Top Circuits Page 168
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This simple circuit allows a 12V battery pack to be charged via a bike generator. The generator is rated at 3W and with this voltage multiplier circuit provides about 200mA at about 15km/h. A 12V system was chosen because it allows the use of a car horn (get....
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This circuit was designed to allow microphone cables or other cables to be easily tested for intermittent breaks that can often be difficult to find using a multimeter. The circuit can test cables with up to four cores. Both switches used in the circuit are....
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This circuit could be used (depending on your circumstances) by a gentleman to summon his butler, a manager his secretary or as in the author`s case to call the kids down to dinner without having to shout above the level of the CD player/TV/games console in....
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The electronic dog repellent circuit diagram below is a high output ultrasonic transmitter which is primarily intended to act as a dog and cat repeller, which can be used individuals to act as a deterrent against some animals. It should NOT be relied upon as....
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How often does it happen that you close down Windows and then forget to turn off the computer This circuit does that automatically. After Windows is shut down there is a click` a second later and the PC is disconnected from the mains. Surprisingly enough,....
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This simple circuit uses a 741 op-amp in differential mode as a continuity tester. The voltage difference between the non-inverting and inverting inputs is amplified by the full open loop gain of the op-amp. Ignore the 470k and the 10k control for the....
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This unit employs a dual trace oscilloscope with X-Y function as a display to test and demonstrate the action of circuits and components such as transistors, diodes, zener diodes, and terminated and unterminated transformers. A low frequency sinewave (ie....
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When it is necessary to send a digital signal between two electrically isolated circuits you would normally choose an optoisolator or some form of transformer coupling. Neither of these solutions is ideal; optocouplers run out of steam beyond about 10 MHz....
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This simple robot, which responds to light and avoids obstacles, can be built without using a microcontroller, programmer or PC. The only special` component in the circuit is a window discriminator (a fancy version of a window comparator). Resistors R1 and....
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Many cable testers have been published before, some quite complex, but here`s a cheap and simple alternative. It uses only a 9V battery, two mating connecators and a few resistors, as well as a multimeter for voltage measurements. Begin by soldering the....
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Using this design, you can construct an electromagnetically impulsed pendulum clock with a 1-second beat. On the prototype, the pendulum rod is 115cm long with a bob adjusted to make it beat every second. It is suspended on a short piece of mainspring from a....
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Although not a new device, the LM317 is still a high-performance regulator. Its output voltage is essentially immune to fluctuations in load, supply voltage and temperature and this makes it ideal as the central element in a float charger for NiMH cells.....
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This circuit enables you to display four signals simultaneously using only one channel of your oscilloscope. Essentially, it switches each of the inputs through to the output in turn, with some signal massaging in between. As shown, it is suitable only for....
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When designing bass reflex loudspeaker cabinets, it is necessary to measure the resonance of the speaker to an accuracy of about 1%. To do this, you need an audio oscillator and a frequency counter. However, the typical accuracy and resolution of a frequency....
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The alarm may be used for a variety of applications, such as frost monitor, room temperature monitor, and so on. In the quiescent state, the circuit draws a current of only a few microamperes, so that, in theory at least, a 9 V dry battery (PP3, 6AM6,....
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In all cases where Darlington transistors are used as the output devices it is essential that the sensing transistor (Q4) should be in as close thermal contact with the output transistors as possible. Therefore a TO126-case transistor type was chosen for....
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This simple circuit is a two-person game of strategy and speed - and potentially, agility and athletic fitness. Each player has a row of four LEDs before him/her. Beside each LED, there is a push-button which, when pressed, lights up the corresponding LED.....
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In these times with viruses and other threats from the Internet it would be nice to have reassurance that the PC cannot be infected. That is why this circuit was designed. It makes it possible to install multiple hard disks inside the case of a PC, which are....
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With the storm season recently upon us, it`s not uncommon to switch car headlights on during the daytime. Unfortunately, it`s easy to forget to turn them off again when parking, with the result being a flat battery. This circuit will sound an alarm if the....
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Both halves of the circuit are identical. Both inputs have a dc path to ground via the input 47k control which should be a dual log type potentiometer. The balance control is a single 47k linear potentiometer, which at center adjustment prevents even....
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Strictly speaking, this simple circuit shouldn`t work! How could anyone expect an ordinary light dependent resistor photo cell to `see` through a fingertip in natural daylight and detect the change in blood flow as the heart pulsates The secret is a high....
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Many blind and deaf-blind people use portable electronic devices to assist their everyday lives but it is difficult for them to test the batteries used in that equipment. Talking voltmeters are available for the blind but there is no commercially available....
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As I was developing my IR Extender Circuit, I needed to find a way of measuring the relative intensities of different Infra red light sources. This circuit is the result of my research. I have used a photodiode, SFH2030 as an infra red sensor. A MOSFET....
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The input impedance of a. c. -coupled op amp circuits depends almost entirely on the resistance that sets the d. c. operating point. If CMOS op amps are used, the input is high, in current op amps up to 10 M. If a higher value is needed, a bootstrap may be....
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This circuit is designed to check the condition of lead-acid and gel cell batteries with capacities greater than 20Ah. It switches a load of about 18A at a rate close to 50Hz so that the internal resistance of the battery can be measured using a digital....
