New Circuits Page 220
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This circuit is for a QRP (low power) antenna tuner, a.k.a. a transmatch, for use in the short wave amateur radio bands from 3-30 Mhz. It allows a wide variety of antennas to be connected to a low power transmitter. When the circuit is properly tuned, the.... -
This circuit is very basic to build. To open a the lock which is connected to the K1 Load you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switches are pressed the circuit.... -
This transmitter has a range of up to 100 feet. It generates a complete multiplex stereo signal and is useful for cordless headphone applications in which an inexpensive socket stereo receiver can be used. .. -
These items were sold nationally several years ago. The fish would sing, open its mouth, turn its head, and flap its tail. After removing the back panel, all of the existing electronics were removed leaving only the 3 servo motors, speaker and photocell. The.... -
Signetics" type NE575 compander IC is intended primarily for use with battery power supplies of 3 to 7 V (max. 8 V). It.. -
The small single turn magnetic loop (SSTML) antenna consists of a single winding inductor, about 3 feet (1 meter) in diameter, and a tuning capacitor. A second loop, which is one fifth of the diameter of the large loop, is connected to the feedline and this.... -
Many times we needed to use a simple circuit of preamplifier, with few components and facility of made. This circuit use a opamp. the Motorola, TCA5550, that contains a double amplifier, as outputs for the adjust of volume, balance, treble and bass. These.... -
The circuit shown in Figure 1 uses only two ICs, and has a bandwidth that is adjustable from more than one octave down to a tenth of an octave. As shown, the frequency range is 20 Hz. to 20 KHz. in three bands, although a fourth subsonic band could be added.... -
I came up with this idea when I was in a situation where ... * I had an amplifier with an unused RIAA input and * I was missing another input for a standard audio signal at this amplifier. So I designed a miniature passive network to convert a.... -
The original TX was designed to be only PULSE Modulated for a proportional R/C system, but I later used the same circuit to make an HF bands Amplitude Modulation (AM) transmitter using PA-Base Modulation. It eliminated the need for a modulation transformer;.... -
This circuit is for a temperature controlled constant current battery charger. It works with NICD, NIMH, and other rechargeable cells. The circuit works on the principle that most rechargeable batteries show an increase in temperature when the cells becomes.... -
This version of the familiar current loop offers a simplified and somewhat novel implementation in which optocouplers serve triple duty as level converters, isolation/protection devices, and bus interfaces. Galvanic isolation avoids ground loops, increases.... -
The strobe controller is essentially a stand-alone device, even though it is part of the console PCB. It connects through a two-wire cable to the remote strobe head. Control, input source selection and output routing are on the console. The input to the.... -
The circuit in Figure 1 allows you to compensate for both of these temperature-dependent problems, using only the TSF-102 sensor from Texas Instruments (www.ti.com). The device is a temperature-dependent positive-temperature-coefficient resistor with a....
