New Circuits Page 237
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When a large number of channels are multiplexed, the outputs of two or more multiplexers can be connected together and each multiplexer sequentially enabled. In the inhibit mode. the multiplexer draws less power and its output and inputs act as open....
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This is adjustable elctronic fuse that can be used to protect power supplies from short circuits or can be also used to limit the current usage. It can be adjusted for currents from 100mA up to 4.3A...
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This circuit provides a regulated dc with less than 100 mV of ripple for microprocessor applications. Necessary operating voltages are taken from the bleeder resistor network connected across the unregulated 28 V supply. The output of the LM710 comparator....
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Switch-mode power supplies offer the benefit of a much greater efficiency than obtainable with a traditional ..
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This circuit takes audio from a receiver that might have a weak CW or tone signal and uses a PLL (Ul) to recover the wea..
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The decision to use either AM, narrowband FM Oess than 15kHz), or wideband FM (greater than 30 kHz) depends on the application. For the transmission of music, FM is better because it has greater noise immunity. For speech or other noncritical applications,....
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This regulator provides 12 V at 1 A out with an input voltage of 8 to 20 V. Output voltage can be changed by c..
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Clean the surface to be glued components to the printed circuit. Use a sheet of very fine sandpaper to smooth bumps fortunes. First attach the resistors and diodes. Pay attention to the polarity of the diodes! Then glue the two finished watching the first....
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Nowadays the batteries are gaining more and more power, being the only components that fail to provide energy for portable electronic devices. The evolution is rapid, leading manufacturers electronic equipment to attempt to minimize the consumption of their....
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A crucial point in the design is the input/decoder section, and the question of what ICs to use for decoding the input video to component digital video streams. The choice for this project was the Philips IC SAA7114H, new on the market at the time. This chip....
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During normal' 'hold'' mode, the replicated analog voltage is buffered straight through the S/H amplifier to the output. Upon issuance of a SAMPLE signal, the S/H amplifier is placed in the hold mode, holding the voltage until the new analog voltage is....
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This project is a real winner in more ways than one. When you understand how the circuit works, it is really 4 projects in one. And it has two modes of operation: MANUAL and AUTOMATIC.
Everyone likes a little flutter. The introduction of so many outlets in....
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The circuit consists of a multivibrator (Ql & Q2), and a low power output stage Q3. The speaker should have an impedance in the region of 40 to 80 ohms. To use a low impedance speaker, connect an output transformer from the emitter of Q3 to ground. Cl and C2....
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The Circuit is composed of two sections, the light sensing and the power switching. The light sensing part consists of a photo-resistor R4, connected like a voltage divider to R2. Since the resistance of the photo-resistor changes depending on the amount of....
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In a basic astable timer, configuration timing periods 11 and 12 are not controlled independently. The lack of control makes it difficult to maintain a constant period, T, if either 11 or 12 is varied. In this circuit, charge RAB and discharge R8 c....
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A high signal-to-noise ratio is important in signal construction and combination. The HA-5147 aids in lowering overall system noise and thereby raises system sensitivity. The signal combination circuit incorporates input bufferiug with several other....
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In this circuit, the 7815 regulatates the positive supply, and the 7915 regulates the negative supply. The transformer should have a primary rating of 240/220 volts for europe, or 120 volts for North America. The centre tapped secondary coil should be rated....
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The circuit is essentially a constant source modified by the feedback components R2 and R3 to give a constant voltage output. The output of the ZN424E need only be 2 volts above the negative rail, by placing the load in the collector of the output transistor....
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The assembly code given here was written to see what it would take to make an AT90S1200 generate 8 channels of proper PWM. In this case, by proper, I mean with the maximum high frequency content consistent with the needed duty cycle and give clock. Take a....
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Many people experienced sleeping well in natural surroundings, into a tent or a wooden hut. This fact is due not only to the healthy atmosphere but also from our unconscious ability to perceive natural Earth`s magnetic-fields.
The circuit generates this....
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This circuit provides complete speed control over car"s windshield wipers. They can be slowed down to any rate even down to four sweeps per minute..
