New Circuits Page 216
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The circuit of Figure 1 produces an accurate, variable-frequency sine wave for use as a general-purpose reference signal. It includes an eighth-order elliptic, switched-capacitor lowpass filter, IC3, which uses a 100-kHz square-wave clock signal that....
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This circuit is a Logic Probe. It indicates the logic state of the node of any TTL logic circuit. To do that, we have to supply the probe with the same power of the circuit that we want to analyse: same Vcc and same GND. To check the logic level, we must....
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This must be the most efficient bipolar transistor motor driver design for this application and I recommend it for the solar roller competitions. A 1381E is used to trigger at 2.4V. While it takes a total of 10 components plus motor compared to the stock....
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The scheme presented delivers waveforms from any function generator producing a triangular output and a synchronized TTL square wave. A1 and A2 act as a two-phase current fectifier by inverting the negative voltage appearing at the input of Al. Positive....
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The ramp generator, an inexpensive alternative to commercial function generators, provides a more linear and repeatable output than conventional analog integrators. The circuit provides a triangle waveform in burst mode; in this case, two cycles of 10.24....
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The three schematics represent three building blocks for a 10-meter SSB transmitter. Or these blocks can be used separately as circuit modules for other transmitters. The VFO board uses an FET transmittal oscillator, the VFO signal is mixed in an NE602....
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Field effect transistor, Ql, operates in the linear resistive region to provide automatic gain control. Because the attenuation of the RC network is one-third at the zero phase-shift oscillation frequency, the amplifier gain determined by resistor R2 and....
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This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. Pushing P1 the device is switched-on feeding any appliance connected to SK1. Input audio signal is boosted and squared....
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If you use different batteries with actual capacity, with different self-discharge rate of batteries from different manufacturers, you will perhaps throw further described charger. Because each cell can be discharged separately recharge, can be charged with....
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The IC8211 provides the voltage reference and regulator amplifier, while Ql is the series pass transistor. Rl defines the output current of the IC8211, while Cl and C2 provide loop stability and also act to suppress feedthrough of input transients to the....
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This circuit is designed around a 4049 hex inverter/buffer. Two inverters are used ina dual-frequency signal-injector circuit, another inverter is used as a logic probe, and the remaining three inverters are used as a sensitive dual-input, audio-signal....
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This is a simple serial port buffer circuit I designed for a friend to speed up his SLIP connection in campus computer network "TRINET" of Helsinki University of Technology. The problem in the network was that the RS232 commections from rooms to terminal....
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RS-232C serial port lines are quite prone to be damaged by overvoltages. The damaged to computer serial ports have become more and more expensive to replace because of higher intergaration: usually you have to buy new motherboard if one serial port in it....
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The LT®1932 is a fixed frequency step-up DC/DC converter designed to operate as a constant-current source. Because it directly regulates output current, the LT1932 is ideal for driving light emitting diodes (LEDs) whose light intensity is proportional to the....
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Light filtering through the finger tip is detected by the cadmium sulphide photoresistor CD1 which forms the feedback network for transducer amplifier section ICA producing a weak signal which is further amplified by ICB. This signal is now compared against....
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This circuit uses the output of the IGL8049 to control the frequency of the IGL3038 waveform generator; the 741 op amp is used to linearize the voltage-frequency response. The input voltage to the 8049 can be, for example, from the horizontal sweep signal....
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This is a compass circuit based at AT90S2313. The output drives 8 LEDs to indicate the different horizon directions...
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A pair of diodes and a quarter-wave transmission line are used as an automatic TR switch. D1 and D2 conduct during transmit periods, short- circuiting the scanner input. In this mode,-the K-wave line appears as an open circuit...
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In the Fig.1, exist a circuit, which is a sensitive switch that corresponds in AC signals of input, for signals above 5mV. Corresponds in all the signals from 50 HZ until 3KHZ, region in which found the human voice. The RV1 is regulated so much what RL1 it?s....
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The 555 is wired as an astable and the capacitor is charged only through the 4,7Kohm trimmer (notice the diode) and discharged only through the 2.2 Kohm trimmer, making the duty cycle full adjustable. The square wave is then feed in a totem pole made up of a....
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Infrared emissions detected by Ql are fed through Ula to Ulb, which amplifies the signal by a factor of 100. The amplified output ofUlb is fed to Ulc through R9, C2, and R6. Potentiometer R9 serves as a volume control. With R9 set to pass the maximum....
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H ere is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. A....
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If you are familiar with LED flashers using transistor, you may know the basic one uses two transistor, one capacitor and three resistors. There is other kind of oscillator called "flip-flop". As I'm starting to develop some basic circuits, I need a simple....
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Built around an LM380, this amplifier includes tone controls and electronic "soft switching". The soft switching circuitry ensures power is built up gradually eliminating the dc thump. The soft switching is enabled by a BD131 transistor wired as a switch in....
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The unit consists of a direct conversion receiver and 1-W transmitter. The direct conversion receiver VFO is tuned just off frequency from the incoming signal. This difference in frequency produces a clean, strong, and solid audio tone signal. Detect the....
