Top Circuits Page 196
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Detects the amount of salt contained in liquid foods, Three-level LED indicator This circuit was designed to detect the approximate percentage of salt con....
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This circuit runs a fast battery test without the need of power supply or expensive moving-coil voltmeters. It features two ranges: when SW1 is set as shown in the circuit diagram, the device can test 3V to 15V batteries. When SW1 is switched to the other....
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Everybody who regularly works with servos will know several instances when such a servo tester will come in handy. The function of a servo tester is to generate a pulsing signal where the width of the positive pulse can be varied between 1 and 2 ms. This....
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The main part of this circuit is the LM386 amplifier chip. It also uses a transistor input to buffer the input signal and provide extra gain for the LM386....
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This simple alarm circuit was designed for use in a combined garage and rumpus room. It can be assembled on Veroboard and uses just one IC plus a handful....
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The circuit presented here is a very simple and yet highly effective alarm system for protecting an object. The circuit requires no special devices and can be built using components that you will no doubt be able to find in the junk box. The alarm-triggering....
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This circuit is essentially an amplified crystal set. The inductor could be a standard AM radio ferrite rod antenna while the tuning capacitor is a variab....
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There are not many AM transmitters that are easier to build than this one because the inductor is not tapped and has a single winding. There is no need to wind the inductor as it is a readily available RF choke (eg, Jaycar Cat LF-1536). To make the circuit....
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This audio peak detector allows a pair of stereo channels to be monitored on a single LED. Identical circuitry is used in the left and right channels. Use....
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This handy circuit can be used to charge from one to 12 NiCd cells from a car battery. Up to six cells can be charged with switch S1 in the normal posit....
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This circuit came from a need for a quick and dirty network tester that could be operated by one person. All the commercial units I tried required a per....
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This circuit came from a need for a quick and dirty network tester that could be operated by one person. All the commercial units I tried required a person at the other end to check the remote LEDs, as the transmitters could not be made to cycle through....
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This simple combination lock accommodates codes from 1-9 digits long, with the only restriction being that the same digit cannot be used twice. The circui....
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The circuit is intended for carrying out harmless experiments with high-voltage pulses and functions in a similar way as an electrified fence generator. T....
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This is an automatic emergency lamp with day light sensing, means it senses darkness/night and turns ON automatically. Similarly it senses day light and turns OFF automatically. A simple emergency lamp which does not require any special equipment; even a....
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Simple triangle-wave generators have a weakness in that the waveform of their output signal normally cannot be modified. The circuit presented here makes....
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These two headlight reminder circuits are easy to install and operate on the KISS (Keep It Simple Stupid) principle. The simple circuit involves adding just a 12V piezo buzzer between the lights circuit and a door switch. The buzzer sounds if the lights are....
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The debate still goes on as to which are better, valves or transistors. We don t intend to get involved in that argument here. But if you can t make your....
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Lots of consumer electronic equipment like TV sets, VCRs, CD and DVD players employs infrared remote control. In some cases, it is desirable to extend the....
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This circuit uses a thin piezoelectric sensor to sense the vibrations generated by knocking on a surface; eg, a door or table. Basically, it amplifies and....
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This simple logic probe has both LEDs on with no signal at the input but due to the nor gates connected to the probe, indicates correctly when a high or low signal is present. It also works correctly for pulse trains. Normally both LEDs are forward biased....
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A simple NiCd charger can be built using junk box components and an inexpensive LM317 or 78xx voltage regulator. Using a current limiter composed of R3....
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Sometimes the need arises to construct a really simple oscillator. This could hardly be simpler than the circuit shown here, which uses just three compone....
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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....
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In the circuit here it simply biases the BC558 which, in turn, makes LED D1 flash in sympathy with the telegram from the remote control. The preset in the circuit determines the sensitivity...
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This project will indicate the volume level of the audio going to your speakers by lighting up LEDS. The LEDS can be any color so mix them up and really make it look good. The input of the circuit is connected to the speaker output of your audio amplifier.....
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This simple telephone switching system is designed by Dr. Mustafa Kemal PEKER for training purposes. All responsibility is belong to user. Schematic and c....
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This circuit was requested by an school teacher. It is a simple intercom that anyone can put together and get to work. It is based on the LM380 IC chip. T....
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As the title implies, the present circuit is intended to convert sinusoidal input signals to TTL output signals. It can handle inputs of more than 100 mV....
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Using any camera in a dull or dark environment generally requires the use of supplementary light. This is a standard technique, and even where adequate na....
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While smoke alarms are quite cheap devices, the cost of 9V batteries quickly exceeds their purchase price. Added to that is the irritation of random beeps....
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Ordinary LED flashers turn the LED on and off abruptly, which can get a little irritating after a while. The circuit shown here is more gentle on the eyes....