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This circuit generates a good 1KHz sinewave adopting the inverted Wien bridge configuration (C1-R3 & C2-R4). It features a variable output, low distortion and low output impedance in order to obtain good overload capability. A small filament bulb ensures.... -
The circuit will generate precision triangle and square waves. The output amplitude of the square wave is set by the output swing of op amp Al, xndRl/R2 sets the triangle amplitude. The frequency of oscillation in either case is approximately l/0.69ftC. The.... -
The compact test probe provides rapid "measurement" of voltage levels at digital gates, fuses, diodes, batteries, and .. -
The circuit is an inverter set up as a linear amplifier. Adding the· crystal and capacitors to the feedback path, we turn the amplifier into an oscillator and force it to oscillate at, or least very near, the crystal"s resonant frequency. Trimmer capacitor.... -
Six components can configure a circuit whose output voltage is proportional to its input frequency. The average current (hvc from the 40106 Schmitt trigger inverter"s ground pin 8 is linearly dependent on the frequency at which CO is discharged into the.... -
This page covers only the details of MIDI communication on the Arduino module. For a more general introduction to MIDI on a microprocessor, see the MIDI notes on Tom's physical computing site. MIDI, the Musical Instrument Digital Interface, is a useful.... -
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The alarm plugs into the earphone jack on a receiver. Then when a signal (normally fed to the headphones) is detected and applied to the gate of SCR1, it conducts, sounding whatever alarm is connected to SOI. The signaling device can be an audible alarm or a.... -
This bridge will measure inductances from about 1 to 30 at a test frequency of 5 mHz. A 365-pF AM-type tuning capacitor .. -
The advent of new high-speed technology and the growing computer capacity provided realistic opportunity for new robot controls and realization of new methods of control theory. This technical improvement together with the need for high performance robots.... -
This circuit measures RF voltages beyond 200 MHz and up to about 5 V. The diode should be mounted in a remote probe, close to the probe tip. Sensitivity is excellent and voltages less than 1 V peak can be easily measured.. -
The JFETs, Ql and Q2, provide complete buffering to Cl, the sample and hold capacitor. During sample, Ql is turned on and provides a path, rds(on), for charging Cl. During hold, Ql is turned off, thus leaving Ql Id (< 100 pA) and Q2 Igss (< 100 pA) as the.... -
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Transistor Ql and its associated components comprise a tuneable rf oscillator. The rf signal is fed to transistor Q2, the modulator. Operational amplifier ICl increases the audio signal and applies it through resistor R4 to the base of Q2. Tune an AM radio.... -
This circuit responds to RF signals from below the standard broadcast band to well over 500 MHz, and provides a visual and audible indication when a signal is received. The circuit is designed to receive low-powered signals as well as strong sources of.... -
The gain control element is a Light Dependent Resistor (LDR). These are blessed with a few very useful features for our purposes, one of which is low distortion even at quite high signal levels. Being light activated, all we need is a LED to provide.... -
his Design Idea describes a virtual instrument that uses a desktop or notebook computer with an analog data-acquisition card and National Instruments` (www.ni.com) LabView software (Version 7.1 or above). In operation, the software extracts B-H-loop....
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Display interface uses the ICM7218A/B with an 8048 family microcontroller. The 8-bit data bus (DBO/ DB7-IDO/ID7) transfers control and data information to the 7218 display interface on successive WRITE pulses. The mode input pins on the microcontroller..... -
The most common appl icat ion for the NTC thermistor is temperature measurement. Accurate temperature measurement can easily be accomplished by interfacing a Wheatstone Bridge, 6K/30K ohm thermistor network and a digital voltmeter integrated circuit.... -
In this circuit, an additional exclusive-OR gate is connected after the modulo-2 feedback, with CI and R2 applying the supply turn-on ramp into the feedback loop. This provides sufficient transient signal so that the PRBS generator can self-start a.... -
This charger will charge any 12V lead acid battery including flooded, gel and AGM. It is fully automatic and will charge at a rate up to about 4A until the battery voltage reaches a preset point at which it will switch to a very low current float charge. If.... -
Those of you who frequently use devices that work on battery or you need a negative trend at the moment you have a single positive, will definitely look for a converter like the one described below. Constructing it, you can convert a positive voltage of a.... -
Detects the presence of a live mains conductor. Minimum parts counting. If the unit is brought close to a live conductor (insulated, and even buried in plaster) capacitive coupling between the live conductor and the probe clocks the counter, and causes the.... -
This design uses a Motorola MPX4115 Silicon Pressure Sensor, a Dallas Semiconductor DS2438 Smart Battery Monitor (to perform 1-Wire analog to digital conversion), an operational amplifier, a voltage regulator, a diode, and several resistors and capacitors..... -
This unit would be mounted in a small plastic or preferably metal box, with a 9V battery, level control, a male XLR connector (same as on a mic) and a switch. Current drain is low, since the circuit only uses one dual opamp. There is no need for a high.... -
This is a rather sensitive circuit which will detect minute variations of a magnetic field, particularly the Earth magnetic field. The principle is based on an audio beat tone generated by two identical oscillators. These must be built in the same manner.... -
I recently purchased 10 SLM1608 (SLM1606) LED matrix display units from Ebay (you might also contact the seller directly at [email protected]). These are 16x16 LED matrix units with a green and a red LED per pixel allowing each pixel to be switched to either.... -
The output frequency of this simple low-cost active voltage-controlled oscillator circuit is based upon the inherent frequency dependent characteristics of our operational amplifier. The oscillator circuit shown uses a TL082 op amp. When power is applied,.... -
A wide variety of low power wireless communication systems have surfaced in recent years. Automotive keyless entry, home security, bar code readers, and child monitors are just a few of the many applications for this technology. Most low power wireless....
