New Circuits Page 241
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Pulse width modulation (PWM) is a technique to control analog circuits with a digital output. PWM is used in many applications, Specially to control light intensity and speed on motors. A PWM circuit makes a square wave with a variable width. The pulse width....
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Chu Moy designed a very popular headphone amplifier that`s easy to build, and it can be built small enough to fit in a pocket, power supply and all. It`s powerful enough to drive very inefficient headphones to thunderous volumes from even weak sources, and....
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This 60-W. 28-V broadband amplifier covers the 225-400 MHz military communications band. The amplifier may be used singly as a 60-W output stage in a 225-400 MHz transmitter. or by using two of these amplifiers combined with quadrature couplers, a 100-W....
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The major device in the circuit is SRI (a TGS812 toxic-gas sensor manufactured by Figaro Engineering Inc.) The gas-sensitive semiconductor (acting like a variable resistor in the presence of toxic gas) decreases in electrical resistance when gaseous toxins....
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A Selective Amplifier 10dB for FM/VHF region. Note that some devices to be used SMD components and may have a minimum sales volume. Device works very well as an FM external amplifier "when used for example in car / boat etc . Thanks to GF3 filter, amplifier....
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The circuit provides a simple and cost-effective solution to matching resistors and capacitors. Impedances ZR and Zx form a half-bridge, while OSC and OSC excite the bridge differentially. The external op amp is a FET input amplifier (LF356) with very low....
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This circuit is an ETHERNET controller I use the PIC18F452 and the mikroC C Compiler. I use also the JAVA SCRIPT information you can get from www.w3school.com I Control 8 outputs throw the WEB and transfer time information also. I use 3 timer and 3 buffers....
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This circuit represents a Dive computer interface for RS232. Uses the MAX232A...
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Some microcontroller applications usually use too many I/O pins to read keys or onboard switches; in many cases, few pins remain available for other uses. Some alternative ways to read keys yield more free pins. First, consider some ways to effect key....
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This receiver uses the NE5212, the Signetics 10116 ECL line receiver, and the Phillips/Amperex BPF31 pin diode. The circuit is a capacitor-coupled receiver and utilizes positive feedback in the last stage to provide the hysteresis. The amount of hysteresis....
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Use a pair of Maxim"s 5V-powered MAX231 RS-232C transmitters as drivers to obtain a 2-color LED. The transmitters require only a singleended, 5-V input to generate ± 10 V internally. Their outputs are short-circuit-proof and can supply as much as 10....
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This tester provides an audible indication of the logic level of the signal presented to its input. A logic high is indicated by a high tone, a logic low is indicated by a low tone, and oscillation is indicated by an alternating tone. The input is high....
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An infra-red or wireless remote control has the disadvantage that the small, handy, remote transmitter is often misplaced. The sound operated switch has the advantage that the transmitter is always with you. This project offers a way to control up to four....
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Some channels offer a separate audio mode (SAP) in a second language. It is usually transmitted on 6.8 MHz, whi..
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If your ear is good, you can use this IR-pulse-to-audio converter to troubleshoot infrared remote-controls. It is also a good project for detecting infrared-light sources. A photo cell module (Radio Shack P/N 276-137) detects IR radiation and drives audio....
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General filters are bandpass filters that usually employ bridging couplings between nonadjacent interstage couplings (Reference 1). This class of filters also includes bridging coupling across the filter input and output ports. The implementation of....
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The amplifier provides a total power gain of about 25 dB, and the construction technique allows the use of inexpensive components throughout. The MRF476 is specified as a 3 watt device and the MRF475 has an output power of 12 watts. Both are extremely....
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Basic operation of the monitor attached to the circuit is to detect objects (obstacles), at distances ranging from a few millimeters to and a few centimeters. Depending circuits used in industry and hospitals. The position sensor IC2 optoapomonotis used a....
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With a constant current excitation, the voltage dropped across an inductance increases with frequency. Thus, an active device whose output increases with frequency can be characterized as an inductance. The circuit yields such a response with the effective....
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The crystal operates into a complex load at series resonance. Ll, Cl, and C2 balance the crystal at zero reactance. Capacitor Cl fine-tunes the center frequency..
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This is a very simple circuit utilising a 555 timer IC to generate square wave of frequency that can be adjusted by a potentiometer. With values given the frequency can be adjusted from a few Hz to several Khz. To get very low frequencies replace the 0.01uF....
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At startup, the voltage in the trigger input at pin 2 is less than the trigger level voltage, "13 VDD. caus ing the timer to be triggered via pin 2. The output of the timer at pin 3 becomes high, allowing capacitor c, to charge very rapidly through diode Dl....
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Some circuits that add binary numbers have problems with time delay caused by carry propagation. This has been ..
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This Design Idea describes an inexpensive circuit to generate two extremely high-quality, crystal-clock-reference-signals, one of which is a PWM-controlled VCXO (voltage-controlled crystal oscillator) clock signal (Figure 1)...
