New Circuits Page 246
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Timing resistor R may be adjusted to any value between 10 K and 50 M to obtain a frequency range from 400 kHz to 100 Hz. Returning the timing resistor to the collector of Q1 ensures that Q1 draws its base current only from the timing capacitor Ct. The timing....
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The MP3 player is a new kind of portable audio player. It will be shipped simultaneously from many audio makers in the early part of 2000, and will start a new generation of portable audio. I have omitted a general description of the MP3 player and format....
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When power is applied to the circuit, SCRl is off, so there is no bias-current path to ground; thus, L~317 acts as a current regulator. The LM317 is umnected to the battery through steering diode Dl, limiting resistor Rl, and bias resistor R2. The....
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Useful for liquids level detection and proximity devices
Up to 50 cm. range, optional relay operation. This circuit is useful in liquids level or proximity detection. It operates detecting the distance from the target by reflection of an infra-red beam. It....
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Tests transistors and diodes for polarity. A three-phase wave form is derived from the 350Hz ring-of-three oscillator formed by IC1A, IC1B and IC1C, and applied to the device under test via the LEDs. The oscillator wave form enables each pair of device....
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This circuit is not a novelty, but it proved so useful, simple and cheap that it is worth building.
When the positive (Red) probe is connected to a DC positive voltage and the Black probe to the negative, the Red LED will illuminate.
Reversing polarities....
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The circuit useful for distortion measurements notches out the fundamental frequency of 1 kHz to allow measurement of the residual level of harmonics. First a true RMS meter is used to measure the 1-kHz input level E^ by setting SA to the input position.....
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You can use a low-cost PC sound card as an analog-function generator by controlling the PC with the program "SoundArb." [To obtain SoundArb, download di2409setup.exe, a 1.06-Mbyte self-extracting installation program.] The program generates standard....
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The sensors used are silicon phototransistors and Cadmium Sulfide (CdS) photocells. Both of these sensors allow less current to flow when they are dark than when lighted. Phototransistors change their conductance while photocells change their resistance....
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The LED flasher circuits below operate on a single 1.5 volt battery. The circuit on the upper right uses the popular LM3909 LED flasher IC and requires only a timing capacitor and LED. The top left circuit, designed by Andre De-Guerin illustrates using a....
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Figure 1 shows the LT1618 driving a 1W, white Lumileds (www.lumileds.com) LXHL-BW02 Luxeon LED.
You need no external op amps for this compact approach. The LXHL-BW02 has a forward voltage of 3.1 to 3.5V for 250 mA of current. Although the maximum dc....
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Cascading two identical integrators will thus result in an overall phase shift of 180° and an amplification of unity (p..
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A negative pulse at the input is fed via capacitor Cl to the input pin (2) of the IC, Pin 2 is held slightly above its triggering voltage of 1/3 Vcc by the voltage divider comprising Rl, R2 and RV1, The negative pulse triggers the IC and the output (pin 3)....
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The circuit uses a Signetics NE565 PLL (Phase-Locked Loop) as a detector to recover the SCA signal. The input to the SCA decoder circuit is connected to an FM receiver at a point between the FM discriminator and the de-emphasis filter network. The PLL, IC1,....
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Capacitor C4 couples the output of U1 to a simple attenuator, which is used to provide a loss of 0 dB, 20 dB, or 40 dB, depending on the setting of range switch Sl. The circuits sensitivity is 10-V rms for fullscale deflection, so the attenuator gives....
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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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This project is exactly what you need. It is simple to construct and can be connected to almost any analogue multimeter.
The scales are accurate over each range - certainly good enough to provide you with the value of any capacitor between 1p and 10u.
The....
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Noise level measured into 75ohm 3.1kHz BW using Siemens D2006 level meter: -80dBU (77.5mV)
from zero to 1MHz and drops 3dB on 17MHz. Decrease the first coupling capacitor (68nF) to 10nF
to increase the lower limit to 50kHz. The amplifier is copied from....
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Q1 and Q2 are used to form the basis of an interface circuit for attaching a cassette recorder to the phone line. The circuit does not require a power supply because operating power is drawn from the telephone line itself. The incoming signal is fed across....