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The frequency covered is from 0.1Hz to 10Hz and useful signals are received up to 16Hz. The first Op-Amp, properly shielded, must be installed close to the antenna (1-3m long) and connected to the rest of the circuit with a 5-core shielded cable. Adjust the....
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Although the output is low level and cannot be loaded significantly without harming -accuracy, a single I.C. operational or instrumentation amplifier can supply both the linear gain and buffering for use with a variety of loads.
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The only adjustments that require close attention are input, output, and neutralization. The 150-pF capacitor in the input line compensates for impedance mismatch. You tune for maximum signal transfer from exiter to final with an in-line meter or external....
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This circuit is very basic to build. To open a lock which is connected to the K1 Load, you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1, S2, S3 and finally S4. If any of the other switches are pressed the....
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This simple circuit will find many applications as a battery eliminator for low power requirements. It consists of a transformer, a bridge rectifier and an electrolytic capacitor followed by a zener controlled series pass transistor. The output is stabilized....
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When the phototransistor is stroken by IR light it conducts and the voltage between the 1Mohm resistor(arbitrary) and the phototrans drops from VCC to lower values. When the voltage drops lower than VCC/3 the 555 is triggered and goes high (from 0 TO VCC).....
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The Clock Controller was designed to be an exemplary of using 'C' language to control timer0interrupt, 7-segment LED and keypad scanning. It provides 1-bit sink currentdriving output, for driving a relay, opto-triac, say. Many projects requiring7-segment....
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Because of its high amplification factor and built-in power-output stage, an integrated power operational amplifier makes a convenient driver for ac motors. One op amp can be configured as an oscillator to generate the required ac signal. The power-output....
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The circuit has a flat frequency response from about 20Hz to well over 50Khz. Input sensitivity is 100mV for a full scale deflection on a 100uA meter. Built on two common emitter amplifiers, the first stage has a preset resistor which may be adjusted for a....
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The circuit generates low-level rf bursts having frequencies as high as 10 MHz, thus permitting field testing of high frequency receivers. A jumper-selectable binary fraction (liz to "1256 of the Y1 crystal frequency gates the output rf signal. Output....
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One application of this handy circuit is a graphic equalizer, created by feeding a signal to a number of parallel band-pass filters each tuned to a different frequency; typically octaves apart. Then, you can adjust the strength in each band via a front panel....
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This contributed project is a result of considerable collaboration between Sergio and myself, and should not be seen as necessarily a complete project in itself, but a stepping stone to understanding switching power supplies, how they work, and what you can....
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this circuit rougly doubles the voltage of the input, however the current output is low. doubled output is at `V source.`..
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The tuning range is determined by coil (L) dimensions and setting of Cl. Coils can be plugged in for multirange use or soldered in place if only limited frequency range is of interest. Cl = 36 pF variable, C2 = 047 disc, D = 1N60 (germanium) and M=0-1 mA meter..
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Here is a circuit for using the printer port of a PC, for control application using software and some interface hardware. The interface circuit along with the given software can be used with the printer port of any PC for controlling up to eight equipment .....
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Most car door switches are simply single-pole switches, with one side grounded. When the door is opened the switch grounds the other line thus completing the light circuit. In a car where the negative terminal of the battery is connected to the chassis, the....
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The circuit is shown in Figure 1, and as described above, uses a voltage doubler rectifier. Diodes D1 and D2 are 1N4004 or similar. From there, a pair of resistors provide additional smoothing to the secondary filter caps. R3 is used to balance the voltage....
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With this circuit, we can have a acoustic clue, frequency 2KHZ, when we have a short vibration in his entry. It is constituted from monostable multivibritor (with schmitt trigger inputs), with duration roughly 100msec, oscillator TTL, that oscillating in....
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This circuit uses a CA5422 dual BiMOS microprocessor op amp. The bootstrap amplifiers minimize bias currents while maintaining electrostatic discharge protection. ..
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IC3 acts as an oscillator which operates if the output of ICl is high. With the values used the two frequencies produced are about 800 Hz and 2500 Hz. The output is buffered by Ql which drives the speaker. The first IC is used to generate the tone duration....
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You can divide a large keypad or keyboard into sections of 12 keys each (Figure 1). Each section connects to a separate comparator circuit, which detects a keystroke and generates a trigger pulse using the monostable circuit of IC4, and you can add more....
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Pulse Generator kit will generate a frequency in KHz which can form a good test gear project. This kit is based on the classic LM555 timer IC. Input - 12 VDC Max @ 40 mA. Range - jumper selectable and preset tunable range of 1 Hz to 180 KHz. Power-On LED....
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if the timer is triggered with a continuous pulse train in the monostable mode of operation, the charge time of the capacitor can be varied by changing the control voltage at pin 3..
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This circuit is useful for removing ground loop hum on a remote line level audio signal line. It can be used to to connect a computer sound card to a stereo amplifier`s line input. Other uses include tapping into a line level signal for powering a remote....