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The design of solar panel systems with a (lead-acid) buffer battery is normally such that the battery is charged even when there is not much sunshine. This means, however, that when there is plenty of sunshine, a regulator is needed to prevent the battery....
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This circuit is essentially a light chaser but it can also be set to provides heads or tails (Two Up) or a Dice (die). It also has a speaker to simulate the sound of a spinning roulette wheel. Note that the dice and heads/tails features can be deleted if....
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Here`s a twist to the age-old game of noughts and crosses. Instead of pen and paper, it uses nine 10mm tri-colour LEDs arranged in a 3 x 3 grid. One player has nine red buttons while the other player has nine green, set out in identical grids. The aim, of....
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The two circuits below illustrate generating low frequency sinewaves by shifting the phase of the signal through an RC network so that oscillation occurs where the total phase shift is 360 degrees. The transistor circuit on the right produces a reasonable....
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This simple circuit protects an SLA battery from over-discharge by disconnecting the load when the terminal voltage drops below a preset level. In operation, a sample of the battery voltage is derived from the 22k © resistor and 20k © trimpot divider. This....
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In contrast to an ordinary voltmeter, the input of an oscilloscope generally has one side (GND) connected to ground via the mains lead. In certain situations this can be very problematic. When the measuring probe is connected to a circuit that is also....
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Short circuits in the tracks, points or wiring are almost inevitable when building or operating a model railway. Although transformers for model systems must be protected against short circuits by built-in bimetallic switches, the response time of such....
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This small circuit can be used to control model railway turnouts operated by AC voltages. A logic level in the range of 5 12 V can be used as the control signal. The coils of the turnout are switched using triacs. Changes in the logic level of the input....
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This circuit allows an SPST momentary pushbutton to act as a push-on push-off switch, using a DPDT latching (bi-stable) relay. It was originally intended to allow a single pushbutton switch on the dash of a vintage car to provide a latched function. The....
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This circuit was designed to protect a computer monitor from overheating. It is recommended to attach this circuit to power users` monitors! Most computer monitors of the CRT type fail owing to over-heating. After one or two hours of use, the rear of a....
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This particular timing circuit can be used to time one-shot events from a few seconds to a few hours. And in standby mode (ie, with RLY1 and LED1 off), its power consumption is very low. The heart of this circuit is a low-cost CMOS 4011 quad NAND gate, with....
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Even if a large number of album titles once available on vinyl are now, little by little, being proposed as CDs, not all are available and far from it. You may have treasures in your collection that you would like to burn on CDs. First, preserving a CD is....
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This circuit charges two NiCad cells with a constant current and features dual charging rates, voltage cutoff and an audible alarm. The circuit is powered by a 12VAC centre-tapped mains transformer, together with two rectifier diodes (D1 & D2) and a 1000mF....
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It is impossible to imagine present day society without any batteries. Count the number of gadgets in your house that are powered from batteries, you will be stunned by the number of batteries you will find. The majority of these devices use penlight....
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IC1 forms an oscillator driving the infra-red LED by means of 0. 8mSec. pulses at 120Hz frequency and about 300mA peak current. D1 & D2 are placed facing the car on the same line, a couple of centimeters apart, on a short breadboard strip fastened to the....
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There are two types of pre-amplifiers for magnetic phono cartridges. An example of the most common type is the one described in the March 2002 issue of SILICON CHIP. It has the RIAA equalisation network in the feedback loop. The second type was previously....
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Here`s how to build a pendulum-controlled clock which can be made really accurate. Retro - yes, but an interesting project all the same. You`ll need a spare quartz clock which must be adapted by first isolating the two pads on the chip which lead to the....
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My current vehicle, a Pajero, was modified for dual fuel - ie, petrol and gas. However, it`s necessary to run the vehicle on petrol at regular intervals to stop the injectors from clogging up. This simple circuit allows the vehicle to be started using petrol....
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The clock of the circuit is made of a stable oscillator built around two inverters embedded into IC1 and a Watch crystal oscillating at 32. 768kHz. This frequency is divided by 16384 by the internal flip-flop chain of IC1 and a 2Hz very stable clock....
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For many years now, magnetic (or electromagnetic) water descaler devices have been showing up on the shelves of Home Improvement and other DIY stores all over Europe. Despite the numerous studies completed on that subject, by manufacturers as well as by....
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For some time now, there have been a number of tape cassette decks available at low prices from mail order businesses and electronics retailers. Such decks do not contain any electronics, of course. It is not easy to build a recording amplifier and the....
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Parallax, well known for its successful Basic Stamp IC, has recently introduced the Propeller: a new microcontroller with a certain difference. It packs no less than eight 32-bit processors (referred to as COGs in Propeller jargon) into a single package with....
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Track occupancy detectors are needed for hidden yards and other sections of track that are hard to see, but they are also necessary for block operation. The circuit described here uses an LED to indicate track occupancy for digitally controlled MG¤rklin HO....
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This circuit is a toy to encourage young children to count. Power is turned on by switch S1, then S2 is closed. This makes nine LEDs flash slowly. S2 is then opened and the LEDs go out. Pressing push-button PB1 turns on a random number of LEDs - briefly -....
