New Circuits Page 236
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Double-tone Police sound
Single-tone old ambulance sound 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....
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This timer circuit uses a 555 IC timer and three 74LS193 counters to drive an LED display. SI is activated by one person, who turns on piezo buzzer BZ1 via Ql and also starts the clock; SI is activated by the other person being timed. ..
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Because NiCad batteries maintain a constant output voltage, it is difficult to determine how much of the battery"s charge remains. The circuit provides a way of determining the capacity of a battery by draining it at a preset current to its depleted voltage....
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Many function generators are based on a rectangular waveform generator that consists of a Schmitt..
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This circuit is designed to make a short pull-up antenna perform like a long wire antenna, while offering no voltage gain...
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The power drain is approximately 150 mA. IC1 provides a regulated 5-volt supply for the filament heater of the sensor. The gas sensitive element is connected as one arm of a resistance bridge consisting of R4, R7, R8 and the meter Ml with its associated....
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This design is based on the video DVM design. Furthermore, it adds support for color, so you will get red and green semaphore lights (as those in formula 1) and sound: you will even hear the starting-horn sound! Up to 3 times are displayed on YOUR TV....
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The burglar chaser makes a great accessory for any alarm system. It creates brilliant flashes of white light and a loud, irritating sound from a metal horn buzzer. Transformer T1 is connected to Ql, Rl, and R2 to form a blocking oscillator. This creates a....
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U1a is an oscillator and U1b tbe measurement part of tbe circuit. It converts unknown capacity into a pulse-width modulated signal the same way an·automotive dwell meter works. The meteris linear so tbe fraction or percentage of time that tbe output is....
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A sensitive-gate SCR provides a line-holding current of 20 to 40 mA, depending on loop resistance. It also lights an LED to give the user a positive indication that the telephone line is on hold. The 20 to 40 mA should prove sufficient to hold the majority....
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Light Sensitive Switch is a simple project which operates a relay when the light falling on the LDR goes below a set point. ..
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The photodiode specified responds linearly to light intensity over a 100 dB range. Digitizing the diodes linearly amplified output would require an A-D converter with 17 bits of range. This requirement can be eliminated by logarithmically compressing the....
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For those who dont like microcontroller projects, pretend the micro is a dedicated LED driver IC that just happens to have been designed to control 30 LEDs in the shape of a Heart (what a stroke of luck!). And it wont be declared obsolete just after....
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Five pins RA0 to RA4 are used as inputs. The pins are connected to the 5V average resistance 10K (Pull-up). So when no switch is not depressed all the pins have a high potential (HI +5 V). When one of them is pressed then the foot is connected to get a low....
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The circuit in Figure 1 satisfies all these criteria. The circuit delivers a unipolar (adjustable from 0 to 12V) pulse with adjustable frequency and pulse width. The first half of a dual, retriggerable monostable multivibrator, IC1A, generates the frequency....
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The principle of operation is counting the pulse number derived from a constant frequency oscillator during a fixed time interval produced by another lower frequency oscillator. This oscillator uses the capacitor being measured as the timing. The capacitance....
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TR1 (BC547) is an inverted Hartley oscillator which based upon an inductor fabricated on the PCB. This makes it megga-stable, and setable anywhere in the VHF FM band (76MHz to 119MHz) and the BB105 varicap makes it voltage tuneable over about 8MHz of that....
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A gate voltage is applied to initiate the proceedings. When the gate voltage is in the ON state, Q..
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The system makes use of the A/D to read the input and
output voltages, the Capture/Compare/Pulse module to
generate a PWM output, and Timer2 to regulate how
fast the program runs. External hardware includes a
switching power converter and a suitable....
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This circuit will run from a single 5 V power supply. The LTC1043 switched-capacitor instrumentation building block provides a differential-to-single-ended transition using a flying-capacitor technique. Cl alternately samples the differential input signal....
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With switch SI in the off position, as shown, battery voltage is applied across timing-capacitor CI, which stays charged while the rest of the circuitry has no power supplied to it. ..
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The IRPLLNR2 is a high efficiency, high power factor, fixed output
electronic ballast designed for driving rapid start fluorescent lamp types. The design contains an EMI
filter, active power factor correction and a ballast control circuit using the....
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This circuit provides for accurate half wave rectification of the incoming signal. For positive signals, the gain is 0; for negative signals, the gain is — 1. By reversing both diodes, the polarity can be inverted. This circuit provides an accurate output,....
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The bat ultrasounds are picked up by the microphone SPKR1 and go through two stages of amplification at Q1 and Q2.
Separately, a tunable (R12) single frequency is produced by the LM567 oscillator U1. The LM567 is a tone decoder but here its input is....