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This decade box can be set for any resistance value between 10 and 11.1 in 10- stops. A switch can be used to configure several RC configurations. Use close tolerance components in the circuit. If possible, check components with-an accurate bridge or....
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The HI-506 multiplexer is used as an analog input selector, controlled by a binary counter to address the appropr..
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Its an adaptation of the 2X 16 LCD project, by adding a fettite loop antenna, two resistors, and a capacitor. Here the display shows the output of the 10 bit scanning voltmeter with Minimum Mass Wireless Coupler. Both the ferrite loop antenna and the....
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Connect two 24 V / 3 W bulbs in parallel to the output and set the right frequency on PLL. Now turn on the transmitter. You should tune it on a receiver. Maybe you might stretch coils of the L1. Fix the L1 in position when the tuning voltage (on C4) is in....
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If your application uses a relatively powerful microcontroller, you can use several free I/O pins or an unused input with an ADC to effect an easy keyboard connection. But, if the microcontroller in your system has too few free I/O pins and no on-chip ADC,....
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A 555 timer, IC1, drives a 4017 CMOS decade counter. Each of the 4017's first four outputs drives a CA3079 zero-voltage switch. Pin 9 of the CA3079 is used to inhibit output from pin 4, thereby disabling the string of pulses that IC normally delivers. Those....
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The output of the CA3179 is fed through the Dl!Q1 circuit. Those components serve to boost the 1-V output of the CA3179 to a standard TTL level. Then, depending on the position of range switch S2b, the signal is passed directly to the 7216, or through the....
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Combining high speed analog-to-digital conversion with low power dissipation, the 500ksps LTC®1278 and 600ksps LTC1279 12-bit ADCs solve major challenges confronting designers of high speed systems: conversion performance, power dissipation, circuit board....
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A high performance op-amp that sets a new standard of excellence in noise performance only 0.9nV/Hz with low source resistances. Total harmonic distortion is less than 0.01%. The op-amp is suitable for use in high quality audio, low noise frequency....
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In this circuit, Ul is a frequency converter that feeds the 455-kHz IF stage U2 and detector..
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This broadband amplifier covers the 225-400 MHz military communications band producing 10 watt RF output power and operating from a 28 volt supply. The amplifier can be used as a driver for higher power devices such as 2N6439 and MRF327. The circuit is....
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Integrated circuit gates ICl-a and TCl-b form a monostable, whose time constant is determined by C2 and R3. When the transmitter is dekeyed (and then almost immediately rekeyed) point TX+ goes low and takes pin 1 low for a short time. This triggers the....
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The circuit shows a simplex fiber link between the NE5080 transmitter and the NE5081 receiver. The components shown are for a center frequency of 5 MHz, although this frequency can be increased to 20 MHz with proper selection of external component values.....
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Photo. This is the test circuit -the basic driver is only two transistors, two resistors, the circuit was evaluated using a white LED, but when it was time to button it up and archive it, I replaced the expensive white LED with a cheap green one...
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A photocell circuit provides automatic threshold adjustment. Monostable action prevents undesired retriggering of the output. With only one op amp IC, the circuit offers: Automatic adjustment of its trigger level to accommodate various light sources, changes....
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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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The LM3915 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs providing a logarithmic 3 dB/step analog display. LED current drive is regulated and programmable, eliminating the need for current limiting resistors...
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This is my second-generation guitar reverb circuit. The fidelity is much improved over the earlier design, it is suitable for use as a front-end to a guitar amplifier. This circuit features clipping indicators on the preamp and reverb recovery stages,....
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This circuit will synthesize two rear channels for quadraphonic sound when fed with a stereo signal. The rear output for the left channel, is a combination of the left channel input 180 out of phase, added to a proportion of the right hand channel (also out....
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The linear charging ramp is most useful where linear control of voltage is required. Some possible applications are a long period voltage controlled timer, a voltage to pulse width converter, or a linear pulse width modulator. Ql is the current source....
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The automatic porch-light control circuit holds a triac on until a 4020 divider counts a number of 60-Hz powerlinc pulses. The circuit turns off a light after a predetermined time by using pins other than pin 3 of III. Various times can be set...
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Thiscircuit matches the very high impedance of ceramic cartridges, unity gain, and low impedance output. By "loading" the cartridge with a 2M2 input resistance, the cartridge characteristics are such as to quite closely compensate for the RIAA recording curve...
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The traditional potentiometer is implemented with an electrical contact that slides over a resistive layer. An example of a well-known audio-grade potmeter is the Alps Blue. I still use this one myself. A high-end (good and costly) alternative is the rotary....
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This approach to automatic level control (ALC) makes use of digitally switched audio attenuators in the signal path. The output level of the system is sensed, compared to a reference, and audio pads are inserted via analog switches...