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The following circuit Diagram of (DUAL VOLTAGE POWER SUPPLY ) can be used for Misc.. application. It requires a few components to built. The most important components of this circuit are REGULATORS. 1 : (AN) 7812 and 2 : (AN) 7912 AN7812 is the Positive....
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When I was recently debugging a design, I discovered that a short circuit existed from a ground plane to a power plane. I did not have access to a milliohmmeter or an equivalent tester for locating this type of short circuit. So, I logged onto the Internet....
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This, circuit is a programmable current source in which op amp LT1102 (Linear Technology Corp.) is used..
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Here is a schematic of a rechargeable 9-LED flashlight using two Gates SLA cells and nine LEDs. It is as bright as when the single bulb was used, and lasts 3 times longer per charge. That is about 10 hours of bright light, at a lower brightness, is available....
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A Wien-bridge oscillator can be made Vllriable by using two frequency-determining parts that are varied simultaneously at high tracking accuracy. High-quality tracking potentiometers or variable capacitors are, however, expensive and difficult to obtain.....
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This circuit can be used to recieve AM stations in an FM radio. Is a regenerative circuit that samples AM signals of all frequency and retransmits them in the FM band or in TV band...
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This circuit has proved very useful in keeping away from a terrace or a porch some bats and other nocturnal animals. You can use it for similar or different purposes. The lamp illuminates for a 4-5 seconds delay and stays off about one minute and 15 seconds.....
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This circuit has been designed to drive an 8-W fluorescent lamp from a 12-V source using an inexpensive inverter based on the ZTX652 transistor. The inverter will operate from supplies in the range of 10 to 16.5 V, thus making it suitable for use in....
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This amplifier employs a cascaded op amp integrator and transistor buffer, Q1, to drive the gain control element. Except for a simple modification, the HA-5190/5195 stage is connected as a conventional noninverting op amp, and includes input and output....
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This circuit is intended for use with motors, lamps,heatings etc. Continuously from nearly zero up to maximum capacity (5-95%). Almost lossfree control by means of this impulse control. Nearly total turning moment of motors. The transistior T3 must....
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In the miniature high-voltage dc generator, the input to the circuit, taken from a 12-Vdc power supply, is magnified to provide a 10,000-Vdc output causing a pulsating signal, of opposite polarity, to be induced in Tl`s secondary winding. The pulsating dc....
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A TMOS MTM7N45 (Q2) is used as a series pass element in a linear high voltage supply that accepts +275-V unregulated and produces 250 V regulated with foldback current limiting. A 15-V zener, Dlf provides the dc reference for operational amplifier Ul, whose....
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Stepdown transformer T1 drops the incoming line voltage to approximately 48 Vac which is rectified by diode D1; the resultant de charges capacitor C1-through current limiting resistor Rl-to a voltage level preset by R4. When the voltage on R4"s wiper....
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This schematic uses the 555 timer and the 4017 IC to drive 3 LED, to simulate the trafic lights...
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This circuit has proved to be an effective video buffer and will easily drive a 75- load to 1.5-V p-p output. BW is better than 20 MHz and there is less than 0.05-V dc offset, which is the difference in VBE of Ql and Q2...
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This circuit functions with inaudible (ultrasonic) sound. Sound of frequency up to 20 kHz is audible to human beings. The sound of frequency above 20 kHz is called ultrasonic sound. The circuit described generates (transmits) ultrasonic sound of frequency....
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The LM3909 is configured so that the frequency of oscillation is dependent on a single RC timing circuit, which consists of..
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This simple and inexpensive circuit can produce a dual (positive and negative) voltage from a single supply input. It is therefore extremely useful for powering opamp and other circuits that require a dual voltage from a single battery. The circuit will....
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Signals of identical frequency are applied to sync input (Pin 6) and to the demodulator input (Pin 4), respectively, the demodulator functions as a phase detector with output dc component being proportional to phase difference between the two inputs. The....
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The circuit this month is a simple 8 light chaser built around a PIC. This will demonstrate how easy it is to program a PIC and to utilize it in a circuit. The circuit works as follows. When power is supplied to the circuit the PIC resets and starts to....
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The easy way to clamp a signal to a given value is to use two zener diodes, connected back-to-back. This method has several disadvantages. The accuracy of the clamping depends on the tolerance of the zener diodes, and the clamping is not adjustable, except....
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A VCO (voltage-controlled oscillator) is an analog circuit, so you cannot find it in the libraries for the design of digital programmable chips. When you need such a circuit for synchronization or clock multiplication, you need to find a circuit that works....
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Circuit provides a minimum of 7 V until the 9-V battery voltage falls to less than 2 V. When the battery voltage is above 7 V, the MAX630"s IC pin is low, putting it into the shutdown mode which draws only 10 nA. When the battery voltage falls to 7 V, the....
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This current source has continuous control of the magnitude and polarity of its amplifier gain and needs only one voltage reference. The circuit includes reference ~, voltage-amplifier circuit A1 with gainsetting resistor Rs, and bootstrap-follower....