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A unijunction transistor audio oscillator drives a small speaker. The oscillator"s frequency is determined by resistor R2 and capacitor C2. The ope rating voltage is supplied from the car"s turn-signal circuit(s) through Dl and D2. ..
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The untuned, but amplified FSM can almost sense that mythical flea"s whisper-from 3 through 148 MHz no less-and yet, is so immune to overload that the meter pointer won"t pin. The key to the circuit is the amplifier, a 324 quad op amp, of which only one....
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The PowerSaver Flasher uses capacitive output coupling to produce brighter shorter flashes and has a much lower average current drain than standard bicore or 74HC14 flashers. The PS Flasher with one LED circuit (2 LEDs) runs all night from a 1F capacitor....
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Electronic applications such as distortion and communications measurements require pure (distortionless) sine waves as input test signals. Distortion contained in test signals causes two problems. First, the test signal distortion content must be calibrated....
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Amplifying and limiting of the AM carrier is accomplished by the if gain block providing 55 dB of gain or higher with a limiting of 40 µ\. The limited carrier is then applied to the detector at the carrier ports to provide the desired switching function.....
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With SI open, base bias is supplied to Q2 through a voltage divider (formed by R2 and R3), thus turning on the green element in the LED. That indicates that power is being supplied to the project. If you close SI, current through R1 biases Ql on, thereby....
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Use for this antenna tube of 10mm diameter. Or you can use a brass rod of about 7mm diameter. The top one is a strong copper (brass) wire of 5 to 7 mm diameter soldered directly to the coil and mounted to the PVC isolator to give a strong construction...
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The heart of the PWM Fan Controller is a PIC 12F675 microcontroller. This microcontroller is reading the analog output of a LM35 temperature sensor using a ADC (analog to digital converter) . The resulting digital value is converted to a temperature and a....
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The rapid, widespread use of 3.3V logic circuits complicates
the selection of RS232 interface circuits. The optimum choice
of an interface circuit should be based upon several application
dependent factors:
1) Logic circuitry connected to interface chip....
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Since the output buffer of P1 can sink 20mA (each output pin, but maximum IOL for all outputs was limited at 80mA), thus we can use P1 to drive LED display directly. As shown in the circuit, Two common-anode 7-segment LEDs are connected to P1 with 180 Ohms....
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The piezo transducer operates as a sound-pickup device as well as a frequency-selective filter. By controlling the gain of the op amps, the oscillator can be transformed into a sensitive and frequency-selective tone-decoder circuit. With the gain of U1a....
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The circuit shown is completely conventional. The Q of the filters has been optimised to allow a higher input impedance than would otherwise be possible, with the final Q of the two filters being almost exactly 0.707 (i.e. a traditional Butterworth filter).....
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Audio signals as music or speech have big dynamic ranges. There are silent and loud sections. These audio signals aren't too good for a transmitter, which requires audio signal with constant level on the input. Limiter is a device, which weakens loud signals....
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When Sl is depressed, Cl begins to charge to the supply voltage. That places a forward bias on the gate of Ql turning it on and supplying current to load resistor RL. When the charge on Clleaks off, the transistor shuts off, cutting off current to the....
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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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A simple digital mixer, based on two dual-Schmitt triggers (4583B) and three exclusive-OR gates, uses an RC time-delay circui..
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This transmitter consists of a keyed crystal oscillator/driver and a high efficiency final, each with a TMOS Power FET as the active element. The total parts cost less than $20, and no special construction skills or circuit boards are required. The Pierce....
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This circuit provides a continuous supply of regulated + 5 V, with automatic switch-over between line power and battery backup. When the line-powered input voltage is a + 5 V, it provides 4A V to the MAX630 and trickle charges the battery, If the....
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This is a simple rev-counter which can measure up to 100,000 rpm with method of strobe synchronization. Its usage is easy. Put a marker on the shaft before measureing, light on the shaft by flashing LED and adjust flashing frequency with the potentiometer as....
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The CS209 is designed to detect the presence or proximity ofmagnetic metals. It has an internal oscillator that, along with its external lc resonant circuit, provides oscillations whose amplitude is dependent upon the Q of the lc network. Close proximity to....
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With this dataselector, only one RS-232 port is used to connect two RS-232 devices (i.e., printer, plotter, etc.) with a mini-or microcomputer. The operation is very simple. Power on will reset FFI (QFFT ~ Low), which enables gates N1, N5, and N7. Now....
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Figure 1 shows the classic way to use a backlight-driver IC to provide dimming. By modulating an external PWM signal, the circuit controls the white-LED current. By adjusting the on/off-time ratio, or duty cycle, the circuit can provide drive ranging....
