New Circuits Page 208
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This is one of the most accurate and simplest LC inductance / capacitance Meters that one can find, yet one that you can easily build yourself. This LC Meter allows to measure incredibly small inductances starting from 10nH to 1000nH, 1uH to 1000uH, 1mH to....
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Digital ICs and opto-isolators provide the drive for this TMOS servo amplifier, resulting in fewer analog circuits and less drift. Fast and consistent turn-on and turn-off characteristics also enable accurate analog output results directly from the digital....
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This page features a replacement circuit for the LM3909 LED Flasher / Oscillator using discrete components. The circuit is functionally the same as the integrated LM3909 but has a minor variation of the components used. Naturally the circuit will not be as....
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The reading lamp consists of a small solar panel, a standard UPS style lead acid battery, and an LED circuit board. The circuit board contains a low power solar charge controller (regulator), a set of 8 white LEDs, a switch, an LED current regulator, and a....
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A monostable relay has two states: operative when a large enough current flows through its coil and quiesc..
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The circuit uses a NTE1690 DTMF dialer chip and a PIC16F690 microcontroller. Because this is an IP phone and I cannot just send the DTMF tones over the line, the easiest place to plug in the box is between the phone and the handset. The box has two RJ9 ports....
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Capacitor Cl is charged to +28 V through Rl and stores energy for firing the squib. A positive pulse of 1 mA applied to the gate of SCR1 will cause it to conduct, discharging Cl into the squib load XI. With the load in the cathode circuit, the cathode rises....
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If you are interested in model aeroplanes and have the capital, a radio controlled electric park flyer is a must have. An RC aeroplane under 400 grams floats around like the rubber models of my youth and contact with the ground doesn`t seems to involve that....
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This meter differs from the norm in that it does not use a D`Arsonval movement or digital display to give a reading of the input frequency. Instead, the measured frequency is read from a hand-cali-brated dial. Any audio signal applied to the circuit is....
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Simple and low cost. The optimal supply voltage is around 50V, but this amp work from 30 to 60V. The maximal input voltage is around 0.8 - 1V. As you can see, in this design the components have a big tolerance, so you can build it almost of the components,....
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This simple tone control can be used in may audio applications. It can be added to amplifers, used as a stand alone control module, or even built into new and exciting instruments. It's one IC construction makes it a very compact circuit, as only a few....
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This circuit has `suffered` a lot of modifications over its long life... Even the lettering on the integrated circuit was partially erased of the years.
The main motive of the mods was not that the circuit didn`t work right, but were several tries to add....
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This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply.....
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The common JFET current-source in Figure 1a has average output impedance and depends heavily on the JFET`s VP and IDSS variations. These manufacturing variations limit the initial accuracy of the current setpoint that the circuit can obtain with a fixed R1.....
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The 555 is a monostable that wants a negativegoing trigger. If the pulse you"re feeding it with is positive-going, you can run it through an inverter made up of either an inverting gate or, if you"re tight on space, a single transistor. Both ways are....
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A pressure sensor (IC4) is used with a dc: amplifier to convert the bridge output (IC4) to a single-ended voltage. ICld provides a reference voltage for setting barometric pressure. IC3 is an A/D converter manufactured by Intersil. This drives an LCD....
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Functions are provided to set the temperature read interval and the FTP interval for upload, The program alters a sample file called base.html and replaces variables in it with information from the PC. When run the program can be minimised at which point it....
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The sensing circuit consists of a 741 op amp set up as a voltage comparator, using a zener diode as a voltage referen..
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Using a pickup coil to drive an amplifier (IC3A-B-C-D), this meter circuit can be directly calibrated in field-intensi..
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The HT-12E is a CMOS IC. This encoder serially transmits data as defined by the state of the A0 to A7 and D0 to D3 input pints. On power-up, the DOUT pin is low. The HT-12E begins a 4-word transmission cycle on receipt of a transmission enable, or TE,....