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According to current legislation in many countries, vintage cars must also be fitted with a fog lamp at the rear. In modern cars, there is a bit of circuitry associated with the fog lamp switch to prevent the fog lamp from going on when the lights are....
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This circuit operates an automotive windscreen washer pump to fill a 20-litre drum from a 205-litre water reservoir. The drum is suspended above a drip line, which irrigates a vegetable garden. Two stainless steel probes mounted in the drum act as sensors....
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There are times when a small servo tester for modeling comes in very useful. 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....
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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 is made of the switching levels of Schmitt trigger NAND gates inside the familiar 4093 IC. The....
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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" position. The LM317regulator operates as a simple current source, providing about 530mA when R1 = 2. 35O (two....
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This circuit is even simpler and employs a 6V feed from one of the stator connections on the vehicle`s alternator. This is connected to a 6V automotive relay (RLY1) which controls a Continuous Duty Solenoid (RLY2). This solenoid electrically connects or....
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Most darkness activated alarms employ opamps and some logic ICs. Here, a less expensive approach is shown based on the eternal 555, this time in monostable multivibrator mode. Components R2 and C1 represent a one-second network. When the LDR (light dependent....
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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 and a transistor, it can charge as many cells as desired until a fully charged` voltage determined by the....
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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 % efficiency provided the available voltage exceeds the fully charged` battery voltage by the drop across one....
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Although 60/40 solder melts at about 200°C, the tip temperature of a soldering iron should be at about 370°C. This is necessary to make a good quick joint, without the risk of overheating delicate components because the iron has to be kept on the joint....
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IC1 forms a differential amplifier for the electromagnetic pulses generated by the engine sparking-plugs, picked-up by sensor coil L1. IC2A further amplifies the pulses and IC2B to IC2F inverters provide clean pulse squaring. The monostable multivibrator....
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This 9-minute timer switch can be used to control the light in a toilet or bathroom. The timer is started by pushing S1 and stopped by pushing S1 again. If you forget to turn it off, the controlled light will go off after nine minutes. If you need the light....
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It provides a means of temporarily silencing a battery-powered smoke detector after you`ve burnt the toast, scorched the baked beans or whatever! Unlike the earlier design, this more sophisticated version does not cause strange chirps and whistles to emanate....
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CMOS circuits are known for their low current consumption. This is particularly important for battery-powered circuits. Unfortunately, oscillators often require quite a bit of current. We therefore propose this oscillator circuit that has a very low current....
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This up/down timer was designed to control a power antenna on a late-model vehicle. Normally, this vehicle uses a body computer to control the antenna. However, the person who owned the vehicle wanted to install his own high-powered audio stereo system. The....
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A small 325mW amplifier with a voltage gain of 200 that can be used as a bench amplifier, signal tracer or used to amplify the output from personal radios, etc. The circuit is based on the National Semiconductor LM386 amplifier. In the diagram above, the....
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This be delay timer circuit model to be simple. It be the character delays to close electric all appliances. By fix the time about 5 minute. It can fine decorate the time. When see the circuit uses digital IC number CD4093 make good easy. And use transistor....
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This circuit uses a very simple approach to detecting smoke in the air. Quite simply, it uses a bulb as a light source, and an LDR (Light Dependent Resistor) as a light detector. As fire smoke comes between the bulb and LDR, the resistance of the LDR....
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In this page we will introduce a great project designed by Toon Beerten. His project named "DIY Led Mood Lamp" can become a very interesting add-on for your room that`s absolutely sure it will impress everyone. As you can see on the photos, we talk about a....
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The switching power supply provides 12 volts, at 10 amps, maximum, using a discrete transistor regulator with an op-amp functioning as a comparator in the feedback circuit. With reference to the schematic, the front panel power-on light is not shown. There....
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This be the circuit delays to have for a long time. By use the integrated circuit Timer 555 or Ultra-Long Time Delay By IC Timer 555 by R2 use for fine the frequency of pulse from the integrated circuit NE555 bring divide by wasp with 4017 each 10 in the end....
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Make a sound card is no more a complex issue. If you use great IC PCM2702 from BURR BROWN / Texas Instruments you can create a fully functional USB sound card. This sound card can be powered from USB port and has one stereo output. You don ½t need to install....
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Anyone who has to reduce the amplitudes of RF signals in a controlled manner needs an attenuator. Linearly adjustable attenuation networks using special PIN diodes are available for this, but they require quite intricate control circuitry. A simpler solution....
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Nowadays, it is no longer necessary to use discrete components to build oscillators. Instead, many manufacturers provide ready-made voltage-controlled oscillator (VCO) ICs that need only a few frequency-determining external components. One example is the RF....
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Integrated AF power amps have seen great improvements in recent years offering improved power and easier use. The TDA1519C from Philips contains two power amplifiers providing 11 W per channel stereo or 22 W mono when the two channels are connected in a....
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Since high frequency voltage-controlled oscillators, or VCOs, are not easy to construct, Maxim ( has produced an integrated 1. 2GHz oscillator, the MAX2754. The center frequency is set using the TUNE input, and a linear modulation input allows the frequency....