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The idea to produce a standard TV PAL signal using a SVGA graphics card was born a few years ago, where cheap graphics cards with TV output were still not available. To achieve a CCIR conform TV signal with 50 Hz vertical interlaced refresh and 15.625 kHz....
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The previous version of this device used pulse width modulation (pwm) to control the power from the five solar panels to charge the battery bank. Under full sun conditions the MOSFETS got a bit warm and the whole unit radiated a lot of RFI. This design....
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This project it´s based on a PIC18F25K20, with the purpose of control a FAN with PWM (Pulse with Modulation). It offers a variable speed control, low acoustic noise, reliability, long lifetime, low power consumption, protection features. The MCU get the....
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Simplified Analog Input Schematic
This schematic represents the input circuitry for a single input.
This circuit is a track and hold. The idea is that the input waveform may reach a peak at any instant as the drummer strikes the pad. When that....
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Intermittent failures in electronic systems are some of most difficult to diagnose. This device is designed to run for days at a time looking for a failure and logging the event. The unit is based on a PIC16F84. Six digital data lines are brought in via a....
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the AD844 was still used, but this time the feedback loop went all the way from output and back to input. The DC servo was removed and the current source was made faster, using an extra transistor. The local feedback was turned into global feedback, lowering....
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The local oscillator is crystal-controlled and the i-f swing is hardly compressed. The deviation of the transmitted carrier frequency, because of modulation, must therefore be limited to prevent severe distortion of the demodulated audio signal. The....
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The portable charger is intended primarily to give model enthusiasts the opportunity of charging their Nicad batteri..
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It is a simple circuit regulated power supply, based on the known LM 723, that drive a transistor Q1 [2N3055]. The regulation of voltage, of expense becomes with potentiometer R1 from 0v-30v DC roughly. In order to we achieve 30 V, will should the....
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This project entitled Remote Control Through Internet allows us to monitor, control and automate our home from remote locations. In existing system home automation and security are separate systems working independently. Also in existing system if any one....
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The schematic show that the AccelR8 only uses 3 IC`s. An AVR 8515 microcontroller do the calculation work and controls the other circuits. An MAX603 controls voltage and power-on/power-off. And the chip that makes it all possible, the ADXL202 from Analog....
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If you want a powerful, free and portable compiler for the AVR you'll end up with gcc. Fortunately, gcc is supporting the AVR cpu for quite some time now and e.g. the WinAVR toolchain for AVR development under windows is based on this compiler. Many people....
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PC parallel port was never designed to provide any output power to divices connected to it. it was only designed for connecting printer to your PC. But in this weird PC business everything changes. Suddenly the parallel port have become a port where you can....
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The circuit is based on IC1, an LTC1430 PWM controller. The current-limiting feature of the IC operates by sensing the voltage across the high-side MOSFET and compares it with a threshold voltage developed across R3...
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These two circuits are SSB generators. One uses a crystal filter by KVG Electronics at 9 MHz, the other uses a 455-kHz mecha..
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In an effort to conserve energy, simple shutdown schemes
are incorporated into many battery-operated circuits. Not
all circuits lend themselves to direct control, however, and
instead the supply must be turned off by a switch. The
LTC®1477 high side....
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This circuit serves as an ultra-low power replacement for multiple LED on-off indicators. It also has the advantage of being easy to read in full daylight. With the parts shown, it is possible to display four bits of information.
The display that I used....
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Automatic gain control is a very useful feature in a number of audio amplifier circuits: tape recorders, telephone speaker phones, communication systems and PA systems. This circuit consists of a HA-5144 quad op amp and a FET transistor used as a....
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The timer can be used wherever time periods of up to seven minutes duration are needed. To turn on just touch the turn-on plate, and after the selected time has elapsed, an alarm will sound for a short period, then automatically turn off. The turn-on touch....
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The µA2240 consists of four basic circuit elements: (1) a time-base oscillator, (2) an eight-bit counter, (3) a control flip-flop, and (4) a voltage regulator. The basic frequency of the time-base oscillator (TBO) is set by the external time constant....
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One preset resistor is used for all the ranges, simplifying the setting up. Diode clamping is included to prevent damage to the meter if the unknown resistor is higher than the range selected..
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The heart of the circuit is a string of 10 white LEDs. These are wired in series and connected to a current-regulated step-up switching power supply circuit. DC powered LED lighting circuits can vary from the trivial, with a single LED and a series resistor,....
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The circuit provides complete, linearized signal conditioning for a platinum RTD. This LTC1043 based circuit is considerably simpler than instrumentation or multi-amplifier based designs, and will operate form a single 5 V supply. Al serves as a....