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The indicator flashes an LED when the battery voltage drops below a certain threshold. 2N4274 emitter-base junction serves as a zener which establishes about 6V on the L161"s positive input. As the battery drops, the L161 output goes high. This turns on the....
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A 2N5777 photo-Darlington cell picks up blinking light from the transparent plastic buttons. The power is switched ON and OFF by a hi-beta 2N3904 transistor. The circuit's 9 V battery can be left continuously connected. Less than a micro-ampere is drawn-even....
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This simple metal detector requires only a handful of components and an evening's work. Built around a cmos4011 IC, is very robust and versatile. The 250 kHz reference oscillator is built with two gates (U1/1 and U1/2), C1, R1 and P1. The search oscillator....
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The circuit is a simple, but accurate Digital Guitar Tuner. It samples the input, which can be directly from the mics of an electric guitar, or from a microphone, it you`re using an acoustic guitar. It can ofcourse also be used for tuning other instruments.....
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CMOS Digital Camera Controller and Frame Capture Device...
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The heart of the circuit is IC2, a 50240 top-octave generator. That device uses a single input-frequency to generate all twelve notes of the musical scale. The input signal is provided by IC1, a 4001 quad 2-input NOR gate. Two sections of that IC are used to....
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The circuit consists of a white noise generator which only switches on with the high part of the square wave output from the clock circuit. The frequency of the clock is adjusted with the 10 pot and the output voltage of the clock is adjusted by the 100 k....
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Amplifier A increases the microphone"s output to a usable level. The output signal is fed to op amp B, which inverts the signal180°. A balance-control potentiometer connects across the outputs of amplifiers A and B. 1f an audio tone is fed into the....
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The oscillator circuit (see Figure 1) involves two unity gain phase shift stages, A1 and A2, in tandem and a gain stage, A3, with back to back diodes and resistor network providing non-linear negative feedback. At a particular frequency (determined by RT and....
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The circuit is composed of a relaxation oscillator formed by Q1 and an SCR flip-flop formed by Q2 and Q3. With the supply voltage applied to the circuit, the timing capacitor CI charges to the firing point of the PUT, 2 volts plus a diode drop. The output of....
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Instrumentation amplifiers (differential amplifiers) are specifically designed to extract and amplify small differential signals from much larger common mode voltages. To serve as building blocks in instrumentation amplifiers, op amps must have very low....
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The mixer circuit below has 3 line inputs and 3 mic inputs. The mic inputs are suitable for low impedance 200-1000R dynamic microphones. An ECM or condenser mic can also be used, but must have bias applied via a series resistor. As with any mixer circuit, a....
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What exactly is a multivibrator? I suppose one definition would be 'a circuit which has several states'. This will do for now, it's quite loose so leaves plenty to the imagination! Conventional multivibrators have only two stages and come in three flavours:....
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One of the unusual features of the out-of-production Programmable Drum Set was its use of touch switches for control. Like most touch switches, these detect the difference in the capacitance of a plate when it is being touched by a finger versus the....
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A truly timeless circuit. LM317 is a versatile and highly efficient 1.2-37V voltage regulator that can provide up to 1.5A of current with a large heat sink. It`s ideal for just about any application. This was my first workbench power supply and I still use....
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The circuit is a linear regulator providing galvanic isolation from main line through the use of isolation transformer. Quite safe for experimenting with AC voltage. Below pictures show the example of input/output terminal connections, labeling and....
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I use the lm10 IC because it has a reference voltage and that?s useful for dc power supply. With two ICs can take different output voltage and amperage. This circuit is protected from short circuit.P2 is for controlling the current at the range of 0-2A.....
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This Project is made up with AT89C2051 and the RTC DS1307. It has a large Seven segment display. The standard remote control is used to change the Time...
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This page describes my home-built ICOM CI-V interface. In order to connect most all ICOM radios to a computer, an additional interface is required. The interface bridges the gap between the RS-232 electrical levels used by the computer serial port, and the....
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Using a modern multimeter to measure current can sometimes be difficult. Many of these meters will only measure up to one amp. However, may 112-volt DC powered projects draw a lot more than that. If you have ever thought of purchasing a commercial shunt to....
