Top Circuits Page 48
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Various embodiments of the BB metal detector have been published, and it has been widely described in the press as a new genre. Instead of using a search and a reference oscillator as with BFO, or Tx and Rx coils as with IB, it uses two transmitters or....
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A single chip metal detecor with a range of a few inches. This is useful for decting nails or screws in walls and floors, or for locating buried mains cable. The heart of the circuit is a single IC the CS209A made by Cherry Semiconductor. The detector, is a....
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This circuit detects metal and also magnets. When a magnet is brought close to the 10mH choke, the output frequency changes. ..
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A single chip metal detecor with a range of a few inches. This is useful for decting nails or screws in walls and floors, or for locating buried mains cable. The heart of the circuit is a single IC the CS209A made by Cherry Semiconductor. The detector, is a....
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LED 1 will light and the buzzer turns on when the coil is changing inductance. The setup is easy, VR1 is adjusted ( away from any metal objects ) so that LED 1 will light and the buzzor sounds on, and then VR1 will be trimmed until led and buzzer are off...
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A Simple design based on a CS209A IC that can give surprising results and draws very little current from a 9 volt battery. It worked good on the Bench, But not so good outside for general metal detecting. But Definately a good design for detecting studs in a....
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This basic oscillator will detect the Earth magnetic field. The ferrite rod and coil are taken from an old Medium Wave receiver and a small magnet is glued at one end. Tune to a medium wave commercial station until you hear a beat note. Any movement of the....
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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....
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Our project demo is also successfully finished and the only thing left to do for this project is the final project report which is due June 15 since we are integrating that report with a conference paper. This is the last update I`ll be making to our....
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The Metal detector project is designed for metallic body detection by
sensing variations in high frequency Eddy current losses. Using an
externally-tuned circuit, they act as oscillators. The output signal
level is altered by an approaching metallic....
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As shown in the following figure is double coil metal detector circuit. The probe by the probe, a transmitter, a receiver, a timer and sound transmitters and other components. ..
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The simple and inexpensive circuit in Figure 1 monitors the liquid level in a container. The piezo crystal, carefully mounted at the bottom surface of the container, receives it activation from the 74HCT14 hex Schmitt trigger. The crystal generates stable....
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Save fuel bills and the economy of the planet with this circuit. SW1 is a normally open press button switch which allows you to view the level of hot water in a hot water tank. When pressed the voltage difference at the junction of the thermistor and preset....
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The circuit uses approximately 150 µA of current, allowing the circuit to steal its power from the bus via the Schottky diode, D1. Because the circuit is sensing water that is part of the electrical circuit, you should use an ac-coupled signal to avoid....
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Following a hunch, the author discovered (or re-discovered?) that all plants carry an electric charge relative to the ground. This charge is more or less constant regardless of the size of the plant - a kind of "background voltage" in nature. This electric....
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This simple device checks if their is water in a pot plant. You stick the two probes(paperclips)into the pot plant and if the LED lights, it means there is water in the pot plant...
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In his circuit Marin has used two transistors wired as a high gain compound pair. Transistor T1 may be a 2N2222A and T2 a BC108. The current gain will be the product of each transistors beta, which will be a minimum of 140 x 110 or 15400. The power supply....
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The circuit uses a 555 timer wired as an astable oscillator and powered by the emitter current of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. As the probes get wet, a small current flows between base and....
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A circuit that offers visual indication of fluid level in a vessel, with a switchable audible alarm. Example uses would be to monitor the level of water in a bath or cold storage tank. Conductance is the reciprocal of resistance. The conductance of fluids....
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A flashing LED signals the necessity to water a plant
Very low current consumption - 3V powered circuit. This circuit is intended to signal when a plant is needing water. A LED flashes at a low rate when the ground in the flower-pot is too dry, turning off....
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This circuit will emit an intermittent beep (or will flash a LED) when the water contained into a recipient has reached the desired level. It should be mounted on top of the recipient (e.g. a plastic tank) by means of two crocodile clips, acting also as....
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The water detection time is less than 10 seconds. Since the microcontroller enters a low consumption state between readings to preserve battery life, this state is always 10 seconds long. If water reaches the probes while being in the low power state it will....
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IC1D is a CMOS Schmitt trigger oscillator at about 2KHz. It starts and continues to oscillate with a supply down to 1.24V (the lowest output voltage of my LM317 variable power supply) or less. IC1A is an inverter. IC1B is a Schmitt trigger NAND gate. Its....
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I found some similar circuits but aren't good enough for me. Some circuits measure the water's resistance to determine the level. That is dangerous for drinking water (contamination) or explosive liquids because electricity is in contact with water. The....
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A simple Sump Pump Control Circuit using NE555...
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This circuit gives out an alarm when its sensor is wetted by water.
A 555 astable multivibrator is used here which gives a tone of about 1kHz upon detecting water.