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The ASUS Eee is a fantastic ultra-portable notebook with almost everything required for geeks (and nothing that isn`t). Plus it features fantastic build quality and is very well priced. If you live in New Zealand you can get them from DSE ; at the time of....
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Inductors can be mimicked quite easily using operational amplifiers. The circuit shown here was developed to have an inductance of 1000 H (say, one thousand Henry) with good damping. Using this design you can build a resonant circuit with a center frequency....
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The AN7147 Dual 5. 3-watt Audio Power Amplifier from Panasonic is listed as a replacement type` so hopefully will be around for some time to come. Together with some extra components, it can represent a simple surround-sound system requiring no opamps or a....
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With just a low cost DC adapter and the circuit described here it is possible to build a low cost stabilized, uninterruptable 9V supply. On the grounds of safety and economy, a simple unstabilized 12V D. C. adapter is used as the power source, a universal....
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An additional push-button switch is normally required for the ATX Power Switch/Soft Power Switch signal, but you can do without it if you use this simple circuit. It is an artful design, but it has been repeatedly tested. The zener diode is intended to....
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The humidifier circuit is based on a special humidity sensor Type NH-3 from Figaro. Depending on the sensor output, the circuit drives a ventilator that is part of an air humidifying installation. The ventilator is switched on an off by a triac. So as to....
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Downloading and CD-burning programs usually provide the option of automatically shutting down the PC on completion of their tasks. However, this energy-saving feature is of little benet if even after the PC has been switched off, all of the peripheral....
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This circuit is intended to program AVR controllers such as the AT90S1200 via the parallel port. The circuit is extremely simple. IC1 provides buffering for the signals that travel from the parallel port to the microcontroller and vice versa. This is....
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The Over-the-Top type of operational amplifier is ideal for use as a current sense for battery charger applications. The design described here can be used with chargers for rechargeable batteries (Lead/acid or NiCd etc). The 5 V operating supply for the....
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In this article, an RC oscillator is used as a baud rate generator. If you can calibrate the frequency of such a circuit sufficiently accurately (within a few percent) using a frequency meter, it will work very well. However, it may well drift a bit after....
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On many cars, the boot light will not go out until the lid is properly closed. It is all too easy when unloading the car, to leave the lid ajar. If you are unlucky and the car remains unused for some time, the next time you try to start it, the lamp will....
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Most cars do not have delayed interior lights. The circuit presented can put this right. It switches the interior lights of a car on and off gradually. This makes it a lot easier, for instance, to find the ignition keyhole when the lights have gone off after....
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The aesthetics of case modding` (modifying a PC`s enclosure) offer plenty of scope for debate and plenty of scope for original circuits. Low current LED indicators are usuallytted in PC enclosures. Although this certainly saves energy, the LEDs do not light....
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The circuit of the Celsius thermometer in the diagram is based on the well-known Type LM334 from National Semiconductor. This IC is a sensor that provides a current which is directly proportional to the temperature in kelvin (K). Unfortunately, this is a....
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By using a simple visual indicating system, this small transistor tester allows you to run a quick go/non-go` check on NPN as well as PNP transistors. If the device under test is a working NPN then the green LED (D1) will‚ash, while the red counterpart....
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Switch-mode power supplies are used in electronic circuits to increase (step up) or reduce (step down) voltage levels in the most efficient manner possible. Compared to linear voltage regulators, switch-mode supplies convert relatively little energy into....
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Although a simple crystal oscillator may be built from one comparator of an LT1720/LT1721, this will suffer from a number of inherent shortcomings and design problems. Although the LT1720/LT1721 will give the correct logic output when one input is outside....
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If you ever look at construction notes for building old detector type radios the type of headphones specified always have an impedance of 2 G— 2000. Nowadays the most commonly available headphones have an impedance of 2 G— 32 , this relatively low value....
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This circuit allows an ECG signal to be displayed on an oscilloscope. Opamps IC1a, b and d form an instrumentation amplifier with a gain of 201. IC1c amplifies the common-mode signal by a factor of 31, and supplies this signal to the right leg. The first....
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This egg timer, which is both simple and functional, shows once again that it is not essential to use a microcontroller for everything these days. The circuit consists of only two ICs from the standard 4000 logic family, a multi-position rotary switch and a....
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The simplicity of a traditional die makes it exceptionally difficult to create a fully equivalent electronic version, if only because an electronic version requires a power supply and a collection of electronic components that occupy a much larger volume....
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One interface that is missing in the Lego MindStorms system is an electronic ear. We don`t mean that the RCX should respond to spoken commands (which requires a large amount of electronics and software), but it would be handy if it could respond to basic....
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The Maxim MAX 6665 ( provides a complete temperature-dependent fan controller. It can switch fans operating at voltages of up to 24 V and currents of up to 250 mA. The IC is available from the manufacturer in versions with preset threshold temperatures....
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This circuit shows how a 4017 CMOS decade counter can be used to build a timer circuit. Push-button S1 will discharge capacitor C1 through resistor R2. When S1 is released, C1 will charge up through R1 causing a rising edge at the clock input of IC1. This....