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The design also overcomes the shortcomings of modem interference protectors. The design eliminates mutual interference between phones and modems, is compatible with the line-usage indicators on multiline phones, can search for an idle phone line in multiline....
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When power is first turned on, two of the LEDs are on and the other two remain off until the timing cycle reverses. The LEDs flash in pairs, but by pressing and holding Sl closed until only one of the LEDs is on, and then releasing it, the four LEDs can be....
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The circuit in Figure 1 tests these characteristics. It charges the capacitor under test through 100 k for approximately 1 msec and then discharges it through 10 for approximately 40 nsec. The cycle then repeats. The circuit uses a double-sided copper-clad....
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Some RISC controllers, like the NEC V850 family, use an internal 32-bit architecture with an external 16-bit bus. The architecture also allows interfaces with 8-bit memories. However, with 8-bit memories, accesses to and from odd locations automatically....
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With AudioWave 2.0 your soundcard becomes a comfortable LF-signal-generator, which produces signals from 1Hz to 20 kHz with a resolution of 1 Hz. Phase shift between left and right channel is adjustable from 180° to +180° and an attenuator can be used for....
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The full wave phase control circuit below was found in a RCA power circuits book from 1969. The load is placed in series with the AC line and the four diodes provide a full wave rectified voltage to the anode of a SCR. Two small signal transistors are....
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Using this low cost Project one can reproduce AUDIO from TV without disturbing anyone. It does not use any wire between TV and HEADPHONE. In place of pair of wires it uses invisible Infrared light to transmit audio signals from TV to Headphone. Without using....
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This circuit uses readily available parts to implement a 0-to-200-nA current source. The circuit borrows a PMOS ..
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Simplicity and repeatability are featured in this 1 watt S-band amplifier design. The design uses an MRF2001 transistor as a common base, Class C amplifier. The amplifier delivers 1 watt output with 8 dB minimum gain at 24 V, and is tunable from 2.25 to 2.35....
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Probably the easiest way of doing automatic switch off is with relay logic. In the diagram, the box marked RL1 is the coil, the 2 in the coil box tells you there are two sets of contacts somewhere on the circuit, operated by this coil. In this simple....
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This circuit is used to measure the voltage on a 12V (nominal) lead acid rechargeable battery system. It was specifically designed for use in solar powered systems, but is general enough that it can be used for automotive or other 12V systems. Lead acid....
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This tester can be used to check the polarity of any power source, and is therefore very useful when installing automotive equipment, alarm systems or anything else you can think of. Because this circuit is so simple and cheap, even frying one with an over....
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This circuit is designed to detect a low light level at the sensor, amplify the signal, and provide a TTLlevet output. When the optical sensor detects low-levellight, on condition, its output is small and must be amplified. An amp with very low input bias....
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The SIMD1 V3 is very similar to the NPN flavor of SIMD1 V2, but with the addition of a FET on the output line. This makes life easier for its attached load (since there`s no need here for something that can use an "enable line"), by providing power that`s....
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In this circuit, a square wave is filtered by a high-order low-pass filter so that a -3-dB frequency will eliminate most harmonics of the waveform. As a result, the filter outputs a fundamental sine wave. This method is applied to generate a sine wave by....
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DTMF (Dual Tone Multiple Frequency) is associated with digital telephony, and provides two selected output frequencies (one high band, one low band) for a duration of 100 ms. DTMF generation consists of selecting and combining two audio tone frequencies....
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Mark Tilden`s 6-transistor H-bridge
Design, limitations, usage
This is the six transistor "Tilden style" H-bridge; while not as old as the original "basic H-bridge," this goes "way back," and is the basis for many BEAM driver circuits
* Up to 800....
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The GB4551 is a high performance video buffer with DC
restore primarily used for accurate back porch clamping.
The circuit features a wideband differential amplifier that
can be configured as a gain stage. The output signal
voltage is limited to +2V....
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U2 is a decade counter /divider, Ul is used as a switch debouncer. For a self-generating system, connect a resisor..
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For the regulation needs a transmitter or generator in mpa'nta the CB, that is to say in the region 27MHz. If you have a certain friend with CB, you convince you to help. Connect a piece of cable around in the one metre in the place of aerial. Be supplied....