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The circuit consists of a frequency modulated oscillator, an audio preamplifier with pre emphasis to supply the frequency modulating signal, and a buffer amplifier to drive the antenna connector. Oscillator's frequency is determined by L1 resonating with the....
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The schematic shows a 50W power supply with a 5-V 10-A output. It is a flyback converter operating in the continuous mode. The circuit features a primary side and secondary side controller will full-protection from fault conditions such as overcurrent. ..
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You can obtain well over 360° of phase delay by cascading two monostable multivibrators. In a typical configuration, a single monostable multivibrator is used to introduce delay in a pulse train; the multivibrator triggers on each incoming pulse, provided....
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This circuit prevents making transmissions that are too long, which "time out" repeaters and/or tie up a communicatio..
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Push-pull outputs are used in this transformer-coupled dc-dc regulating converter. Note that the oscillator must be set at twice the desired output frequency as the SGI 524"s internal flip-flop divides the frequency by 2 as it switches the PWM signal from....
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The ATMEL, with family AVR, was consolidated in the field of microcontrollers. The microcontrollers are, providing fast core and a variety of peripherals. These features continue to occupy the attention of engineers and earn their preference. The developer....
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The circuit protection output of power amplifiers and loudspeakers, dispose certain interesting elements, as the isolation of loudspeakers from the exit of amplifier, when is presented continuous voltage in his exit or when the temperature of heatsink, goes....
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The project described in this article is a constant Q, fully expandable graphic equaliser. Where most "conventional" graphic EQ circuits have a Q that is dependent on the setting of the pot, this one maintains the same Q at all settings. This is achieved by....
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A few months ago, I decided to build a compact, yet effective alarm. My demands were:- simple construction, reliable operation, very small power consumption, and, most of all, small size. I started with CMOS logic gates, but was soon forced to abandon the....
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This power supply uses an LM317J adjustable regulator and an MJ2955 pass transistor. Ql and U2 as..
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Our CONTINUITY TESTER gives an audible indication of continuity between the probes so you can keep your eyes on the probe tip. Secondly its response-time is very short so that you can make lots of tests very quickly while listening for the beep.
And....
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This design is for an external signal strength meter that is analog, digital, and audible for mobile transmitter hunters. The S meter also incorporates a gain circuit. The digital LED bar graph display has a very fast response time. The 3.3-KO resistor....
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There is, and always has been, a marked lack of good, inexpensive lighting controllers for small theatre groups or musicians. The LX-800 Lighting System was designed with these applications in mind...
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This transmitter uses a 741 op amp as a high-gain audio amplifier, which is driven by a microphone. The output of the 741 is coupled to Ql, which serves as the driver for a LED. Potentiometer R1 is the amplifier`s gain control. Miniature trimmer resistor R6....
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A voltage-variable capacitance tuning diode is placed in series with the crystal feedback path. Changing the voltage on VR varies the luning diode capacitance and tunes the oscillator. The 510-KO resistor, R1, establishes a reference voltage for VR -ground....
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This circuit controls a solenoid by the operation of a single push-button switch. The circuit will supply loads of over 1 A and can be operated up to a maximum speed of once every 0.6 second. When power is first applied to the circuit, the solenoid will....
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Using inexpensive components, you can fit a simple probe circuit into a pencil-sized enclosure. When both LEDs are on, the probe indicates the presence of an ac voltage; either LED alone indicates the presence and polarity of a de voltage. The....
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This circuit uses a pair of Zener diodes to monitor battery voltage of a 12-V battery. If below 11 V, 1)1 ceases to conduct, pin 3 of 102 goes high, setting FF IC2 turning on Ql, Kl, and the battery charger...
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For wiring to the microphones I used a wiring harness from an old portable headphone set. Find one with a 90 degree miniplug if possible. Cut off the headphones, solder the condensor mics to the leads and voila. Anything larger than the pencil soldering....
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This is an image Schematic. No Description available...
