New Circuits Page 239
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This Design Idea presents a simplified ac high-voltage amplifier that uses complementary, cascaded NMOS and PMOS transistors (Figure 1). The OP07 op amp has low input-offset voltage, low input-bias current, and high open-loop gain...
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This circuit consists of twin-T sine-wave oscillators. Each oscillator has a filter in the feedback loop. If the loop gain is greater than unity, the circuit will oscillate. Gain is adjusted to be just less than unity. Touching the touch plate starts the....
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Two complementary MOSFETs are used to deliver 20 W into 8 . A TL071 op amp is used as an input amplifier. The MOSFETs should be heatsinked with a heatsink of better than 5C/W capability...
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This basically the frequency meter section of the frequency meter/pulse generator based on the AT90S2313 described elsewhere on this site, combined with the 100 MHz RF interface described in the page about the RS-232 to 100 MHz RF desktop channel adapter.....
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The ratio of capacitors Cl and C2 determines division. With a positive pulse applied to the base of Ql, assume that Cl = C2 and that Cl and C2 are discharged. When {31 turns off, both Cl and C2 charge to 10 volts each through R3. On the next pulse to the....
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The circuit uses the primary current of a small 6 volt filament transformer to actuate a triac and energize the load. When switch Si, in the six-volt secondary, of the transformer is open, a small "magnetizing" current flows through the primary winding. This....
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A general purpose audio power amplifier is a must have for the electronics amateur. It's not a good thing to use your HiFi set for an experiment, when there's a risk of blowing it's transistor out. Amplifier for your experiments should be simple in....
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The quad operational amplifier circuit yields full 0 to 100 percent pulse width control. The controller uses an LM3900 requires only a single supply voltage of 4-30 V. The pulse repetition frequency is set by a 1 kHz oscillator amplifier that integrates AI.....
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Astable or free-running multivibrators have been used in home-built amateur radio equipment for many years. The basic circuit is a two stage amplifier with AC-coupled feedback from output to input. One transistor stage is on ( conducting current ) while the....
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This project is basically what I use for a quick prototype, or for just mucking about with an idea. It is easy to make, and only needs a medium size sheet of un-etched printed circuit board (or possibly two). This can usually be obtained from electronics....
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Ring detection is a common task in telephony-related digital design. The goal is to sense an ac ringing voltage applied to the telephone line by a central office or PBX (private branch exchange) and then pass an appropriate signal to the µC or µP. Figure 1a....
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The fax mate separates the fax machine from the phorie line, rings the fax machine on command, connects equipment to incoming lines, and senses the end of the message. When a touch tone pound signal (#) is detected, it actuates a ring greater and driver for....
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LED's are great display tools. Their prices have decreased to a point where they are replacing more conventional light sources. In one sense their characteristic need for low voltages is an advantage e.g compatibility with I.C drives, but this voltage....
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The regenerative detector uses a field effect transistor (FET). Like with the better valve designs, feedback is controlled by a variable capacitor. A ferrite rod was used to allow reception of local stations without an external antenna. This FET stage forms....
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This circuit senses the video from the VCR. When the VCR is turned on, video signal is amplified by U3A and to drive Ql, activating Kl. In this manner, it is not necessary to turn on and off two video devices every time. In many cases, this avoids the use....
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The circuit below uses a CMOS dual D flip flop (CD4013) to toggle a relay or other load with a momentary push button. Several push buttons can be wired in parallel to control the relay from multiple locations...
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The HllC supplies the de latching relay function and reverse polarity blocking, for currents up to 300 mA, depending on ambient temperature. For de use, the gate cathode resistor can be supplemented by a capacitor to minimize transient and dV/dt....
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Ll, Ql, L2, and L3 compose an RF amplifier stage that feeds Ml, a doubly balanced mixer. Q4 is a l..
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This circuit is intended to let the user turn off a lamp by means of a switch placed far from bed, allowing him enough time to lie down before the lamp really switches off. 15 seconds delayed switch-off
A good idea for bedroom lamps.
Obviously, users will....
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You won't be disappointed with the performance of this sensitive ultrasonic receiver. It can let you listen to bugs, bats, engines, and virtually any other source of ultrasonic sounds. The circuit uses a piezo tweeter as an ultrasonic microphone, amplifier....
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The 555 timer produces a rapid series of pulses whenever switch SI is open. These pulses are counted in groups of 16 and converted into binary form by the 7493 and applied to the 74154 (a l-of-16 decoder/demultiplexer) wired so that each of its 16 output....
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Pretty nice design for a cheap consumer grade flashlight. The power switch was not exactly as shown since there was an option to have the lamp on solid...