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This circuit can be used to measure exhaust gas temperature in a furnace. The 10-bit LTC1091A gives 0.5°C resolution over a ooc to 500°C range. The LTC1050 amplifies and filters the thermocouple signal, the LT1025A provides cold junction compensation and....
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The EEprom programmer software supports the following devices 28C16 28C256 28C17 29C256 28C64. Diode D1 and resistor R1 provide the VDD isolation when programming the 24 pin devices. The jumper J3 must be shorted for 24 pin devices, and open circuit for 28....
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One of the nicest features of the 8-bit KX8 microcontroller (manufactured by Freescale Semiconductor) is that it includes an internal clock generator (ICG). This allows the chip to run without the trouble and expense of an external crystal or canned....
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We assume that most of our readers are thoughtful drivers who do not switch on their rear fog lights w..
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The circuit mixes LEDs of different forward-bias requirements, yet keeps the loads reasonably well-balanced through use of a current mirror comprising transistors Q1 through Q4. It also eliminates the need for a separate current-limiting "ballast" resistor....
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The reader mechanism shown was purchased from All Electronics for $1.50. The unit provides the magnetic head on a spring mechanism along with low level head signal amplifiers and data slicers. Three signal lines comming from the unit provide card presence,....
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This page features H-Bridge circuits used for controlling direct current motors. Several designs are shown using both CMOS and Bi-Polar power devices. These circuits could be used as the basis for Model Railroad DCC Boosters or PWM motor controllers. The....
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The circuit is an open loop rms voltage regulator that will provide 500 watts of power at 90 V rms with good regulation for an input voltage range of 110-130 V rms. With the input voltage applied, capacitor Cl charges until the firing point of Q3 is reached....
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BoardMaker3 is an integrated environment for the design of Printed circuit boards, offering a comprehensive set of tools that allow schematic entry, Spice simulation, 3D viewing and an Autorouter Interface. With a Customised graphics engine and a user....
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This circuit based on ATtiny26 but it could be anyone microcontroller of AVR family. Produce stable one MIDI tone and you can change it by press some keys like to change midi channel 0-15 , velocity 0-127, pitch 0-127. It is start from center tone (C) at....
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This circuit consists of two basic parts: an oscillator tuned to 40kHz, and a voltage doubler with pulse generator. The pulses are about 10 ms long and occur 2-3 per s to reduce battery drain and increase the annoyance factor for a cat, dog, hedgehog, etc. ..
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The transmitter keyboard is arranged as a scanned matrix. The matrix consists of 7 driver outputs and 7 sense inputs. The driver outputs DRVON to DRV6N are open-drain n-channel transistors and they are conductive in the stand-by mode. The 7 sense inputs....
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The circuit consists of a variable current source that charges a capacitor, which is rapidly discharged by a Schmitt-trigger comparator. The sawtooth waveform thus produced is fed to another comparator, one with a variable switching level. The output from....
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Using an EXAR XR2206, this generator will produce sine, square, and triangular waves from 10 Hz to 100 kHz. Ul is ..
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The circuit's operating principle is that if you make a pulse width proportioal to inductance, and keep the pulse frequency and amplitude constant, and then pass the pulse through a low pass filter so that only the average voltage comes out, the resulting DC....
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The LTC®1197/LTC1199 10-bit serial ADCs offer small size, low power operation and fast sample rates with good AC and DC performance. These parts are ideal for low power, high speed and/or compact designs. This Design Note discusses the features and....
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The circuit is based on an inverting op amp using discrete transistors to overcome poor slew rate, fairly high distortion, and high noise problems. The output stage is driven by a constant current source, biased by a green LED to provide temperature....
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BFO is a simple device which helps us to listen SSB and CW transmissions. Reception of SSB and CW signals requires a product detector or BFO (Beat Frequency Oscillator) to reinsert the missing carrier. This circuit is very simple since it requires no turned....
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This mini audio amplifier will test the audio stages in amplifiers such as the front end of FM bugs. You can also use it on lots of our other projects as well as the output stages of radios. It is a very handy piece of test equipment and will make a perfect....