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The AD8055-based amplifier has greater-than-100-MHz bandwidth, fully adequate for the 10-MHz oscilloscope. Its input impedance is 1 M in parallel with 30 pF to match the oscilloscope`s input and its low-capacitance probes. Figure 2b shows the final eye....
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Inverters ICl-a and ICl-b form a multivibrator and ICl-c is a buffer. Inverter ICl-d is connected so that its output is opposite that of ICl-c; when pin 6 is high, then pin 8 is low and vice versa. Because pins 6 and 8 are constantly changing state, first....
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Long-distance optical communications and medical equipment, such as CT scanners, can benefit from a fast and accurate data-acquisition system. Optical power systems, such as laser pumps, need to constantly monitor their power levels. In such systems, the....
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Analog-to-digital converters (ADCs) represent the link between analog and digital worlds in receivers, test equipment and other electronic devices. As outlined in Part 1 of this article series, a number of key dynamic parameters provide an accurate....
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20W Bridge Audio Amplifier kit, based on the TDA2005 IC, a class B dual audio amplifier, specifically designed for car radio applications etc...
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An amplifier to drive low to medium impedance headphones built using discrete components. Both halves of the circuit are identical. Both inputs have a dc path to ground via the input 47k control which should be a dual log type potentiometer. The balance....
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This digital volume control has no pot to wear out and introduces almost no noise in the circuit. Instead, the volume is controlled by pressing UP and DOWN buttons. This simple circuit would be a great touch to any home audio project...
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This one-valve (ECL82) CW Transmitter occupies a very special place in my amateur radio history. I was first licensed in 1994 but did not operate on air. I committed to only ever operate equipment which I had made myself. I had no time for radio construction....
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Using this circuit will give Good Charging results to the Gell Cell Battery
used in the Metal Detector, or any other simular and smaller type battery.
This charger is both Current and Voltage Regulated...
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This kit provides a variable output power supply ranging from 1.2 to 15 V @ 3 A. It uses Low Dropout Positive Regulator LM1084 in TO220 package for delivering variable output voltage. Input - 18 VAC/DC. Output - variable output from 1.2 ~ 15 V @ 3 A....
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In this circuit. a negative output voltage de-de converter generates a -5 V output at pin A. In order to generate -5 Vat point A, the primary of the transformer must fly back to a diode drop more negative than -5 V. If the transformer has a tightly coupled....
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This circuit will power up a water pump when the water reaches a predetermined level. Then it turns itself off when the..
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The completed board may be driven by voltages between .8 and 3 Volts. While the basic design goal was candle like light from a single cell, the values used were chosen to allow safe operation from 3 Volts so you can, for example, use it to drain the last bit....
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A 555 timer operating in the astable mode generates the driving pulses and two 4518 dual BCD (binary coded decimal) counters provide the square waves. A TL081 op amp serves as an output buffer-amplifier, and potentiometers Rl and R2 are used in order to....
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The following applications circuits are intended to illustrate the following points: A 2-KO resistor should be in series with V + to limit supply current with negative ringing oi the bit. inputs. Temperature compensation for Rns(on) can be provided in the....
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Flash slaves are used when you need to supplement one flash unit with one or several more. This slave trigger simply triggers those other units. It does this by "seeing" the first flash (using a phototransistor) and triggering the other flashes a few....
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The Tab antenna is a folded monopole that you miniaturize by forming it into an inverted L with a downward bend at the end (Figure 1). You can solder it perpendicular to a pc board or build it as part of a pc board and place it at a corner. The folded....
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Often, people attempt to control DC motors with a variable resistor or variable resistor connected to a transistor. While the latter approach works well, it generates heat and hence wastes power. This simple pulse width modulation DC motor control eliminates....
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The circuit in Figure 1 produces a single debounced pulse each time you press S1. Moreover, the circuit uses only logic power from the remote pull-up resistor, R2. You can use the circuit to detect when a key is pressed in a nonenergized device, such as a....
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The main box of the Transmit Selector system is designed to be located in the technical rack of a small radio broadcast station. There are four stereo balanced line inputs, either of which can be routed to a stereo balanced output. The signal routing is....
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This game tests a player"s reaction time. It is activated by closing switch SI, which starts the tone generator and arms the circuit. The touchplate, labeled PLAY in the diagram, consists of two metal strips about l/16th-inch apart. The first player to....
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The noninverting amplifier has a gain of R2/R3 (1 in this case) and produces a voltage of V,"" during a positive excursion of Vin with respect to ground. The inverting amplifier accommodates the negative excursions of V..; its gain is given by -R6/R7,....
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The circuit uses a track-and-hold amplifier in a closed-loop configuration to clamp the back-porch voltage of a standard video waveform to 0 V. The circuit"s outputs include a clamped composite-video signal and a TTL-level horizontal-blanking pulse.....
