New Circuits Page 248
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This project couldn't be any simpler if it tried. Using the PC's internal 12V supply to operate a relay, it is 100% reliable. If the PC is on, the peripherals are on and vice versa - it can't be otherwise (unless the relay fails). Other solutions have been....
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The circuit in Figure 1 generates 100V from 25V. The circuit is a typical flyback regulator that uses a couple of well-established circuit techniques to handle the high voltage...
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I have had requests to add a VHF FM transmitter, to the QRP collection. This project is a simple transmitter using only one crystal and will cover 145.00 to 146.00 MHz. The crystal is a 44.9333 MHz crystal for 145.500 receive, as used in the Trio (Kenwood)....
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The device emits ultrasonic sound waves that sweep between 65,000 and 25,000 hertz. Designed around a 556 dual timer, one half operated as an astable multivibrator with an adjustable frequency of 1 to 3 Hz. The second half is also operated as an astable....
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An Inverter is a device that converts 12 volts d.c to 120 volts a.c. , which is what we use in our homes. This project will handle about 300 watts, which is perfect for lights, small T.V.`s and radio equipment.
This Inverter takes 12 volt d.c and steps....
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The "burn and learn" method of firmware development excludes an in-circuit emulator and a serial port. With this method, it is common practice to use spare I/O pins on a µC as a debugging aid. By strategically placing instructions to set and clear these I/O....
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The task of sensing dc current at high voltage is often problematic. Most high-side current-sensing ICs available off the shelf are good only to 30 or 40V. Combining an optocoupler with such an IC yields a sensing circuit in which the only limitation of the....
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Commercially available IR distance rangers typically handle a 3- to 30-in. detection distance. Many times, it is necessary to determine smaller distances. The circuit in Figure 1 is useful for measuring small distances to reflective surfaces. Its measurement....
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This logic probe has four channels and uses two IF quad comparators to drive four bicolor LEDs. SI and SIB program the co..
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A simple bridge rectifier and a 12-V regUlator powers the MOSFET sensing circuit. The unregUlated output of the bridge rectifier operates the drain solenoid via switch S1: The sensor itself is built from two electrodes: one made of copper, -the other....
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I got a problem with my notebook, because it has only COM1. My programmer board, Easy-Downloader must use serial port and the application board also needs to communicate via the same serial port. I do remembered I have to swap DB9 connector of both devices....
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With both the ignition and the car lights on, piezo transducer BZl draws no current and remains silent. With only the ignition on, diode Dl is reverse-biased and so prevents current flow through BZL. However, when the lights are on and the ignition is....
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A highly-stable 60-Hz sine wave can be delivered with this circuit, which offers a different and much simpler approach to gaining a stable amplitude...
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This circuit protects expensive portable equipment against all types of improper hookups and environmental hazards that could cause an overvoltage condition. It operates very quickly and does not latchup, that is, it recovers when the overvoltage condition....
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The circuit consists of two sections, one being a DC/DC
converter and the other being a pair of dual N-channel
MOSFETs and their associated high-side drivers that effectively
form a DPDT switch...
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This circuit uses a couple of Op-amps to produce an interesting sound effect. The left hand CA741 is wired as a standard astable and produces the timing pulses, controlled by C1, R2 and VR1. The output is fed via C2 to the second op-amp and is also direct....
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This application note describes a complete flyback switched
mode power supply that uses a Fairchild Power Switch. The
MOSFET and its control IC are built into one package. The
MOSFET is in fact a SenseFET. Various protection features
are also included.....
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The Stereo Power Meter is made up of two identical circuits and a power supply. Each circuit contains Jwo LM3914 display chips which contain 10 voltage comparators, a 10-step voltage divider, a referencevoltage source, and a mode-select circuit that....
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It is well know that pests like rats, mice etc are repelled by ultrasonic frequency in the range of 30 kHz to 50 kHz. Human beings can't hear these high-frequency sounds. Unfortunately, all pests do not react at the same ultrasonic frequency. While some....
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The circuit is built around a 4001 quad two-input NOR gate, it provides switch selectable auto-advance times of 5, 10, 15, 20, 25 or 30 seconds through the remote-control socket of your projector. Ula and Ulb form an astable multivibrator, with its operating....
