New Circuits Page 229
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In the precision circuit, an operational amplifier provides a buffered output and also acts as a 2-pole filter. The ripple will beless than 5 mV peak for all frequencies above 1 kHz, and the response time will be much quicker than in Part 1. However, for....
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The schematic requires few components, because the timer function has been incorporated by Nutchip. For once, from the start, made up of contacts of the relay RE1 connected to terminal M2. If we turn on an appliance at the end of time, we will use the relay....
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A triac controller for switching resistive loads directly from the mains supply using the zero crossing technique. The device is powered directly from the mains via a diode and dropper resistor, and the IC has its own regulator to limit its supply to 9.25V.....
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The circuit described in this article is a MOSFET follower for driving headphones. FET followers can supply high current, but have a voltage gain of slightly less than unity. They are most suitable in applications where the input signal does not require....
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This circuit is of an 2x 2,500W RMS stereo amplifier, super-light and without switching-mode power supply. The circuit just shows a channel, and the power supply that it assists to the two channels. The audio circuit should be duplicated, but the power....
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This 3 volts Car Adapter circuit is based on a standard LT1074CT switching regulator IC. The schematic shows the LT1074CT used as a positive step-down or ‘buck’ converter. The ‘switcher’ is used to convert a +12-volt car battery voltage down to +3 volts for....
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Sometimes amateurs like to home-brew their power supplies instead of purchasing one off the shelf at any of the major ham radio retail dealers. The advantage to rolling your own power supply is that it teaches us how they work and makes it easier to....
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To get enough outputs from the PIC chip, a pair of 74HC164 shift registers was used. These need only two lines from the PIC (data & shift) to produce the twelve signal pulses for the servos. A single bit is shifted into the first shift register, then, after....
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The circuit will provide a dc output equal to the rms value of the input. Accuracy is typically 2% for a 20 Vpp input signal from 50 Hz to 100 kHz, although it"s usable to about 500 kHz. The lower frequency is limited by the size of the filter capacitor..
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This circuit uses an LED and 4081 CMOS integrated circuit. The variable resistor sets the voltage at which the LED turns on. Set the control so that the LED lights when the voltage from the car"s ignition switch drops below 13 volts..
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Photo diode outputs light current that is well proportional to input light power when it is used in short mode. In this lux meter, the output current is converted to voltage with an I-V converter, it is captured by a micrcontroller and displayed it in term....
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The 4- to 20-mA current loop is ubiquitous in the world of controls in manufacturing plants. Discrete logic, microprocessors, and microcontrollers easily cover the digital portions of control schemes, such as limit switches, pushbuttons, and signal lights.....
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A commercial diode is the detector in this highly accurate radiation monitor. The lowdrift FET-input op amp amplifies detector current to a usable level, and the chopper-stabilized amplifier then provides additional gain while minimizing any error caused by....
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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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CI capacitor in series with the crystal may be used to adjust the output frequency of the oscillator. The valu..
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Recently many kind of robot contests have being opened and some interesting reports of the challenge are found on the web. The Line Following is a kind of the robot contests to vie running speed on the line. I build a tiny line following robot which can run....
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This window generator uses a single LM324 op amp and features two adjustable set points. When the two comparators formed b..
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When the door is pushed, you hear a whisper that "slide up" to a higher frequency. The oscillator frequency is determined by AF coupling capacitance, C 1 and the value of the resistor connected between the base of IQ and the earth. This resistance, RBG is....
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As Moore`s Law plunges us into the realm of multigigahertz processors and PCs with gigabytes of RAM, engineers face the task of removing the heat that these state-of-the-art components produce. Cooling such systems poses a dilemma. If you optimize the fan....
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A regulator allows you to power a 7.5-V cassette recorder or other device from a 12-Vdc au..
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I like to see lights move to music. 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....
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Press SI. The 100 µF electrolytic capacitor rapidly charges up at about 0 V. The transistor will be forward biased, and collector current will flow operating the relay. Release SI. The capacitor will begin to discharge via the 33 K resistor at the base of....
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The GT4124 is a broadcast quality monolithic integrated circuit
specifically designed to linearly mix two video signals under
the control of a third channel.
Referring to the Functional Block Diagram, the input signals
are applied to conventional....
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An exclusive-OR gate, IClD, turns a simple CMOS oscillator into an FSK generator. When the data input increases, IClD inverts, and negative feedback through R2 lowers the circuit"s output frequency. A low input results in positive feedback and a higher....
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The system is designed to regulate an 860 watt lamp load from half to full power. This is achieved by the controlled-half-plus-fixed-half-wave phase control method. Half power applied to an incandescent lamp results in 30% of the full light output..