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This circuit works REALLY well. Notice how it will fire even in complete silence. This provides a sort of automatic gain control...
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An alternate LED driver which uses the 74F3040 line driver was incorporated in this particular application example. The 74F3040.has a higher current rating, but not the variable threshold capabilities at the NE522. The LED diode is operated in the....
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The crystal is in a feedback circuit from collector to base. A trimmer capacitor in series shifts the point on the reactance curve where the crystal operates, thus providing a frequency trim..
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The probe indicates a high or low at 70% and 30% of V+ (5 to 12 V). One section of the voltage comparator (LM393) senses V in over 70% of supply and the second section senses V in under 30%. These two sections direct-drive the appropriate LEDs. The pulse....
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The application involves observing the light pulse emerging from a thick specimen after transillumination by a laser pulse. Pulses derived from the laser source are amplified using a Video Amplifier LM733. The reference level is set to 1 V in the comparator....
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Using a product developed for PC-motherboard environmental monitoring, you can configure a low-cost, general-purpose DAS (data-acquisition system) (Figure 1). The DAS can directly monitor multiple voltage channels as well as temperature and frequency. It can....
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This is it. It`s a STEREO LED LEVEL METER. It`s the cheapest and best bar graph display available and best of all, it uses readily available components.
You only need a handful of LEDs, 22 transistors, some resistors, diodes and a set of electros - it....
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The circuit in Figure 1 is a quadrature-output VCO that provides both positive and negative output frequencies, depending on the polarity of the control-voltage input. The circuit provides a function that designers traditionally implement in analog....
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This tiny circuit comprising of a single 3 terminal IC UM66 can be built small enough to be placed inside a greeting card and operated off a single 3V flat button cell.
There is not much to the circuit. The UM66 is connected to its supply and its output fed....
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Power is fed to transformer Tl, a small neon-sign transformer, which steps the voltage up to about 3000 Vac. The stepped-up output of Tl is fed through L1 and L2 and across Cl, causing the capacitor to charge until enough power is stored in the unit to....
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Continually monitors battery voltage during use and consumes only about 250 ? A (until the end point is reached). Near the end point Trl turns off, allowing Tr2 to illuminate the LED to increase current drain further leading to a distinct turn off point...
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The amp is built according to the Morgan Jones design. In the spirit of DIY, I made a few modifications. I did not change the circuit topology at all, but used Svetlana 6N1P tubes, as noted. I also used a conventional power supply instead of the wall....
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This circuit can be used as a mixer and a stereo track four. The quad op-RNAP IC gives a little gain for each track, the pan control provides panning between one and two tracks with the switch to high, and with the switch to low, it is possible to pan....
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This stereo mixer has two mono mixers and a modification to the microphone inputs. When a microphone is in u..
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The circuit has two ranges: 10 sees to 5 mins and 1 min to 80 mins. It can be powered by a 9-V battery. With the LED connected as shown a reasonable frequency of flashing occurs throughout the range of operation. ..
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The ELC presented here has some flexibility, thanks to being software-controlled, but also has its limitations: It's intended for microhydro systems that employ a single-phase synchronous alternator, working at 220-240V, 50Hz, in a power range up to 25....
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This detector is useful in sine wave squaring circuits and A/D converters. The positive input may either be grounded or con-output nected a nulling voltage which cancels input offsets and enables accuracy to within microvolts of ground..
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The result was a project that includes a waveform capture circuit, a graphic LCD (Liquid Crystal Display) and a control panel with LED indicators. As described, the display plugs directly into the waveform capture and control unit, which is what the what the....
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In recent years more and more, have a tendency ket demanded higher reimbursement structures with lights and music lovers in general and manufacturers of tube amplifiers. The reason, in their view is that the sound of tubes is more sweet, how rich and....
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This source code module provides the low-level control of the port, implementing code to control 12 outputs and read 5 inputs. This code was written for Borland C/C++ v3.1, but you should be able to adapt it for other compilers. You can view the source code....
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Tihs circuit has: automatic switch on on rear gear. led-bargraph display. audible bleep on last led. "good old" design style, no microcontrollers! Based on an ultrasonic amplifier from an article seen on a 1982 magazine, it was once installed on the rear....