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The circuit has both square-wave and triangle-wave output. The left section is similar in function to a comparator circuit that uses positive feedback for hysteresis. The inverting input is biased at one-half the Vcc voltage by resistors R4 and R5. The....
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This CMOS circuit can be used as a 1-shot time delay switch and general-purpose timer. The circuit consists of a gated oscillator and a latch made from one CD4001 quad 2-input NOR gate as shown and a CD4020 14-stage counter. TON is a function of the....
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The following article takes the knowledge of advantages and disadvantages of the pipeline architecture and compares its features with four of the most popular architectures (flash, dual-slope, sigma-delta, and successive approximation) for analog-to-digital....
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When a discharged gel cell is connected, the charger goes into a fast charge mode at a fixed rate of 400 ma. After the chip detects the voltage leveling off or when 4 1/2 hours has elapsed. (which ever happens first.) the fast charge will stop. After the....
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Build-in charger for instruments powered by single lithium-ion or Li-Pol accumulator. If external power supply not conected to charger, current back from the accu charger is very small. New version improved temperature stability and Not Needed NTC....
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Intended for extreme temperature, radiation-hardened environments, this linear supply is capable of supplying 28 Vdc at 125 A from an ac-driven power unit. In operation, power supply output voltage is sensed by the voltage divider consisting of R24 to R28....
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Many systems require one or more relatively low-current voltage sources which can be programmed tna few predetermined levels. The circuit shown above produces positive output levels, but could be modified for negative or bipolar outputs. Q1 is the series....
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This Field Strength Meter is simple and also quite sensitive. It uses an ordinary digital voltmeter to measure RF signal strength up to a few hundred MHz. The multimeter should be set to the lowest dc volts range for maximum sensitivity. This is normally....
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This circuit differs from similar circuits in view of its simplicity and a totally different concept of generating the control signals. Usually remote control circuits make use of infrared light to transmit control signals. Their use is thus limited to a....
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Wine doesn`t like subzero temperatures, and during wintertime, my "winecellar" got pretty cold. There was an electric heating element, but the thermostat was broken, so it was either full burn or nothing. That`s how the temperature monitor/controller came to....
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The signal emitted by an IR remote control contains two parts, the control pulses and a modulated carrier wave. The control pulses are used to modulate the carrier, a popular modulation frequency being 36 and 42KHz. The signal is radiated by an IR diode,....
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The simple circuit design in Figure 1 lets you measure all components of a current flowing in a dc servo motor. The rectified output of the circuit uses ground as a reference, so you can measure the output by using a single-ended A/D converter. The....
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The circuit of the mains current detector is shown in Figure 1. By using a few cheap diodes, a resistor, LED and LDR, a simple opto-isolated detector can be created. This entire circuit dissipates very low power, and can safely be housed in a heatshrink....
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By repetitively charging and discharging a capacitor through the primary of an induction coil with a high voltage, an ultra high emf is induced in the secondary. Switching is performed by the triac, triggered by the disc at times set by Cl and Rl. With a 12....
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This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc..). The whole thing is very easy to build....
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Two low voltage, low power zeners are used to control electronically the level of an audio signal. The attenuation range is from 6 to 58dB for an input current from 0.042 to 77mA corresponding to a control voltage from 2.7 to 7.5V. If control voltage is....
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The schematic in Figure 1 is the discrete-element version of an A/D-converter drive circuit. The circuit converts a single-ended input to a differential output. The ADC`s reference voltage determines the common-mode range of the differential outputs. The....
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Output-clamp diodes are mandatory because loudspeakers are inductive loads. Output LR isolation is also used because audio amplifiers are usually expected to handle up to 2 mF load capacitance. Large, supply-bypass capacitors located close to the IC are used....
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In applications involving strain gauges, accelerometers, and thermal sensors, a bridge transducer is often used. Frequently, the sensor elements are high resistance units requiring equally high bridge resistance for good sensitivity. This type of circuit....
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The amplifier"s input stage is a dual-gate GaAs FET, which provides low input capacitance and high transconductance. The dual-gate structure accepts the signal on input 1. Input 2 controls the gain of the amplifier. The amplifier has a third input for use....
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Since my page was first posted, I have received a number of emails asking about a high current power supply. I looked around, but couldn`t find one that was suitable. So, I designed this. It is a linear supply, which might have a few of you rolling your....
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The program loaded in the 12F675 device which has no osccal value will force a pulse on GPIO.4 and it will make a loop while increasing the osccal value internally.
GPIO.5 will send the current osccal value used for each pulse sent. Because the device has....
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This report deals with the design for a small asynchronous serial data switch. The switch architecture allows 14 serial ports supporting a subset of the RS-232 protocol. The requirements for the switch are discussed. The hardware interfaces are described in....
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Differential multiplexers are generally used in process control applications to eliminate errors due to common mode signals. In this circuit however, advantage is taken of the dual multiplexing capability of the switch. This is achieved by using the....
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The F84 MRTC was my second design of a miniature real-time controller. This version uses PIC16F84 running with a low power X-tal 32,768Hz. The scheduler for 6-channel output was saved in EEPROM. No terminal for serial downloading of the scheduler. It`s....