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Description is not in English language...
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Simple circuitry suitable for moving-magnet cartridges
Passive high-frequency equalization. This simple but efficient circuit devised for cheap moving-magnet cartridges, can be used in connection with the audio power amplifiers shown in these webpages,....
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Correctly adjusted, the voltage on the pot wiper is slightly less than half D+ (appx. 0.47*D+) and Q1 will conduct if (D+)-(Vp)>6.2+0.7+0.7, or 0.53*(D+) > 7.6V, (D+) > 14.3V. If D+ is lower than 13.7V, Q1 will not conduct, Q2 will get driven via....
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While there is a list of features that I would like to add (32k EEPROM support, line numbers to 65,535, more stack space, strings, arrays, 16 bit variables and arithmatic, possibly named variables and REM statements for starters), I have not been able to....
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The simplest technique for measuring current in an actuator or a motor is to monitor the ground current with a resistive element between the load and the ground. Because the device and its associated electronics share a ground potential, you need to amplify....
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This circuit will flash a string of LED's, typically 16, with direct connection to the mains and with a period adjustable between 1 and 4 seconds depending on the setting of the 22K/1W pot. Operation at 110V should also be possible but has not been tested.....
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The hardware (as I have bullt it) is constructed from two modules, one to capture the signal and provide timing functions, and the second as transmitter placed somewhere near the target equipment. I have interfaced this to my IBM compatible PC on the printer....
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This simple circuit generates a good and stable 1V peak-to-peak square wave at 100Hz, 1KHz and 10KHz using a single 1.5V cell as power supply. An useful feature of this circuit is that frequency changes can be obtained by switching only one capacitor at a....
Double-tone Police sound Single-tone old ambulance sound 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....
This timer circuit uses a 555 IC timer and three 74LS193 counters to drive an LED display. SI is activated by one person, who turns on piezo buzzer BZ1 via Ql and also starts the clock; SI is activated by the other person being timed. ..
Because NiCad batteries maintain a constant output voltage, it is difficult to determine how much of the battery"s charge remains. The circuit provides a way of determining the capacity of a battery by draining it at a preset current to its depleted voltage....
Many function generators are based on a rectangular waveform generator that consists of a Schmitt..
This circuit is designed to make a short pull-up antenna perform like a long wire antenna, while offering no voltage gain...
The power drain is approximately 150 mA. IC1 provides a regulated 5-volt supply for the filament heater of the sensor. The gas sensitive element is connected as one arm of a resistance bridge consisting of R4, R7, R8 and the meter Ml with its associated....
This design is based on the video DVM design. Furthermore, it adds support for color, so you will get red and green semaphore lights (as those in formula 1) and sound: you will even hear the starting-horn sound! Up to 3 times are displayed on YOUR TV....
The burglar chaser makes a great accessory for any alarm system. It creates brilliant flashes of white light and a loud, irritating sound from a metal horn buzzer. Transformer T1 is connected to Ql, Rl, and R2 to form a blocking oscillator. This creates a....
U1a is an oscillator and U1b tbe measurement part of tbe circuit. It converts unknown capacity into a pulse-width modulated signal the same way an·automotive dwell meter works. The meteris linear so tbe fraction or percentage of time that tbe output is....
A sensitive-gate SCR provides a line-holding current of 20 to 40 mA, depending on loop resistance. It also lights an LED to give the user a positive indication that the telephone line is on hold. The 20 to 40 mA should prove sufficient to hold the majority....
Light Sensitive Switch is a simple project which operates a relay when the light falling on the LDR goes below a set point. ..
The photodiode specified responds linearly to light intensity over a 100 dB range. Digitizing the diodes linearly amplified output would require an A-D converter with 17 bits of range. This requirement can be eliminated by logarithmically compressing the....
For those who dont like microcontroller projects, pretend the micro is a dedicated LED driver IC that just happens to have been designed to control 30 LEDs in the shape of a Heart (what a stroke of luck!). And it wont be declared obsolete just after....
Five pins RA0 to RA4 are used as inputs. The pins are connected to the 5V average resistance 10K (Pull-up). So when no switch is not depressed all the pins have a high potential (HI +5 V). When one of them is pressed then the foot is connected to get a low....
The principle of operation is counting the pulse number derived from a constant frequency oscillator during a fixed time interval produced by another lower frequency oscillator. This oscillator uses the capacitor being measured as the timing. The capacitance....
TR1 (BC547) is an inverted Hartley oscillator which based upon an inductor fabricated on the PCB. This makes it megga-stable, and setable anywhere in the VHF FM band (76MHz to 119MHz) and the BB105 varicap makes it voltage tuneable over about 8MHz of that....