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Proposed power supply for amplifier 100W v-mosfet [ 1 ] is what appears in the above form. It has separated supply for the various stages of supply, stage for power, stage for control, supply for preamplifier and for stage of protection. Whoever wants it can....
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This simple window detector uses only half of a 7400 quad NAND gate plus four resistors, chosen so that the voltage at point A exc.,eds the voltage at point B for any input voltage. With no input applied or when VIN is at ground, the output of gate Gl is....
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The circuit uses a CA3130 BiMOS op amp as the sample-readout amplifier for the storage (sample-holding) capacitor Cl, and a CA3080A as the sample-control amplifier. ..
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The transmitter includes RDS/SCA input and Audio/MPX input with optional preemphasis. It can be used with or without stereo encoder. Tuning over the FM band is provided by two buttons that control dual-speed PLL. The transmitter can work also without the LCD....
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The circuit consists of four parts: a binary counter, a D/A converter, a VCO, and an audio output amplifier. The speed at which the counter counts depends on the frequency of the output of the VCO, which in turn is determined by the output of the counter.....
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The output goes high when a preset temperature is exceeded. A fixed half-supply reference voltage feeds a reference..
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In microprocessor control of multiple loads, the minimum cost per load is critical. A typical application example is a large display involving driving arrays of incandescent lamps. This circuit provides minimal component cost per stage and optocoupler....
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CR1, CR2, CR3, and CR4 form a bridge circuit with the SCR across the dc legs. With light on the photoconductor PCI, CI charges through Rl to about 150 Vdc. The resistance of PCI is low when illuminated, so very little voltage appears across it or C2. At....
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Here is a simple tachometer circuit for use with a hand-held DVM or portable chart recorder. A novel feature is that the source frequency pulse/rev rate can be directly set on a ten-turn potentiometer to provide a convenient calibration of one V per 1000....
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This is a 40 meter transmitter which uses two valves, the 6AU6 and 6GV8. The construction is easy. Just be carefull due to high voltage present...
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Most universal chargers to charge the battery 9 V (8.4 V more). However, while the charging of NiCd or NiMH rechargeable governed by a special circuit or a microprocessor, 9 V batteries are recharged mostly from current sources. I use several of these....
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The approaches using on-chip A-to-D converters on AVR, PIC, and Cypress controllers reached sample rates of up to about 60 kHz. Not really very useful for the sort of thing I was thinking about using this for: encoded data, radio control signals, A-to-D....
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The ^generator output is rectified then filtered and applied between the positive supply voltage and the base of the detector transistor. This provides a negative voltage which reduces the base-voltage when the speed increases. In normal operation, if the....
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This tester is for tracing wiring on Printed Circuit Boards. Resistors below 50 ohms act as a short circuit; above 100 ohms as an open circuit. The circuit is a simple multivibrator switched on by transistor T3. The components in the base of T3 are Dl, Rl,....
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This logic probe uses a single CMOS IC and shows three logic conditions, High, Low and Pulsing. In addition if the probe input is neither hi or low (the high impedance state of tri-output logic ic`s) then no LED`s will light. Power from the logic probe is....
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Here are photos of a tube unit including an analog multiplier, phase discriminator and a relay control driver (a big relay was inserted in a socket near two potentiometers on the left). Used in ground control gear (don`t ask me - control of what..., all I....
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The zener breakdown of a transistor junction is used as a noise generator. The breakdown mechanism is random and this voltage has a high source impedance. By using the op amp as a high input impedance, high ac gain amplifier, a low impedance, large signal....
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The coil is about 25 turns #28 wire on a T-44-6 core, tapped at about 5 turns. I'm too lazy to open my VFO and count it for you -- besides, you'll probably have to tweak it yourself with your available components. Once the turns are squeezed to the right....
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This paper describes an RF amplifier circuit which is suitable for the frequencies between
10MHz and 500MHz. These kind of amplifiers are called wide band amplifiers.
Wide band amplifiers are used in communication receivers, RF measuring equipment and....
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There will be many times where it is desirable to use the P05 supply module from a higher voltage source. For example, if you want to add balanced inputs to a power amplifier, then you need a +/-15V supply, but the amp`s supply voltage will be much too high....
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This project is a 4 channel DMX512 driver board. It features four power MOSFETs that can be configured to operate in PWM mode or as on/off outputs. The driver can be configured to use any four consecutive addresses across the full 512 channel address....
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Anyway, Fluffy is a SX programmer for people who have already experimented with PIC chips, and want to try out the Scenix SX family. I built Fluffy because I wanted to experiment with the SX's, but didn't want to spend $300 or so bucks on the official....
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The Inter-Power SWR-5 - upper right - "isn't worth a penny". Got it from a mate to use with a beacon, but I burnt it out with only 3.5-4W morse signal on 70cm. Removed the bridge and installed my own pick-up line (suggested by LA8OJ) and now it is fb for....
