adjustable from approximately 50 MHz to 100....
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Crosspoint switches are ideal for use in video-security systems, which accept multiple camera inputs while providing playback and multiple loop-through to multiple monitors. To provide video loop-through or monitor outputs, these systems often require....
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One very important Part of a Tube Amplifier is the Power Supply. It is crucial for the quality of the whole system. Especially beginners encounter problems like Hum or Drift that can become quite annoying. But resue is ahead: The following circuit uses a....
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This amplifier is designed to be as flexible as possible, with no bad habits. Indeed, it will operate stably with supply voltages as low as +/-5V (completely pointless, but interesting), all the way to the maximum supply voltage of +/-70V. The only change....
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A classic circuit of regulation of tone of three way, with which we can regulate low, mid and high frequencies, of acoustic signal. The boost/cut can be regulated in the range of ± 18 dB/oct. In the circuit the supply is ± 15V, but can be also supplied with....
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Multi-spark ignition is very useful especially in the case of startings at low temperature and at low rpm range. Basic idea, is to apply to spark plugs instead of only one spark, a spark-burst” having big energy. In this case, combustion of air/fuel mixture....
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Elecret microphones have a small electret melement and FET amplifier built to same case. Electret microphones needs some power to operate. The power (typically 4-10V) is fed to microphone through resistor (typically 1-10 kohm). The electret microphone....
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The block diagram in Figure 1 shows the basic functions
performed by a battery charger IC using this patented
topology*. The LT1511 is a high efficiency 200kHz switching
regulator IC in a step-down configuration suitable for
charging lithium-ion....
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So you`ve read about my Computerized Room or have seen those nifty home automation products advertised in the back of electronics magazines? Or perhaps someone you know has done something similar. At any rate, you have decided to try it yourself. The first....
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The telephone-line decibel meter and line-voltage sensor shown lets you accurately monitor and adjust telephone sound levels. The 600-0 resistor properly terminates the line. ..
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The XR-T8205 Tone Ringer is primarily intended as a replacement for the mechanical telephone bell. The device can be.powered directly from telephone ac ringing voltage or from a separate dc supply. An adjustable trigger level is provided with an external....
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White LEDs have a rated current at a voltage drop of about 3.3 to 3.4 V. It is ideal to be powered from the battery voltage which is slightly larger. Then there is the best energy used. In this I used a flashlight battery, Li-ion battery, which lasts the....
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A limiter circuit that requires matched zener diodes can instead use one zener with a full-wave diode bridge. The..
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The tester provides an audible indication of the logic level of the signal presented to its input. A logic high is indicated by a high tone, a logic low is indicated by a low tone, and oscillation is indicated by an alternating tone. The input is high....
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This 555 timer based PWM controller features almost 0..100% pulse width regulation using R1, while keeping the oscillator frequency relatively stable. The frequency is dependent on values of R1 and C1, values shown will give a frequency range from about 170....
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This high-voltage power supply has an inverter around Q1 that supplies 150-V pulses to the converter of SCR1 and C2. The output of ?2 is a 4.5-kV pulse that is multiplied by the voltage-tripler network (right) to produce 13.5 kV.
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On those occasions when we want to see if an amp works, the best tool we can use is a source of acoustic signal with a frequency around the 1 kHz. These characteristics can be merely 'tolerated', because in cases of rapid tests rarely consider whether the....
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This temperature controller has a range of -50 to +150°C and permits defrosting. R7, VR3, and R8 ..
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EMI from offline switching power supplies typically causes all sorts of problems for power-supply designers. You may need a large EMI filter to meet FCC emission requirements. Switchers for high efficiency produce high-frequency switching noise that can....
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The present trend is to use ever higher frequencies. But by doing so it becomes more difficult to filter out the RF noise inevitably generated by the switching. So I decided to stay at a low switching frequency of only 25 kHz for the full cycle, which due to....
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The Max650 switching regulator produces a regulated 5 V from large negative voltages, such as the -48 V found on telephone lines. The resulting power supply operates with several external components, including a transformer, and it delivers 250 mA. The....