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A clock-recovery architecture can operate with NRZ digital signals, even at low SNRs. A clock-recovery subsystem is based on a PLL comprising a phase comparator, a loop filter, and a voltage-controlled oscillator (VCO)...
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The alarm will switch off when the 4 keys connected to "A,B,C,D" are pushed in the right order.The circuit works because each gate `Stands` upon its predecessor.If any key other than the correct key is pushed, then gate 1 is knocked out of the stack, and the....
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This voltage-to-frequency converter (VFC) accepts the bipolar-ac inputs. For -10- to + 10-V inputs, the c..
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The ac line-operated on/off controller is a simple, reliable solid-state alternative to a motive driven cam switch. Time 1 and time 2 are programmed by diodes to be 8 hours and 20 hours respectively. The TIM1 output is buffered by a transistor to supply gate....
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This VFO circuit covers from 2.13 to 2.58 MHz and is intended for use with an external mixer to heterodyne the signal to desired..
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This instrument requires two precision components: A precision capacitor and a precision inductor. You only need to start with one precision component, either the reference capacitor or the reference inductor, and using this meter, you can select or adjust....
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The lamps are usually used as ballast or electronic ballast inverter. Here it is used to reduce voltage capacitor reactance. Interesting is also the method of ignition of the auxiliary electrodes involved over 150 Ohm resistors. To start simply involve only....
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This circuit is basically the same as the 10 channel LED sequencer with the addition of solid state relays to control the AC lamps. The relay shown in the diagram is a Radio Shack 3 amp unit (part no. 275-310) that requires 1.2 volts DC to activate. No....
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Although you can obtain universal, resistor-programmable switched -capacitor filters that are configurable as notch filters, most cannot operate at bandwidths higher than 100 kHz. Further, the typically 16- to 20-pin packages do not include a continuous....
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Here is my design for a modern receiving converter for pre-war FM sets. Accordingly, this article presents a design for listening to present day FM stations on a prewar FM set based on a MOSFET transistor and a TTL (transistor-transistor logic) packaged....
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Transformer T1 supplies power to the heater of the sensor. Since the sensor is fairly sensitive to heater voltage, diodes Da, D4, and D5 regulate the heater voltage. Tl, together with D1 and CZ, forms a de power supply, whose current is regulated by Q1 and....
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This device is built around a PIC12F675 (a dandy little part from Microchip). The number of cells (1 to 8) is programmed in using the one button. The cell count is saved in EEPROM the next time you power up the device. Using just one button for all....
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Many applications require highly efficient negative-voltage post regulators with low dropout voltage ..
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This is a new design of a tutorial board based on the popular PIC16F84A microcontroller. It features eight single leds, a 7-segment display, an LCD display and five push buttons. It is an ideal solution for the beginner to take his/her first programming....
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Variable-reluctance sensors are preferred for industrial and automotive environments, because they sustain mechanical vibration and operation to 300°C. In most applications, they sense a steel target that is part of a rotating assembly. Because the....
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This is a very simple circuit to interface a current loop sensor to an input which is designed for a voltage, such as that from a standard potentiometer. This page is technical so that interested persons can build the circuit themselves, but 4QD can also....
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a low cost, high-speed monolithic analog multiplexer. The system works as follows: Selects a channel and initiates a conversion at G = 1 and then looks at the MSB of the conversion result. If the MSB = 1, the ?? will store the value. If the MSB = 0, the ??....
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IC1D is a CMOS Schmitt trigger oscillator at about 2KHz. It starts and continues to oscillate with a supply down to 1.24V (the lowest output voltage of my LM317 variable power supply) or less. IC1A is an inverter. IC1B is a Schmitt trigger NAND gate. Its....
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A basic Imfra Red Link for audio communication for distances upto 3 metres. Transistors can be replaced with 2N3904 and 2N2222. In his circuit Milan has created a basic Infra Red transmitter and receiver. The transmitter comprises a single amplifying stage....
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What is the purpose of this circuit? Basically it has two roles: to pass the desired low frequency signals and stop the unwanted high frequency signals. Open the netlist file lpfilter1.cir” with your SPICE simulator. Most simulators display the netlist in a....