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This document describes the HSETI PCB. This PCB is a small simple application for the Atmel AT89C2051 microprocessor - a 20 pin 8051 variant, with FLASH (reprogrammable) program memory. The board has just two chips on it, the CPU and a driver/buffer...
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The circuit will come handy when you have to follow the mains wires buried in the wall or even water pipes provided they are not too far away (2-4cm max). It will also detect a conversation on a telephone cable without actually touching it (for testing....
The circuit of Figure 1 produces an accurate, variable-frequency sine wave for use as a general-purpose reference signal. It includes an eighth-order elliptic, switched-capacitor lowpass filter, IC3, which uses a 100-kHz square-wave clock signal that....
This circuit is a Logic Probe. It indicates the logic state of the node of any TTL logic circuit. To do that, we have to supply the probe with the same power of the circuit that we want to analyse: same Vcc and same GND. To check the logic level, we must....
This must be the most efficient bipolar transistor motor driver design for this application and I recommend it for the solar roller competitions. A 1381E is used to trigger at 2.4V. While it takes a total of 10 components plus motor compared to the stock....
The scheme presented delivers waveforms from any function generator producing a triangular output and a synchronized TTL square wave. A1 and A2 act as a two-phase current fectifier by inverting the negative voltage appearing at the input of Al. Positive....
The ramp generator, an inexpensive alternative to commercial function generators, provides a more linear and repeatable output than conventional analog integrators. The circuit provides a triangle waveform in burst mode; in this case, two cycles of 10.24....
The three schematics represent three building blocks for a 10-meter SSB transmitter. Or these blocks can be used separately as circuit modules for other transmitters. The VFO board uses an FET transmittal oscillator, the VFO signal is mixed in an NE602....
Field effect transistor, Ql, operates in the linear resistive region to provide automatic gain control. Because the attenuation of the RC network is one-third at the zero phase-shift oscillation frequency, the amplifier gain determined by resistor R2 and....
This circuit turns-off an amplifier or any other device when a low level audio signal fed to its input is absent for 15 minutes at least. Pushing P1 the device is switched-on feeding any appliance connected to SK1. Input audio signal is boosted and squared....
If you use different batteries with actual capacity, with different self-discharge rate of batteries from different manufacturers, you will perhaps throw further described charger. Because each cell can be discharged separately recharge, can be charged with....
The IC8211 provides the voltage reference and regulator amplifier, while Ql is the series pass transistor. Rl defines the output current of the IC8211, while Cl and C2 provide loop stability and also act to suppress feedthrough of input transients to the....
This circuit is designed around a 4049 hex inverter/buffer. Two inverters are used ina dual-frequency signal-injector circuit, another inverter is used as a logic probe, and the remaining three inverters are used as a sensitive dual-input, audio-signal....
This is a simple serial port buffer circuit I designed for a friend to speed up his SLIP connection in campus computer network "TRINET" of Helsinki University of Technology. The problem in the network was that the RS232 commections from rooms to terminal....
RS-232C serial port lines are quite prone to be damaged by overvoltages. The damaged to computer serial ports have become more and more expensive to replace because of higher intergaration: usually you have to buy new motherboard if one serial port in it....
The LT®1932 is a fixed frequency step-up DC/DC converter designed to operate as a constant-current source. Because it directly regulates output current, the LT1932 is ideal for driving light emitting diodes (LEDs) whose light intensity is proportional to the....
Light filtering through the finger tip is detected by the cadmium sulphide photoresistor CD1 which forms the feedback network for transducer amplifier section ICA producing a weak signal which is further amplified by ICB. This signal is now compared against....
This circuit uses the output of the IGL8049 to control the frequency of the IGL3038 waveform generator; the 741 op amp is used to linearize the voltage-frequency response. The input voltage to the 8049 can be, for example, from the horizontal sweep signal....
This is a compass circuit based at AT90S2313. The output drives 8 LEDs to indicate the different horizon directions...
A pair of diodes and a quarter-wave transmission line are used as an automatic TR switch. D1 and D2 conduct during transmit periods, short- circuiting the scanner input. In this mode,-the K-wave line appears as an open circuit...
In the Fig.1, exist a circuit, which is a sensitive switch that corresponds in AC signals of input, for signals above 5mV. Corresponds in all the signals from 50 HZ until 3KHZ, region in which found the human voice. The RV1 is regulated so much what RL1 it?s....
The 555 is wired as an astable and the capacitor is charged only through the 4,7Kohm trimmer (notice the diode) and discharged only through the 2.2 Kohm trimmer, making the duty cycle full adjustable. The square wave is then feed in a totem pole made up of a....
Infrared emissions detected by Ql are fed through Ula to Ulb, which amplifies the signal by a factor of 100. The amplified output ofUlb is fed to Ulc through R9, C2, and R6. Potentiometer R9 serves as a volume control. With R9 set to pass the maximum....