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One of the key challenges in the design of 4- to 20-mA current transmitters is the voltage-to-current conversion stage. Conventional transmitters use multiple op amps and transistors to perform the conversion function. These approaches have been around for a....
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This is a low watt audio amplifier with a different technique in design. The 1.8K resistor has been connected to output of the circuit instead of VCC line. The output power of the circuit is about 250mW on an 8 ohms small speaker...
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The precision audio-frequency-generator consists of several sub circuitsan audio-amplifier/filter circuit, an automatic level control, a variable voltage-controlled oscillator, a frequency divider circuit, an integrator, and an audio output amplifier. An....
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This circuit provides up to 20 V output from a 12-V automotive supply, to enable constant current charging o..
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Input, voltages can range from 8 V to 30 V. The load range on the 5 V is 0,05 A to 5 A while the 3.3-V load range is 0.1 A to 1 A. The circuit is self-protected under no-load conditions. Over all load and line conditions, .including cross regulation, the....
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The purpose of the terminal interface is to allow my computer to communicate with Minimum Mass Wireless Coupler equipped devices using a terminal emulator program. Consequently, the Base Unit is basically an RS-232 interface and Minimum Mass Wireless....
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Requiring only two ICs to monitor a train of positive pulses, this circuit produces a single positive output pulse for each input pulse whose duration is either too long or too short. You specify the minimum and maximum limits by adjusting the trimming....
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The use of public-key-encrypted algorithms within licensed applications can prevent hackers from cracking the licensed algorithms. Moreover, you can use them to disable licensed features that a user doesn`t purchase. Licensing schemes eventually arrive at....
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Infrared interruption counter is a reliable circuit that takes over the task of counting number of interruptions very accurately. When somebody enters into the room, then the Counter is Incremented by one. The total number of Persons inside the Room is....
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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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This circuit"s frequency of oscillation increases directly with light intensity. The greater the light intensity, the higher the frequency of the oscillator. The 555 timer operates in the astable oscillator mode where frequency and duty cycle are....
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The author's articles of months past focus on the application of 32-bit high-powered processors to amateur robotics and more recently applying CPLD technologies to the same. Continuing on this high-tech trend, this article will cover the concepts and....
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Digitally programmable current sources that feature automatic trimming and retain the setting despite power-down cycles are useful in applications such as RF- and laser-communications drivers. The circuit in Figure 1, for example, is particularly suited for....
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These circuits allow an ON-ON type DPDT toggle switch to control a twin coil switch machine motor. The handle of switch can then be used to indicate the route selected. The circuits are also able to control LEDs that could be used to indicate the selected....
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For the absolute measurement of temperatures, a thermometer is indispensable. However, in many situations, an ..
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This circuit is useful where fast signal acquisition and high precision are required, as in electronic scales. The filter's time constant is set by the 2 ohm resistor and the 1 µ capacitor until comparator No. 1 switches. The time constant is then set by....
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Here is a Simple Circuit to give a Flashing LED, With a "Rising and Falling" Brightness. It Uses the Sawtooth waveform from pins 2 and 6 to create the rise and fall. The Resistor and LED on Pin 3 are Optional. The 10K Potentiometer give a reasonable range of....
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A hot topic of amplifier design in the 1970s was "transient intermodulation distortion" (TIM). Other names which were used for this phenomenon were "slewing induced distortion" (SID), and "dynamic intermodulation distortion" (DIM). TIM occurs when a....
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It is very useful (and has Best Quality) for 1 -100watt AUDIO AMPLIFIERS..
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Inverters Ula and Ulb are connected in a simple RC oscillator circuit. The frequency is determined by the values of Rl, Cl, C2; and the internal characteristics of the integrated circuit. As long as the circuit is oscillating, a positive dc voltage is....
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This is an image Schematic. No Description available...
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The LED power Meter is a simple RF detector using diodes to charge a capacitor. The voltage developed across the capacitor is indicated by a multimeter set to a low voltage range. The circuit is soldered together without the need for a PC board, as can be....
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Ll and L2 form a tuned transformer. About a 1:3 turns ratio is optimum. L2 and CI tune to the desired frequency. The fre..
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When the phone rings, the ring signal from the telephone company lights a neon lamp within a CLM3120 optocoupler. That causes a drop in the resistance of the CdS cell output of the device, turning on transistor Ql. ..
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Locator uses a transistor radio as the de-tector. With the radio tuned to a weak station, adjust Cl so the locator oscillator beats against the received signal. When the search head pas¬ses over metal, the inductance of LI changes thereby changing the....