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Using just two NAND or inverter gates its possible to build a D type (or toggle`)‚ip-‚op with a push-button input. At power-up the output of gate N2 is at a logical 1`, ensuring that transistor T2 is switched off. When the push-button is pressed the output....
This simple circuit allows a 12V battery pack to be charged via a bike generator. The generator is rated at 3W and with this voltage multiplier circuit provides about 200mA at about 15km/h. A 12V system was chosen because it allows the use of a car horn (get....
This circuit was designed to allow microphone cables or other cables to be easily tested for intermittent breaks that can often be difficult to find using a multimeter. The circuit can test cables with up to four cores. Both switches used in the circuit are....
This circuit could be used (depending on your circumstances) by a gentleman to summon his butler, a manager his secretary or as in the author`s case to call the kids down to dinner without having to shout above the level of the CD player/TV/games console in....
The electronic dog repellent circuit diagram below is a high output ultrasonic transmitter which is primarily intended to act as a dog and cat repeller, which can be used individuals to act as a deterrent against some animals. It should NOT be relied upon as....
How often does it happen that you close down Windows and then forget to turn off the computer This circuit does that automatically. After Windows is shut down there is a click` a second later and the PC is disconnected from the mains. Surprisingly enough,....
This simple circuit uses a 741 op-amp in differential mode as a continuity tester. The voltage difference between the non-inverting and inverting inputs is amplified by the full open loop gain of the op-amp. Ignore the 470k and the 10k control for the....
This unit employs a dual trace oscilloscope with X-Y function as a display to test and demonstrate the action of circuits and components such as transistors, diodes, zener diodes, and terminated and unterminated transformers. A low frequency sinewave (ie....
When it is necessary to send a digital signal between two electrically isolated circuits you would normally choose an optoisolator or some form of transformer coupling. Neither of these solutions is ideal; optocouplers run out of steam beyond about 10 MHz....
This simple robot, which responds to light and avoids obstacles, can be built without using a microcontroller, programmer or PC. The only special` component in the circuit is a window discriminator (a fancy version of a window comparator). Resistors R1 and....
Many cable testers have been published before, some quite complex, but here`s a cheap and simple alternative. It uses only a 9V battery, two mating connecators and a few resistors, as well as a multimeter for voltage measurements. Begin by soldering the....
Using this design, you can construct an electromagnetically impulsed pendulum clock with a 1-second beat. On the prototype, the pendulum rod is 115cm long with a bob adjusted to make it beat every second. It is suspended on a short piece of mainspring from a....
Although not a new device, the LM317 is still a high-performance regulator. Its output voltage is essentially immune to fluctuations in load, supply voltage and temperature and this makes it ideal as the central element in a float charger for NiMH cells.....
This circuit enables you to display four signals simultaneously using only one channel of your oscilloscope. Essentially, it switches each of the inputs through to the output in turn, with some signal massaging in between. As shown, it is suitable only for....
When designing bass reflex loudspeaker cabinets, it is necessary to measure the resonance of the speaker to an accuracy of about 1%. To do this, you need an audio oscillator and a frequency counter. However, the typical accuracy and resolution of a frequency....
The alarm may be used for a variety of applications, such as frost monitor, room temperature monitor, and so on. In the quiescent state, the circuit draws a current of only a few microamperes, so that, in theory at least, a 9 V dry battery (PP3, 6AM6,....
In all cases where Darlington transistors are used as the output devices it is essential that the sensing transistor (Q4) should be in as close thermal contact with the output transistors as possible. Therefore a TO126-case transistor type was chosen for....
This simple circuit is a two-person game of strategy and speed - and potentially, agility and athletic fitness. Each player has a row of four LEDs before him/her. Beside each LED, there is a push-button which, when pressed, lights up the corresponding LED.....
In these times with viruses and other threats from the Internet it would be nice to have reassurance that the PC cannot be infected. That is why this circuit was designed. It makes it possible to install multiple hard disks inside the case of a PC, which are....
With the storm season recently upon us, it`s not uncommon to switch car headlights on during the daytime. Unfortunately, it`s easy to forget to turn them off again when parking, with the result being a flat battery. This circuit will sound an alarm if the....
Both halves of the circuit are identical. Both inputs have a dc path to ground via the input 47k control which should be a dual log type potentiometer. The balance control is a single 47k linear potentiometer, which at center adjustment prevents even....
Strictly speaking, this simple circuit shouldn`t work! How could anyone expect an ordinary light dependent resistor photo cell to `see` through a fingertip in natural daylight and detect the change in blood flow as the heart pulsates The secret is a high....
Many blind and deaf-blind people use portable electronic devices to assist their everyday lives but it is difficult for them to test the batteries used in that equipment. Talking voltmeters are available for the blind but there is no commercially available....
As I was developing my IR Extender Circuit, I needed to find a way of measuring the relative intensities of different Infra red light sources. This circuit is the result of my research. I have used a photodiode, SFH2030 as an infra red sensor. A MOSFET....
The input impedance of a. c. -coupled op amp circuits depends almost entirely on the resistance that sets the d. c. operating point. If CMOS op amps are used, the input is high, in current op amps up to 10 M. If a higher value is needed, a bootstrap may be....