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A Wien bridge oscillator produces sine waves with very low distortion level. The Wien bridge oscillator produces zero phase shift at only one frequency (f = Vx t RC) which will be the oscillation frequency. Stable oscillation can occur only if the loop gain....
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Three op amps Ul, U2, and U3 are connected in the basic instrumentation amplifier configuration. Operating from ± 5 V, pin 8 of each op amp is connected directly to ground and provides the ac performance desired in this application (high bias mode). PI is....
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This is a 3-W, single-circuit board, VFO-controlled CW transceiver for 40 or 30 meters, featuring a direct-conversion receiver with audio filtering, Receiver Incremental Tuning (RIT), and speaker level audio volume. The transmit frequency is generated by....
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This instrument is a one or two channel frequency synthesizer. DC to 35 MHz frequency with 0.1 Hz resolution. +16 to -48 dBm signal level with 0.1 dB resolution. adjustable phase between the 2 channels with 11.25 degree resolution. pushbutton and knob....
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The circuit charges and discharges a capacitor at a crystal-controlled rate, and stores on a sample-anddifference amplifier the change in voltage achieved. The current that flows during the discharge cycle is averaged, and ratiometrically measured in the....
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The circuit is based on the grid-dip or absorption effect, which occurs when a parallel resonant circuit is coupled to an oscillator of tbe same frequency. Ql operates in a conventional Colpitts oscillator circuit at a fixed frequency of approximately 4....
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Remote, noncontact, measurement of the speed of rotating objects is the purpose of this simple circuit. Linearity and accuracy are extremely high and normally limited by the milliammeter used and the initial calibration. This circuit is configured to count....
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A Simple design based on a CS209A IC that can give surprising results and draws very little current from a 9 volt battery. It worked good on the Bench, But not so good outside for general metal detecting. But Definately a good design for detecting studs in a....
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The I2C serial bus is a popular two-wire bus lor small-area networks. I2C Clock and Data lines have open collector (or drain) outputs for each device-on the network. Only a single pull-up resistor is needed. With this arcliitecture, each device can talk on....
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A major feature of the PWM servo amplifier is elimination of a pulse transformer. A 150 kHz pulsewidth modulated signal is applied to U3, with its complementary outputs applied to identical circuits to drive the load. When point A increases, Q2 is on and....
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What is the effect of crosstalk from the digital data signals into the clock signal of a data-conversion system? This is a more obscure problem than crosstalk from digital bits into the analog signal path, which was the subject discussed in the previous....
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Any good power transistor can be used in this circuit. The base resistor should be adjusted to obtain a pulse rate of about 50 pulses per minute. The range of values shown can go from 10 pulses to 100 pulses per minute. The single fence wire must be....
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The circuit uses a Hall-effect sensor, which consists of an IC that resides in a small gap in a flux-collector ..
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This device 'listens' to a conversations and then interjects words and phrases at inappropriate times. I got this box at a local thrift store for $1.50 (special, this week only). It has a nice hinged top and a place to insert a panel with a designed glued....
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The 4046 PPL is used as the heart of a tunable ultrasonic receiver that can be used to locate unheard ultrasonic sounds. The receiver might also be used, along with a simple ultrasonic generator, to send and receive Morse code. The incoming ultrasonic....
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U1 is a 4060 12-stage binary ripple counter that is used as a free-running oscillator; its frequency of oscillation is: 1/2.2 CIR2. The output of U1 is applied to U2, a 14-stage binary ripple counter that provides square-wave outputs of lfz, 1/4, "is, and....
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In this TMOS pulser, a negative-going pulse is applied to Ul, a high-speed CMOS buffer, which directly drives the gate ofQl, an MTP3N35. If only a 100-V pulse is required, the MTA6Nl0 can be used. ..
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The VLF whistler receiver is intended to listen to natural radio noise and signals that occur below 20 kHz. LI is a large loop antenna that is 250 to 300 turns #26 gauge wire on a form 3` diameter...
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Many electronic-control systems have digital outputs that use transistors. One method of improving the security in these outputs is to use an oscillating signal to represent a logic-high state instead of a fixed voltage level (Figure 1). This type of signal,....
