New Circuits Page 244
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In Fig.1 A precision DC under?voltage relay switch. The opamp is wind as a voltage comparator, with a reference voltage applied to pin 2 and the test voltage applied to pin 3: the relay turns on when the pin 3 voltage exceeds that of pin 2. The circuit can....
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From 230 V AC a DC supply of + 5 V is obtained. The power supply is given to the other blocks. The pulse generator at a particular frequency generates the clock pulses. The clock pulses are counted by a counter and gives output after every 10 pulses. The....
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This flasher operates from a 12-volt car or boat battery. It offers 36 to 40-watts output, variable flash rate (up to 60 flashes per minute), independent control of both on and off cycles and photoelectric night and day control that turns the flasher on at....
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This circuit is built around one of the most popular timer integrated circuits, the 555 timer. It will flash the led on and of at regular intervals. From left to right, the two resistors and the capacitor set the time it takes to turn the led on or off, by....
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The article describes a simple and very cheap to drive white, blue or UV LEDs, used for example in small lamps and testers. The cost of components shall not exceed CZK 10. Converters for white LED has been on the pages of journals described quite enough.....
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The circuit in Figure 1 produces clock pulses with variable duty cycle from a gated clock. The output of the circuit, pulse, is always 180° out of phase with the clock input. When the delay-logic elements, IC5 and IC7, have the same propagation delays, the....
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First of all you have to build one cable adapter to connect the female 9pins connector of the modem, with female 9pins connector of the base of E-10G HPC. To build the null modem cable you will need: 2 male connectors with 9 pins. 15cm cable with 7 wires.....
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It is a relatively simple circuit of electronic lock of safety with code of 7 digits. It should is given attention in the time that will be stepped the keys, that shape code and it does not exist it delays. With the right step of keys and if code is right....
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Power supplies that operate at a fixed frequency have their largest EMI emission at this fundamental, fixed frequency. Emissions also occur at multiples of the switching frequency but at diminished amplitudes. The simple circuit in Figure 1 makes the....
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To share a regional press like the USB printer, scanner etc. two computers, it is relatively easy. Just connect the two computers on a network device and say the printer as shared. This method however requires the continued operation of the computer we....
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The Tri-Waveform Generator can be used for a number of different uses. The one that I use it for is a signal generator to test circuits. The frequency range is 20 to 20khz. and can be adjusted by R1. The duty cycle or the time that the waveform is high and....
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The AquaCont is an electronic system witch permits to manage and to monitor most of the parameters of all the electrics devices that can be found in a aquarium. The PIC18F4520 used to realize it, combines a real time clock and a temperature sensor in order....
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The two-pole, five-position switch, coils and 365-pF variable capacitor cover a range from 1.5 to 30 MHz. The amplifier uses Darlington npn transistors whose high beta, 5000, provides high sensitivity with Sl used as the amplifier on/off switch. Switch S2....
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When the handset is lifted and power is applied to the circuit, Q2 is fed base current through R2, which in turn drives Ql. C2 is charged via R3 in series with D1 to (Vz1 -0. 7) V. When the minimum operating Vnv voltage is reached, power on reset occurs....
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Two hybrids (Tl and T2) are used to allow direct connection to a telephone line. This circuit uses the common speech-inversion algorithm where the frequency of an audio signal is inverted about a center frequency. ..
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This circuit utilizes an HA-5152 dual op amp and FET to produce a low-voltage, low-power, Weinbridge sine-wave oscillator. Resistors R and capacitors C control the frequency of oscillation; the FET, used as a voltage-controlled resistor, maintains the gain....
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The LT1886 is a high speed dual power amplifier with
excellent high frequency distortion performance. The
LT1886 features a 700MHz gain-bandwidth product,
200V/ms slew rate and over 200mA of output current
drive in a small SO-8 package. Using only a....
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A sensor turns on Ql to activate the low-frequency 555 oscillator, which pulses LAMP II. Sensor may be sensitive to changes in light or temperature. Either RA or RB can be sensors, as desired. A decrease in RB or an increase in RA will cause the NE555 to....