This circuit is designed to check the condition of lead-acid and gel cell batteries with capacities greater than 20Ah. It switches a load of about 18A at a rate close to 50Hz so that the internal resistance of the battery can be measured using a digital....
The design of solar panel systems with a (lead-acid) buffer battery is normally such that the battery is charged even when there is not much sunshine. This means, however, that when there is plenty of sunshine, a regulator is needed to prevent the battery....
This circuit is essentially a light chaser but it can also be set to provides heads or tails (Two Up) or a Dice (die). It also has a speaker to simulate the sound of a spinning roulette wheel. Note that the dice and heads/tails features can be deleted if....
Here`s a twist to the age-old game of noughts and crosses. Instead of pen and paper, it uses nine 10mm tri-colour LEDs arranged in a 3 x 3 grid. One player has nine red buttons while the other player has nine green, set out in identical grids. The aim, of....
The two circuits below illustrate generating low frequency sinewaves by shifting the phase of the signal through an RC network so that oscillation occurs where the total phase shift is 360 degrees. The transistor circuit on the right produces a reasonable....
This simple circuit protects an SLA battery from over-discharge by disconnecting the load when the terminal voltage drops below a preset level. In operation, a sample of the battery voltage is derived from the 22k © resistor and 20k © trimpot divider. This....
In contrast to an ordinary voltmeter, the input of an oscilloscope generally has one side (GND) connected to ground via the mains lead. In certain situations this can be very problematic. When the measuring probe is connected to a circuit that is also....
Short circuits in the tracks, points or wiring are almost inevitable when building or operating a model railway. Although transformers for model systems must be protected against short circuits by built-in bimetallic switches, the response time of such....
This small circuit can be used to control model railway turnouts operated by AC voltages. A logic level in the range of 5 12 V can be used as the control signal. The coils of the turnout are switched using triacs. Changes in the logic level of the input....
This circuit allows an SPST momentary pushbutton to act as a push-on push-off switch, using a DPDT latching (bi-stable) relay. It was originally intended to allow a single pushbutton switch on the dash of a vintage car to provide a latched function. The....
This circuit was designed to protect a computer monitor from overheating. It is recommended to attach this circuit to power users` monitors! Most computer monitors of the CRT type fail owing to over-heating. After one or two hours of use, the rear of a....
This particular timing circuit can be used to time one-shot events from a few seconds to a few hours. And in standby mode (ie, with RLY1 and LED1 off), its power consumption is very low. The heart of this circuit is a low-cost CMOS 4011 quad NAND gate, with....
Even if a large number of album titles once available on vinyl are now, little by little, being proposed as CDs, not all are available and far from it. You may have treasures in your collection that you would like to burn on CDs. First, preserving a CD is....
This circuit charges two NiCad cells with a constant current and features dual charging rates, voltage cutoff and an audible alarm. The circuit is powered by a 12VAC centre-tapped mains transformer, together with two rectifier diodes (D1 & D2) and a 1000mF....
It is impossible to imagine present day society without any batteries. Count the number of gadgets in your house that are powered from batteries, you will be stunned by the number of batteries you will find. The majority of these devices use penlight....
IC1 forms an oscillator driving the infra-red LED by means of 0. 8mSec. pulses at 120Hz frequency and about 300mA peak current. D1 & D2 are placed facing the car on the same line, a couple of centimeters apart, on a short breadboard strip fastened to the....
There are two types of pre-amplifiers for magnetic phono cartridges. An example of the most common type is the one described in the March 2002 issue of SILICON CHIP. It has the RIAA equalisation network in the feedback loop. The second type was previously....
Here`s how to build a pendulum-controlled clock which can be made really accurate. Retro - yes, but an interesting project all the same. You`ll need a spare quartz clock which must be adapted by first isolating the two pads on the chip which lead to the....
My current vehicle, a Pajero, was modified for dual fuel - ie, petrol and gas. However, it`s necessary to run the vehicle on petrol at regular intervals to stop the injectors from clogging up. This simple circuit allows the vehicle to be started using petrol....
The clock of the circuit is made of a stable oscillator built around two inverters embedded into IC1 and a Watch crystal oscillating at 32. 768kHz. This frequency is divided by 16384 by the internal flip-flop chain of IC1 and a 2Hz very stable clock....
For many years now, magnetic (or electromagnetic) water descaler devices have been showing up on the shelves of Home Improvement and other DIY stores all over Europe. Despite the numerous studies completed on that subject, by manufacturers as well as by....
For some time now, there have been a number of tape cassette decks available at low prices from mail order businesses and electronics retailers. Such decks do not contain any electronics, of course. It is not easy to build a recording amplifier and the....
Parallax, well known for its successful Basic Stamp IC, has recently introduced the Propeller: a new microcontroller with a certain difference. It packs no less than eight 32-bit processors (referred to as COGs in Propeller jargon) into a single package with....
Track occupancy detectors are needed for hidden yards and other sections of track that are hard to see, but they are also necessary for block operation. The circuit described here uses an LED to indicate track occupancy for digitally controlled MG¤rklin HO....
This circuit is a toy to encourage young children to count. Power is turned on by switch S1, then S2 is closed. This makes nine LEDs flash slowly. S2 is then opened and the LEDs go out. Pressing push-button PB1 turns on a random number of LEDs - briefly -....