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This hardware-software combination deletes clocks from the slave until both /iPs synchronize. The firmware..
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This light-wave receiver consists of a 741 operated as a preamplifier and an LM386 operated as a power amplifier. Potentiometer R2 is the gain control. Various kinds of detectors can be used as the front end of the receiver. Phototransistors are very....
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The LED driver in Figure 1 illuminates retinal neurons in a biological experiment that has similar requirements. For a given LED at a given current, the intensity is stable, so switching a stable current is a simple and effective way to obtain the needed....
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This circuit rapidly charges capacitor CST0 to a voltage equal to an input signal. The input signal is then electrically disconnected from the capacitor with the charge still remaining on CSTO. Since CST0 is in the negative feedback loop of the operational....
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This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2. The supply voltage, Vcc must be higher than the highest input voltage by at least 2 volts. One application here is to monitor a 12V car battery. V1....
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Designers of microcontroller-based products that require a keypad for user data entry can select from dedicating an input line for each key, continuously polling the keypad`s x and y lines, or generating an interrupt whenever a user presses a key. Although....
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Flash lamp is made ??with experimental parts removed from a disposable camera flash circuit.Xenon try to use what I think is easily affordable experiment. AC100V to a voltage doubler rectifier, DC voltage of about 270V is derived. This voltage is R2, C3 is....
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The GY4102A is a bipolar, monolithic SPDT video switch
incorporating fast control logic. The analog signal path is
characterised by low differential gain, low differential phase
and low insertion loss, coupled with a ±0.1 dB bandwidth
of typically 100....
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The circuit is based on the type EL2020 (or similar) operational amplifier which is marled by large bandwidth. The LL2020 amplifies the video signal applied to the input stage, with a gain adjustment range of ±6 dB. Output transistor Q1, a 2N3866, applies....
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The meter will indicate the frequency from a power generator. Incoming sine waves are converted to square waves by the 100K resistor and the 6,8 V zener. The square wave is differentiated by the capacitor and the current is averaged by the diodes. The....
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The amplifier operates primarily in the current domain. The first stage is a voltage controlled current sink. The second stage is a current-controlled voltage source. The fourth stage is a constant current sink. The main advantage of current domain....
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The source connection is tapped into the tuning coil low down, as a means of impedance matching with the headphones and acts as the anode, while the drain connects with your headphones as the cathode, to complete the detector part of the circuit. According....
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A bubble vial with external aluminum-foil electrodes is the sensing element for a simple indicating tiltmeter. To measure bubble displacement, a bridge circuit detects the difference in capacitance between the two sensing electrodes and the reference....
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This reciever uses the TDA1072A which is a complete AM reciever on a chip and it only requires comparitively few peripheral components to complete a high quality AM radio Circuit. Unlike some other AM radio ICs, a minimum number of external tuned inductors....
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This is a variation on the astable multivibrator. Circuit was recently developed to test for N-mosfets(the power kind e.g irf830). I don?t claim circuit can test all bad mosfets or all fault mosfet conditions. If mosfet is working it will operate in the....
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The MiniLOGGER provides 8-channel analog input(-99mV to +999mV), 1-channel pulse input, battery backup 256kB SRAM, Real-time Clock, and RS232C. Start/Stop recording can be made by MANUAL switch or preprogrammed Start/Stop Time. The format of uploading data....
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Many Video Operated Relay (VOR) circuits have been published in recent years for use in connection with ATV repeater controllers or automatic videotape logging systems. Unfortunately, many of these circuits fail to properly detect certain video signals....
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An AC triggered switch for low frequency signals. This is a basic ac voltage operated switch made from discrete components. Both Q1 and Q2 work as common emitter amplifiers, but the biasing of Q1 is arranged by R3 and R4 so that about 0.5V is applied to its....
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A simple circuit for evaluating the performance of the fi lter. The LTC1560-1 offers a pinselectable cutoff frequency of either 500kHz or 1MHz. The fi lter gain response is shown in Figure 2. In the 1MHz mode, the passband gain is fl at up to (0.55)(fC) with....
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The LT1328, in the MS8 and SO-8 packages, contains all the necessary circuitry to convert current pulses from an external photodiode to a digital TTL output while rejecting unwanted lower frequency interference. The LT1328 plus fi ve external components is....
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Figure 1 shows the block diagram of a direct conversion RF receiver—the receiver demodulates an RF carrier directly into a baseband signal without an intermediate frequency down-conversion (a zero IF receiver). The antenna, shared by both the transmitter and....