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This electronic lock can be used with any type of iButtons you may already have, since the only thing needed is the internal serial number, that's different for every iButton. The command used to read the serial number is the same for all iButtons. The.... -
Counter speeds for CMOS- and TTL-programmable counters are limited to under 100 MHz. ECL-type devices can approach.. -
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Flash analog-to-digital converters, also known as parallel ADCs, are the fastest way to convert an analog signal to a digital signal. Flash ADCs are ideal for applications requiring very large bandwidth, however, they typically consume more power than other....
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This amplifier has a high quality circuit that includes full sort circuit protection and very low T.H.D. at full range of frequency. It needs simmetrical power supply +-40V. The power transistors at the output are connected as DARLINGTON and both needs.... -
The tracer receiver is a stereo audio amplifier/detector circuit operating near 1 kHz. Inductors Ll and 12-hand-wound coils, consisting of 200 turns of #26 wire on 2-inch ferrite cores-are tunea to the operating frequency of the amplifier/detector. The.... -
In the article you will find a description of the universal PIC programmer, which suggested the involvement of Jens Madsen Dyekjar [ http://www.jdm.homepage.dk/newpic.htm ]. Program allows districts PIC12C5XX, 12C67X, 16C55X, 16C61, 16C62X, 16C71, 16C71X,.... -
Often a need arises for connection of two telephone instruments in parallel to one line. But it creates quite a few problems in their proper performance, such as overloading and overhearing of the conversation by an undesired person. In order to eliminate.... -
This is a programmable infrared (remote control) transmitter, which can be controlled from a PC serial port. It is capable of sending many remote control formats, including the Philips RC-5 standard. Exact formats with the timing parameter names are shown on.... -
The greatest sensitivity is achieved if R1 is approximately equal to the probe resistance. The circuit can be zeroed with R2, while the full-scale voltage is controlled by R5. The correlation between pH and output voltage might not be linear, which would.... -
This circuit produces a pure, - 80-dB THD sine wave with a frequency that is equal to the fc of IC3"s filter. A TT.. -
An alternative approach for this application takes advantage of low-offset op-amp characteristics to design a circuit that works with a wide voltage range and needs no other supply. The V+ and inverting and noninverting terminals of the OP07 op amp need a....
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The IC1 is a 555 timer IC is connected for, Astable operation the clock pulses are fed to the IC2 via the 10K resistor. The IC2 is a 10 stage counter, output 6 (pin 5) is connected to RESET (pin 15), thus giving us a 6 stage counter , outputs 0 to 5. The 6.... -
A low power, low cost dc lamp dimmer for a two-wire portable "flashlight" can be realized with little or no heatsinking. In addition, a single potentiometer, R3 adjusts lamp brightness. Battery power is stored in Cl for Ul, which is a free-running.... -
The charger described in this article can charge packs of 4 to 7 cells with capacities ranging from 600mAh to 2Ah. The charger automatically begins charging when a pack is connected. It charges at a (nearly) constant current (adjustable), and terminates the.... -
When the input voltage is 0 the LED glows. The LED stops glowing when the voltage rises to the level determined by R2. Reverse + and - pins to reverse operating mode. To set voltage at which LED goes off, (1) Set 0V at input. (2) Set input voltage at desired.... -
Most of the circuitry is contained in the LM3914 dot/bar-graph driver IC chip. In addition to the comparator circuitry within the package, it also contains a stable reference supply and the drivers for the LEDs. Resistor R2 acts as the current limiter.... -