A gate voltage is applied to initiate the proceedings. When the gate voltage is in the ON state, Q..
This circuit will run from a single 5 V power supply. The LTC1043 switched-capacitor instrumentation building block provides a differential-to-single-ended transition using a flying-capacitor technique. Cl alternately samples the differential input signal....
With switch SI in the off position, as shown, battery voltage is applied across timing-capacitor CI, which stays charged while the rest of the circuitry has no power supplied to it. ..
The IRPLLNR2 is a high efficiency, high power factor, fixed output electronic ballast designed for driving rapid start fluorescent lamp types. The design contains an EMI filter, active power factor correction and a ballast control circuit using the....
This circuit provides for accurate half wave rectification of the incoming signal. For positive signals, the gain is 0; for negative signals, the gain is — 1. By reversing both diodes, the polarity can be inverted. This circuit provides an accurate output,....
The bat ultrasounds are picked up by the microphone SPKR1 and go through two stages of amplification at Q1 and Q2. Separately, a tunable (R12) single frequency is produced by the LM567 oscillator U1. The LM567 is a tone decoder but here its input is....
A unijunction transistor audio oscillator drives a small speaker. The oscillator"s frequency is determined by resistor R2 and capacitor C2. The ope rating voltage is supplied from the car"s turn-signal circuit(s) through Dl and D2. ..
The untuned, but amplified FSM can almost sense that mythical flea"s whisper-from 3 through 148 MHz no less-and yet, is so immune to overload that the meter pointer won"t pin. The key to the circuit is the amplifier, a 324 quad op amp, of which only one....
The PowerSaver Flasher uses capacitive output coupling to produce brighter shorter flashes and has a much lower average current drain than standard bicore or 74HC14 flashers. The PS Flasher with one LED circuit (2 LEDs) runs all night from a 1F capacitor....
Amplifying and limiting of the AM carrier is accomplished by the if gain block providing 55 dB of gain or higher with a limiting of 40 µ\. The limited carrier is then applied to the detector at the carrier ports to provide the desired switching function.....
With SI open, base bias is supplied to Q2 through a voltage divider (formed by R2 and R3), thus turning on the green element in the LED. That indicates that power is being supplied to the project. If you close SI, current through R1 biases Ql on, thereby....
The heart of the PWM Fan Controller is a PIC 12F675 microcontroller. This microcontroller is reading the analog output of a LM35 temperature sensor using a ADC (analog to digital converter) . The resulting digital value is converted to a temperature and a....
Since the output buffer of P1 can sink 20mA (each output pin, but maximum IOL for all outputs was limited at 80mA), thus we can use P1 to drive LED display directly. As shown in the circuit, Two common-anode 7-segment LEDs are connected to P1 with 180 Ohms....
The piezo transducer operates as a sound-pickup device as well as a frequency-selective filter. By controlling the gain of the op amps, the oscillator can be transformed into a sensitive and frequency-selective tone-decoder circuit. With the gain of U1a....
The circuit shown is completely conventional. The Q of the filters has been optimised to allow a higher input impedance than would otherwise be possible, with the final Q of the two filters being almost exactly 0.707 (i.e. a traditional Butterworth filter).....
Audio signals as music or speech have big dynamic ranges. There are silent and loud sections. These audio signals aren't too good for a transmitter, which requires audio signal with constant level on the input. Limiter is a device, which weakens loud signals....
When Sl is depressed, Cl begins to charge to the supply voltage. That places a forward bias on the gate of Ql turning it on and supplying current to load resistor RL. When the charge on Clleaks off, the transistor shuts off, cutting off current to the....
The circuit presented here guarantees that if bulb Lai "gives up the ghost," bulb La2 will take over its tas..
A simple digital mixer, based on two dual-Schmitt triggers (4583B) and three exclusive-OR gates, uses an RC time-delay circui..
This transmitter consists of a keyed crystal oscillator/driver and a high efficiency final, each with a TMOS Power FET as the active element. The total parts cost less than $20, and no special construction skills or circuit boards are required. The Pierce....
This circuit provides a continuous supply of regulated + 5 V, with automatic switch-over between line power and battery backup. When the line-powered input voltage is a + 5 V, it provides 4A V to the MAX630 and trickle charges the battery, If the....
This is a simple rev-counter which can measure up to 100,000 rpm with method of strobe synchronization. Its usage is easy. Put a marker on the shaft before measureing, light on the shaft by flashing LED and adjust flashing frequency with the potentiometer as....
The CS209 is designed to detect the presence or proximity ofmagnetic metals. It has an internal oscillator that, along with its external lc resonant circuit, provides oscillations whose amplitude is dependent upon the Q of the lc network. Close proximity to....