The sensor when wetted by water completes the circuit and makes the 555 oscillate at about....
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This circuit not only indicates the amount of water present in the overhead tank but also gives an alarm when the tank is full.
The circuit uses the widely available CD4066, bilateral switch CMOS IC to indicate the water level through LEDs.
When the water....
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This moisture detector with pump controller is built around the special purpose LM1830 IC. The LM1830 is designed to detect moisture by passing an AC current through a set of probes. An internal comparator compares the resistance of the probes to an internal....
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Electronic ignition circuit for the water heater is shown. When you open the faucet, switch K 3V battery, since the charging C2 need room, so VT6 is off, the power supply while..
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Electric water heater temperature control circuit, with water level indication, temperature and anti-dry, leakage power automatic protection function, safe and reliable. (1) Th..
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A control two (namely a frequency control two motors) Frequency constant pressure water supply control circuit shown in Figure 5-23. Figure, 1,2 fault output terminal; 6,7 anal..
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After 3t40V power Sutra T seats is reduced to 6.3V low voltage by VDi - V sulfone full transition rectified. c1 filter provide after - when caution circuit NI/555 operating vol..
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Are the flowers in pots need watering if the soil surface moist observation alone is sometimes unreliable. For this reason, the production of dry flower instructions which, whe..
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As shown in FIG lantern control circuit 30 outputs can be controlled by an external driver circuit 30 lights for water sports, as large decorative lantern controller circuit as..
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Automatic water tank as shown in the circuit diagram. IC is PSSR AC solid state relay, which is developed in the SSR on the basis of a new type of solid-state relays AC non-con..
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Autotransformer voltage starting, starting time 30-60s adjustable. Figure, SDJ electrode liquid level sensor HJ-13-type, pump control system box with HKD-21B type, 1MK level mo..
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Boil water on the kitchen gas stove, once the water is boiling, if not stalled, spilling boiling water will come out, the flame extinguished. Gas spills, very safe. Water can s..
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By the oscillator circuit, a counter, Iseki circuit of three parts. Oscillation circuit by the time base manifold NE555 and several external RC element. Its function is to prov..
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Circuit, if the thermistor K273 temperature reaches the setting level or not two sensor electrodes immersed in liquid, so that it is heated by turning on the relay. This ensure..
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Darlington phototransistor type light-triggered switching circuit application As a result of the sub-type Darlington phototransistor and the op amp, so very faint light can fli..
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My circuit adds a transistor, to add feedback, and two resistors, to tailor the range of the control, with the result that a single-turn potentiometer gives a control range of about 2 to 30 microamps. I installed my circuit in a small plastic box, and....
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This idea demonstrates three uses for the humble LED. The circuit in Figure 1a forms a simple light detector that latches and turns on an LED when the ambient light exceeds a preset limit determined by potentiometer P1. LED D1 is both the indicator and the....
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Many people favor different light and temperature settings for different rooms depending upon their mood or whether they are working or relaxing. The circuit in Figure 1 controls the intensity of the artificial light in a room and monitors the temperature of....
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This page presents information on infrared - `Across The Track` train detection circuits. The circuits are designed around the LM339 comparator chip and can use a wide assortment of matched infrared - emitter / detector pairs. The basic circuit shown below....
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In some applications, you need to detect light signals in the presence of background light whose intensity can change by orders of magnitude. The circuit in Figure 1 uses an integrated photodiode/amplifier (OPT201) in conjunction with an integrator that....
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The sensors used are silicon phototransistors and Cadmium Sulfide (CdS) photocells. Both of these sensors allow less current to flow when they are dark than when lighted. Phototransistors change their conductance while photocells change their resistance....
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The circuit on this page is for a simple light detector circuit board that has 8 detectors that can be used with visible or infrared light systems. The detectors use LM339 voltage comparators as the active element.
Phototransistors or CdS photocells can be....
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This circuit is used to measure the current from a solar panel. It has very low power loss for currents in the 0-10A range. It also works as a general purpose DC current meter. The circuit can be used on either the positive or negative side of a DC circuit...
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The SPC2 is a solar power center, it can be used to handle all of the power functions for small 12 Volt solar powered devices. It contains a photovoltaic charge controller and a low voltage load disconnect circuit. The low voltage disconnect has a load....
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a more complex detector circuit which turns the relay on for an adjustable period of time. When the beam is broken, the LED goes on, your effect is powered, and capacitor C1 begins charging. As C1 is charging, the transistor will be kept on. Once C1 is....
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Darlington phototransistor type light-sensitive switch control circuit application As a result of Darlington type phototransistor do sensitive element, the low light sensitive ..
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When the phototransistor is stroken by IR light it conducts and the voltage between the 1Mohm resistor(arbitrary) and the phototrans drops from VCC to lower values. When the voltage drops lower than VCC/3 the 555 is triggered and goes high (from 0 TO VCC).....