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This is a complete alarm system with 5 independent zones suitable for a small office or home environment. It uses just 3 CMOS IC`s and features a timed entry / exit zone, 4 immediate zones and a panic button. There are indicators for each zone a "system....
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This tester is designed to locate stray electromagnetic (EM) fields. It will easily detect both audio and RF signals up to frequencies of around 100kHz. Note, however that this circuit is NOT a metal detector, but will detect metal wiring if it conducting ac....
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The PIC16F870 chosen for this project has seval analog channels. One of these is used to capture the DTMF tones and decode the digits. The actual phone connections are made using a 'hacked' 5 line expandor from Radio Shack. This device connects between....
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This is the hardware and source code for an Atmel ATmega8 / MX-614 based UI only TNC. The intent was to provide inexpensive basic TNC functionality for APRS related packet activities. We also have the flexibility to modify the operations of the TNC by....
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This circuit is used to measure the current from a solar panel. It has very low power loss for currents in the 0-10A range. It also works as a general purpose DC current meter. The circuit can be used on either the positive or negative side of a DC circuit...
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When the lights of an on-coming car are sensed by photo-transistor Ql, things get going. Sensitivity is set by the 22-megohm resistor, R5, to about half a foot-candle. The relay used has a 12-volt, 0.3A coil.
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The temperature controller must meet some unusual
requirements. Most notably, because of ambient temperature
variation and laser operation uncertainties, the controller
must be capable of either sourcing or removing heat
to maintain control...
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Many electronic circuits need an indication that they are under power; for most ac circuits, a neon lamp is ..
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The detector circuit shown in Figure 1 (1) is simple and works well, and as shown will not trigger with a 30V RMS signal at 5Hz, but operates in 60ms with 30V DC applied, and in 50mS with a 45V DC supply. This should be sufficient for most applications, and....
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Power supply: 12-14 V stab., 100 mA. RF power: 400 mW. Impedance: 50-75 ohm. Frequency range: 87,5-108 MHz. Modulation: wideband FM. Connect the 6 V / 0,1 A bulb to the output and use R1 to tune the right frequency. Maybe you might stretch coils of the L1.....
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This simple and easy to make circuit is a 5 LED VU Meter based on LB1409 IC from SANYO, which will indicates the volume level of the audio signal it senses. SUPPLY 12V DC @ 50mA. PR1 REF SET. PR2 AUDIO LEVEL SET..
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By adding a small amount of noise to a signal to be digitized (about 0.7 bit): where: n = #..
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This circuit uses a germanium diode (marked Ge) as a temperature sensor. I used an OA90 diode but others should do. The 'ring' of Tr1 and Tr2 bias each other. Tr1's collector current is stabilized by the 5v6 zener, causing Tr2 to operate at about 5mA: this....
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Switch-mode driven 1.5V bulbs. This device was designed on request, to control the light intensity of four filament lamps (i.e. a ring illuminator) powered by two AA or AAA batteries, for close-up pictures with a digital camera. Obviously it can be used in....
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This circuit is a real core of the dimmer system. This circuit generates ramp 100 Hz signal which is syncronized to the incoming mains voltage. The ramp signal which is generated will start form 10V and go linearly down to 0V in 10 milliseconds. At the next....
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LEDs indicate at a glance what the status of the circuit is at any given moment. Once the reset switch, SI, makes contact,..
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Q3 is an IR phototransistor that responds to a modulated IR beam. Q1 amplifies the ac component of the IR beam. Q2 drives a ..
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An attempt at an Arduino guitar pedal. The guitar signal feeds through a PT2399 delay circuit, modified to include a JFET preamp phase. The delay circuit has Echo and Delay knobs. From there, it feeds into an optoisolated-Arduino-5V preamp, and out to the....
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Figure 1 shows the circuit. A major change from all of the designs from that era is the speaker coupling capacitor - 1000uF (for a -3dB of 20Hz and a 8 Ohm load) was the most common value. This is too small, and the 2200uF shown is actually marginal. 4700uF....