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Decoding this bit stream into ASCII hex values is an ideal job for a low-cost 8-bit microcontroller. Using a microcontroller with onboard flash memory, such as the NEC Electronics µPD78F9418A (www.necelam.com), eliminates the need for external memory. The....
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This circuit was built to stabilize a radio frequency VFO (Variable Frequency Oscillator) for ham radio applications. The circuit has also been used to lower the drift of a Ramsey FM10a micropower FM transmitter...
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The circuit drives the LCD pins with 50% square waves. Each segment on this LCD is connected to the COM backplane and a separate pin. When a pin is driven in phase with the COM pin, the corresponding LCD segment gets zero voltage, and is off. When a pin is....
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This circuit provides a linear increase of frequency of 10 Hz/°C over 0-100 °C and can thus be used with logic systems, including microprocessors. Temperature probes Ql Vbe changes 2 mV/°C. This transistor is incorporated in a constant current source....
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An opto-interrupter made with Lego beams, regular parts, a 6 hole pulley wheel and an axle...
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The figures below illustrate using opamps as active 2nd order filters. Three 2nd order filters are shown, low pass, high pass, and bandpass. Each of these filters will attenuate frequencies outside their passband at a rate of 12dB per octave or 1/4 the....
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The GLMDA is designed to detect the motion of a human or animal both in daylight and at
night and to provide a normally open relay output that can be used to activate many types of
loads. The GLMDA also has terminals for connecting an optional photocell....
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The eight SDI input stages use the new GENLINX¾II GS9024
Equalizer IC. Input Return Loss of the PCB is optimized by using
R-L circuits at each input. Each GS9024 performs high quality
signal equalization over a wide range of data rates from as low
as 30....
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This circuit consists of a CMOS square wave oscillator on a frequency of approximately 1 kHz. The RC filter, which has a roll-off frequency of 500 Hz, filters the harmonics, providing a sine-wave output.
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This circuit generates a symmetrical, 10-m V pk-pk triangle waveform which is summed with a de level and connected to the aid analog input for noise/DNL testing. The de level input offsets the triangle waveform over the input range of the ADC. ..
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In order to display polar quantities (magnitude and direction of a received radio signal), a sine and cosine voltage proportional to an angle (antenna direction) is needed. In this case, a sine-cosine potentiometer coupled to a directional antenna and a....
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The circuit converts frequency to voltage by taking the average de value of the pulses from the 7 4121 monostable multivibrator. The one shot is triggered by the positive-going ac signal at the input of the 529 comparator. The amplifier acts as a de....
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If two of these circuits are made in the same enclosure for stereo, then there can be a single power supply to run both of them. There should be a resistor in series with the incoming 9V+ lead so as to minimize crosstalk, and reduce the PLOP when it's....
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This is an image Schematic. No Description available...
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R2 = (192 x Vout) - 240, where R2 in ohms, Vout is in volts and must be at between 1.2 V and 35 V. Vin should be at least 2.5V greater than Vout. Select a wall adapter with a voltage at least 2.5 V greater than your regulated output at full load. Maximum....
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The circuit will provide a 20 ±0.1 dB voltage gain from 500 kHz to 50 MHz. The low-frequency response of the amplifier can be extended by increasing the value of the 0.05-JLF capacitor connected in series with the input terminal. This circuit will yield....
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This recorder can be connected to the telephone lines just about any place, and no external power source is needed. The tape recorder"s switch terminals are applied to a pair of transistors, connected as Darlingtons, that are used to turn the recorder on....
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This circuit detects the 20-Hz approximately 86-Vrms ring signal on telephone lines and initiates action in an electri..
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Sensing unit consists of infrared emitter OP295 to produce the infrared beam, & two detectors in front of the emitter to detect the infrared beam OP598. Since the main idea in this device is to know person direction; and so, to get this approach, we have to....
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This indicator is basically a switch with hysteresis characteristics. If the input voltage momentarily (or permanently) exceeds the most positive reference level, LEDl is switched on. If, on the other hand, the voltage falls below the negative, or least....
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When the mains voltage is present at the input terminals, the transistor in the optocoupler is on, T1 is off, and s..