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This is a circuit that generates white noise, rolled-off to drive earphones or a small speaker. White noise creates is a "rushing" sound, which sounds something like air rushing by your ear(s). White noise would be flat with frequency, and since this circuit....
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In Figure 1 , a basic and versatile 5V supply uses a zener diode and an emitter-follower transistor. You must calculate and design the transformer such that Q1 is close to saturation at low mains voltages and nominal output current. Additionally, you must....
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Transistors Ql and Q2, with feedback provided via Cl from the collector of Ql to the base of Q2, forms a voltage-controlled oscillator (VCO). De- pending on the voltage applied to Q2 "s base, the VCO frequency ranges from around 60 Hz to 7.5 kHz. The....
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When setting up photographic floodlamps, it is sometimes desirable to operate the lamps at lower power levels until actually ready to take the photograph. The circuit allows the lamps to operate on half cycle power when the switch is open, and full power,....
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No description available...
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Many amplifiers have phono inputs for connecting record players to the amplifier. Phono input is designed to take a up to few millivolt signal from phono pickup and amplify it. The amplifier stage does also some equalization based on standardized RIAA curve.....
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This 49-MHz FM transmitter consists of an audio amplifier, a low-pass filter, three RF stages, and a regulated-dc power supply. The output is about 16 mW into a 50- load. This transmitter can be used in many 49-MHz applications, such as in a baby monitor,....
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This 3A charger was originally designed to work with small batteries like those used in motorcycles. In principle it
can be used to charge car batteries also but will take a lot longer.
The charger below charges a battery with a constant current to....
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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 the....
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Use this circuit to keep the fluid level of a liquid between two fixed points. Two modes, for filling or emptying are possible by simple reversing the contact connections of Kl. The loads can be either electric motors or solenoid operated valves, operating....
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The circuit`s 90% conversion efficiency offers a distinct power-saving advantage over resistor-limited and linearly regulated designs. It might appear that a series-LED connection is unsuitable for applications in which some (but not all) LEDs must be off. A....
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Safety devices like fuses provide protection against excess current, but do nothing for transients and short duration spikes of high voltahe on the power supply lines.This circuit uses the "crowbar" method and provides fast protection against transient....
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The schematic below illustrates 4 methods of controlling a relay with a digital logic signal. Figure (A) can probably be used in most cases where the relay coil requires 100 mA or less and the input current is 2 milliamps or more. The resistor value (R) is....
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The system shown consists of the HA-2542, a small 12-Vdc motor, and a position encoder. During operation, the encode..
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A circuit of measurement of level based on a typical application of National. The circuit round the IC1 makes input adaptation and amplification with the trimmer TR1 [GAIN]. The circuit round the IC2 makes half-wave rectification of acoustic signal. With....
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For those who don't know what a Theremin is, it's one of the first synths ever made and it's named after his inventor, Mr. Leon Theremin (a Russian guy). It's perhaps the only instrument which you don't actually touch: there's an antenna, and as the musician....
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This is not a sophisticated automatic keyer but it is lot QRP to build and to have fun operating it.
When the paddle is connected to the DOT terminal, C1 starts to charge. When C1's charge reaches sufficiently high value, it causes the transistor BC157B....
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The circuit is activated by an LED/photoresistor isolator (Ul), which is a combination of a light-dependent resistor (LDR) and an LED in a single package. That device was chosen because of its high isolation (2000 V) characteristic, which is necessary....
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This circuit could be used to drive a monostable relay by a singol momentary switch. Powered by 24 Volts it works for a 12 Volts relay. When the button is pressed Q1 is energized and the capacitor charges, while the relay coil is shorted. Once the button is....
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I had a Basic Stamp project that needed to measure a nominal 12 volt battery, and I wanted a simple solution. This is the simplest I could come up with. The 555 timer will put out positive pulses. The pulse width is inversely proportional to the difference....
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A muscle-powered capacitor charger contains only a few components: a storage capacitor, a bridge rectifier, and a voltage-limiting zener diode that protects the capacitor from excessive voltages (Figure 1)...
