Top Circuits Page 23
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This circuit changes the average value of the dc supply voltage because of the high switching frequency. The tungsten lamp will have an almost continuous adjustable light output between 0 and 100%..
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The 5AH will trigger when the voltage across the two 0 juF capacitors reaches the breakdown voltage of the lamp. Control can be obtained full off to 95% of the half wave RMS output voltage..
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This simple circuit providers battery operated emergency lighting instantaneously upon failure of the regular ac service. When line power is restored, the emergency light turns off and the battery recharges automatically. The circuit is ideal for use in....
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An input signal of less than 1 mA and 1V is required to switch on CS1. As long as this input -signal is maintained, CS1 will conduct during each positive half cycle of anode voltage, thereby energizing load LI with half-wave rectified dc. L2 remains....
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The shift pulse amplitude is less than 15 volts. If a stage is off, the shift pulse will not be coupled to the next stage. If it is on, the diode will conduct and trigger the next stage. Just prior to the shift pulse the anode supply is interrupted to tum....
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This circuit uses a low-input-bias op amp to give a steady dc indication of light level. To reduce circuit sensitivity to light, Rl can be reduced, but should not be less than 100 K..
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The meter reading is directlyjproportiona! to the logarithm of the input light power. The logarithmic circuit behavior arises from the nonlineardiode pnjunction current/voltage relationship..
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This counter uses a four-digit display, but with a flip of the range switch, it can display frequencies from 1 to 40 MHz, with a resolution of 100Hz. The MM74C926 CMOS IC contains a four-digit decimal counter that can latch a given count and then use this....
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The circuit consists of ICM7208 seven-decade counter U1, ICM7207A oscillator controller U2, and CA3130 biFET op amp U3. IC U1 counts input signals, decodes them to 7-segment format, and outputs signals that are used to drive a 7-digit display. IC U2....
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This CMOS circuit can be used as a 1-shot time delay switch and general-purpose timer. The circuit consists of a gated oscillator and a latch made from one CD4001 quad 2-input NOR gate as shown and a CD4020 14-stage counter. TON is a function of the....
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This circuit can be used to measure frequencies up to 40 MHz. To obtain the correct measured value, it is necessary to divide the oscillator frequency and the input frequency by four. ..
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By using the preamplifier with a short length of shielded cable and clip leads, signals that generally could not generate a readout, generate precise and stable readouts on the counter. The DPDT switch is used to bypass the circuit when amplification is....
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The output of the CA3179 is fed through the Dl!Q1 circuit. Those components serve to boost the 1-V output of the CA3179 to a standard TTL level. Then, depending on the position of range switch S2b, the signal is passed directly to the 7216, or through the....
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Opening SA, changes the indicator lamp from flashing to steady-lit condition. The 6-V incandescent lamp on the collector of Q2 requires about 0.3 A. A 1-KO load resistor limits Ql"s collector current to about 6 mA. ..
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The circuit is built around two power FETs, which are configured as a simple astable multivibrator to alternately switch the two lamps on and off. The rc values given sets the flash rate to about 1/3 Hz. By varying either the resistor or capacitor....
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This circuit is suitable for fitting into slide projectors without a dimmer facility as witb 24-Vac fed halogen lamps. With a few small alterations, it can also be used for dimming 12-V halogen lamps, but not those in a car, because these are fed from a de....
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This pseudorandom sequencer drives a solid-state relay. If you power a low-wattage lamp from the relay, the lamp will appear to flicker like a candle"s flame in the wind; using higher-wattage lamps allows you to simulate the blaze of a fireplace or....
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The lights seem to dance in time with the music. Line-voltage lamps of about 40 to 100 W do nicely. The current for the lamp is from an SCR. When low-level audio is present across Tl, SCR1 is not triggered into conduction. A louder signal, however,....
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Lamp life can be extended by improving the conditions under which its filament is operated. This includes eliminating the inrush overcurrent surge and reduclog the mechanical stress (vibration) on the filament caused by an ac source. The circuit shown....
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This circuit uses a PUT for phases control of an SCR. The relaxation oscillator formed by Q2 provides conduction control of Ql from 1 to 7.8 ms or 21.6° to 168.5°. This constitutes control of over 97% of the power available to the load. ..
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The dimming action is controlled by varying the amount of current passed through triac Q4 and, thus, the lamp plugged into ac receptacle SOL Unijunction transistor Q3 operates as a relaxation oscillator whose output pulse frequency depends on how fast....
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At half brightness, the lamp current is pulsed on and off (Fig. 50-12b) by the voltage developed across the resistor and capacitor at the current-sense output. Lamp current is sensed by the current-sense output. A simple pulse-width modulation....
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A 1-V amplitude pulse triggers SCSl, but has insufficient amplitude to trigger SCS2. A 3-V input pulse is delayed in reaching SCSl by the 10-KO and .001-!"F integrating network. Instead, it triggers SCS2, then raises the common emitter voltage to prevent....