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The first SUPERTEF version was using a 68HC11 microprocessor in extended mode i.e. with an external memory program which necessitated many integrated circuits (IC) such as the 74C138, 74C373, 68HC24 and 27C64 making the printed circuit board densely....
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The VTSE uses the popular 1381 chip and that is its main advantage. The potentiometer (or two fixed resistors) connects one leg between the output and input of the 1381 and the other leg to the supply voltage. These resistors acts like a voltage divider....
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A positive-going trigger pulse can be used to start the timing cycle with the circuit shown. In this design, trigger input pin 2 is biased to 6V (1/z Vvv) by divider Rl and R2. Control input pin 5 is biased to 8 V (213 Vvvl by the internal divider circuit.....
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This circuit amplifies the output of a regular electret condensor microphone quite nicely.. adjust sensitivity by turning R1..
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The circuit, shown Figure 1, depicts an application with
two keys. The PIC16C54 is normally in SLEEP mode
consuming very little operating current. If either of the
two keys is pressed, the PIC16C5X wakes up, scans
the keys and turns on one or both of the....
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This is a simple one-valve irrigation controller made for our greenhouse. The code contains a software real-time clock (RTC) and a multiplexed 8-digit LED display and keyboard you can use in other projects. The operating software is simple, it contains a....
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This fucntion gernerator IC is specified to work to 20 MHz. So far, this unit works nicely to 50KHz. Since I seldom need signals higher than that, it has taken up a happy home on my workbench and further development is iffy at best. There are two basic....
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A music-to-light modulator is a circuit which controls the
intensity of one or more lights in response to an audio
input. The problem in older circuits is that there was a
direct electrical connection between the lights using mains
voltages (110 to 250V....
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Brief full-power flashes are obtained when the SCR conducts during positive half cycles of the line voltage. The SCR fires when the voltage at the divider, R3 and R4, reaches the gate-firing level.
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The popular USB interface can charge a portable device while transferring data. But for high-capacity batteries, the 500-mA output current of USB hosts and powered hubs greatly extends the charging time. (Unpowered USB hubs supply no more than 100 mA.) Thus,....
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Most audio tone controls affect midband gain, and !bey often create booming or hissing sounds when activated. You can avoid tbese problems by using a dual Wien-bridge filter to provide independent control of tbe treble and bass frequencies. Experiments....
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THE GAS SENSOR is mainly composed of tin dioxide on a ceramic base; the resistance of the sensor varies depending on the concentration of reducing gases in the air. The circuit shown is useful for the detection of dangerous levels of combustible fumes or....
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A basic full wave rectified power supply is shown below. The transformer is chosen according to the desired load. For example, if the load requires 12V at 1amp current, then a 12V, 1 amp rated transformer would do. However, when designing power supplies or....
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With this circuit can determine whether any of the phones of the same line is busy (it's up the handset), with the help of a LED.To circuit has no measurable effect on the telephone, so that there are problems with phone line company . The circuit is....
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This circuit allows you to record audio from a telephone line into a tape recorder or computer soundcard. Most of the parts for this circuit can be scrounged from an old modem, with some work, it is possible to rewire the modem circuitry and use the old....
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The electronic bell needs no power supply. Most of the resistors are not critical, although C2, R2, and R3 work best at the values given. Leaving out Rl will make the unit ring louder. The piezo buzzer may vary from store to store. If it has two leads,....
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If you choose to make your own moisture sensor,; this foil pattern should come in handy. A sensor connected to J1 causes S..
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Some Garmin GPS receivers are capable of running off external power ranging up to +32VDC or more, whereas others can only accept a maximum of +8VDC...
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When an antenna is attached, (or even if not, in the presence of a strong RF field) the field strength meter has a moving coil meter to indicate relative field strength. The box holds a Schottky diode detector, a DC amplifier, and a meter display. If the....
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This circuit uses an SAD 512D (Reticon) chip, which is a 512-stage analog shift register. By varying th..
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The core voltages for FPGAs are moving lower as a result
of advances in the fabrication process. The newest FPGA
family from Altera, the Stratix® II, now requires a core
voltage of 1.2V and the Stratix, Stratix GX, HardCopy®
Stratix and CycloneTM....