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The Pierce-gate oscillator of Figure 1 is well recognized by most designers, but few understand how to specify the crystal correctly. The crystal used in the topology of
Figure 1 can be either a fundamental AT-CUT or BT-CUT. A BT-CUT crystal has poor....
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e circuit, is a classic circuit of electronic crossover. Stand in for, the circuits of passive crossover that exist in all loudspeaker three way. The difference is in that, it should anymore we use for each loudspeaker a separate final amplifier. Thus for....
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This alarm circuit activates when SI through S5 are activated. This lights LED1 and activates Ql via IC1C and IC1D. RY..
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The speaker emits a distinctive warble tone when ring pulses are applied to the phone line. Use this circuit as a remote bell or disconnect the phone"s ringer for direct use. Rl adjusts the duration of the output; R2 and R3 control the tone"s duty cycle and....
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A cadmium sulfide photocell (LDR1, which is a light-dependent resistor) is connected to the base and collector of an npn transistor, Ql. When light hits LDR1, the internal resistance goes from a very high (dark) value to a low (light) value, supplying base....
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A relay and two diodes are all tliat is needed the relay performs the job of a buzzer so no annunciator is required. When the lights are left on, but the ignition is off, the normally closcd relay contacts are in series with the relay coil. That means the....
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Hardware is located in a small box slipped in pants` pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1....
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Circuit (a) lets you delay the leading edge of a positive pulse while leaving the trailing edge almost unaffected. A positive input transition, inverted hy IC2, has no effect on IC1B. However, when the positive transition reaches IC1A, (delayed hy the....
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I used the original board layout shown in the magazine article as well as the original driver transistors. However, due to the unavailability of the original power transistors, I opted for a more robust output stage using Toshiba 2SA1943 and 2SC5200....
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This wideband amplifier uses only five components. External signals enter pin 3 of IC1 via ac coupling capacitor Cl. Following amplification, the boosted signals from IC1 pin 1 are coupled to the output by capacitor C2. Capacitor C3 decouples the de....
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This circuit requires the bridging of two circuits to activate the electronic switch. That circuit does not require a 60-Hz field to operate and can be battery or ac powered. The two-pickup terminals can be made from most any clean metal; they should be....
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I have had a lot of queries about getting a low power negative supply in cars, to power Linkwitz transform circuits and the like. There is a switchmode converter, but I must admit that it is overkill for what most people need. Another project describes how....
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This is a simple capacitance meter which can measure capacitance value easy. There are some measurement methods for capacitance, at one time the capacitance was measured with a impedance bridge or a dip meter. Recently typical capacitance meters can measure....
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This circuit switches car headlights to the low beam state when it senses the lights of an on-coming car. The received light is very low level and highly directional, indicating the use of a lens with the detector. A relatively large amount of hysteresis is....
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The circuit requires neither a battery nor an ac supply to make it work. Set the recorder to the record position and ..
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This Project Line Following Autonomous Robot is based on 8 bit Microcontroller AT89C2051. This Robot follows the black line which is drawn over the white surface or it follows the white line which is drawn over the black surface. The infrared sensors are....
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A normally open pushbutton switch (SI) delivers a positive input pulse to pin 4 of Ul, triggering the 1C into action. The output of Ul at pin 6 supplies base-drive current to a Darlington pair comprised of Q1 and Q2, activating . 10- capacitor and any....
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This basic VFO for the 3- to 6-MHz range is coirimonly used in amateur applications, using a Colpitis circuit. For 5 to 5.5 MHz, C = C2 = 70 pF and for 3.5 to 4.0 MHz, use 1000 pF. C3 is typically 10 to 220 pF, depending on the frequency. C4, C5, and C6,....
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In FSK, two discrete frequencies are used to represent the binary digits 0 and 1. The heart of the circuit consists of two Wien-bridge oscillators built using a dual op amp LM 1458, for the two frequencies. The two frequencies are enabled corresponding to....
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The spark developed by the circuit is suitable for a gas ignitor. Capacitor Cl is charged through Rl and Dl toward peak line voltage. C2 is simultaneously being charged at a slower rate through R5. When the charge on C2 is sufficient.to trigger the PUT,....
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This version of the Link uses DTMF tones for dialling both internally between handsets, and externally for outside calls. Remember, in some countries, it is ILLEGAL to simply connect unapproved and untested equipment to Telco lines, so avoid the fine and....
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Flat-panel LCD monitors offer excellent image quality and more compact form factor than CRTshence, their steadily increasing popularity. Unfortunately, the complexity of their manufacturing process makes LCD monitors considerably more expensive than CRTs.....