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Assume first that SCR1 is on and SCR2 is off so that CI is fully charged, with its LMP2 end positive. The..
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A three-way switch to control a lamp (off-dim-bright, etc.) uses an NE555 timer to generate a one-second pulse, trigge..
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This unit uses a Nicad battery to provide power to an emergency lighting setup. When power fails, T1 beco..
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This hookup is useful in some house wiring situations, where only two wires are available between switches, rather than..
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The circuit presented here guarantees that if bulb Lai "gives up the ghost," bulb La2 will take over its tas..
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After the SCR turns on, CI charges up to almost the full supply voltage via R3 and the anode of the SCR. Whe..
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The ac line power is brought back into the circuit through Fl, a protective 5-A fuse. One side of the ac line is connected to one side of each ac outlet. The other side of the ac line is connected to each SGR or silicon-controlled rectifier. Each SCR is, in....
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The automatic porch-light control circuit holds a triac on until a 4020 divider counts a number of 60-Hz powerlinc pulses. The circuit turns off a light after a predetermined time by using pins other than pin 3 of III. Various times can be set...
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You can turn any ordinary household bulb into one that shimmers or blinks. This circuit works on any incandescent light up to 200 W, arid runs on standard 120 Vac. The circuit uses an SCR to cause an ordinary lamp to sliimmer. Note that one side of the lamp....
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The battery-operated black light uses a U-shaped, unfiltered, black-light tube, which requires approximately 250 Vac to operate. To create the 250-Vac 6-V battery, the circuit uses a one-transis-tor blocking oscillator that drives a ferrite inverter....
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This circuit features an intermittent siren output and automatic reset. It can be operated manually using a key-switch or a hidden switch; but it can also be wired to set itself automatically when you turn-off the ignition. By adding external relays you can....
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In operation. the alarm circuit allows a 0-47 second time delay, as determined by the Rl/Cl combination, after the switch is armed to allow the vehicle"s motion sensor to settle down. This allows you time to get a bag of groceries out of the trunk and not....
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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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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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SI is external key switch. The alarm allows a 0- to 45-s delay after SI is operated before the circuit is armed. During this per..
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The FM oscillator/modulator is a voltage-control led oscillator, which exhibits a nearly linear output frequency versus input voltage characteristic for a wide deviation. It provides a good FM source with a few inexpensive external parts..
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The VHF frequency is generated by a tuned Hartley oscillator circuit. Resistors R2, R3, and R4 bias the transistor, with tapped inductor LI and trimmer capacitor Cl forming the tank circuit. Adjusting Cl determines the frequency. Capacitor C2 provides....
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if the timer is triggered with a continuous pulse train in the monostable mode of operation, the charge time of the capacitor can be varied by changing the control voltage at pin 3..
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Two IC rf modulators convert a suitable baseband video and audio signal up to a low VHF modulated carrier-Channel2 through 6 in the U.S., and 1 through 3 in japan-the LM1889 and the LM2889. Both !Cs are identical regarding the rf modulation function,....
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Because the transconductance of an operational transconductance amplifier is directly proportionai to /ABc. the amplification of a signal can be controlled easily. The output current is the product from transconductance X input voltage. The circuit is....
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Adding a diode, a resistor, and a capacitor to the SAW (surface-acoustic-wave) oscillator allows you to use the oscillator in FSK (frequency-shift-keying) applications. Dl, Rl, and Cl form a simple diode switch in which Dl shunts Cl to ground. When the....
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Because power MOSFETs offer high power gain at both audio and radio frequencies, they are useful in many areas of radio-circuit design. For rf applications, a MOSFET"s large safe operating area, V0 s vs ! 0, protects it against damage from reflected rf....
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Switching diodes are used to fire the neon lamps when negative-peak modulation hits 50. 60, and 100%. To use the circuit, keep an eye on the lamps. ..
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This application uses the timer connected for astable (free-running) operation, with a modulating signal again applied to the control voltage terminal. ..
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In this application, the timer is connected in the monostable mode. The circuit is triggered with a continuous pulse train and the threshold voltage is modulated by the signal applied to the control voltage terminal at pin 5. This has the effect of....
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When the carrier level is adequate to switch the cross-coupled pair of differential amplifiers, the modu· lation signal, which has been applied to the gate, will be switched at the carrier rate, between the collector loads. When switching occurs, it will....
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The transmitter we recommend to build is quite simple. It can even be built by a beginner. However, unlike the ease of construction and its small size, it is almost certain that it will impress you with its outstanding performance. Its autonomy is 12-15....
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This document presents technical details, hardware and software of a complete imaging system which uses a fast CCD sensor and a 41 Msample/s A/D converter to acquire full-frame 12 bit/pixel digitised images with a time resolution of 1.25 ms/image. The noise....