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This circuit provides a simple means of obtaining phase shifts between zero and 170°. The transistor operates as a phase splitter, the output at point A being 180° out of phase with the input. Point B is in phase with the input phase. Adjusting Rl provides....
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I2C are widely use for to communicate with external peripheral such as port expender, EEPROM, Real Time Clock etc. The Master Synchronous Serial Port (MSSP) module in PIC18 can be used to communicated with I2C peripheral. MSSP module can be configure to work....
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The high voltage section of the CRT is unchanged from the original vacuum tube oscilloscope used as the basis of this design. The CRT requires shielding from the main power transformer. Cold roll steel around the CRT does not provide enough shielding from....
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The circuit that has been used is shown in picture 1. Through the experimental part we will explain each of the parts function, but in order to have a notion of the basic idea, let just say, that this circuit besides the 5V power supply, is fed with a pulse....
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A window detector is a specialized comparator circuit designed to detect the presence of a voltage between two prescribed limits; that is, within a voltage window. This circuit is implemented by logically combining the outputs of two single-ended....
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The circuit uses a free-running push-pull dc to dc high voltage converter to get the necessary voltage for the laser plasma tube supply. The supply voltage Vc of this converter, is adjusted by a switch-mode power supply in order to keep the load current....
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Powered from two alkaline cells, the circuit in Figure 2 can
illuminate a 1W LXHL-BW02 LumiledsTM white LED with a
constant 320mA current at 85% efficiency. The forward
voltage of the 1W LED, 3.6V typical, requires a boosted
voltage from the 2-cell....
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The circuit uses CA3290 BiMOS dual voltage comparators. Non-inverting inputs of A1 and A2 are tied to voltage divider reference. The input signal is applied to the inverting inputs.
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The technique applies to highpass filters. You derive a composite highpass filter by using m-derived terminating half-sections with one or more constant-k interior full sections. Classic image-parameter design used m-derived half-sections with m=0.6 for best....
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This flash circuit is a typical camera flash. ..
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The load described here is capable of handling up to 10 watts of RF power for a couple of minutes, and is designed for the widely used 50 ohms impedance. It consists of ten parallel connected 560 ohms 1 watt resistors, R1 through R10, a voltage divider,....
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Fan-control circuits range from simple switches that boost the fan speed at a certain temperature, to digitally controlled fans with continuously-variable speed. High-speed/low-speed switches are inexpensive, but the sound of sudden speed changes can be....
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Touch operated switches are an attractive project for DIY electronics but they are not so common in commercial products. The reason for this is that, although there are many different ways of implementing a touch switch (leakage, hum pickup, capacitance,....
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Here are some utility circuits for use with the Ramsey FM10a, and other small FM stereo transmitter kits. This information may be helpful for setting up a micro powered FM radio station. The FM10a and similar kits tend to put out a low quality, broad band....
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When power is applied, the thermistor, a negative tc device, is at a high value. A1 saturates positive. This forces the LT3525A switching regulator"s output low, biasing Ql. As the heater warms, the thermistor"s value decreases. When itsinputs finally....
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The acoustic filters are met in various points in the sound systems. The knownest application they are the filters baxandal for regulating tone low and high frequencies and filters crossover where the acoustic region is separated in subareas, in order to it....
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You can use the parallel port of your PC and a few additional components to generate a powerful, easy-to-use arbitrary-waveform generator. By using a Visual Basic program with the circuit in Figure 1, you can generate any waveform (for example, sinusoid,....
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This circuit provides a cheap alternative to the LM3915 series LED displays. The meter relies on a square-wave oscillat..
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The transceiver mixer and carrier oscillator in the band-imaging (7- and 14-MHz) CW transceiver. Careful selection of ..
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The circuit uses a 555 timer wired as an astable oscillator and powered by the emitter current of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. As the probes get wet, a small current flows between base and....
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This circuit is useful if you need a low-energy flashing alarm. The 200 to 400-dc supply should have enough internal resistance to charge the 0.5 capacitor between flashes, about 2 or 3 time constants, which means about 500 kQ to 1 for a 1-s rate. ..
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Sometimes amateurs like to home-brew their power supplies instead of purchasing one off the shelf at any of the major ham radio retail dealers. The advantage to rolling your own power supply is that it teaches us how they work and makes it easier to....