According to current legislation in many countries, vintage cars must also be fitted with a fog lamp at the rear. In modern cars, there is a bit of circuitry associated with the fog lamp switch to prevent the fog lamp from going on when the lights are....
This circuit operates an automotive windscreen washer pump to fill a 20-litre drum from a 205-litre water reservoir. The drum is suspended above a drip line, which irrigates a vegetable garden. Two stainless steel probes mounted in the drum act as sensors....
There are times when a small servo tester for modeling comes in very useful. 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....
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 is made of the switching levels of Schmitt trigger NAND gates inside the familiar 4093 IC. The....
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" position. The LM317regulator operates as a simple current source, providing about 530mA when R1 = 2. 35O (two....
This circuit is even simpler and employs a 6V feed from one of the stator connections on the vehicle`s alternator. This is connected to a 6V automotive relay (RLY1) which controls a Continuous Duty Solenoid (RLY2). This solenoid electrically connects or....
Most darkness activated alarms employ opamps and some logic ICs. Here, a less expensive approach is shown based on the eternal 555, this time in monostable multivibrator mode. Components R2 and C1 represent a one-second network. When the LDR (light dependent....
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 and a transistor, it can charge as many cells as desired until a fully charged` voltage determined by the....
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 % efficiency provided the available voltage exceeds the fully charged` battery voltage by the drop across one....
Although 60/40 solder melts at about 200°C, the tip temperature of a soldering iron should be at about 370°C. This is necessary to make a good quick joint, without the risk of overheating delicate components because the iron has to be kept on the joint....
IC1 forms a differential amplifier for the electromagnetic pulses generated by the engine sparking-plugs, picked-up by sensor coil L1. IC2A further amplifies the pulses and IC2B to IC2F inverters provide clean pulse squaring. The monostable multivibrator....
This 9-minute timer switch can be used to control the light in a toilet or bathroom. The timer is started by pushing S1 and stopped by pushing S1 again. If you forget to turn it off, the controlled light will go off after nine minutes. If you need the light....
It provides a means of temporarily silencing a battery-powered smoke detector after you`ve burnt the toast, scorched the baked beans or whatever! Unlike the earlier design, this more sophisticated version does not cause strange chirps and whistles to emanate....
CMOS circuits are known for their low current consumption. This is particularly important for battery-powered circuits. Unfortunately, oscillators often require quite a bit of current. We therefore propose this oscillator circuit that has a very low current....
This up/down timer was designed to control a power antenna on a late-model vehicle. Normally, this vehicle uses a body computer to control the antenna. However, the person who owned the vehicle wanted to install his own high-powered audio stereo system. The....
A small 325mW amplifier with a voltage gain of 200 that can be used as a bench amplifier, signal tracer or used to amplify the output from personal radios, etc. The circuit is based on the National Semiconductor LM386 amplifier. In the diagram above, the....
This be delay timer circuit model to be simple. It be the character delays to close electric all appliances. By fix the time about 5 minute. It can fine decorate the time. When see the circuit uses digital IC number CD4093 make good easy. And use transistor....
This circuit uses a very simple approach to detecting smoke in the air. Quite simply, it uses a bulb as a light source, and an LDR (Light Dependent Resistor) as a light detector. As fire smoke comes between the bulb and LDR, the resistance of the LDR....
In this page we will introduce a great project designed by Toon Beerten. His project named "DIY Led Mood Lamp" can become a very interesting add-on for your room that`s absolutely sure it will impress everyone. As you can see on the photos, we talk about a....
The switching power supply provides 12 volts, at 10 amps, maximum, using a discrete transistor regulator with an op-amp functioning as a comparator in the feedback circuit. With reference to the schematic, the front panel power-on light is not shown. There....
This be the circuit delays to have for a long time. By use the integrated circuit Timer 555 or Ultra-Long Time Delay By IC Timer 555 by R2 use for fine the frequency of pulse from the integrated circuit NE555 bring divide by wasp with 4017 each 10 in the end....
Make a sound card is no more a complex issue. If you use great IC PCM2702 from BURR BROWN / Texas Instruments you can create a fully functional USB sound card. This sound card can be powered from USB port and has one stereo output. You don ½t need to install....
Anyone who has to reduce the amplitudes of RF signals in a controlled manner needs an attenuator. Linearly adjustable attenuation networks using special PIN diodes are available for this, but they require quite intricate control circuitry. A simpler solution....
Nowadays, it is no longer necessary to use discrete components to build oscillators. Instead, many manufacturers provide ready-made voltage-controlled oscillator (VCO) ICs that need only a few frequency-determining external components. One example is the RF....
Integrated AF power amps have seen great improvements in recent years offering improved power and easier use. The TDA1519C from Philips contains two power amplifiers providing 11 W per channel stereo or 22 W mono when the two channels are connected in a....
Since high frequency voltage-controlled oscillators, or VCOs, are not easy to construct, Maxim ( has produced an integrated 1. 2GHz oscillator, the MAX2754. The center frequency is set using the TUNE input, and a linear modulation input allows the frequency....