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Switched mode power supply units (SMPSUs) are popular but difficult to build oneself as well problematic when it comes to understanding their design princ....
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This device is designed to be a simple, inexpensive comparator`, intended for use in a solar cell power supply setup where a quick too low` or just right` voltage indicator is needed. The circuit consists only of one 5V regulator, two transistors, two LEDs,....
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The PR4403 is an enhanced cousin of the PR4402 40mA LED driver. It has an extra input called LS which can be taken low to turn the LED on. This makes it v....
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You can save on your electricity bills by switching to alternative sources of power. The photovoltaic module or solar panel described here is capable of d....
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Here is a solar powered Flasher to scare away the nocturnal animals like bats and cats from the farm yard or premises of the house. The brilliant multicol....
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This is a simple NiCd battery charger powered by solar cells. A solar cell panel or an array of solar cells can charge a battery at more than 80 % efficie....
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This simple circuit shown int the schematic diagram actives the switch using sound. We can use this circuit for various applications, such as automatic (s....
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In normal suburban driving you pass through so many different speed zones that it can be a nuisance having to switch speed settings. The speed display can....
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This circuit generates speed pulses from the speed-dependent voltage spikes generated by commonly used types of PC power supply fans, which are superimpos....
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Dynamic flip-flops ignore pulses at their inputs that are shorter than 40 ns or do not have TTL levels. This means that TTL flip-flops are poorly suited to....
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The TPS6420x controller is designed to operate from one to three series-connected cells or from a 3.3 V or 5 V supply obtained from a USB port. At its out....
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Louder music, sirens or speech in response to higher ambient noise levels? This simple circuit has the answer, and it may enable your robot to be at least....
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Stepper motors are available in several versions and sizes with a variety of operating voltages. The advantage of this general-purpose controller is that....
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Any stepper motor can be used as a generator. In contrast to other generators, a stepper motor produces a large induced voltage even at low rotational spe....
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Stepper motors are a subject that keeps recurring. This little circuit changes a clock signal (from a square wave generator) into signals with a 90-degree....
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A motorcycle or boat battery that is not needed over the winter is usually charged before being put away for the winter, after which it remains standing unused for months on end. As a result, it accumulates deposits of lead sludge, which can result in....
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This stroboscope circuit uses 16 high-brightness white LEDs in a torch housing and it provides a signal output to a frequency counter to provide a rev cou....
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This Super Light Sensor responds to minute fluctuations in light level, auto-adjusting over the range from about 200 lux up to 60, 000 lux (ie, from a modestly lit room to direct sunlight). It has lots of potential uses eg, detecting a car entering a....
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Portable radios, CD-players and cassette recorders that can also be operated from mains power often do not have a mains power switch, but instead are swit....
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National Semiconductor has been producing and designing ICs for use in switch-mode power supplies for many years. The application of these devices is norm....
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This oscillator circuit permits crystals to be electronically switched by logic commands. The circuit is best understood by initially ignoring all crystal....
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This circuit may be used to replace the single current limiting resistor often found in dirt cheap battery chargers. The alternative shown here will event....
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This device is used as a reminder to take medicine every day. This device actually contains a crystal watch and a 4001 quad 2-input NOR gate with two of the gates (IC1a & IC1b) wired as an RS flipflop. The watch is set to tablet time , usually mornings,....
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With the aid of an (old) moving coil instrument it is very little effort to make a simple voltmeter that, at a glance, indicates the status of a telephone....
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A telephone ringer capable of making any mains-powered device work from the ringer of your fixed line. With it, you will be able to control a high-powered siren or horn, as you like, in order to relay and amplify the low-level sound of your telephone (making....
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One reason why commercial soldering stations are expensive is that, in general, they require the use of soldering irons with inbuilt temperature sensors,....
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The equalizer presented in this article is suitable for use with hi-fi installations, public-address systems. mixers and electronic musical instruments. T....
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The test beeper generates a sinusoidal signal with a frequency of 1,000 Hz, a common test frequency for audio amplifiers. It consists of a classical Wien-....
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Consumer appliances these days hardly ever have a proper mains switch. Instead, appliances are turned on and off at the touch of a button on the remote control, just like any other function. This circuit shows how a device (as long as it does not draw too....
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It plugs into the USB port and is just the shot for checking motherboard switch and jumper settings. Many readers will remember a commercial product of a....
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CMOS circuits are known for their low current consumption. This is particularly important for battery-powered circuits. Unfortunately, oscillators often r....
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Sure, listening to VHF FM has great advantages over MW/LW AM from the old days now we have bright stereo free from interference, fading and noise! Howev....