With this dataselector, only one RS-232 port is used to connect two RS-232 devices (i.e., printer, plotter, etc.) with a mini-or microcomputer. The operation is very simple. Power on will reset FFI (QFFT ~ Low), which enables gates N1, N5, and N7. Now....
The idea to produce a standard TV PAL signal using a SVGA graphics card was born a few years ago, where cheap graphics cards with TV output were still not available. To achieve a CCIR conform TV signal with 50 Hz vertical interlaced refresh and 15.625 kHz....
The previous version of this device used pulse width modulation (pwm) to control the power from the five solar panels to charge the battery bank. Under full sun conditions the MOSFETS got a bit warm and the whole unit radiated a lot of RFI. This design....
This project it´s based on a PIC18F25K20, with the purpose of control a FAN with PWM (Pulse with Modulation). It offers a variable speed control, low acoustic noise, reliability, long lifetime, low power consumption, protection features. The MCU get the....
Simplified Analog Input Schematic This schematic represents the input circuitry for a single input. This circuit is a track and hold. The idea is that the input waveform may reach a peak at any instant as the drummer strikes the pad. When that....
Intermittent failures in electronic systems are some of most difficult to diagnose. This device is designed to run for days at a time looking for a failure and logging the event. The unit is based on a PIC16F84. Six digital data lines are brought in via a....
the AD844 was still used, but this time the feedback loop went all the way from output and back to input. The DC servo was removed and the current source was made faster, using an extra transistor. The local feedback was turned into global feedback, lowering....
The local oscillator is crystal-controlled and the i-f swing is hardly compressed. The deviation of the transmitted carrier frequency, because of modulation, must therefore be limited to prevent severe distortion of the demodulated audio signal. The....
The portable charger is intended primarily to give model enthusiasts the opportunity of charging their Nicad batteri..
It is a simple circuit regulated power supply, based on the known LM 723, that drive a transistor Q1 [2N3055]. The regulation of voltage, of expense becomes with potentiometer R1 from 0v-30v DC roughly. In order to we achieve 30 V, will should the....
This project entitled Remote Control Through Internet allows us to monitor, control and automate our home from remote locations. In existing system home automation and security are separate systems working independently. Also in existing system if any one....
The schematic show that the AccelR8 only uses 3 IC`s. An AVR 8515 microcontroller do the calculation work and controls the other circuits. An MAX603 controls voltage and power-on/power-off. And the chip that makes it all possible, the ADXL202 from Analog....
These two circuits are SSB generators. One uses a crystal filter by KVG Electronics at 9 MHz, the other uses a 455-kHz mecha..
This circuit serves as an ultra-low power replacement for multiple LED on-off indicators. It also has the advantage of being easy to read in full daylight. With the parts shown, it is possible to display four bits of information. The display that I used....
Automatic gain control is a very useful feature in a number of audio amplifier circuits: tape recorders, telephone speaker phones, communication systems and PA systems. This circuit consists of a HA-5144 quad op amp and a FET transistor used as a....
The timer can be used wherever time periods of up to seven minutes duration are needed. To turn on just touch the turn-on plate, and after the selected time has elapsed, an alarm will sound for a short period, then automatically turn off. The turn-on touch....
The µA2240 consists of four basic circuit elements: (1) a time-base oscillator, (2) an eight-bit counter, (3) a control flip-flop, and (4) a voltage regulator. The basic frequency of the time-base oscillator (TBO) is set by the external time constant....
One preset resistor is used for all the ranges, simplifying the setting up. Diode clamping is included to prevent damage to the meter if the unknown resistor is higher than the range selected..
The heart of the circuit is a string of 10 white LEDs. These are wired in series and connected to a current-regulated step-up switching power supply circuit. DC powered LED lighting circuits can vary from the trivial, with a single LED and a series resistor,....
The circuit provides complete, linearized signal conditioning for a platinum RTD. This LTC1043 based circuit is considerably simpler than instrumentation or multi-amplifier based designs, and will operate form a single 5 V supply. Al serves as a....
Inverters ICl-a and ICl-b form a multivibrator and ICl-c is a buffer. Inverter ICl-d is connected so that its output is opposite that of ICl-c; when pin 6 is high, then pin 8 is low and vice versa. Because pins 6 and 8 are constantly changing state, first....
20W Bridge Audio Amplifier kit, based on the TDA2005 IC, a class B dual audio amplifier, specifically designed for car radio applications etc...
An amplifier to drive low to medium impedance headphones built using discrete components. Both halves of the circuit are identical. Both inputs have a dc path to ground via the input 47k control which should be a dual log type potentiometer. The balance....