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This power booster functions as a high-efficiency "power multiplexer" or, if you supply an external signal-source, ..
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This circuit provides a means of detecting the presence of anything by the reflection of infra-red light and provides a direct digital output of object detection. By the use of modulation and high power bursts of infra-red at a very low duty cycle, a....
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This circuit can extract harmonics from various waveforms. With a sloped input waveform, the comparator produces a pulse..
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See (a) for the timing information for the alarm circuit in (b). When leaving your vehicle, flip the arming switch and close the door to arm the device. Subsequent opening of an entrance triggers both timers. After the expiration of the entry delay timer,....
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This is a nice 2 Watts FM transmitter. It has a Super-Sensitive pre-amplification with BC109 and BC177 with more than 100% signal modulation. The job finish the 2N2219 by Motorola. For the Coils you should use 1mm wire(enameled), L1= 3 turns - 10mm diameter,....
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A small amplifier with nice characteristics: Tendency of catering: 15V. Force of expense: 4,2Wrms in the 4W. Minimal signal of entry: 94mVp-p with preamplifier, 0,65Vp-p without the preamplifier...
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This original design is a variation on a well-known design, examples of which can be found in a great many texts. My variation was to add a second differential stage to replace the usual common emitter-plus-constant current source. Doing so opens up a second....
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The circuit makes excellent use of the high slew rate, wide bandwidth, high input impedance, and high-output voltage capability of the CA3140 BiMOS op amp. The wideband gain of this circuit is equal to the ultimate boost or cut plus one, in this case a gain....
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Perfect pitch, which is based on the 8751 microprocessor, is an inexpensive and easy-to-build instrument tuner/frequency counter with a built-in headphone amplifier and a visual metronome. Perfect pitch converts the audio signal from your instrument to a....
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This simple circuit makes it posible to monitor the charging process to a higher level. If you need more information then check out the LM3914 Datasheet. Final adjustsments are simple and the only thing needed is a digital voltmeter for the necessary....
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Using this circuit you can convert the 12V dc in to the 220V Ac. In this circuit 4047 is use to generate the square wave of 50hz and amplify the current and then amplify the voltage by using the step transformer...
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The circuit outputs power to the drive motor when one or no sheets are being fed, but interrupts motor power when two or more superimposed sheets pass through the optodetector slot. The optodetector can be either an H2aB darlington interruptor module or an....
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The ECM circuit consists of four sections, as shown in the block diagram. A power converter generates a voltage that is proportional to the true of real power consumed by the load. That voltage feeds both a bargraph and a voltage-to-pulse converter. The....
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This unit uses switches and resistors to provide a number of current ranges. It allows you to test most of the meters availabl..
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This paper gives a practical example of the design of an off-line switching power supply.
Factors governing the choice of a discontinuous flyback topology are discussed. The design
uses a pulsed-width modulation (PWM) control scheme implemented....
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This is an UHF band TV antenna preamplifier circuit With 15dB gain to build easily. It is formed based on BF180 UHF Transistor. The first stage is an band pass filter constructed by the C1, CV1, L1, L4, C7 and C3, the second stage is a base-common voltage....
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This application involves demodulation of a frequency-modulated subcarrier of the main channel. This popular example uses the PLL to recover the SCA (Subsidiary Carrier Authorization or storecast music) signal from the combined signal of many commercial FM....
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The design presented here works by applying a 50kHz, 200mV square wave to the capacitor under test, in series with a 10 Ohm resistor. The AC voltage appearing across that resistor is measured and displayed on a meter. So the whole thing is nothing else than....
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The basic circuit can be operated at 80 kHz and is limited by the PUT capacitor combination. 60 kHz is the maximum modulation frequency. The pulse repetition rate is a linear function of Vin, the modulating voltage. Lenses or reflectors minimizes stray light....