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The operation of the unit revolves around three !Cs: a 4093 quad NAND Schmitt trigger, a 4066 quad analog switch, and a 7555 timer. When a high is fed to probe 1 in, it is inverted to IC1a and once again by IC1b, so that the input to IC2a is high. Thathigh....
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This circuit uses the speed and drive capability of the HA-5190 coupled with two high-speed DMOS FET switches. The input amplifier is allowed to operate at a gain of -5, although the overall circuit gain is unity. ..
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The 16F84 has 13 outputs. All 13 can serve as inputs, but only 12 are normal outputs, one is an open-drain. An open-drain output has no active pull up- you have to provide an external (passive) pull up. Since the `F84 is CMOS based, this leaves us 12 outputs....
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White LEDs are widely used in small LCD backlight
applications for simplicity, high reliability and low cost.
However, due to variations in the forward voltage drop of
white LEDs, matching the brightness becomes a major
design consideration for multiple....
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Using a PC parallel port to control external devices is a popular approach these days but I certainly couldn’t afford to tie up a PC for the few weeks leading up to Christmas just to flash a few LEDs! Not to mention the power bill! So, why not use a small....
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This economical signal tracer is useful for servicing and alignment work in receivers and low power transmitters. When switched to RF, the modulation on any signal is detected by the diode and amplified by the FET..
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The four 1K resistors on the output of U6 are too high in value for some parallel ports. Change these to 100ohm. Some LSI based parallel ports use active pull-up resistors and these are lower than the nominal 4K7 which causes a voltage divider effect. A bad....
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Beeps 7.5 seconds after a preset time
Adjustable time settings: 15 s. 30 s. 1 min. 2 min. & others This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a....
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H-Bridge
This circuit drives small DC motors up to about 100 watts or 5 amps or 40 volts, whichever comes first. Using bigger parts could make it more powerful. Using a real H-bridge IC makes sense for this size of motor, but hobbyists love to do it....
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This circuit can be used to operate an electric strike or an electromagnetic lock on a door. It is not the door being opened/closed, but a small electromagnetic strike which unlocks the door. The opener has the following features currently programmed in....
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This circuit uses the Holtek HT2884 IC to produce 8 different sound effects. All sound effects are generated internally by the HT2884 IC. Power is a 3 Volt battery, but the IC will work with any voltage between 2.5 and 5 Volts. Switch S1 is the on / off....
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An economical and commercially available quartz temperature sensor, Y1 and IC1, an LTC-485 RS485 transceiver in transmitter mode, form a Pierce crystal oscillator. The sensor, an Epson HTS-206, presents a nominal frequency of 40 kHz at 25°C and a temperature....
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The circuit shown in Fig. 62-15A is designed to drive a 15-V, two-phase, bipolar stepping motor, providing a bidirectional single level voltage across each winding at currents of up to 9.6 A. The circuit consists of two identical transistor bridge stages....
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Use of IR (infrared) light as a method for wireless communication has become popular
for remote control applications. There are a number of different standards for such
communication. In this application note the widely used RC5 coding scheme from
Philips....
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The GB4550 and GB4550A are high performance monolithic
video buffer/clamps made on Gennum's LSI process.
They feature a wideband differential amplifier that can be
configured as a gain stage. The output signal voltage is
limited to +2V above the clamp....
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This circuit has a Schmitt trigger and integrator built around one op amp. Timing is controlled by the RC network. Voltage at the inverting input follows the RC charging exponential within the upper and lower hysteresis levels. By closing the switch SWI, the....
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One still designing that it uses in the exit transistor of technology V-mosfet. This transistors to us offer a lot of virtues concerning the simple bipolar transistors, as high speeds, thermic stability, low distortion etc. Beyond this circuit use also other....
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With this circuit you can mix four separate audio inputs. Each input will accept high or low impedance microphones, phonograph, tape or aux signals. You can adjust the gain of each input by adjusting each respective pot. With the Stereo/Mono switch you can....
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The moisture detector uses two transistors and a piezoelectric transducer to sound an alarm tone when water is present. Transistor Ql forms a crystal-controlled oscillator, using a portion of piezoelectric transducer XDCwhich contains two piezoelectric....
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The major disadvantages of usual linear power supplies are high power dissipation, the size and the appropriated weight. When looking for an alternative solution, I decided to use a switch mode power supply (SMPS). The efficiency of such power supplies is....
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The circuit is based on the IC1 that is 555, for the creation of alternate flashes from the two led D1-2, that can be also different colour. The frequency of alternation can be regulated from the trimmer R3 and from the C1, if changes his capacity. The....
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It consisted of 16 LEDs in a circle with two touch pads. By placing your fingers on the touch pads, the circuit started and ran the LEDs in a "chaser" pattern around the display, with a beep each time a LED was illuminated.
The circuit gradually slowed down....
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This circuit, adds a power-down function to analog I/O ports (for example, the AD7769 and AD7774). Moreover, the diodes ordinarily needed to protect the devices against power-supply mis-sequencing can be eliminated (see the figure).In the circuit, MOSFETs....