H ere is a circuit of an off-line telephone tester which does not require any telephone line for testing a telephone instrument. The circuit is so simple that it can be easily assembled even by a novice having very little knowledge of electronics. A....
If you are familiar with LED flashers using transistor, you may know the basic one uses two transistor, one capacitor and three resistors. There is other kind of oscillator called "flip-flop". As I'm starting to develop some basic circuits, I need a simple....
Built around an LM380, this amplifier includes tone controls and electronic "soft switching". The soft switching circuitry ensures power is built up gradually eliminating the dc thump. The soft switching is enabled by a BD131 transistor wired as a switch in....
The unit consists of a direct conversion receiver and 1-W transmitter. The direct conversion receiver VFO is tuned just off frequency from the incoming signal. This difference in frequency produces a clean, strong, and solid audio tone signal. Detect the....
The frequency covered is from 0.1Hz to 10Hz and useful signals are received up to 16Hz. The first Op-Amp, properly shielded, must be installed close to the antenna (1-3m long) and connected to the rest of the circuit with a 5-core shielded cable. Adjust the....
Although the output is low level and cannot be loaded significantly without harming -accuracy, a single I.C. operational or instrumentation amplifier can supply both the linear gain and buffering for use with a variety of loads. ..
The only adjustments that require close attention are input, output, and neutralization. The 150-pF capacitor in the input line compensates for impedance mismatch. You tune for maximum signal transfer from exiter to final with an in-line meter or external....
This circuit is very basic to build. To open a lock which is connected to the K1 Load, you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1, S2, S3 and finally S4. If any of the other switches are pressed the....
This simple circuit will find many applications as a battery eliminator for low power requirements. It consists of a transformer, a bridge rectifier and an electrolytic capacitor followed by a zener controlled series pass transistor. The output is stabilized....
When the phototransistor is stroken by IR light it conducts and the voltage between the 1Mohm resistor(arbitrary) and the phototrans drops from VCC to lower values. When the voltage drops lower than VCC/3 the 555 is triggered and goes high (from 0 TO VCC).....
The Clock Controller was designed to be an exemplary of using 'C' language to control timer0interrupt, 7-segment LED and keypad scanning. It provides 1-bit sink currentdriving output, for driving a relay, opto-triac, say. Many projects requiring7-segment....
Because of its high amplification factor and built-in power-output stage, an integrated power operational amplifier makes a convenient driver for ac motors. One op amp can be configured as an oscillator to generate the required ac signal. The power-output....
The circuit has a flat frequency response from about 20Hz to well over 50Khz. Input sensitivity is 100mV for a full scale deflection on a 100uA meter. Built on two common emitter amplifiers, the first stage has a preset resistor which may be adjusted for a....
The circuit generates low-level rf bursts having frequencies as high as 10 MHz, thus permitting field testing of high frequency receivers. A jumper-selectable binary fraction (liz to "1256 of the Y1 crystal frequency gates the output rf signal. Output....
One application of this handy circuit is a graphic equalizer, created by feeding a signal to a number of parallel band-pass filters each tuned to a different frequency; typically octaves apart. Then, you can adjust the strength in each band via a front panel....
This contributed project is a result of considerable collaboration between Sergio and myself, and should not be seen as necessarily a complete project in itself, but a stepping stone to understanding switching power supplies, how they work, and what you can....
this circuit rougly doubles the voltage of the input, however the current output is low. doubled output is at `V source.`..
The tuning range is determined by coil (L) dimensions and setting of Cl. Coils can be plugged in for multirange use or soldered in place if only limited frequency range is of interest. Cl = 36 pF variable, C2 = 047 disc, D = 1N60 (germanium) and M=0-1 mA meter..
Here is a circuit for using the printer port of a PC, for control application using software and some interface hardware. The interface circuit along with the given software can be used with the printer port of any PC for controlling up to eight equipment .....
Most car door switches are simply single-pole switches, with one side grounded. When the door is opened the switch grounds the other line thus completing the light circuit. In a car where the negative terminal of the battery is connected to the chassis, the....
The circuit is shown in Figure 1, and as described above, uses a voltage doubler rectifier. Diodes D1 and D2 are 1N4004 or similar. From there, a pair of resistors provide additional smoothing to the secondary filter caps. R3 is used to balance the voltage....
With this circuit, we can have a acoustic clue, frequency 2KHZ, when we have a short vibration in his entry. It is constituted from monostable multivibritor (with schmitt trigger inputs), with duration roughly 100msec, oscillator TTL, that oscillating in....
This circuit uses a CA5422 dual BiMOS microprocessor op amp. The bootstrap amplifiers minimize bias currents while maintaining electrostatic discharge protection. ..
IC3 acts as an oscillator which operates if the output of ICl is high. With the values used the two frequencies produced are about 800 Hz and 2500 Hz. The output is buffered by Ql which drives the speaker. The first IC is used to generate the tone duration....