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Laser based projects used to be expensive, until the development of solid state lasers. This project is designed for the entry level laser experimenter. The circuit allows any two computers with serial (RS-232) communication capability to communicate over....
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A clamp-on "current probe" such as the Tektronix P6021 is a useful means of displaying current waveforms on an oscilloscope. Unfortunately, the low-frequency response is somewhat limited, as shown in the Table. The more sensitive range on the P6021 is 2....
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The monitoring circuit consists of four tri-color LEDs driven by an equal number of op amps configured as gain-of-one inverting amplifiers. Each LED is wired in the circuit so that it glows red when the input to the op amp is high, and green when the input....
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A professional suggestion for those interested in improving sound. The circuit constitutes the part of input mixing console sound from the microphone or source of high level . It can be used on it's own or be multiplied to the number of channels required.....
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When the panel isn't generating, the entire circuit is off and there is absolutely no current drain from the battery. When the sun gets up and panel starts producing at least 10 Volt, the LED lights and the two small transistors switch on. This powers the....
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This application note interfaces a midrange PICmicro
device to a Hitachi LM032L LCD character display
module, with a two line by twenty character display. LCD
modules are useful for displaying text information from a
system. In large volume applications,....
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A PC usually requires a plug-in ADC card to process analog signals. However, with the circuitry in Figure 1, a PC can communicate with an 18-bit ADC through its serial port. The port provides both positive and negative power supplies as well as control....
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Many of today`s instrumentation and process control applications convert the analog output of a sensor for processing and/or storage using an analog-to-digital converter (ADC). For voltage input ADCs, three different input structure types exist:....
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Class-A is ideal for this application, since headphones are such an intimate way of listening. An amplifier for 'phones should be as clean and free from crossover distortion as possible, and must also be quiet. A background of hiss and hum does nothing to....
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The circuit, built around an LM741 op amp configured as an inverting amplifier, is used to drive complementary transistors (Ql and Q2). The op amp`s feedback loop includes the base-emitter junctions of both transistorsan arrangement that helps to reduce....
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A Hartley oscillator is shown at the right. It uses most of the same components as the Clapp oscillator. A capacitor is necessary to block the gate bias voltage from the tuned circuit. The tuning capacitor is a 100 pF poly capacitor. L1 is a coil wound with....
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Battery-operated, ionization chamber smoke detector includes a circuit to generate a unique alarm when the battery reaches the end of its useful life. The circuit uses the MCMOS MC14572 for two alarm oscillators (smoke and low battery)..
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The baby-alert transmitter is built around an LM324 quad op amp (Ul), two LMC555CM CMOS oscillator/timers (U2 and U3), and a few support components. The transmitter sends a signal on receipt of a sound at MIC1...
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Useful for checking diodes, transistors, triacs, SCRs, resistors, and LEDs, this curve tracer should prove useful in the experimenter`s lab. It displays the volt-ampere characteristic of a two-ter-minal device on an oscilloscope. This is a simple block....
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Metal detectors are usually very complicated and it may be consist of very costly components and metal detector DIY circuits are rare. However this metal detector hobby circuit can be constructed by only a few components such as BC548 and an ordinary AM....
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A current-feedback amplifier is a well-known component with many uses. Its basic block diagram shows that its input stage is a voltage followerin practice, a symmetrical emitter follower (Figure 1). The configuration samples the output current, converts it....
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This simple circuit can convert a single supply voltage, such as a battery, into a bipolar supply. Sense resistors Rl and R2 establish relative magnitudes for the resulting positive and negative voltages. Their rail-to-rail value, of course, equals....
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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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The circuit can control up to 6 kW of heating, with moderate gain, using a 25-amp triac (SC260D). Feedback is provided by the negative temperature co-efficient (NTC) thermistor, which is mounted adjacent to the environment being temperature controlled. The....
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The circuit uses a CA3130 BiMOS op amp as a multivibrator to control the siren's rate. A CA3094 used as a VCO is followed by a CA3082 transistor array used to drive a speaker. A "Manual" or "Auto" mode switch allows the user to select either intermittent or....