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This circuit is basically tbe classic bucking regulator, except it uses a TMOS N-channel power FET for the chopper and creates its own supply for the gate control. Tht unique aspect of this circuit is how it generates a separate supply for the gate....
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This is a small but quite powerful FM transmitter having three RF stages incorporating an audio preamplifier for better modulation. t has an output power of 4 Watts and works off 12-18 VDC which makes it easily portable. It is the ideal project for the....
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A standard dual integrator filter can be constructed using a few CA3080s. By varying LABC, the reso..
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If the output is low, application of a negative-going pulse to the trigger input sets the flip-flop (Q goes low), drives the output high, and turns off 1. Capacitor C is then charged through Ra until the voltage across the capacitor reaches the threshold....
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Two circuits of audio tubes amplifiers...
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This transmitters' intended purpose is for morse-code only in the 30 meter band (10Mhz). It is a low-power QRP type and needs to be connected to your existing tranceiver. The harmonic rejections on the prototype were measured at 40dB on 20Mhz and 50dB on....
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As the resolution of ADCs increases from 12 to 16 bits and higher, the difficulty in testing the "no- missing-codes" specification grows proportionately. To fully guarantee no missing codes for a 16-bit ADC requires testing all 2161 possible output codes.....
In the precision circuit, an operational amplifier provides a buffered output and also acts as a 2-pole filter. The ripple will beless than 5 mV peak for all frequencies above 1 kHz, and the response time will be much quicker than in Part 1. However, for....
The schematic requires few components, because the timer function has been incorporated by Nutchip. For once, from the start, made up of contacts of the relay RE1 connected to terminal M2. If we turn on an appliance at the end of time, we will use the relay....
A triac controller for switching resistive loads directly from the mains supply using the zero crossing technique. The device is powered directly from the mains via a diode and dropper resistor, and the IC has its own regulator to limit its supply to 9.25V.....
The circuit described in this article is a MOSFET follower for driving headphones. FET followers can supply high current, but have a voltage gain of slightly less than unity. They are most suitable in applications where the input signal does not require....
This circuit is of an 2x 2,500W RMS stereo amplifier, super-light and without switching-mode power supply. The circuit just shows a channel, and the power supply that it assists to the two channels. The audio circuit should be duplicated, but the power....
This 3 volts Car Adapter circuit is based on a standard LT1074CT switching regulator IC. The schematic shows the LT1074CT used as a positive step-down or ‘buck’ converter. The ‘switcher’ is used to convert a +12-volt car battery voltage down to +3 volts for....
Sometimes amateurs like to home-brew their power supplies instead of purchasing one off the shelf at any of the major ham radio retail dealers. The advantage to rolling your own power supply is that it teaches us how they work and makes it easier to....
To get enough outputs from the PIC chip, a pair of 74HC164 shift registers was used. These need only two lines from the PIC (data & shift) to produce the twelve signal pulses for the servos. A single bit is shifted into the first shift register, then, after....
The circuit will provide a dc output equal to the rms value of the input. Accuracy is typically 2% for a 20 Vpp input signal from 50 Hz to 100 kHz, although it"s usable to about 500 kHz. The lower frequency is limited by the size of the filter capacitor..
This circuit uses an LED and 4081 CMOS integrated circuit. The variable resistor sets the voltage at which the LED turns on. Set the control so that the LED lights when the voltage from the car"s ignition switch drops below 13 volts..
Photo diode outputs light current that is well proportional to input light power when it is used in short mode. In this lux meter, the output current is converted to voltage with an I-V converter, it is captured by a micrcontroller and displayed it in term....
The 4- to 20-mA current loop is ubiquitous in the world of controls in manufacturing plants. Discrete logic, microprocessors, and microcontrollers easily cover the digital portions of control schemes, such as limit switches, pushbuttons, and signal lights.....
A commercial diode is the detector in this highly accurate radiation monitor. The lowdrift FET-input op amp amplifies detector current to a usable level, and the chopper-stabilized amplifier then provides additional gain while minimizing any error caused by....
CI capacitor in series with the crystal may be used to adjust the output frequency of the oscillator. The valu..
Recently many kind of robot contests have being opened and some interesting reports of the challenge are found on the web. The Line Following is a kind of the robot contests to vie running speed on the line. I build a tiny line following robot which can run....
This window generator uses a single LM324 op amp and features two adjustable set points. When the two comparators formed b..
When the door is pushed, you hear a whisper that "slide up" to a higher frequency. The oscillator frequency is determined by AF coupling capacitance, C 1 and the value of the resistor connected between the base of IQ and the earth. This resistance, RBG is....