Pulse Generator kit will generate a frequency in KHz which can form a good test gear project. This kit is based on the classic LM555 timer IC. Input - 12 VDC Max @ 40 mA. Range - jumper selectable and preset tunable range of 1 Hz to 180 KHz. Power-On LED....
if the timer is triggered with a continuous pulse train in the monostable mode of operation, the charge time of the capacitor can be varied by changing the control voltage at pin 3..
This circuit is useful for removing ground loop hum on a remote line level audio signal line. It can be used to to connect a computer sound card to a stereo amplifier`s line input. Other uses include tapping into a line level signal for powering a remote....
The following circuit Diagram of (DUAL VOLTAGE POWER SUPPLY ) can be used for Misc.. application. It requires a few components to built. The most important components of this circuit are REGULATORS. 1 : (AN) 7812 and 2 : (AN) 7912 AN7812 is the Positive....
This, circuit is a programmable current source in which op amp LT1102 (Linear Technology Corp.) is used..
Here is a schematic of a rechargeable 9-LED flashlight using two Gates SLA cells and nine LEDs. It is as bright as when the single bulb was used, and lasts 3 times longer per charge. That is about 10 hours of bright light, at a lower brightness, is available....
A Wien-bridge oscillator can be made Vllriable by using two frequency-determining parts that are varied simultaneously at high tracking accuracy. High-quality tracking potentiometers or variable capacitors are, however, expensive and difficult to obtain.....
This circuit can be used to recieve AM stations in an FM radio. Is a regenerative circuit that samples AM signals of all frequency and retransmits them in the FM band or in TV band...
This circuit has proved very useful in keeping away from a terrace or a porch some bats and other nocturnal animals. You can use it for similar or different purposes. The lamp illuminates for a 4-5 seconds delay and stays off about one minute and 15 seconds.....
This circuit has been designed to drive an 8-W fluorescent lamp from a 12-V source using an inexpensive inverter based on the ZTX652 transistor. The inverter will operate from supplies in the range of 10 to 16.5 V, thus making it suitable for use in....
This amplifier employs a cascaded op amp integrator and transistor buffer, Q1, to drive the gain control element. Except for a simple modification, the HA-5190/5195 stage is connected as a conventional noninverting op amp, and includes input and output....
This circuit is intended for use with motors, lamps,heatings etc. Continuously from nearly zero up to maximum capacity (5-95%). Almost lossfree control by means of this impulse control. Nearly total turning moment of motors. The transistior T3 must....
In the miniature high-voltage dc generator, the input to the circuit, taken from a 12-Vdc power supply, is magnified to provide a 10,000-Vdc output causing a pulsating signal, of opposite polarity, to be induced in Tl`s secondary winding. The pulsating dc....
A TMOS MTM7N45 (Q2) is used as a series pass element in a linear high voltage supply that accepts +275-V unregulated and produces 250 V regulated with foldback current limiting. A 15-V zener, Dlf provides the dc reference for operational amplifier Ul, whose....
Stepdown transformer T1 drops the incoming line voltage to approximately 48 Vac which is rectified by diode D1; the resultant de charges capacitor C1-through current limiting resistor Rl-to a voltage level preset by R4. When the voltage on R4"s wiper....
This schematic uses the 555 timer and the 4017 IC to drive 3 LED, to simulate the trafic lights...
This circuit has proved to be an effective video buffer and will easily drive a 75- load to 1.5-V p-p output. BW is better than 20 MHz and there is less than 0.05-V dc offset, which is the difference in VBE of Ql and Q2...
This circuit functions with inaudible (ultrasonic) sound. Sound of frequency up to 20 kHz is audible to human beings. The sound of frequency above 20 kHz is called ultrasonic sound. The circuit described generates (transmits) ultrasonic sound of frequency....
The LM3909 is configured so that the frequency of oscillation is dependent on a single RC timing circuit, which consists of..
This simple and inexpensive circuit can produce a dual (positive and negative) voltage from a single supply input. It is therefore extremely useful for powering opamp and other circuits that require a dual voltage from a single battery. The circuit will....
Signals of identical frequency are applied to sync input (Pin 6) and to the demodulator input (Pin 4), respectively, the demodulator functions as a phase detector with output dc component being proportional to phase difference between the two inputs. The....
The circuit this month is a simple 8 light chaser built around a PIC. This will demonstrate how easy it is to program a PIC and to utilize it in a circuit. The circuit works as follows. When power is supplied to the circuit the PIC resets and starts to....
Circuit provides a minimum of 7 V until the 9-V battery voltage falls to less than 2 V. When the battery voltage is above 7 V, the MAX630"s IC pin is low, putting it into the shutdown mode which draws only 10 nA. When the battery voltage falls to 7 V, the....
This current source has continuous control of the magnitude and polarity of its amplifier gain and needs only one voltage reference. The circuit includes reference ~, voltage-amplifier circuit A1 with gainsetting resistor Rs, and bootstrap-follower....
The circuit has both square-wave and triangle-wave output. The left section is similar in function to a comparator circuit that uses positive feedback for hysteresis. The inverting input is biased at one-half the Vcc voltage by resistors R4 and R5. The....