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This circuit leads palmorefmata coils,, engine. Each coil is driven by a transistor type Darlington. Darlington Transistors internally comprise two transistors connected in series. The "hfe" Darlington is equal to the multiplication of "hfe" of both its....
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This circuit enables observation of movement between other stroboscopes. Generation of rectangular signal is based on NE555. This circuit requires a low power supply that is made from a simple transformer TR1, traditional rectifier bridge and zener diode.....
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This is a useful instrument for works hops. The standard of the produced frequencies is 10 to 1. The basic frequency is produced by a crystal with high accuracy. The circuit is consisted by the oscillator, around the crystal and the frequency divider, which....
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An aid conversion technique which combines some of the speed advantages of flash conversion with the circuitry savings of successive approximation is termed half-flash. In an 8-bit, half-flash converter, two 4-bit flash aid sections are combined. The upper....
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The circuit works from a symmetrical 40 VDC power supply and draws a maximum current of 2.6 A. The input circuit of the amplifier is a differential amplifier built around Q4 and Q5 that employ DC feedback thus preventing any DC voltage from appearing....
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This preamplifier provides proper loading ratio of better than - 70 dB (referenced to 10 to a reluctance phono cartridge. It provides mV input at 1 kHz) and has a dynamic range of approximately 35 dB of gain at 1 kHz (2 mV 84 dB (referenced to 1 kHz). The....
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A DSB transmitter is much cheaper to build than an SSB transmitter because no filter or phasing networks are required. This circuit produces up to 1-W output on the 10-meter band. The frequency 28.322 MHz is used, which is a commonly available clock....
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Charge current: I=0,45V/R2
Power-dissipation by R2: (0,45 * 0,45 / R2) !
Please adjust 13,8V by R5 without connected battery...
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This circuit requires low noise, low and stable offset voltages, high open loop gain, and high speed. These requirements are met by the HA514 7. The standard variations of this circuit can easily be implemented using the HA-5147. For example, hysteresis....
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This project has 3 features.
1. It`s a Field Strength Meter,
2. A Frequency Meter and,
3. An aid for testing detuned transmitters.
Its uses will become clear in a moment but firstly let`s go over the background of a Field Strength Meter.
A Field....
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The above diagram is a standard low-pass telephone line filter (L1,C1,L3,C2). L2 and L4 are needed since we're dealing with the 'Tip' and 'Ring' of a phone line which may carry up to 90VAC. I used a similar circuit on 3 phone-lines back in the early 80's....
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The circuit is designed to light (via SCR1 and SCR2) only when both the left and right brake lights are activated. The ci..
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This site contains complete schematics and code for a 68HC11 based frequency counter, square wave synthesizer, sine wave synthesizer, programmable filter, capacitance and inductance meter, with a digitalker speech synthesizer output. Project specifications....
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The adjustable circuit breaker responds in 0.02 sunder all conditions-provided you select a fast relay for Kl. For moderate overload conditions, it"s preferable to use the fuse or the fast-acting breaker. Toroid transformer Tl senses ac load current and....
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This little circuit can be used to dim lights up to about 350 watts. It uses a simple, standard TRIAC circuit that, in my expirience, generates very little heat. Please note that this circuit cannot be used with fluorescent lights...
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In order to simplify the transmitter design, we've used the new pll circuit from Motorola :the MC145170. This PLL includes the prescaler and a serial standard bus called SPI. We advise to use the P2 version that fixes some init issues during the Power Up.....
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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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ADCs with differential inputs are becoming increasingly popular. This popularity isn`t surprising, because differential inputs in the ADC offer several advantages: good common-mode noise rejection, a doubling of the available dynamic range without doubling....
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When the start switch is pushed, the output of the charger goes to 14.5 V. As the batttery approaches full charge, the charging current decreases and the output voltage is reduced form 14.5V to about 12.5V, terminating the charging process. Transistor Q1....
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When driving MOSPOWER in a totem-pole output configuration, it is necessary to have the gate voltage 10 to 15 V positive with respect to the source in order to handle load currents near the MOSPOWER maximum ratings. The D169 lends itself to....