To prevent battery damage due to over -disc barge, a low-voltage detector and switch should be included in the design of the battery backup circuit. The detector circuit should consume extremely low current. The switch should exlnbit a low-voltage drop and.... -
A quad op amp can simultaneously generate four synchronized waveforms. The two comparators (Al and A3) produce square and pulse waves, while the tWo integrators (A2 and A4) give triangular and sawtooth waves. .. -
Here is the schematic for an 8 watt audio amp. This amp can be used as a simple booster, the heart of a more complicated amplifier or used as a guitar amp. The circuit can be built on a perf board, universal solder board or PC board, the PC board is.... -
The MOSFETS we are dealing with are three terminal devices which are used to control electron flow in a circuit. Two of the pins (the source and drain) pass the current, and the third pin (the gate) is used to control the current. The control of current, as.... -
This linear post regulator provides 12 V at 3 A. It employs TL431 reference Ul which, without additional amplification, drives TMOS MTP3055A gate Ql series pass regulator. Bias voltage is applied through Rl to Q1"s gate, which is protected against.... -
I decided to implement this using a PIC 16F84 for both an encoder and decoder, and use RS-485 drivers (DS26C31 and DS26C32) to drive the 350m cable. I only needed five I/O pins per PIC, so this could have been implemented using the smaller 8pin 12C508.... -
The calibrator can be used to check the accuracy of a time-base generator, as well as to calibrate the input level of amplifiers. The calibrator consists of an NE555 connected in the astable mode. The oscillator is set to exactly 1 kHz by adjusting.... -
This is a small, portable set, designed for those aiming at look improvement. The Bio-Stimulator provides muscles` stimulation and invigoration but, mainly, it could be an aid in removing cellulite. Tape the electrodes to the skin at both ends of the chosen.... -
A simple two tone water alarm that is light enough to be worn on the upper arm of a sleeper is described. It uses two LMC555 CMOS timer chips followed by a complimentary pair of emitter followers to drive an 8 ohm speaker. Power is supplied by a 9 volt.... -
This circuit will divide the frequency of a TTL compatible square wave signal by a factor from 0 to 999. The circuit comprises three decade counters IC1 to IC3 and a few NAND gates. The three 7490?s are cascaded and count is the input signal. When the.... -
This logic probe uses a CD4009 CMOS hex inverter. The characteristic high-input impedance of CMOS gives the advantage.. -
· This circuit is used for analog signal selection or time division multiplexing. As shown, the feedback signal places the selected amplifier channel in a voltage follower (noninverting unity gain) configuration, and provides very high input impedance and.... -
The 650 MHz Prescaler Probe's input is terminated by resistor Rl and is fed through Cl to the diode limiter composed ofD1 through D4. Those diodes are forward-biased by the +5 volt supply for small-input signals and, in turn, feed the signal to Ul. However,.... -
In this circuit the switches are power MOSFETs driven to conduct alternately by windings on a current transformer. The primary of this transformer is driven by the current in the lamp circuit and operates at the resonant frequency of L-C. Unfortunately,....
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The voltage required to ignite the neon tube is obtained by using an ordinary filament transformer (240-6 V) in reverse. Battery drain is quite low, around 1 to 2 milliamps for a nine volt battery. The pulses from Ql, unijunction transistor, operated as a.... -
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This circuit can be used to measure frequencies up to 40 MHz. To obtain the correct measured value, it is necessary to divide the oscillator frequency and the input frequency by four. .. -
Four new sampling A/D converters from Linear Technology stand out above the rest of the crowd. These new 5V and 3V 12-bit ADCs offer the best speed/power performance available today (see Figure 1). They also provide precision reference, internally trimmed....