This CMOS circuit can be used as a 1-shot time delay switch and general-purpose timer. The circuit consists of a gated oscillator and a latch made from one CD4001 quad 2-input NOR gate as shown and a CD4020 14-stage counter. TON is a function of the....
When a discharged gel cell is connected, the charger goes into a fast charge mode at a fixed rate of 400 ma. After the chip detects the voltage leveling off or when 4 1/2 hours has elapsed. (which ever happens first.) the fast charge will stop. After the....
Build-in charger for instruments powered by single lithium-ion or Li-Pol accumulator. If external power supply not conected to charger, current back from the accu charger is very small. New version improved temperature stability and Not Needed NTC....
Intended for extreme temperature, radiation-hardened environments, this linear supply is capable of supplying 28 Vdc at 125 A from an ac-driven power unit. In operation, power supply output voltage is sensed by the voltage divider consisting of R24 to R28....
Many systems require one or more relatively low-current voltage sources which can be programmed tna few predetermined levels. The circuit shown above produces positive output levels, but could be modified for negative or bipolar outputs. Q1 is the series....
This Field Strength Meter is simple and also quite sensitive. It uses an ordinary digital voltmeter to measure RF signal strength up to a few hundred MHz. The multimeter should be set to the lowest dc volts range for maximum sensitivity. This is normally....
This circuit differs from similar circuits in view of its simplicity and a totally different concept of generating the control signals. Usually remote control circuits make use of infrared light to transmit control signals. Their use is thus limited to a....
Wine doesn`t like subzero temperatures, and during wintertime, my "winecellar" got pretty cold. There was an electric heating element, but the thermostat was broken, so it was either full burn or nothing. That`s how the temperature monitor/controller came to....
The signal emitted by an IR remote control contains two parts, the control pulses and a modulated carrier wave. The control pulses are used to modulate the carrier, a popular modulation frequency being 36 and 42KHz. The signal is radiated by an IR diode,....
The simple circuit design in Figure 1 lets you measure all components of a current flowing in a dc servo motor. The rectified output of the circuit uses ground as a reference, so you can measure the output by using a single-ended A/D converter. The....
The circuit of the mains current detector is shown in Figure 1. By using a few cheap diodes, a resistor, LED and LDR, a simple opto-isolated detector can be created. This entire circuit dissipates very low power, and can safely be housed in a heatshrink....
By repetitively charging and discharging a capacitor through the primary of an induction coil with a high voltage, an ultra high emf is induced in the secondary. Switching is performed by the triac, triggered by the disc at times set by Cl and Rl. With a 12....
This set of two circuits from the basis for a very simple light wave transmitter. A LASER beam is modulated and then aimed at a receiver that demodulates the signal and then presents the information (voice, data, etc..). The whole thing is very easy to build....
Two low voltage, low power zeners are used to control electronically the level of an audio signal. The attenuation range is from 6 to 58dB for an input current from 0.042 to 77mA corresponding to a control voltage from 2.7 to 7.5V. If control voltage is....
Output-clamp diodes are mandatory because loudspeakers are inductive loads. Output LR isolation is also used because audio amplifiers are usually expected to handle up to 2 mF load capacitance. Large, supply-bypass capacitors located close to the IC are used....
In applications involving strain gauges, accelerometers, and thermal sensors, a bridge transducer is often used. Frequently, the sensor elements are high resistance units requiring equally high bridge resistance for good sensitivity. This type of circuit....
The amplifier"s input stage is a dual-gate GaAs FET, which provides low input capacitance and high transconductance. The dual-gate structure accepts the signal on input 1. Input 2 controls the gain of the amplifier. The amplifier has a third input for use....
Since my page was first posted, I have received a number of emails asking about a high current power supply. I looked around, but couldn`t find one that was suitable. So, I designed this. It is a linear supply, which might have a few of you rolling your....
The program loaded in the 12F675 device which has no osccal value will force a pulse on GPIO.4 and it will make a loop while increasing the osccal value internally. GPIO.5 will send the current osccal value used for each pulse sent. Because the device has....
This report deals with the design for a small asynchronous serial data switch. The switch architecture allows 14 serial ports supporting a subset of the RS-232 protocol. The requirements for the switch are discussed. The hardware interfaces are described in....
Differential multiplexers are generally used in process control applications to eliminate errors due to common mode signals. In this circuit however, advantage is taken of the dual multiplexing capability of the switch. This is achieved by using the....
The F84 MRTC was my second design of a miniature real-time controller. This version uses PIC16F84 running with a low power X-tal 32,768Hz. The scheduler for 6-channel output was saved in EEPROM. No terminal for serial downloading of the scheduler. It`s....
This document describes the HSETI PCB. This PCB is a small simple application for the Atmel AT89C2051 microprocessor - a 20 pin 8051 variant, with FLASH (reprogrammable) program memory. The board has just two chips on it, the CPU and a driver/buffer...
The circuit will come handy when you have to follow the mains wires buried in the wall or even water pipes provided they are not too far away (2-4cm max). It will also detect a conversation on a telephone cable without actually touching it (for testing....