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In the case where analog signals are being used as the logic control, hysteresis from a Schmitt-trigger input can be used to prevent haH-wave power output. The circuit operation is as follows: at low input voltages, Q1 is biased in the off state. Q2....
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Vacuum Tubes 807 and 1625 are commonly used by hams as power amplifiers. Both tubes are audio power amplifier beam tetrodes in the output stage of high power amplifiers but they are suitable for high frequencies also. Both tubes are equal in their....
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The indicator is intended for use with an audio amplifier or preamplifier, but it can also be used in othe..
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A differential amplifier makes an excellent audio clipper and can provide precise, symmetrical clipping. The circuit shown commences clipping at an input of 100 mV. The output commences clipping at ±3 V. Matching Q7 and Q2 is necessary for good symmetrical....
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This function generator uses a CA3260 BiMOS op amp to petform both the integrator and switching functions. A 620-pF capacitor and 2-KO resistor shape feedback square wave to reduce spikes. Full audio spectrum, 10Hz to 20kHz, is covered with a single 100....
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This converter allows coverage from 25 kHz up to 500 kHz. Use short coax from the converter to receiver antenna input..
Pulse width modulation (PWM) is a technique to control analog circuits with a digital output. PWM is used in many applications, Specially to control light intensity and speed on motors. A PWM circuit makes a square wave with a variable width. The pulse width....
Chu Moy designed a very popular headphone amplifier that`s easy to build, and it can be built small enough to fit in a pocket, power supply and all. It`s powerful enough to drive very inefficient headphones to thunderous volumes from even weak sources, and....
This 60-W. 28-V broadband amplifier covers the 225-400 MHz military communications band. The amplifier may be used singly as a 60-W output stage in a 225-400 MHz transmitter. or by using two of these amplifiers combined with quadrature couplers, a 100-W....
The major device in the circuit is SRI (a TGS812 toxic-gas sensor manufactured by Figaro Engineering Inc.) The gas-sensitive semiconductor (acting like a variable resistor in the presence of toxic gas) decreases in electrical resistance when gaseous toxins....
A Selective Amplifier 10dB for FM/VHF region. Note that some devices to be used SMD components and may have a minimum sales volume. Device works very well as an FM external amplifier "when used for example in car / boat etc . Thanks to GF3 filter, amplifier....
The circuit provides a simple and cost-effective solution to matching resistors and capacitors. Impedances ZR and Zx form a half-bridge, while OSC and OSC excite the bridge differentially. The external op amp is a FET input amplifier (LF356) with very low....
This circuit is an ETHERNET controller I use the PIC18F452 and the mikroC C Compiler. I use also the JAVA SCRIPT information you can get from www.w3school.com I Control 8 outputs throw the WEB and transfer time information also. I use 3 timer and 3 buffers....
This circuit represents a Dive computer interface for RS232. Uses the MAX232A...
Some microcontroller applications usually use too many I/O pins to read keys or onboard switches; in many cases, few pins remain available for other uses. Some alternative ways to read keys yield more free pins. First, consider some ways to effect key....
This receiver uses the NE5212, the Signetics 10116 ECL line receiver, and the Phillips/Amperex BPF31 pin diode. The circuit is a capacitor-coupled receiver and utilizes positive feedback in the last stage to provide the hysteresis. The amount of hysteresis....
Use a pair of Maxim"s 5V-powered MAX231 RS-232C transmitters as drivers to obtain a 2-color LED. The transmitters require only a singleended, 5-V input to generate ± 10 V internally. Their outputs are short-circuit-proof and can supply as much as 10....
This tester provides an audible indication of the logic level of the signal presented to its input. A logic high is indicated by a high tone, a logic low is indicated by a low tone, and oscillation is indicated by an alternating tone. The input is high....
An infra-red or wireless remote control has the disadvantage that the small, handy, remote transmitter is often misplaced. The sound operated switch has the advantage that the transmitter is always with you. This project offers a way to control up to four....
Some channels offer a separate audio mode (SAP) in a second language. It is usually transmitted on 6.8 MHz, whi..
If your ear is good, you can use this IR-pulse-to-audio converter to troubleshoot infrared remote-controls. It is also a good project for detecting infrared-light sources. A photo cell module (Radio Shack P/N 276-137) detects IR radiation and drives audio....
The amplifier provides a total power gain of about 25 dB, and the construction technique allows the use of inexpensive components throughout. The MRF476 is specified as a 3 watt device and the MRF475 has an output power of 12 watts. Both are extremely....
Basic operation of the monitor attached to the circuit is to detect objects (obstacles), at distances ranging from a few millimeters to and a few centimeters. Depending circuits used in industry and hospitals. The position sensor IC2 optoapomonotis used a....
With a constant current excitation, the voltage dropped across an inductance increases with frequency. Thus, an active device whose output increases with frequency can be characterized as an inductance. The circuit yields such a response with the effective....