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Here is an interesting circuit for a magnetic proximity switch which can be used in various applications. The magnetic proximity switch circuit, in principle, consists of a reed switch at its heart. When a magnet is brought in the vicinity of the sensor....
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As a followup to my VCR Pong project, here is a gadget that is actually useful in the Real World! It superimposes the time of day, in "HH MM SS" format, in the bottom right-hand corner of an existing video signal. My friend Scott uses it with his home....
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A design example for a portable data acquisition system is offered that greatly simplifies the circuit design task. A reduction from seven components down to three components is accomplished with a design that has lower system cost, faster time-to-market,....
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Latching is obtained by storing the gate trigger energy from the preceding half cycle in the capacitors. Powe..
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A motor driver! I'm sure you knew that already but that's what it is. A motor driver is required in pretty much all walkers including all of my CW series walkers. You need to use it any time you need to supply more current to the motors because the circuit....
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The circuit shown here can be used to control the speed and direction of rotation of a series-wound dc motor. Silicon controlled rectifiers Q1-Q4, which are connected in a bridge arrangement, are triggered in diagonal pairs. Which pair is turned on is....
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Here's PLL FM transmitter circuit from china. This circuit uses the familiar 2SC1971 for final power amplifier stage. The PLL controller of the FM transmitter use SAA1057 and PIC16F628 (download HEX file)...
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Predictable time delays from as low as 0 milliseconds to over 3 minutes are obtainable without resorting to a large value electrolytic-type timing capacitor..
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The gate drive that phase controls the four parallel SCRs is accomplished with complementary MOS hex gate MC14572 and two bipolar transistors. This adjustable line-synchronized driver pennits SCR conduction from near zero to 180 degrees. A Schmitt trigger....
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This is a simple triangle-wave generator using two IC devices and a transistor. The triangle wave is used as feedback to the square-wave generator. SI allows range switching in three ranges from 100 Hz to 100 kHz...
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The target of this project was the design of a small portable mixer supplied by a 9V PP3 battery, keeping high quality performance. The mixer is formed assembling three main modules that can be varied in number and/or disposition to suit everyone needs...
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The circuit, shown will produce up to 5-W RF output in the 40-m (7 MHz) amateur band. The coils shown are wound on toroidal cores (Armdon Associates Inc.). The part numbers are given in the schematic...
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This circuit furnishes an initial voltage of 2.5 V per cell at 25° C to rapidly charge a battery. The charging current decreases as the battery charges, and when the current drops to 180 mA, the charging circuit reduces the output voltage to 2.35 V per....
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The simple ADC in Figure 1 is perfect for getting analog signals into a purely digital microcontroller. Using just five surface-mount parts, you can assemble it for less than 50 cents (1000), which is approximately half the cost of a single-chip-ADC approach....
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This circuit is from Tomi Engdahl's page. It describes a nifty little TDR that, when combined with a regular oscilloscope, can be used to find discontinuities on long runs of cables...
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The vertical deflection amplifier uses a 180 degree phase splitter to generate a differential signal. The CRT requires large drive voltages, but almost no current. The oscilloscope bandwidth is limited by the amplifier chain as almost all electrostatic CRTs....
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The tachometer, on the same shaft as the dc motor, is simply a generator. It gives a dc output voltage proportional to the speed of the motor. A summing amplifier, Al, controls its output so that the tachometer voltage equals the input voltage, but of....
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The low-cost circuit in Figure 1 allows you to track four remote temperatures with thermistor sensors through the parallel port on your PC. This four-zone thermometer instrument has a temperature range of 40 to +90°C and a resolution of better than ±1°C. You....
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The circuit incorporates two oscillators, both operating at about 40kHz. The first, IC1a, is a standard CMOS oscillator with its frequency adjustable via VR1. The frequency of the second, IC1b, is highly dependent on the inductance of coil L1, so that its....
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This is a mini strobe light. NE555 is used as a self oscillator. The width of output pulse is changed by the variable resister. 25msec means 40Hz. 6m sec means 166Hz. A LED is connected on the output of this oscillator. Therefore LED twinkles from 40Hz to....