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Many things can go wrong in a modern recording studio, but few are as difficult to track down as reversed microphone polarity. When a microphone is placed in front of a sound source, a positive pressure on its diaphragm caused by forward-moving air results....
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This Design Idea describes a versatile test circuit for zener diodes after yet another misread zener diode had infiltrated the ranks of 1N4148 diodes assembled on a pc board. As a bonus, the circuit can serve as a moderate-voltage, power-limited adjustable....
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This Circuit is based on the UM5100 which can record speech into a digital memory and then play it back. The device is designed to be used directly with static RAM's up to 256K bits, or with EPROM 's or ROM's for playback only. High quality voice....
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This circuit is mainly intended to provide common home stereo amplifiers with a microphone input.
This circuit is mainly intended to provide common home stereo amplifiers with a microphone input.
Using a stereo microphone the circuit must be doubled. In....
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The circuit is a microphone amplifier for use with low impedance (~200 ohm) microphones. It will work with stabilized voltages between 6-30VDC. If you don`t build the impedance adapter part with T1, you get a micamp for higher impedance microphones. In this....
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The interface uses a PIC16F876 microcontroller and not much else. It performs channel mixing, current limiting, and noise rejection. Push the stick forward, both motors move forward, move the stick to the left and the robot moves left. It makes the robot....
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A simple op amp and silicon diode are the heart of the temperature-to-voltage converter that will permit you to use an ordinary voltmeter-either analog or digital-to measure temperature. User adjustments make it possible for a reading of either 10 mV or....
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This timer is ideal for small aplications. Due to its simple structure, its usage and nevertheless its universal character, this mini timer is usable in the most current applications needing time intervals, from some seconds through approximately 60 minutes.....
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The circuit in Figure 1 uses a Centronics printer port to interface an eight-channel, 8-bit ADC to a PC. The circuit cuts the cost of addressing and decoder circuitry and saves one expansion slot for interfacing. The design uses three of the subport`s....
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This preamplifier has a low output impedance, and is designed to drive long cables, allowing you to listen to a remote music source without having to buy expensive screened cables. The very low output impedance of around 16 ohms at 1KHz, makes it possible to....
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Using a 6BW6 vacuum tube, the above transmitter delivers about 5 W output. CI is adjusted for cleanest CW note. C8 and C9 are 365 pF and dual-365 pF (paralleled) tuning capacitors. LI is 35 turns of #24 enamelled wire on a 1 plastic tube. FT-243 crystals....
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Here is a simple radio that is easy to build and inexpensive. In fact, you probobly have all the parts you need in your junk box. You`ll be suprised at the great reception with this little set...
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The circuit is a divider by 64 used in many RF applications like as satellite receiver, digital tuners, frequency counters, PLL, etc. The heart of circuit is an IC named SAB6456, but you can use SDA2101 or other equivalent chips. Each output is NOT of the....
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This circuit detects an object passing in one direction but ignores it going the opposite way. Two sensors define the sense of direction. The object blocks the light to phototransistor Ql or Q2 first dependent on the direction of approach. When the object....
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One LTC 1149 synchronous switching regulator can deliver both 3.3- arid 5-V outputs. The design`s simplicity, low cost, and high efficiency make it a strong contender for portable, battery-powered applications. The circuit described accepts input voltages....
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Companies usually purchase one type of telephone for all employees, which is understandable, especially if they obtain a discount for buying in quantity. One ringer sound for everyone can pose a problem, though, if the sound of a ringing phone makes a dozen....
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This circuit will activate a relay when light falls to a preset level. Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer...
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Fuzz is one of the classic guitar effects, and this simple circuit generates it quite well. The circuit is so compact that it can be built into guitars or amps that do not have built in fuzz to add that capability to the instrument. The circuit does not use....
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Hall-effect switches have several advantages over mechanical and optically coupled switches, They"re insensitive to environmental light and dirt, they don"t bind, and they don"t sustain mechanical wear. Their major drawback is that they require three wires....
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The diac is a common component used to trigger triacs. The construction of a diac is similar to that with a transistor, but with both junctions doped to similar levels so that the two junctions' revers break down characteristics are similar. This is a fun....