The crystal operates into a complex load at series resonance. Ll, Cl, and C2 balance the crystal at zero reactance. Capacitor Cl fine-tunes the center frequency..
This is a very simple circuit utilising a 555 timer IC to generate square wave of frequency that can be adjusted by a potentiometer. With values given the frequency can be adjusted from a few Hz to several Khz. To get very low frequencies replace the 0.01uF....
At startup, the voltage in the trigger input at pin 2 is less than the trigger level voltage, "13 VDD. caus ing the timer to be triggered via pin 2. The output of the timer at pin 3 becomes high, allowing capacitor c, to charge very rapidly through diode Dl....
Some circuits that add binary numbers have problems with time delay caused by carry propagation. This has been ..
This decade box can be set for any resistance value between 10 and 11.1 in 10- stops. A switch can be used to configure several RC configurations. Use close tolerance components in the circuit. If possible, check components with-an accurate bridge or....
The HI-506 multiplexer is used as an analog input selector, controlled by a binary counter to address the appropr..
Its an adaptation of the 2X 16 LCD project, by adding a fettite loop antenna, two resistors, and a capacitor. Here the display shows the output of the 10 bit scanning voltmeter with Minimum Mass Wireless Coupler. Both the ferrite loop antenna and the....
Connect two 24 V / 3 W bulbs in parallel to the output and set the right frequency on PLL. Now turn on the transmitter. You should tune it on a receiver. Maybe you might stretch coils of the L1. Fix the L1 in position when the tuning voltage (on C4) is in....
A 555 timer, IC1, drives a 4017 CMOS decade counter. Each of the 4017's first four outputs drives a CA3079 zero-voltage switch. Pin 9 of the CA3079 is used to inhibit output from pin 4, thereby disabling the string of pulses that IC normally delivers. Those....
The output of the CA3179 is fed through the Dl!Q1 circuit. Those components serve to boost the 1-V output of the CA3179 to a standard TTL level. Then, depending on the position of range switch S2b, the signal is passed directly to the 7216, or through the....
A high performance op-amp that sets a new standard of excellence in noise performance only 0.9nV/Hz with low source resistances. Total harmonic distortion is less than 0.01%. The op-amp is suitable for use in high quality audio, low noise frequency....
In this circuit, Ul is a frequency converter that feeds the 455-kHz IF stage U2 and detector..
This broadband amplifier covers the 225-400 MHz military communications band producing 10 watt RF output power and operating from a 28 volt supply. The amplifier can be used as a driver for higher power devices such as 2N6439 and MRF327. The circuit is....
Integrated circuit gates ICl-a and TCl-b form a monostable, whose time constant is determined by C2 and R3. When the transmitter is dekeyed (and then almost immediately rekeyed) point TX+ goes low and takes pin 1 low for a short time. This triggers the....
The circuit shows a simplex fiber link between the NE5080 transmitter and the NE5081 receiver. The components shown are for a center frequency of 5 MHz, although this frequency can be increased to 20 MHz with proper selection of external component values.....
Photo. This is the test circuit -the basic driver is only two transistors, two resistors, the circuit was evaluated using a white LED, but when it was time to button it up and archive it, I replaced the expensive white LED with a cheap green one...
A photocell circuit provides automatic threshold adjustment. Monostable action prevents undesired retriggering of the output. With only one op amp IC, the circuit offers: Automatic adjustment of its trigger level to accommodate various light sources, changes....
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....
The LM3915 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs providing a logarithmic 3 dB/step analog display. LED current drive is regulated and programmable, eliminating the need for current limiting resistors...
This is my second-generation guitar reverb circuit. The fidelity is much improved over the earlier design, it is suitable for use as a front-end to a guitar amplifier. This circuit features clipping indicators on the preamp and reverb recovery stages,....
This circuit will synthesize two rear channels for quadraphonic sound when fed with a stereo signal. The rear output for the left channel, is a combination of the left channel input 180 out of phase, added to a proportion of the right hand channel (also out....
The linear charging ramp is most useful where linear control of voltage is required. Some possible applications are a long period voltage controlled timer, a voltage to pulse width converter, or a linear pulse width modulator. Ql is the current source....
The automatic porch-light control circuit holds a triac on until a 4020 divider counts a number of 60-Hz powerlinc pulses. The circuit turns off a light after a predetermined time by using pins other than pin 3 of III. Various times can be set...
Thiscircuit matches the very high impedance of ceramic cartridges, unity gain, and low impedance output. By "loading" the cartridge with a 2M2 input resistance, the cartridge characteristics are such as to quite closely compensate for the RIAA recording curve...
The traditional potentiometer is implemented with an electrical contact that slides over a resistive layer. An example of a well-known audio-grade potmeter is the Alps Blue. I still use this one myself. A high-end (good and costly) alternative is the rotary....