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First step is always to look around on the internet. After some searching, I found out that the QAA75-sensor is actually made by Siemens. This broadened my search a bit. Turns out that Siemens refers to the communication as a “Boiler System Bus (BSB)”. This....
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The circuit ICL7134B base is a bipolar input AID converter broadband, using two AM25L03s to form a successive approximation register 14-bit. The comparator is a circuit with two stage amplifier HA2605 front, used to reduce the settling time problems in the....
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The genesis for this hybrid electrostatic headphone amplifier occurred when I was in Hawaii on vacation, at a fancy hotel on Maui. Sitting at the bar on the beach, drinking "Blue Hawaiis," I drew the schematic for the amp on a placemat. The design is my....
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The quad operational amplifier circuit yields full 0 to 100 percent pulse width control. The controller uses an LM3900 requires only a single supply voltage of 4-30 V. The pulse repetition frequency is set by a 1 kHz oscillator amplifier that integrates AI.....
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To amplify small current signals such as from ah electron-collector inside a vacuum chamber, it is convenient for reasons of noise and bandwidth to have a "head-amplifier" attached to the chamber. The op amp N1 is a precision bipolar device with extremely....
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The intention of the following application shows how the NE5517 works in connection with a DAC. In the application, the NE5118 is used—an 8-bit DAC with current output—its input register making this device fully µ-compatible. The circuit consists of....
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Output-clamp diodes are mandatory because loudspeakers are inductive loads. Output LR isolation is also used because audio amplifiers are usually expected to handle up to 2 µ¥ load capacitance. Large, supply-bypass capacitors located close to the IC are....
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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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The amplifier operates from supplies ranging up to 12 volts, and operates (with reduced volume) from supply voltages as low as 1.8 volts without having distortion rise to unacceptable levels. (Its power requirements make it suitable for solar-cell....
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In recent years, following CD`s introduction, vinyl recordings are almost disappeared. Nevertheless, a phone preamplifier is still useful for listening old vinyl discs from a well preserved collection. This simple but efficient circuit devised for cheap....
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A microphone amplifier that may be used with either Electret Condenser Microphone (ECM) inserts or dynamic inserts, made with discrete components. Both transistors should be low noise types. In the original circuit, I used BC650C which is an ultra low noise....
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In recent years, following CD`s introduction, vinyl recordings are almost disappeared. Nevertheless, a phono preamplifier is still useful for listening old vinyl discs from a well preserved collection. This simple but efficient circuit devised for cheap....
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This is a simple microphone preamplifer circuit which you can use between your microphone and stereo amplifier. This circuit amplifier microphone suitable for use with normal home stereo amplifier line/CD/aux/tape inputs. This mic preamp can take both....
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This is a collection of phono (black vinyl for the youngsters) preamps and equalisation circuits, one of which is sure to meet your requirements. These are not my circuits, but were contributed by a reader (see above), so I am not really in a position to....
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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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The phono preamp shown has an accurate RIAA equalisation curve, is very quiet, and offers far better sonic performance than the vast majority of those seen in magazines and application notes. Like most other ESP projects, it is very tolerant of opamps but....
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This project is probably the most ambitious so far, and can be expected to be very expensive. On the positive side, it is also capable of excellent performance, and can be tailored to suit your exact specifications. There are several different input modules....
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The filter should provide adjustable gain to maximize SNR at the audio processor's first stage. The filter's frequency response should also include a notch at 19 kHz to achieve maximum attenuation at the FM-subcarrier pilot-tone frequency and thus minimize....
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The circuit in Figure 1 accommodates lower cutoff frequencies without sacrificing the step-response time. A window comparator monitors the delta (difference) between the filter's input and output. When the delta exceeds ±50 mV, the filter increases its slew....
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The LM1036 is a DC controlled tone (bass/treble), volume and balance circuit for stereo applications in car radio, TV and audio systems. An additional control input allows loudness compensation to be simply effected. Four control inputs provide control of....
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This preamplifier was designed as a stand-alone portable unit, useful to control the signals generated by guitar pick-ups, particularly the contact "bug" types applied to acoustic instruments. Obviously it can be used with any type of instrument and pick-up.....
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The three-amplifier implementation of the state-variable filter in Figure 1 provides for second-order bandpass, highpass, and lowpass responses. The strength of the circuit, however, is in the bandpass response (VOUT/VIN), in which it`s easy to achieve high....
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Using a modified equal-element design for a lumped-circuit lowpass filter has several advantages over the well-known equal-element design (Reference 1 and Reference 2). The modified design exhibits superior passband performance with only modest degradation....
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Sometimes, for a variety of reasons, it would be nice to vary the width of the `sound stage` when listening to stereo recordings. Although technically this is anything but hi-fi, it is a useful addition to PC speakers, or even for the music centre in the....