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The circuit uses the TDA2030 which is a monolithic integrated circuit in Pentawatt® package, intended for use as a low frequency class AB amplifier. Typically it provides 14W output power (d = 0.5%) at 14V/4Ω; at ± 14V or 28V, the guaranteed output.... -
In recent years, following CD`s introduction, vinyl recordings are almost disappeared. Nevertheless, a phono preamplifier is still useful for listening old vinyl discs from a well preserved collection. This simple but efficient circuit devised for cheap.... -
Operation amplifier A1 directly drives the VN64GA with the error signal to control the output voltage. Peak rectifier Dl, CI supplies error amplifier A1 and the reference zener. This extra drive voltage must exceed its source voltage by several volts for the.... -
Large moving-coil meters may require significant amounts of current for full-scale deflection, and using a shunt resistor may prove impractical when the meter current is larger than the current you are measuring. You can solve the problem by driving the....
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A continuity tester that has an audible indicator can be more useful in some cases than a visual indicator, because you n.. -
A discussion recently on the mp3projects discussion board, about using DRAM memory with small 8-bit processors without DRAM controllers, got me to take up an old idea. I thought it should be possible to hook up a DRAM to a small processor (in this case an.... -
One section of the MC10101 is connected as a 100 MHz crystal oscillator with the crystal in series with the feedback loop. The LC tank circuit tunes the 100 MHz harmonic of the crystal and may be used to calibrate the circuit to the exact frequency. A second.... -
This basic RF oscillator circuit is easy to build and the components are not critical. Most of them can be found in your junk parts box. The L1 antenna col can be made by close winding 8 to 10 turns of 22 gauge insulted hookup wire around 1/4 inch form.... -
The monolithic quad operational amplifier provides an inexpensive way to increase display capability of a standard oscilloscope. Binary inputs drive the IC op amp; a dual flip-flop divides the scope"s gate output to obtain channel selection signals. All.... -
This is a very simple design for a phantom supply. This design will work with microphones that have no problem with the phantom supply being only 15V. It also has to be noted that, at high SPL, distortion can become intolerable (totally depending on.... -
This circuit is a static SCR switch for use in a dc circuit. When a low power signal is applied to the gate of SCR1, this SCR is triggered and voltage is applied to the load. The right hand plate of C charges positively with respect to the left hand plate.... -
This circuit uses two balanced modulators to produce a DSB signal and then reinsert the carrier, except t.. -
In the circuit shown, a CMOS op amp controls the current through a p-channel HEXFET power transistor to maintain a constant voltage across RL The current is given by: 1 ~ VREF/Rl. .. -
This circuit employs a potentiometer as the weight sensing element. An object placed upon the scale displaces the potentiometer wiper, an amount proportional to its weight.. -
IC1a, IC1b, and IC1c of the quad two-input NAND gate 4011 are connected as an astable multivibrator; IC1d is connected as an inverter. Terminals 3 and 11 of the 4011 produce square waves with opposite phases. The square waves, eP, at the output of IC1a,.... -
The diode rectifies the ringing signal to supply the operating power to the audio relaxation oscillator made up of LI, L2, Rl, R2, and C. Moreover, L2 together with Ql acts as an opto-isolator, totally isolating the telephone line from the rest of the.... -
This Project Automatic Room Light Controller with Visitor Counter using Microcontroller is a reliable circuit that takes over the task of controlling the room lights as well us counting number of persons/ visitors in the room very accurately. When somebody.... -
Both circuits use the GE. SC146B, 200 V, 10 A Triac as load current contacts. These triacs are triggered by normal SBS (2N4992) trigger circuits, which are controlled by the photo-Darlington, acting through the DA806 bridge as an ac photo switch. To operate.... -
The darkroom timer/controller uses few external components: a display, a digit driver, keyboard, and output switching devices. A 4-digit common-cathode LED display is desirable for dark room environments. The time base is provided by shaping up the 50/60 Hz.... -
A simple, time-honored approach is to use one or more 74*245 chips (normally the 74AC245 is used for maximum current capability) to provide motor drive current. Here, each channel of drive power is provided by one or more buffer on the chip... -
The controller is a prototype and works well in my plane with 7 cells and a Graupner-Speed 600... -
This circuit was submitted by Adam from Canada who is still at school. I have provided the text. The two transistors are used as a direct coupled switch, Adam used 2SC711 but any general purpose transistor will do e.g. 2N3904, BC109C...