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When computer peripheral equipment is interfaced, it is convenient to work with logic signal levels. With a nominal 4 V at the output dropping to - 0.6 V on illumination, this circuit reflects the requirements of a high-speed, paper tape optical reader....
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Testing loudspeakers is covered in some detail in the passive crossover article (see Design of Passive Crossovers), but it is irksome at best to have to fiddle about with clip leads and components lying all over the workbench. This simple project is....
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The outputs from the comparators will swing, in sequence, from high to low as the input voltage rises above the reference voltage applied to each comparator. The output LEDs will then switch on in sequence as the voltage rises. The inverting inputs of the....
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This circuit enables automatic switching-on of the tape recorder when the handset is lifted. The tape recorder gets switched off when the handset is replaced. The signals are suitably attenuated to a level at which they can be recorded using the MIC-IN....
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The TP5700 or TP5710 can reduce the number of components required to build a pulse-dialing telephone, as shown. The usual current source can be eliminated by using the VREGl output to power a TP50982A low-voltage (1. 7 V) pulse dialer via a blocking diode.....
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Driving a bare LCD does not necessarily require specialized interface circuitry or peripherals. This Design Idea describes an alternative drive scheme, which you can easily implement using the general-purpose outputs of a microcontroller. Many....
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Feedback control of the phototransistor in this optical detector helps negate the effects of varying ambient light sources. The output of a modulated visible-light LED is detected, amplified, buffered, and fed through a low-pass filter.
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This circuit will be useful if you have an electret microphone that produces a low audio (sound) level and you want to connect it to an amplifier or something like it. The circuit boosts the microphone output voltage to obtain an acceptable signal level.....
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For multiplying frequencies in the 1-to 150-Hz range, this circuit uses a 4046B and a 100 prescaler. The VCO output..
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This design uses a smart card to enable a relay. A Nutchip recognizes its mating smart card among thousand similar ones, because you choose the code to be programmed in the card's memory. No speacilized knowledge is necessary, as we supply the card program....
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One of the more frequently requested projects on HeadWize has been a switchbox for selecting multiple audio inputs. I built this passive preamp/switchbox several years ago to switch between two stereo sources (a portable FM tuner and portable CD player) AND....
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An extremely simple and low cost Sine/Square wave generator based on the Analog Devices AD9835 Direct Digital Synthesis (DDS) Generator chip. The frequency can be set for any frequency from 1Hz to 10MHz in 1Hz resolution steps! All this with three push....
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The basic Idea was to have Christmas lights flash with the music. In my design I use an ordinary amplified computer speaker, a diode bridge, and a ‘CRYDOM’ SSR (Solid State Relay). In order to increase the time that the lights were on as well as protect the....
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Before power is applied, the input and output are at ground potential and capacitor C is discharged. On power-on, the output goes high (Vdd) and C charges through R until V is reached; the output then goes low (Vss). C is now discharged through R until Vn is....
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This touch-actuated switch stays on as long as you keep your finger on the touch plate. Rl sets the input impedance to a high 22 MO. Ql picks up stray signals coupled through your body to the touch plate and amplifies them to tum on Q2, which turns on lamp....
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Circuit uses a simple RC network to produce an exceptionally shrill tone from a miniature speaker. With the parts values shown, the circuit oscillates at a frequency of 3 kHz and drives a miniature 2W speaker with ear-piercing volume. The output waveform is....
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The intended use of the 24 volts is to power an amplifier that will supply wave forms of up to a couple hundred Hz to bias a varactor or pair of varactors in an RF circuit. This meant that the current requirements would be low - probably a little over a....
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There are 4 timers in PIC18 which are timer0 to timer3. Timers are used when precise timing event need to be generated. Timers are usually used in conjunction with interrupt to keep the timing accurate. This guide will show an example of using timer0 to....
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This circuit provides a visual indication of the input analog voltage level. It has a high input impedance at pin 8 and open-collector outputs capable of sinking up to 40 milliam-peres. It is suitable for driving a linear array of 5 LEDs to indicate the....
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This Project Multi-Pattern Running light is used to generate several designs of Running Lights. We use ten LEDs for display. The designs can be selected by using two switches UP and DOWN. The 8 bit Microcontroller is used to control all the operations. It....