The ASUS Eee is a fantastic ultra-portable notebook with almost everything required for geeks (and nothing that isn`t). Plus it features fantastic build quality and is very well priced. If you live in New Zealand you can get them from DSE ; at the time of....
Inductors can be mimicked quite easily using operational amplifiers. The circuit shown here was developed to have an inductance of 1000 H (say, one thousand Henry) with good damping. Using this design you can build a resonant circuit with a center frequency....
The AN7147 Dual 5. 3-watt Audio Power Amplifier from Panasonic is listed as a replacement type` so hopefully will be around for some time to come. Together with some extra components, it can represent a simple surround-sound system requiring no opamps or a....
With just a low cost DC adapter and the circuit described here it is possible to build a low cost stabilized, uninterruptable 9V supply. On the grounds of safety and economy, a simple unstabilized 12V D. C. adapter is used as the power source, a universal....
An additional push-button switch is normally required for the ATX Power Switch/Soft Power Switch signal, but you can do without it if you use this simple circuit. It is an artful design, but it has been repeatedly tested. The zener diode is intended to....
The humidifier circuit is based on a special humidity sensor Type NH-3 from Figaro. Depending on the sensor output, the circuit drives a ventilator that is part of an air humidifying installation. The ventilator is switched on an off by a triac. So as to....
Downloading and CD-burning programs usually provide the option of automatically shutting down the PC on completion of their tasks. However, this energy-saving feature is of little benet if even after the PC has been switched off, all of the peripheral....
This circuit is intended to program AVR controllers such as the AT90S1200 via the parallel port. The circuit is extremely simple. IC1 provides buffering for the signals that travel from the parallel port to the microcontroller and vice versa. This is....
The Over-the-Top type of operational amplifier is ideal for use as a current sense for battery charger applications. The design described here can be used with chargers for rechargeable batteries (Lead/acid or NiCd etc). The 5 V operating supply for the....
In this article, an RC oscillator is used as a baud rate generator. If you can calibrate the frequency of such a circuit sufficiently accurately (within a few percent) using a frequency meter, it will work very well. However, it may well drift a bit after....
On many cars, the boot light will not go out until the lid is properly closed. It is all too easy when unloading the car, to leave the lid ajar. If you are unlucky and the car remains unused for some time, the next time you try to start it, the lamp will....
Most cars do not have delayed interior lights. The circuit presented can put this right. It switches the interior lights of a car on and off gradually. This makes it a lot easier, for instance, to find the ignition keyhole when the lights have gone off after....
The aesthetics of case modding` (modifying a PC`s enclosure) offer plenty of scope for debate and plenty of scope for original circuits. Low current LED indicators are usuallytted in PC enclosures. Although this certainly saves energy, the LEDs do not light....
The circuit of the Celsius thermometer in the diagram is based on the well-known Type LM334 from National Semiconductor. This IC is a sensor that provides a current which is directly proportional to the temperature in kelvin (K). Unfortunately, this is a....
By using a simple visual indicating system, this small transistor tester allows you to run a quick go/non-go` check on NPN as well as PNP transistors. If the device under test is a working NPN then the green LED (D1) will‚ash, while the red counterpart....
Switch-mode power supplies are used in electronic circuits to increase (step up) or reduce (step down) voltage levels in the most efficient manner possible. Compared to linear voltage regulators, switch-mode supplies convert relatively little energy into....
Although a simple crystal oscillator may be built from one comparator of an LT1720/LT1721, this will suffer from a number of inherent shortcomings and design problems. Although the LT1720/LT1721 will give the correct logic output when one input is outside....
If you ever look at construction notes for building old detector type radios the type of headphones specified always have an impedance of 2 G— 2000. Nowadays the most commonly available headphones have an impedance of 2 G— 32 , this relatively low value....
This circuit allows an ECG signal to be displayed on an oscilloscope. Opamps IC1a, b and d form an instrumentation amplifier with a gain of 201. IC1c amplifies the common-mode signal by a factor of 31, and supplies this signal to the right leg. The first....
This egg timer, which is both simple and functional, shows once again that it is not essential to use a microcontroller for everything these days. The circuit consists of only two ICs from the standard 4000 logic family, a multi-position rotary switch and a....
The simplicity of a traditional die makes it exceptionally difficult to create a fully equivalent electronic version, if only because an electronic version requires a power supply and a collection of electronic components that occupy a much larger volume....
One interface that is missing in the Lego MindStorms system is an electronic ear. We don`t mean that the RCX should respond to spoken commands (which requires a large amount of electronics and software), but it would be handy if it could respond to basic....
The Maxim MAX 6665 ( provides a complete temperature-dependent fan controller. It can switch fans operating at voltages of up to 24 V and currents of up to 250 mA. The IC is available from the manufacturer in versions with preset threshold temperatures....
This circuit shows how a 4017 CMOS decade counter can be used to build a timer circuit. Push-button S1 will discharge capacitor C1 through resistor R2. When S1 is released, C1 will charge up through R1 causing a rising edge at the clock input of IC1. This....
Using just two NAND or inverter gates its possible to build a D type (or toggle`)‚ip-‚op with a push-button input. At power-up the output of gate N2 is at a logical 1`, ensuring that transistor T2 is switched off. When the push-button is pressed the output....