This digital volume control has no pot to wear out and introduces almost no noise in the circuit. Instead, the volume is controlled by pressing UP and DOWN buttons. This simple circuit would be a great touch to any home audio project...
This one-valve (ECL82) CW Transmitter occupies a very special place in my amateur radio history. I was first licensed in 1994 but did not operate on air. I committed to only ever operate equipment which I had made myself. I had no time for radio construction....
Using this circuit will give Good Charging results to the Gell Cell Battery used in the Metal Detector, or any other simular and smaller type battery. This charger is both Current and Voltage Regulated...
This kit provides a variable output power supply ranging from 1.2 to 15 V @ 3 A. It uses Low Dropout Positive Regulator LM1084 in TO220 package for delivering variable output voltage. Input - 18 VAC/DC. Output - variable output from 1.2 ~ 15 V @ 3 A....
In this circuit. a negative output voltage de-de converter generates a -5 V output at pin A. In order to generate -5 Vat point A, the primary of the transformer must fly back to a diode drop more negative than -5 V. If the transformer has a tightly coupled....
This circuit will power up a water pump when the water reaches a predetermined level. Then it turns itself off when the..
The completed board may be driven by voltages between .8 and 3 Volts. While the basic design goal was candle like light from a single cell, the values used were chosen to allow safe operation from 3 Volts so you can, for example, use it to drain the last bit....
A 555 timer operating in the astable mode generates the driving pulses and two 4518 dual BCD (binary coded decimal) counters provide the square waves. A TL081 op amp serves as an output buffer-amplifier, and potentiometers Rl and R2 are used in order to....
The following applications circuits are intended to illustrate the following points: A 2-KO resistor should be in series with V + to limit supply current with negative ringing oi the bit. inputs. Temperature compensation for Rns(on) can be provided in the....
Flash slaves are used when you need to supplement one flash unit with one or several more. This slave trigger simply triggers those other units. It does this by "seeing" the first flash (using a phototransistor) and triggering the other flashes a few....
The Tab antenna is a folded monopole that you miniaturize by forming it into an inverted L with a downward bend at the end (Figure 1). You can solder it perpendicular to a pc board or build it as part of a pc board and place it at a corner. The folded....
Often, people attempt to control DC motors with a variable resistor or variable resistor connected to a transistor. While the latter approach works well, it generates heat and hence wastes power. This simple pulse width modulation DC motor control eliminates....
The main box of the Transmit Selector system is designed to be located in the technical rack of a small radio broadcast station. There are four stereo balanced line inputs, either of which can be routed to a stereo balanced output. The signal routing is....
This game tests a player"s reaction time. It is activated by closing switch SI, which starts the tone generator and arms the circuit. The touchplate, labeled PLAY in the diagram, consists of two metal strips about l/16th-inch apart. The first player to....
The noninverting amplifier has a gain of R2/R3 (1 in this case) and produces a voltage of V,"" during a positive excursion of Vin with respect to ground. The inverting amplifier accommodates the negative excursions of V..; its gain is given by -R6/R7,....
The circuit uses a track-and-hold amplifier in a closed-loop configuration to clamp the back-porch voltage of a standard video waveform to 0 V. The circuit"s outputs include a clamped composite-video signal and a TTL-level horizontal-blanking pulse.....
Simple circuitry suitable for moving-magnet cartridges Passive high-frequency equalization. This simple but efficient circuit devised for cheap moving-magnet cartridges, can be used in connection with the audio power amplifiers shown in these webpages,....
Correctly adjusted, the voltage on the pot wiper is slightly less than half D+ (appx. 0.47*D+) and Q1 will conduct if (D+)-(Vp)>6.2+0.7+0.7, or 0.53*(D+) > 7.6V, (D+) > 14.3V. If D+ is lower than 13.7V, Q1 will not conduct, Q2 will get driven via....
While there is a list of features that I would like to add (32k EEPROM support, line numbers to 65,535, more stack space, strings, arrays, 16 bit variables and arithmatic, possibly named variables and REM statements for starters), I have not been able to....
This circuit will flash a string of LED's, typically 16, with direct connection to the mains and with a period adjustable between 1 and 4 seconds depending on the setting of the 22K/1W pot. Operation at 110V should also be possible but has not been tested.....
The hardware (as I have bullt it) is constructed from two modules, one to capture the signal and provide timing functions, and the second as transmitter placed somewhere near the target equipment. I have interfaced this to my IBM compatible PC on the printer....
This simple circuit generates a good and stable 1V peak-to-peak square wave at 100Hz, 1KHz and 10KHz using a single 1.5V cell as power supply. An useful feature of this circuit is that frequency changes can be obtained by switching only one capacitor at a....