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Tone control of audio systems involves altering the flat response in order to attain more low frequencies or more high ones, dependent upon listener preference...
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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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This was one of my very first transceiver developments. This page was also one of the very first circuit descriptions that I put on the internet quite some years agon. Today I would not build a transceiver like I did then, but it was working, so I have kept....
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The circuit of AM transmitter is designed to transmit (amplitude modulated) DSB (double side band) signals. A modulated AM signal consists of a carrier and two symetrically spaced side bands. The two side bands have the same amplitude and carry the same....
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BFO is a simple device which helps us to listen SSB and CW transmissions. Reception of SSB and CW signals requires a product detector or BFO (Beat Frequency Oscillator) to reinsert the missing carrier. This circuit is very simple since it requires no turned....
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The physical transmission medium for the 429 standard is 78Ω shielded, twisted-pair cable that uses a complementary, differential bipolar RZ (return-to-zero) waveform (Figure 2). The voltages are the net differentials that the biphase drive develops: For....
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The ATV exciter described here uses a pair of Hamtronics model TA451 2-watt narrow-band FM voice transmitters to develop video and audio carriers on 439.250 MHz and 443.750 MHz. The TA451 is a single board, phase modulated exciter designed for amateur radio....
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Ham Radio (amateur radio) is a popular hobby amongst electronics enthusiasts all over the world. Basically the hobby involves a person in making his own gear consisting of a receiver and transmitter or a transceiver (a receiver and a transmitter in one unit)....
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Here is a very simple, inexpensive and interesting project which provides lot of fun to a home experimenter or hobbyist. This simple transmitter can transmit speeches or songs within a short range. The circuit uses only one transistor. The entire circuit can....
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The circuit in Figure 1 meets these criteria and uses only three off-the-shelf ICs and a few passive components. Although dedicated to conditioning the low-level signal a strain-gauge bridge produces, the circuit can operate with almost any resistive....
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One of the key challenges in the design of 4- to 20-mA current transmitters is the voltage-to-current conversion stage. Conventional transmitters use multiple op amps and transistors to perform the conversion function. These approaches have been around for a....
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Sorry, I don`t have any data/instructions for use on this schematic. If anyone knows how this circuit works or is used, please drop me an email at click here or use the feedback form...
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GSM based Automatic meter reading, or AMR, is the technology of automatically collecting data from energy meter and transferring that data to a central database for billing and/or analyzing. The Transmitter is connected to the meter and it counts the pulses....
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This Transmitter can be powered by a battery 9V (not more than 12V). You can connect your music source where the microphone is or use a simple condenser microphone. The range of signal can reach 400 meters in open air. The wide range of frequency is up to....
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I describe a simple direct conversion receiver, thinked for QRSS and DFCW communications, as companion of ARGO or SPECTRAN programs. I don`t pretend to beat the performances of professional or commercial ham radio receiver, the scope is to suggest an easy....
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Once again, this is a project designed by David Sayles. The input can be from a longwire or a loop antenna. The unit covers MW and Sw to 30MHz. Click here for a picture of David`s MW loop. Click here to view a finished picture of this project...
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Building a practical and usable direct conversion receiver for the 40 m CW band is not as simple as it might appear. Broadcast station signals from the adjacent 41 m band, will easily overload most direct conversion mixer designs with their unwanted (and....
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Before World War II the FM radio band was just below 50 Mc. Read all about it. If you have such a radio, you might want to build this converter. It will let your old set receive the modern FM band (88 to 108 Mc.). This design is based on an article I....
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The IC has an FLL (frequency-locked-loop) structure. The filtered output of the FM discriminator frequency-modulates the local oscillator to provide negative-feedback modulation. The result is compression of the signal at the output of the mixer. Thus, the....
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If you`re the sort who`d like to have an HF receiver in every room, but can`t afford it, this idea is for you. It will also appeal to the beginner wishing to build the simplest possible direct conversion receiver. Using a readily-available FM wireless....
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A block diagram and a schematic of the receiver are shown in Figures 2 and 3, respectively. In Figure 3, L6 and L7 are spaced 0.6 inch for a loss of about 0.5 dB. Q4 is the first RF amplifier. L9 and L10 are spaced about 0.8 inch with a partial shield....
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The electronic diagram of the monophonic FM receiver made with TDA7088T is shown on Pic.4.12. If built with SMD components it can be placed in a matchbox, altogether with two button-type batteries. The operating principle of this device is given in the....
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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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An FM regenereative receiver using a single FET and one audio amplifier IC...
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This version sports a 2nd audio amplifier stage at Q3. The output level with this version is sufficient to drive a crystal headphone to a comfortable volume. The "crystal" headphone is like those used on ye olde crystal radios. A "Walkman" type headphone is....