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This is a simple use of the PIC 16F84 about a diode tester. Test procedure : We set «1» to PB0 and «0» to PB3. If diode is ok and opens, then at PA0 we have «1». If PA0 is «0», then the the diode has problem. With the program we manage what the PIC will do....
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The SCHAER+ programmer is a programmer for PIC18 family from a PC parallel port (LPT). It is derivated from the SCHAER programmer I used to download my projects in PIC1684. The SCHAER+ programmer should be improved to use a USB connection, without any....
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The spectrum analyzer circuit takes a stereo input and displays a volume by
frequency display on a standard PC monitor. Finding the amplitude of a waveform at
each frequency and then mapping this to the screen using a discrete number of levels
achieve....
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This circuit is designed to provide an inexpensive way to to create a High Impedance Voltmeter while making use of an inexpensive analog or digital multimeter. When measuring voltages in high resistance circuits the resistance of the voltmeter itself has an....
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This article describes a 2-Digit Counter using a Microchip PIC12F629.
It shows what can be done with an 8-pin chip having just 5 output lines and one input line.
The chip drives two7-segment displays and this would normally require 7 lines to drive the....
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This is a page of analogue interfaces for joysticks. Although these interfaces have been developed for use with 4QD`s controllers they will have plenty of other uses. Also because of the development history, we have printed circuit boards available (either....
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The µPC8211TK, µPC8215TU, and µPC8226TK are silicon germanium (SiGe) microwave monolithic integrated circuits (MMIC) designed as low noise, high-gain amplifiers for GPS and mobile communications. These ICs are manufactured using our 50 GHz fmax UHS2 (Ultra....
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This rf detector can locate low-power transmitters (bugs) that are hidden from sight. It can sense the presence of a 1-mW transmitter at 20 feet. which is sensitive enough to detect the tiniest bug. As you bring the rf detector closer to the bug, more and....
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The circuit is based on operational amplifier IC1 used in the noninverting amplifier mode. Rl and 2 set the gain at about 500. RV1 (sensitivity) biases the noninverting input to the negative supply. Ql provides the relatively high trigger current required by....
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The LTC3455 seamlessly manages power flow
between an AC adapter, USB cable and Li-ion battery,
while complying with USB power standards, all from a
4mm ½§ 4mm QFN package. In addtion, two high efficiency
synchronous buck converters generate low voltage....
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This frequency doubler uses one CMOS quad, two input NAND gate package type 4011. The frequency doubler proper consists of an inverter IC1B, two differentiating networks R1/C1, R2/C2 and NAND gate IC1A, IC1C and IC1D function as input and output buffers. In....
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This circuit is taken from the Progressive Communications Receiver in most of the recent ARRL Handbooks. Values for the 40 meter band are shown. If you want the ultimate in a bandpass filter for 40 or 20 meters, check out the bandpass filters in "An....
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Most of you will certainly already installed on your computer one of the many software tools move freely from hand to hand and is suitable for programming the PIC 16C84. One of the most popular of this kind is the RIR02 of Silicon Studios. The circuit....
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Numbered components are so designated for PC-board layout purposes. C5 and C8 are disc ceramic. C6 and C7 are tantalum or electrolytic. Rl, R2 and R3 are Vi W carbon composition resistors. Silver-mica capacitors may be substituted for polystyrene (P) types...
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Each of these ways have their own advantages and disadvantages. The multiple transformer way is easy to start small and work up to only as many power supplies as you need. It does, however, get more expensive as the number of supply outputs goes up. Suitable....
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It is usually desirable to have the remote transmitter of a 4 to 20 mA current loop system powered directly from the transmission line. In some cases, this is not possible because of the high-power requirements set by the remote sensor/transmitter....
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In this circuit, a full-wave bridge is switched to a full-wave center tap to reduce regulator dissi..
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The JavaBot1 is a small line following robot designed to follow a black line drawn on a dry erase board. It is designed to follow very tight curves. The software still has lot`s of room for improvement but works well as is. The JavaBot1 uses 2 Cirrus CS-70....