A regulator allows you to power a 7.5-V cassette recorder or other device from a 12-Vdc au..
I like to see lights move to music. 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....
Press SI. The 100 µF electrolytic capacitor rapidly charges up at about 0 V. The transistor will be forward biased, and collector current will flow operating the relay. Release SI. The capacitor will begin to discharge via the 33 K resistor at the base of....
An exclusive-OR gate, IClD, turns a simple CMOS oscillator into an FSK generator. When the data input increases, IClD inverts, and negative feedback through R2 lowers the circuit"s output frequency. A low input results in positive feedback and a higher....
The system is designed to regulate an 860 watt lamp load from half to full power. This is achieved by the controlled-half-plus-fixed-half-wave phase control method. Half power applied to an incandescent lamp results in 30% of the full light output..
One of the key challenges in the design of 4- to 20-mA current transmitters is the voltage-to-current conversion stage. Conventional transmitters use multiple op amps and transistors to perform the conversion function. These approaches have been around for a....
This is a low watt audio amplifier with a different technique in design. The 1.8K resistor has been connected to output of the circuit instead of VCC line. The output power of the circuit is about 250mW on an 8 ohms small speaker...
The precision audio-frequency-generator consists of several sub circuitsan audio-amplifier/filter circuit, an automatic level control, a variable voltage-controlled oscillator, a frequency divider circuit, an integrator, and an audio output amplifier. An....
This circuit provides up to 20 V output from a 12-V automotive supply, to enable constant current charging o..
Input, voltages can range from 8 V to 30 V. The load range on the 5 V is 0,05 A to 5 A while the 3.3-V load range is 0.1 A to 1 A. The circuit is self-protected under no-load conditions. Over all load and line conditions, .including cross regulation, the....
The purpose of the terminal interface is to allow my computer to communicate with Minimum Mass Wireless Coupler equipped devices using a terminal emulator program. Consequently, the Base Unit is basically an RS-232 interface and Minimum Mass Wireless....
Requiring only two ICs to monitor a train of positive pulses, this circuit produces a single positive output pulse for each input pulse whose duration is either too long or too short. You specify the minimum and maximum limits by adjusting the trimming....
Infrared interruption counter is a reliable circuit that takes over the task of counting number of interruptions very accurately. When somebody enters into the room, then the Counter is Incremented by one. The total number of Persons inside the Room is....
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....
This circuit"s frequency of oscillation increases directly with light intensity. The greater the light intensity, the higher the frequency of the oscillator. The 555 timer operates in the astable oscillator mode where frequency and duty cycle are....
These circuits allow an ON-ON type DPDT toggle switch to control a twin coil switch machine motor. The handle of switch can then be used to indicate the route selected. The circuits are also able to control LEDs that could be used to indicate the selected....
For the absolute measurement of temperatures, a thermometer is indispensable. However, in many situations, an ..
This circuit is useful where fast signal acquisition and high precision are required, as in electronic scales. The filter's time constant is set by the 2 ohm resistor and the 1 µ capacitor until comparator No. 1 switches. The time constant is then set by....
Here is a Simple Circuit to give a Flashing LED, With a "Rising and Falling" Brightness. It Uses the Sawtooth waveform from pins 2 and 6 to create the rise and fall. The Resistor and LED on Pin 3 are Optional. The 10K Potentiometer give a reasonable range of....
A hot topic of amplifier design in the 1970s was "transient intermodulation distortion" (TIM). Other names which were used for this phenomenon were "slewing induced distortion" (SID), and "dynamic intermodulation distortion" (DIM). TIM occurs when a....
It is very useful (and has Best Quality) for 1 -100watt AUDIO AMPLIFIERS..
Inverters Ula and Ulb are connected in a simple RC oscillator circuit. The frequency is determined by the values of Rl, Cl, C2; and the internal characteristics of the integrated circuit. As long as the circuit is oscillating, a positive dc voltage is....
The LED power Meter is a simple RF detector using diodes to charge a capacitor. The voltage developed across the capacitor is indicated by a multimeter set to a low voltage range. The circuit is soldered together without the need for a PC board, as can be....
Ll and L2 form a tuned transformer. About a 1:3 turns ratio is optimum. L2 and CI tune to the desired frequency. The fre..
When the phone rings, the ring signal from the telephone company lights a neon lamp within a CLM3120 optocoupler. That causes a drop in the resistance of the CdS cell output of the device, turning on transistor Ql. ..
Locator uses a transistor radio as the de-tector. With the radio tuned to a weak station, adjust Cl so the locator oscillator beats against the received signal. When the search head pas¬ses over metal, the inductance of LI changes thereby changing the....