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The circuit consists of a device with low drift LTl012. and a speed amplifier LTl022Jligh. The entire circuit is a unity gain inverter, with the summing node at the junction of three resistors 10k. The monitors what the Tl012 summing node, it compares to the....
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60 kHz transformer consists of a 18 x 11mm ungapped pot core (Siemens, Fer-rocube, etc), utilizing magnetics incorporated type "F" material wound with SOV2 turns of No5 wire for the secondary and turns for the primary..
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No description available...
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This is a very basic infrared detector/emitter circuit. One major downside of this circuit, is that ambient infrared light will interfere with its detecting obstacles...
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This small amplifier was intended to be used in conjunction with an electric guitar to do some low power monitoring, mainly for practice, either via an incorporated small loudspeaker or headphones. The complete circuit, loudspeaker, batteries, input and....
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For this scheme to have satisfactory signal-to-noise and frequency-response parameters, the clip, connecting cable, and amplifier must m be attached parallel to the signal wire and must be as long as is conveniently possiblean inch or moreand preferably....
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The UNIVERSAL HOLD circuit detects the dual tone, multi frequency (DTMF) tone that is
generated when the # key is pressed and then activates a circuit that partially loads the telephone line
so that the central office thinks a phone is still off hook even....
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The XR-T6425 Speakerphone IC makes it possible to carry on conversation without using the handset, while the user is talking into a microphone and listening from a loudspeaker. It is ideal for hands-free conference calls. ..
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This rf probe is coupled with a fiber-optiCJ:able to the test equipment. It utilizes inexpensive components to improve probe performance at UHF frequencies. The receiving antenna in this probe feeds an envelope-detector diode. After amplification by the....
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If you are looking at this page, you probably feel like I did when I tried to run a self-powered PIC programmer with my notebook computer. Yes, the serial port was the ultra-low-power type and wouldn`t provide enough current to power the programmer. The....
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This surround-sound decoder is based on the "Hafler" principle, first discovered by David Hafler sometime in the early 1970s. The original idea was to connect a pair of speakers as shown in Figure 1, for use as the rear speakers in the surround setup. This....
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This power supply delivers plus and minus 9 V to replace two 9-V batteries. The rectifier circuit is actually two separate full-wave rectifiers fed from the secondary of the transformer. One full-wave rectifier is composed of diodes D1 and D2, which....
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Plug an ATtiny12 into the 8 pin socket and hold down "GO!" button. The LED will come on at the end of the programming process, which only takes a couple hundred millisecond. The fuses are now restored to their factory default states. This picture was taken....
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This Circuit uses the ZNA234E IC which makes available all the waveforms necessary to produce the crosshatch, dot and greyscale test patterns on a television screen. The composite video output can be injected directly into the video input of a receiver or....
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This antenna tuner is suitable for use with low-power (less than 5 W) transmitters or SW receivers. S2 selects inductance and S2 connects the 365-pF capacitor to either the transmitter or the side of the inductor. The tiny tuner is comprised of a tapped....
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Solid State Relay Switch is a simple kit which will help you control (ON / OFF) a single high power circuit from a low power drive. Load - 24 to 240 VAC @ 500 W. Trigger voltage - 2 to 5 VDC (TTL) @ 10 mA. Input isolated with use of Optocoupler. Power....
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The relay operates a certain time, td, after power is applied to it, and then it operates for a length of time, tc. The SCR fires when the voltage on Ci reaches VA. This operates the relay, which stays activated until the current charging C2 drops below the....
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A single op amp-one of four contained in the popular LM324-is operating in a variable pulsewidth, free-running squarewave oscillator circuit, with its timed output driving two transistors that control the on/ off cycle of the tape-drive motor. The....
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One of the control circuit"s triacs selects the tap on main transformer Tl, which provides the proper, preregulated voltage to the secondary regulator. T2 and its associated components comprise the secondary regulator. The ADC 0804, IC1, digitizes a....