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The use of power MOSFETs allows a direct interface between logic and motor power, which permits circuit simplicity as well as high efficiency. This speed control circuit can be packaged on a 22-pin, double-sided, 3.5 4-in. pc board. A 12 V control supply....
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This encoder can transmit the state of up to 16 TTL digital inputs using an RF or infrared transmitter. When enabled, the included modulator automatically generates the 38kHz IR carrier. Containing a PIC microcontroller, the circuit is very flexible. You....
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Supply voltage: 12 V. Supply current: 10 mA in stand-by, max. 80 mA. Input voltage: min. 20 mV rms. Indication range: 30 dB. LED currents: 7 mA. Ref. voltage of IC2: 5 V..
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Sensing element Ql is a 2N3904 general-purpose npn transistor, although any general-purpose npn unit in a T0-92 style case will do. IC1, an LM334, supplies Ql with a constant current that is independent of temperature. An LM324 quad op amp, IC2, forms a....
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This device prevents paper notes and memos from being overlooked. A paper note placed between two fingers made of a conducting material (metal or conductive plastic) breaks the circuit, allowing pair 1 of Ul-a to go high...
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This is a very small telephone exchange attached only two ordinary Tele phones. Fully bi-directional facility with an intercom system. When a phone is in off hook condition , Exchange will detect it & send ringing pulse to other phone. When it will be picked....
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This timer can be inserted in a power line to provide a controllable delay before a load is energized. The mains voltag..
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Requiring only 10uA of quiescent current, the circuit of (Fig. 62-1 (a)) produces only 0.1ohm ON-resis-tance...
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This is a very basic circuit for flashing one or more LEDS and also to alternately flash one or more LEDs.
It uses a 555 timer setup as an astable multivibrator with a variable frequency. With the preset at its max. the flashing rate of the LED is about 1/2....
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Normally analogue-to-digital con-verter (ADC) needs interfacing through a microprocessor to convert analogue data into digital format. This requires hardware and necessary software, resulting in increased complexity and hence the total cost.
The circuit of....
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An Apex PB50 Booster Amplifier, plus an IC op amp, can be used in a high-voltage op amp that converts a small analog signal to a 180-V p-p signal.Apex Microtechnology manufactures a number of power op amps...
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In the "Trace" mode the non-linear operation of the amplifier will detect modulated rf signals which will be filtered by the .001 µ¥ capacitor and heard in the headphones.
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This circuit detects the 1050-Hz tone sent by the NOAA (National Oceanic and Atmospheric Administration) Weather..
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This page presents information on infrared - `Across The Track` train detection circuits. The circuits are designed around the LM339 comparator chip and can use a wide assortment of matched infrared - emitter / detector pairs. The basic circuit shown below....
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A 741 op amp is employed as a voltage comparator. The noninverting input is connected to zener reference source. Reference voltage is 5V. R2 is adjusted so that the voltage at the inverting input is half the supply voltage. When supply is higher than 10V,....
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A1 and its associated components furnish an amplitude stable sine wave source. All positive feedback path is a Wein bridge, tuned for 1.5 kHz, Ql, the LT1004 reference, and additional components in Al's negative loop unity-gain stabilize the amplifier. Al's....
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Transistors Ql and Q2 make up the flip-flop while Q3 drives a reed relay. When power is first applied to the circuit, Ql and Q3 are conducting and Q2 is cut off. Momentarily closing SI causes the flip-flop to switch states—Ql cuts off and Q2 conducts. When....
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The triac will be gated on at the start of the positive half cycle by current flow through the 3 µf capacitor as long as the C103 SCR is off. The load voltage then charges up the 1 µF capacitor so that the triac will again be energized during the....
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The two probes shown are held in the hands and the skin resistance applies bias to the transistor. The 5 k ohm pot is set for zero deflection on the meter. When the ' 'subject'' is embarrassed or lies, sweating on the hands takes place, increasing the bias....
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The MAR-x preamp shown will cover up to 1.5 or 2 GHz with the correct MAR-x IC. ATTN1 should be omitted for low noise-figure.appli cations. ATTN1 and ATTN2 provide a means of limiting possible termination range,..