This hardware-software combination deletes clocks from the slave until both /iPs synchronize. The firmware..
This light-wave receiver consists of a 741 operated as a preamplifier and an LM386 operated as a power amplifier. Potentiometer R2 is the gain control. Various kinds of detectors can be used as the front end of the receiver. Phototransistors are very....
This circuit rapidly charges capacitor CST0 to a voltage equal to an input signal. The input signal is then electrically disconnected from the capacitor with the charge still remaining on CSTO. Since CST0 is in the negative feedback loop of the operational....
This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2. The supply voltage, Vcc must be higher than the highest input voltage by at least 2 volts. One application here is to monitor a 12V car battery. V1....
Flash lamp is made ??with experimental parts removed from a disposable camera flash circuit.Xenon try to use what I think is easily affordable experiment. AC100V to a voltage doubler rectifier, DC voltage of about 270V is derived. This voltage is R2, C3 is....
The circuit is based on the type EL2020 (or similar) operational amplifier which is marled by large bandwidth. The LL2020 amplifies the video signal applied to the input stage, with a gain adjustment range of ±6 dB. Output transistor Q1, a 2N3866, applies....
The meter will indicate the frequency from a power generator. Incoming sine waves are converted to square waves by the 100K resistor and the 6,8 V zener. The square wave is differentiated by the capacitor and the current is averaged by the diodes. The....
The amplifier operates primarily in the current domain. The first stage is a voltage controlled current sink. The second stage is a current-controlled voltage source. The fourth stage is a constant current sink. The main advantage of current domain....
The source connection is tapped into the tuning coil low down, as a means of impedance matching with the headphones and acts as the anode, while the drain connects with your headphones as the cathode, to complete the detector part of the circuit. According....
A bubble vial with external aluminum-foil electrodes is the sensing element for a simple indicating tiltmeter. To measure bubble displacement, a bridge circuit detects the difference in capacitance between the two sensing electrodes and the reference....
This reciever uses the TDA1072A which is a complete AM reciever on a chip and it only requires comparitively few peripheral components to complete a high quality AM radio Circuit. Unlike some other AM radio ICs, a minimum number of external tuned inductors....
This is a variation on the astable multivibrator. Circuit was recently developed to test for N-mosfets(the power kind e.g irf830). I don?t claim circuit can test all bad mosfets or all fault mosfet conditions. If mosfet is working it will operate in the....
The MiniLOGGER provides 8-channel analog input(-99mV to +999mV), 1-channel pulse input, battery backup 256kB SRAM, Real-time Clock, and RS232C. Start/Stop recording can be made by MANUAL switch or preprogrammed Start/Stop Time. The format of uploading data....
Many Video Operated Relay (VOR) circuits have been published in recent years for use in connection with ATV repeater controllers or automatic videotape logging systems. Unfortunately, many of these circuits fail to properly detect certain video signals....
An AC triggered switch for low frequency signals. This is a basic ac voltage operated switch made from discrete components. Both Q1 and Q2 work as common emitter amplifiers, but the biasing of Q1 is arranged by R3 and R4 so that about 0.5V is applied to its....
A simple circuit for evaluating the performance of the fi lter. The LTC1560-1 offers a pinselectable cutoff frequency of either 500kHz or 1MHz. The fi lter gain response is shown in Figure 2. In the 1MHz mode, the passband gain is fl at up to (0.55)(fC) with....
The LT1328, in the MS8 and SO-8 packages, contains all the necessary circuitry to convert current pulses from an external photodiode to a digital TTL output while rejecting unwanted lower frequency interference. The LT1328 plus fi ve external components is....
Figure 1 shows the block diagram of a direct conversion RF receiver—the receiver demodulates an RF carrier directly into a baseband signal without an intermediate frequency down-conversion (a zero IF receiver). The antenna, shared by both the transmitter and....
The Pierce-gate oscillator of Figure 1 is well recognized by most designers, but few understand how to specify the crystal correctly. The crystal used in the topology of Figure 1 can be either a fundamental AT-CUT or BT-CUT. A BT-CUT crystal has poor....
e circuit, is a classic circuit of electronic crossover. Stand in for, the circuits of passive crossover that exist in all loudspeaker three way. The difference is in that, it should anymore we use for each loudspeaker a separate final amplifier. Thus for....
This alarm circuit activates when SI through S5 are activated. This lights LED1 and activates Ql via IC1C and IC1D. RY..