This approach to automatic level control (ALC) makes use of digitally switched audio attenuators in the signal path. The output level of the system is sensed, compared to a reference, and audio pads are inserted via analog switches...![Power Supply for Amlifiers [B]](uploads/133-54d133.gif "Power Supply for Amlifiers [B]")
Proposed power supply for amplifier 100W v-mosfet [ 1 ] is what appears in the above form. It has separated supply for the various stages of supply, stage for power, stage for control, supply for preamplifier and for stage of protection. Whoever wants it can....
This simple window detector uses only half of a 7400 quad NAND gate plus four resistors, chosen so that the voltage at point A exc.,eds the voltage at point B for any input voltage. With no input applied or when VIN is at ground, the output of gate Gl is....
The circuit uses a CA3130 BiMOS op amp as the sample-readout amplifier for the storage (sample-holding) capacitor Cl, and a CA3080A as the sample-control amplifier. ..
The transmitter includes RDS/SCA input and Audio/MPX input with optional preemphasis. It can be used with or without stereo encoder. Tuning over the FM band is provided by two buttons that control dual-speed PLL. The transmitter can work also without the LCD....
The circuit consists of four parts: a binary counter, a D/A converter, a VCO, and an audio output amplifier. The speed at which the counter counts depends on the frequency of the output of the VCO, which in turn is determined by the output of the counter.....
The output goes high when a preset temperature is exceeded. A fixed half-supply reference voltage feeds a reference..
In microprocessor control of multiple loads, the minimum cost per load is critical. A typical application example is a large display involving driving arrays of incandescent lamps. This circuit provides minimal component cost per stage and optocoupler....
CR1, CR2, CR3, and CR4 form a bridge circuit with the SCR across the dc legs. With light on the photoconductor PCI, CI charges through Rl to about 150 Vdc. The resistance of PCI is low when illuminated, so very little voltage appears across it or C2. At....
Here is a simple tachometer circuit for use with a hand-held DVM or portable chart recorder. A novel feature is that the source frequency pulse/rev rate can be directly set on a ten-turn potentiometer to provide a convenient calibration of one V per 1000....
This is a 40 meter transmitter which uses two valves, the 6AU6 and 6GV8. The construction is easy. Just be carefull due to high voltage present...
Most universal chargers to charge the battery 9 V (8.4 V more). However, while the charging of NiCd or NiMH rechargeable governed by a special circuit or a microprocessor, 9 V batteries are recharged mostly from current sources. I use several of these....
The approaches using on-chip A-to-D converters on AVR, PIC, and Cypress controllers reached sample rates of up to about 60 kHz. Not really very useful for the sort of thing I was thinking about using this for: encoded data, radio control signals, A-to-D....
The ^generator output is rectified then filtered and applied between the positive supply voltage and the base of the detector transistor. This provides a negative voltage which reduces the base-voltage when the speed increases. In normal operation, if the....
This tester is for tracing wiring on Printed Circuit Boards. Resistors below 50 ohms act as a short circuit; above 100 ohms as an open circuit. The circuit is a simple multivibrator switched on by transistor T3. The components in the base of T3 are Dl, Rl,....
This logic probe uses a single CMOS IC and shows three logic conditions, High, Low and Pulsing. In addition if the probe input is neither hi or low (the high impedance state of tri-output logic ic`s) then no LED`s will light. Power from the logic probe is....
The zener breakdown of a transistor junction is used as a noise generator. The breakdown mechanism is random and this voltage has a high source impedance. By using the op amp as a high input impedance, high ac gain amplifier, a low impedance, large signal....
The coil is about 25 turns #28 wire on a T-44-6 core, tapped at about 5 turns. I'm too lazy to open my VFO and count it for you -- besides, you'll probably have to tweak it yourself with your available components. Once the turns are squeezed to the right....
This paper describes an RF amplifier circuit which is suitable for the frequencies between 10MHz and 500MHz. These kind of amplifiers are called wide band amplifiers. Wide band amplifiers are used in communication receivers, RF measuring equipment and....
There will be many times where it is desirable to use the P05 supply module from a higher voltage source. For example, if you want to add balanced inputs to a power amplifier, then you need a +/-15V supply, but the amp`s supply voltage will be much too high....
Anyway, Fluffy is a SX programmer for people who have already experimented with PIC chips, and want to try out the Scenix SX family. I built Fluffy because I wanted to experiment with the SX's, but didn't want to spend $300 or so bucks on the official....
The Inter-Power SWR-5 - upper right - "isn't worth a penny". Got it from a mate to use with a beacon, but I burnt it out with only 3.5-4W morse signal on 70cm. Removed the bridge and installed my own pick-up line (suggested by LA8OJ) and now it is fb for....
The operation of the unit revolves around three !Cs: a 4093 quad NAND Schmitt trigger, a 4066 quad analog switch, and a 7555 timer. When a high is fed to probe 1 in, it is inverted to IC1a and once again by IC1b, so that the input to IC2a is high. Thathigh....