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At some stage, we will all find ourselves pushing hi-fi equipment just a little too hard, and if lucky, will just find that the sound has become "dirty". If this happens too often or is too severe, tweeters are the first to go - they are damaged by the....
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This circuit is representative of the many applications of up/down counting in monitoring dimensional position. In the tape recorder application, the LOAD REGISTER, EQUAL, and ZERO outputs are used to control the recorder. To make the recorder stop at a....
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This circuit will generate a square wave of 2 Hz to 20 kHz. The circuit uses an op amp in a relaxation-oscil..
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LVDTs (linear variable differential transformers) are electromechanical measuring devices that convert the position of a magnetic core into electrical signals. You generate these signals via excitation on the primary side. The results on the secondary....
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The circuit provides a simple means of determining the succession of phases of a 3-phase 120 V source used in synchro work. Terminals A, BT and C are connected to the three terminals of the source to be checked. If the neon bulb lights, interchange any two....
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Tl is tuned to converter-output frequency Ul to provide 45-to-50-dB gain, depending on the design of Tl and T2. C2, C..
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This is an experiment on the closed loop DC servomotor control system (SMC). It will able to be used for practical use with/without some modifications. The closed loop servo mechanism requires real-time servo operations, such as position control, velocity....
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The controller uses one or more ordinary silicon diodes as a sensor, and uses a cheap opamp as the amplifier. I designed this circuit to use 12V computer fans, as these are now very easy to get cheaply. These fans typically draw about 200mA when running, so....
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A simple FM transmitter links your home-entertainment system to a portable radio that can be carried around the house and into the back yard. For example, you can play music on the CD changer in your living room, and listen to it on a portable radio by the....
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This simple QRP transceiver for the 30 m band did not result from a detailed requirement profile. I simply had some NE592 broadband amplifiers in my junk box, waiting for an application. After performing some tests, that application was quickly found: The....
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The circuit is small regulatorof temperature, us warns for the increase of temperature. The control of temperature becomes from the thermistor TH1, that is negative factor. His resistance is altered between in the 10K in temperature 25° C and roughly in the....
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In order to generate a single note you may try these simple circuits. With only three components you may implement some basic buzzers. You need a telephone earpiece for the first circuit. Any old telephone set has got one of those magnetic earpiece that is....
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Although white LEDs are common in a variety of lighting applications, their 3 to 4V forward-voltage drop makes low-voltage applications challenging. Charge pumps and other ICs are available for driving white LEDs, but they generally don`t work with the low....
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The Sound Blaster 16 PCI and Sound Blaster 16 ISA do not have a very sensitive microphone input. This little one transistor amplifier is powered directly from the microphone jack on the sound card and has LOTS of gain. Just put a 100uF bypass capacitor in....
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In the circuit, U1 amplifies the audio picked up by the condenser microphone. Resistor Rl limits current, while R2 and R3 center the output of the amplifier to %B+ to allow a single-ended supply to be used. Diodes D1 and D2 rectify the output of Ul, and C3....
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Ever needed a low power 120volt AC power source for your car, van or truck? Well this circuit should do the trick for you. It will supply 15 watts of AC power to a device. It should power lamps, shavers, small stereos and small appliances. If you draw to....
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I have received several emails asking how to connect up some lights so that when the phone rings, they flash. This is very useful in a situation were there is lots of noise and it is impossable to hear the phone, such as a workshop. Here is such a device...
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This machine essentially does three things: It controls the process temperature, provides constant agitation of the chemical baths, and performs the timing. The operator must pour in and out the liquids by hand. The heart of the circuit is a Basic Stamp 2p....
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Transistor Q1 can be a 2N2222(A), 2N3904, NTE123A, ECG123A, etc. Not critical at all. It acts only as a switch for the relay so almost any type will work, as long as it can provide the current needed to activate the relay's coil. D1, the 1N4148, acts as a....
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This circuit gives a positive output when the input voltage exceeds 8 volts. Between these limits the output is negative. The positive limit point is determined by the ratio of Rl, R2, and the negative point by Rl, R3. The forward voltage drop across the....