The speaker emits a distinctive warble tone when ring pulses are applied to the phone line. Use this circuit as a remote bell or disconnect the phone"s ringer for direct use. Rl adjusts the duration of the output; R2 and R3 control the tone"s duty cycle and....
A cadmium sulfide photocell (LDR1, which is a light-dependent resistor) is connected to the base and collector of an npn transistor, Ql. When light hits LDR1, the internal resistance goes from a very high (dark) value to a low (light) value, supplying base....
A relay and two diodes are all tliat is needed the relay performs the job of a buzzer so no annunciator is required. When the lights are left on, but the ignition is off, the normally closcd relay contacts are in series with the relay coil. That means the....
Hardware is located in a small box slipped in pants` pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1....
Circuit (a) lets you delay the leading edge of a positive pulse while leaving the trailing edge almost unaffected. A positive input transition, inverted hy IC2, has no effect on IC1B. However, when the positive transition reaches IC1A, (delayed hy the....
I used the original board layout shown in the magazine article as well as the original driver transistors. However, due to the unavailability of the original power transistors, I opted for a more robust output stage using Toshiba 2SA1943 and 2SC5200....
This wideband amplifier uses only five components. External signals enter pin 3 of IC1 via ac coupling capacitor Cl. Following amplification, the boosted signals from IC1 pin 1 are coupled to the output by capacitor C2. Capacitor C3 decouples the de....
This circuit requires the bridging of two circuits to activate the electronic switch. That circuit does not require a 60-Hz field to operate and can be battery or ac powered. The two-pickup terminals can be made from most any clean metal; they should be....
I have had a lot of queries about getting a low power negative supply in cars, to power Linkwitz transform circuits and the like. There is a switchmode converter, but I must admit that it is overkill for what most people need. Another project describes how....
This is a simple capacitance meter which can measure capacitance value easy. There are some measurement methods for capacitance, at one time the capacitance was measured with a impedance bridge or a dip meter. Recently typical capacitance meters can measure....
This circuit switches car headlights to the low beam state when it senses the lights of an on-coming car. The received light is very low level and highly directional, indicating the use of a lens with the detector. A relatively large amount of hysteresis is....
The circuit requires neither a battery nor an ac supply to make it work. Set the recorder to the record position and ..
This Project Line Following Autonomous Robot is based on 8 bit Microcontroller AT89C2051. This Robot follows the black line which is drawn over the white surface or it follows the white line which is drawn over the black surface. The infrared sensors are....
A normally open pushbutton switch (SI) delivers a positive input pulse to pin 4 of Ul, triggering the 1C into action. The output of Ul at pin 6 supplies base-drive current to a Darlington pair comprised of Q1 and Q2, activating . 10- capacitor and any....
This basic VFO for the 3- to 6-MHz range is coirimonly used in amateur applications, using a Colpitis circuit. For 5 to 5.5 MHz, C = C2 = 70 pF and for 3.5 to 4.0 MHz, use 1000 pF. C3 is typically 10 to 220 pF, depending on the frequency. C4, C5, and C6,....
In FSK, two discrete frequencies are used to represent the binary digits 0 and 1. The heart of the circuit consists of two Wien-bridge oscillators built using a dual op amp LM 1458, for the two frequencies. The two frequencies are enabled corresponding to....
The spark developed by the circuit is suitable for a gas ignitor. Capacitor Cl is charged through Rl and Dl toward peak line voltage. C2 is simultaneously being charged at a slower rate through R5. When the charge on C2 is sufficient.to trigger the PUT,....
This version of the Link uses DTMF tones for dialling both internally between handsets, and externally for outside calls. Remember, in some countries, it is ILLEGAL to simply connect unapproved and untested equipment to Telco lines, so avoid the fine and....
This circuit is basically tbe classic bucking regulator, except it uses a TMOS N-channel power FET for the chopper and creates its own supply for the gate control. Tht unique aspect of this circuit is how it generates a separate supply for the gate....
This is a small but quite powerful FM transmitter having three RF stages incorporating an audio preamplifier for better modulation. t has an output power of 4 Watts and works off 12-18 VDC which makes it easily portable. It is the ideal project for the....
A standard dual integrator filter can be constructed using a few CA3080s. By varying LABC, the reso..
If the output is low, application of a negative-going pulse to the trigger input sets the flip-flop (Q goes low), drives the output high, and turns off 1. Capacitor C is then charged through Ra until the voltage across the capacitor reaches the threshold....
This transmitters' intended purpose is for morse-code only in the 30 meter band (10Mhz). It is a low-power QRP type and needs to be connected to your existing tranceiver. The harmonic rejections on the prototype were measured at 40dB on 20Mhz and 50dB on....