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The front end of the DAC is configured differentially using dual eight-input IC multiplexer 1H6216 and three LM156 op amps. Following the differential amplifier is the programmable gain stage discussed earlier, with a low-pass filter on the output feeding....
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Make your own solar powered robot at home using things you probably already have. Transistors, resistor, capacitor, solar battery and flashing LED are available at any electronic store, if you don't already have them. Solar cells out of calculators work as....
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sPlan is a software with already many thousands enthusiastic users. You need a software to design your schematic circuit diagrams easy and fast? You wont get pass sPlan! No matter if you only want to sketch a little circuit diagram or if you need to design a....
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Many designers use small pulse generators to delay signals, open timing windows, drive sample/hold circuits, and other functions. Though the hardware implementation of these generators does not pose any problems, the lack of dedicated circuitry sometimes....
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This generator will supply sine, triangular, and square waves from 2Hz to 20kHz. This complete test instrument can be plugged into a standard 110 Vac line for power. VoVT will be up to ±25 V (50 V pk-pk across loads as small as 10 0 (about 2.5 A maximum....
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Can be directly connected to CD players, tuners and tape recorders. Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohm.
Schematic shows left channel only...
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This is a very simple, low cost, Hi-Fi quality power amplifier. You can build it 5 ways, like its shown in the table (from 20 W to 80 W RMS). The first thing that you must do, is to measure the end transistors (T3 and T4) amplifying coefficient, the hfe or....
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I Specifically Designed this circuit to charge 2 Batteries for my Digital Cameras, but it can be modified to charge 3, 4, 5 or more cell. However, It will Not Work with only One Cell as that voltage is too low for even this LDR Discharge Regulator. If you....
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This supply can serve as a battery eliminator for various devices (such as tape recorders, small..
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The RGB LED driver described on this page uses logic level 'N' channel MOSFETs which allow it to control LED arrays or lamps at up to 5 amps per channel without heatsinks.
The driver uses exactly the same firmware as the small RGB LED driver shown in the....
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The PIC16F870 keeps track of battery voltage as well as both charging and discharging currents. It also drives the 4 digit display, and switches the AC and load relays. The basic operation is as follows: While AC power is available, the battery voltage is....
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No description available...
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Current-limit switches are virtually ubiquitous in system controls. They provide a safe means for regulating the current delivered to a load circuit. The switches allow the load current to increase to a programmed limit but no higher. Typically, the current....
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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....
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The IR2156 incorporates a high voltage half-bridge
gate driver with a programmable oscillator and state
diagram to form a complete ballast control IC. The
IR2156 features include programmable preheat and
run frequencies, programmable preheat time,....
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the entire circuit is comprised of integrated circuits. This makes for some easy organization when it goes to the circuit board for soldering. In addition, I used only 3 of the pins on the 3rd nixie tube for the hundreds position in the display. Since I was....
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This box is a set of nine relaxation oscillators. It blinks random patterns and looks cool. When the voltage on the capacitors charge to 65 volts, the neon gas ionizes and discharges the capacitors to 55 volts. The frequency can be simply calculated from the....
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The infrared remote-control tester uses a sensitive PN-type solar sensor that is connected directly to a Darlington amplifier made up of transistors Q1 and Q2. Biasing is provided by R1 and PI, a variable resistor that serves as a sensitivity control. The....
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This strobe gives a visual indication of a sensor input. The input signal causes Ul, a light dependent resistor, to chaijge CI..
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Sawtooth wave generators using opamp are very common. But the disadvantage is that it requires a bipolar power supply. A sawtooth wave generator can be built using a simple 555 timer IC and a transistor as shown in the circuit diagram. The working of the....
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In this circuit, there are two feedback paths around an op-amp. One is positive dc feedback which forms a Schmitt trigger. The other is a CR timing network. Imagine that the output voltage is +10 V. The voltage at the noninverting terminal is +15 V. The....