This circuit uses the speed and drive capability of the HA-5190 coupled with two high-speed DMOS FET switches. The input amplifier is allowed to operate at a gain of -5, although the overall circuit gain is unity. ..
The 16F84 has 13 outputs. All 13 can serve as inputs, but only 12 are normal outputs, one is an open-drain. An open-drain output has no active pull up- you have to provide an external (passive) pull up. Since the `F84 is CMOS based, this leaves us 12 outputs....
Using a PC parallel port to control external devices is a popular approach these days but I certainly couldn’t afford to tie up a PC for the few weeks leading up to Christmas just to flash a few LEDs! Not to mention the power bill! So, why not use a small....
This economical signal tracer is useful for servicing and alignment work in receivers and low power transmitters. When switched to RF, the modulation on any signal is detected by the diode and amplified by the FET..
Beeps 7.5 seconds after a preset time Adjustable time settings: 15 s. 30 s. 1 min. 2 min. & others This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a....
H-Bridge This circuit drives small DC motors up to about 100 watts or 5 amps or 40 volts, whichever comes first. Using bigger parts could make it more powerful. Using a real H-bridge IC makes sense for this size of motor, but hobbyists love to do it....
This circuit can be used to operate an electric strike or an electromagnetic lock on a door. It is not the door being opened/closed, but a small electromagnetic strike which unlocks the door. The opener has the following features currently programmed in....
This circuit uses the Holtek HT2884 IC to produce 8 different sound effects. All sound effects are generated internally by the HT2884 IC. Power is a 3 Volt battery, but the IC will work with any voltage between 2.5 and 5 Volts. Switch S1 is the on / off....
The circuit shown in Fig. 62-15A is designed to drive a 15-V, two-phase, bipolar stepping motor, providing a bidirectional single level voltage across each winding at currents of up to 9.6 A. The circuit consists of two identical transistor bridge stages....
Use of IR (infrared) light as a method for wireless communication has become popular for remote control applications. There are a number of different standards for such communication. In this application note the widely used RC5 coding scheme from Philips....
This circuit has a Schmitt trigger and integrator built around one op amp. Timing is controlled by the RC network. Voltage at the inverting input follows the RC charging exponential within the upper and lower hysteresis levels. By closing the switch SWI, the....
One still designing that it uses in the exit transistor of technology V-mosfet. This transistors to us offer a lot of virtues concerning the simple bipolar transistors, as high speeds, thermic stability, low distortion etc. Beyond this circuit use also other....
With this circuit you can mix four separate audio inputs. Each input will accept high or low impedance microphones, phonograph, tape or aux signals. You can adjust the gain of each input by adjusting each respective pot. With the Stereo/Mono switch you can....
The moisture detector uses two transistors and a piezoelectric transducer to sound an alarm tone when water is present. Transistor Ql forms a crystal-controlled oscillator, using a portion of piezoelectric transducer XDCwhich contains two piezoelectric....
The major disadvantages of usual linear power supplies are high power dissipation, the size and the appropriated weight. When looking for an alternative solution, I decided to use a switch mode power supply (SMPS). The efficiency of such power supplies is....
The circuit is based on the IC1 that is 555, for the creation of alternate flashes from the two led D1-2, that can be also different colour. The frequency of alternation can be regulated from the trimmer R3 and from the C1, if changes his capacity. The....
It consisted of 16 LEDs in a circle with two touch pads. By placing your fingers on the touch pads, the circuit started and ran the LEDs in a "chaser" pattern around the display, with a beep each time a LED was illuminated. The circuit gradually slowed down....
This circuit, adds a power-down function to analog I/O ports (for example, the AD7769 and AD7774). Moreover, the diodes ordinarily needed to protect the devices against power-supply mis-sequencing can be eliminated (see the figure).In the circuit, MOSFETs....
In the case where analog signals are being used as the logic control, hysteresis from a Schmitt-trigger input can be used to prevent haH-wave power output. The circuit operation is as follows: at low input voltages, Q1 is biased in the off state. Q2....
Vacuum Tubes 807 and 1625 are commonly used by hams as power amplifiers. Both tubes are audio power amplifier beam tetrodes in the output stage of high power amplifiers but they are suitable for high frequencies also. Both tubes are equal in their....
The indicator is intended for use with an audio amplifier or preamplifier, but it can also be used in othe..
A differential amplifier makes an excellent audio clipper and can provide precise, symmetrical clipping. The circuit shown commences clipping at an input of 100 mV. The output commences clipping at ±3 V. Matching Q7 and Q2 is necessary for good symmetrical....
This function generator uses a CA3260 BiMOS op amp to petform both the integrator and switching functions. A 620-pF capacitor and 2-KO resistor shape feedback square wave to reduce spikes. Full audio spectrum, 10Hz to 20kHz, is covered with a single 100....
This converter allows coverage from 25 kHz up to 500 kHz. Use short coax from the converter to receiver antenna input..