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This is a simple circuit that does the day/night switchings you have in mind. POT1 is used to set the light level at which the circuit switches from enable to disable...
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This circuit give low level output, when exist enough lighting, that is a detector of light. It can give, say ,command turn on somebodies lights, when fall the dark. His exit is compatible with TTL level and it give low logic level, when phototransistor Q1,....
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This simple circuit using a single transistor turns ON the relay when light falls on the LDR.
The potentiometer is adjusted for the required sensitivity.
The power supply is 6V.
Be careful about the impedance of the relay. Its impedance should not be less....
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When the tank is cleaned the fish are removed and placed in a small amount of the tank water. The problem is that fish don’t like rapid temperature fluctuations. I guess a simple in tank or stick on thermometer would have done the trick but what is the fun....
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As shown in the circuit, there is the incident at the time, this circuit is connected with photoresistor LDR transistor is turned high or zero level. Amplification factor of tr..
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By the photosensitive resistor of this circuit is a circuit diagram of the automatic lighting for hospitals, dormitories corridor and public places. It automatically lights off..
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By the photosensitive resistor television automatic brightness adjustment circuit shown in Figure photoresistor and contrast potentiometer connected to the intermediate head. U..
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Supervisory circuits normally monitor a microprocessor`s supply voltage, asserting reset to the IC during power-up, power-down, and brownout. In this way, the circuit ensures that the supply voltage is stable before the microprocessor boots, thus preventing....
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The circuit in Figure 1 is a quasi-linear regulator. It functions as a source follower for input voltages greater than a preset level, determined by VR3. For input voltages lower than the preset level, the pass element, Q2, operates as a saturated switch.....
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You often need to know when a telecomm power supply`s output drops below its nominal value. The dropout generally indicates a failure and may dictate replacement of the supply or some other form of system maintenance. The circuit in Figure 1 uses an isolated....
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Low-cost microprocessor supervisors reset controllers when power-supply voltages fall below given levels. As added protection, you can also reset the microcontroller when the power supply is too high by combining a low-cost shunt-voltage regulator with a....
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The op-amp rectifier in Fig 1 operates from a single supply and provides a logic output and an LED that indicate the state of the input voltage. The input-state indications are handy for calibration. Because the circuit operates from a single supply, the....
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This circuit is so sensitive it will detect "mains hum." Simply move it across any wall and it will detect where the mains cable is located. It has a gain of about 200 x 200 x 200 = 6,000,000 and will also detect static electricity and the presence of your....
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LTC1043 can be .png">induced through any of its current shunt supply rails. Many cells and solar system applications..
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This circuit relies upon the extra high input impedance of a FET, and also demonstrates
the gate terminals sensitivity to changes in voltage. The gate terminal here is left open circuit, connected only to the "probe" this being just a few inches of bare....
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This simple circuit can detect the invisible fields of voltage which surround all electrified objects. It acts as an electronic "electroscope." Regular foil-leaf electroscopes deal with electrostatic potentials in the range of many hundreds or thousands of....
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In Fig.1 A precision DC under?voltage relay switch. The opamp is wind as a voltage comparator, with a reference voltage applied to pin 2 and the test voltage applied to pin 3: the relay turns on when the pin 3 voltage exceeds that of pin 2. The circuit can....
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The circuit will come handy when you have to follow the mains wires buried in the wall or even water pipes provided they are not too far away (2-4cm max). It will also detect a conversation on a telephone cable without actually touching it (for testing....
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It operates by PWM (Pulse Width Modulation) - well, actually by PFM - Pulse Frequency Modulation. At power up, C1 charges up via D1 and R1. R2 will conduct, pulling the base of the emitter follower, Tr2, up and feeding gate voltage to the MOSFET. Tr4.....
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This circuit will automatically switch on several mains-powered "slave" loads when a "master" load is turned on. For example, it will switch on the amplifier and CD player in a stereo system when the receiver is turned on. It works by sensing the current....
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This circuit will detect AC line currents of about 250 mA or more without making any electrical connections to the line. Current is detected by passing one of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800....
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When the RTD temperature sensor further away from the amplifier, sensor lead resistance and the lead is vulnerable to interference and other issues will not be ignored. Circuit shown in Figure can solve this problem. The circuit uses a voltage-current ..
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By the voltage output type and angle UZZ9000 KMZ41 constitute detection circuit as shown, it is a + 5V power supply, RP1 ~ RP2 offset voltage adjustment potentiometer, RP3 ~ RP..
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Here is a diagram of the internals of the MAX232A. It shows a double charge pump voltage doubler and a +10v to -10v voltage inverter. The voltages output are used to generate the RS-232 compliant signals. The MAX232A has provisions for two serial ports on....