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The circuit in the diagram is a very handy tool for rapidly checking all kinds of thyristor (SCR, triac, ). In case of a triac, all four quadrants are te....
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This circuit is especially designed for those who often need to wake up early in the morning. Ordinary alarms in electronic watches are not loud enough an....
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With IC SLB0586A from Siemens you can build a simple touch light dimmer circuit that will allow you to adjust the lamp intensity. Together with a TIC206D....
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Kids these days seem to have most things you see in the toy shops, so if you have a son or grandson who has a collection of cars, here is something he wil....
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A Transcutaneous Electrical Nerve Stimulation (TENS) device is, put bluntly, a machine for giving electric shocks. The author was prescribed such a device....
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An increasing number of appliances draw a very small current from the power supply. If you need to design a mains powered device, you could generally choo....
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This circuit will supply up to about 20ma at 12 volts. It uses capacitive reactance instead of resistance; and it doesn t generate very much heat.The circ....
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Inexpensive miniature transformers normally provide one or two secondary voltages, which is sufficient for generating a set of positive and negative suppl....
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Superheterodyne receivers have been mass-produced since around 1924, but for reasons of cost did not become successful until the 1930s. Before the second....
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Many households are still graced by tube-type television sets. If you want to connect one of these large tellies to your stereo system to improve the soun....
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This circuit confuses the infra-red receiver in a TV. It produces a constant signal that interferes with the signal from a remote control and prevents the....
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The two T-notch filter can be used to block unwanted frequencies or if placed in an op amp as a bandpass filter. the notch frequency occurs where the capa....
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Here are two simple 12V DC motor speed controllers that can be built for just a few dollars. They exploit the fact that the rotational speed of a DC motor....
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There are many applications where the accuracy of a digital or analogue (bar graph) is not required but something better than a simple low/high indicator....
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This ultra-bright white LED lamp works on 230V AC with minimal power consumption. It can be used to illuminate VU meters, SWR meters, etc. Ultra-bright LE....
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The LME49830 EF125WT1 amplifier PCB module showcases National Semiconductor s LME ultra-high fidelity power amplifier input stage ICs (drivers). The LME49....
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This circuit serves as an ultra-low power replacement for multiple LED on-off indicators. It also has the advantage of being easy to read in full daylight....
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The first sensor a robot usually gets fitted with is an obstacle detector. It may take three different forms, depending on the type of obstacle you want t....
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Manual stabilisers are still popular because of their simple construction, low cost, and high reliability due to the absence of any relays while covering....
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Life in the 21st century would be almost unbearable without some of the computer peripherals that PC users now look on as essentials take for example th....
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When turning a computer on and off, various peripherals (such as printers, screen, scanner, etc.) often have to be turned on and off as well. By using the....
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A portable USB hard drive is a great way to back up data but what if your USB ports are unable to supply enough juice to power the drive A modified version of the Silicon Chip Usb Power Injector is the answer. For some time now, the author has used a....
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This circuit of multimedia speakers for PCs has single-chip-based design, low-voltage power supply, compatibility with USB power, easy heat-sinking, low c....
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This simple circuit can give regulated 4. 7 volts for charging a mobile phone. USB outlet can give 5 volts DC at 100mA current which is sufficient for the slow charging of mobile phones. Most of the Mobile Phone batteries are rated 3. 6 volts at 1000 to 1300....
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This simple circuit can be used to program the PIC16F84 and similar “flash memory†type parts. It uses a cheap 555 timer IC to generate the programming vo....
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This circuit switches a printer s USB connection from a PC to a laptop. What was needed was a method of allowing a laptop to use the printer occasionally....
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LEDs provide a convenient way to electronically display information. Although the seven-segment LED display, arranged in the form of the digit 8, is commo....
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This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to l....
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A variable power supply with adjustable voltage and current outputs made with the L200 regulator. Using the versatile L200 voltage regulator, this power s....
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The 32-kHz low-power clock oscillator offers numerous advantages over conventional oscillator circuits based on a CMOS inverter. Such inverter circuits present problems, for example, supply currents fluctuate widely over a 3V to 6V supply range, while....
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These days many more audio-visual devices in the home are connected together. This is especially the case with the TV, which may be connected to a DVD pla....
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Nowadays a lot of intercom units are equipped with video cameras so that you can see as well as hear who is at the door. Unfortunately, the camera lens is....
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In this circuit the 555 timer is used in a novel way, as a voltage controlled switch.The old and omnipresent NE555 can be very good at someth....
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This circuit proves that microcoprocessors, PCs and the latest ultra-accurate DACs are overkill when it comes to controlling four relays in sequence in re....
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Have you ever seen the stairs to one of the upper stories in your house turn into a waterfall? Or maybe you ve come home to find your aquarium fish trying....
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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....