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This simple circuit can be used to control the volume of PC speaker. The volume can be adjusted to any value between total silence and full volume...
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This circuit is a simple adapter for PC parallel port to think that there is a printer connected to computer. This adapter is useful for testing printing speed with different software and as a part of your own designs.
You can use this circuit to connect....
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Its a very easy interface to build an requires only a few £/$ worth of components. A you can see by the picture on the right, there`s not much to it. To be honest, the pictur is misleading. This hamcomm interface has an added `extra` facility. The original....
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It can drive up to 128 individual relais, solenoids, motors, fireworks, pyrophones, etc. With a MIDI note-on message you may switch on one of the 128 LEDs (or relais). Outputs may be switched off by sending a note-off message, or by a note-on with zero....
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This is an improved version of the audio interface commonly used to connect a computer soundcard to a transceiver`s receive and transmit audio circuits. This kind of interface is used by computer programs that send and receive SSTV, RTTY, CW, PSK31 and....
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This page describes how to build an adaptor for the Dreamcast serial port that will allow you to connect it to any computer using a standard 9-pin DSUB connector. The main component is a MAX voltage converter, since the Dreamcast serial port uses CMOS (3.3V)....
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This project`s purpose is to design a fully automated machine for drilling a printed circuit board, (PCB) blank at a minimum cost and with the minimum amount of custom machining. This low cost philosophy is achieved by adapting the existing mechanical....
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PC parallel port was never designed to provide any output power to divices connected to it. it was only designed for connecting printer to your PC. But in this weird PC business everything changes. Suddenly the parallel port have become a port where you can....
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PulsePar turns a PC into a multi-channel pulse generator utilizing the parallel port. The period, duty and phase of each channel are adjustable so as to be used in PWM systems as well as in testing servo and stepper (stepping) motors. If you have an old PC,....
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The project we have chosen as our example is an RS232 to RS485 converter. This is a often needed device which can demonstrate a lot of principles of circuit design, and hopefully the finished project will be useful to some people, just as it stands. Without....
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This source code module provides the low-level control of the port, implementing code to control 12 outputs and read 5 inputs. This code was written for Borland C/C++ v3.1, but you should be able to adapt it for other compilers. You can view the source code....
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We have developed a powerful yet inexpensive and easy to construct experiment control system. The construction of the system together with the control software is described here. All circuits and software are free to download and use for nonprofit. The....
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The Dutch magazine Audio & Techniek once published an article about one-way loudspeakers that were based on Audax units 1. Although speakers using just a single full-range unit per audio channel were disregarded in audiophile circles (high intermodulation....
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This ROM emulator improves the easiness to build/use it by reducing down its function which can be used as a ROM emurator. The kind of the ROM types to be emulated, are 2764, 27128 and 27256. The debugging capability is only Load and Run, omit functions such....
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ome games are easier to play with digital joystick instead of analogue type. Unfortunately PC has only analogue joystick connector, which makes it impossible to connect normal digital joystick to it. But with a little adapter circuit, it is possible to use....
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This incredibly simple thermometer plugs on any free serial port. Does not make use of any programmable components as microcontrollers. It gives temperature readings accurate to 0.5°C with no calibration. It's cheap, so I've put one on any PC I use. And it....
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This simple circuit allows you to record any IR remote control signal on your PC, and then play it back. This is particularly useful if you want to control appliances such as TVs, VCRs, CDs etc. from your computer. The device simply connects to the parallel....
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Most of the CDROMS available have an Audio-Out Output to either plug in the headphones or connect it to an amplifier.
This circuit enables one to use the CDROM as a stand alone Audio CD player without the computer.
This circuit is nothing but a power....
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Here is a circuit for using the printer port of a PC, for control application using software and some interface hardware. The interface circuit along with the given software can be used with the printer port of any PC for controlling up to eight equipment .....
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This circuit is a simple adapter for PC parallel port to think that there is a printer connected to computer. This adapter is useful for testing printing speed with different software and as a part of your own designs. You can use this circuit to connect....
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The following circuit is an example how to get power from RS-232 serial port. It gives regulated +5V power for logic circuits and also unregulated positive and negative power supplies for RS-232 transmitting circuit. The circuit gives only few milliampres....
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This is a simple serial port buffer circuit I designed for a friend to speed up his SLIP connection in campus computer network "TRINET" of Helsinki University of Technology. The problem in the network was that the RS232 commections from rooms to terminal....
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RS-232C serial port lines are quite prone to be damaged by overvoltages. The damaged to computer serial ports have become more and more expensive to replace because of higher intergaration: usually you have to buy new motherboard if one serial port in it....
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This smartcard adapter follow exactly the specification ISO 7816. Also, the protocol is the "asynchronous half duplex T=0 protocol" with "active low reset" and "inverse convention" as defined in this standard.
The following description may be used in order....