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The simple circuit transforms the steady beep of an audible-signal device, such as a Mallory sonalert, into a distinctive warble or chirp. The value of R, C2 determines just what tone color you"ll get. With 1k the 1-I"F value shown, the circuit produces....
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This circuit extracts the sync pulses from a video signal over a wide range of amplitudes and operates a single +15 V supply. IC1 buffers and amplifies the incoming signal and applies it via C3 to the peak detector, consisting of D2 and C4. It is also....
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The Above circuits are based on TEA2025 is a monolithic integrated audio amplifier in a 16-pin plastic dual in line package manufactured by UTC .Circuit has an Internal Thermal Protector. It is designed for portable cassette players and radios. You can also....
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The protection circuit output amplifiers and speakers, has some interesting features such as isolating the speaker from the amplifier output when shown a continuous trend in output or when the temperature gets too much cooler while providing a time delay and....
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The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840. The IRF series of power transistors are available in various voltage and power ratings. A single IRF840 can handle maximum power output of 125 watts. Since these....
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Use CA3164A BiMOS detector/alarm system. For operation as smoke detector with electromechanical hom (Fig. 40-la), the output of driver at terminal 8 is used. Large npn transistor Q3,-with an active pull-up and transistor Q2 provide over 300 mA of drive....
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R1 controls the trip-point of the circuit. adjust it accordingly. to reverse the logic (have the led light up when the battery has at least X amount of power,) connect the led to ground through R4...
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As you know the AT90S1200 microcontroller include an internal RC oscillator that is disabled by default. If you want to change it (enable or disable) you must to program it with parallel mode. The most programmers working with serial mode and its not....
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This circuit makes a very compact level indicator where a meter would be impractical or not justified due to cost. Resistor values will depend on type of LED used. For MV50 LEDs the resistors are 2 K for steps of approx 2 V and current drain with all three....
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The circuit consists of 6 building blocks and the first is the inverter between pins 1 and 2. This forms a low frequency oscillator with a 1u and 1M + 2M2 resistor. It governs the overall timing of the ring by creating an ON and OFF time. When the output is....
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Owing to the recent launching in Europe of Cranial Electrotherapy Stimulation (CES) portable sets, we have been "Electronically Stimulated" in designing a similar circuit for the sake of Hobbyists. CES is the most popular technique for electrically boosting....
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The comparator has an output pull-up resistor RL and is connected up to operate as a Schmitt trigger using the single rail supply Vcc. The feedback resistors Rl and R2 give upper and lower threshold levels VT+, VWxw, respectively. VT+ is easily set by....
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Pressing the pushbutton of the transmitter, a sound and/or light alert is activated in the receiver. The system uses no wiring or radio frequencies: the transmitted signal is conveyed into the mains supply line. It can be used at home, in any room from attic....
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ICl, a 555 timer, is set up as an astable multivibrator to produce the signal that triggers IC2, a 7490 decade counter. That IC, in turn, produces a BCD output that is fed to IC3, a 7445 BCD-to-decimal decoder/driver. IC3"s output is inverted by two hex....
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Start-up is a stressful time for the power driver section of
a switching power supply. Because the output voltage is
initially zero, the feedback error initially jumps to its maximum.
The large feedback error then drives the loop filter
to its limit,....
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If you`re an effects builder or repairer, you know by now that it`s a good idea to protect the circuitry in the effect from the consequences of a reversed battery. While many older effects can withstand a momentary reversal, some more modern components can....
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This is a simple servo tester which will comprehensively test the capabilities of almost any modern servo. It has two pushbuttons, CENTRE and SWEEP and a potentiometer which works as follows:
- CENTRE Does exactly that, centers the servo, afterwards the....
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Here exist a small collection from three generators, what using crystal for basic production of oscillations. Each generator uses different topology of circuit for the production of oscillations.
..
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The Analog Interface Unit (AIU) is a simple circuit that connects to a PC parallel port, and allows you to sample and output 8-bit analog signals under software control...
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The reason why I'm using a LCD display is because it allow me to display many characters and it doesn't need to be "refreshed" as 7-segment Led displays. Also, the interface requieres less I/O pins.
For this project I used a 16x1 LCD Display with 4-bits....
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Based on the classic Baxendall tone control circuit, this provides a maximum cut and boost of around 10dB at 10KHz and 50Hz. As the controls are passive, the first transistor, Q1, is configured as common-collector to act as a buffer stage. The last....
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A piezoelectric detector (BZ1) is used in this circuit to detect a change in air pressure. BZ1 produces a volt..
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A battery is a vital element of any battery-backed system. In many cases the battery is more expensive than the system it is backing up. Hence we need to adopt all practical measures to conserve battery life.
As per manufacturer's data sheets, a 12V....
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This power supply is able to deliver adjustable center-tapped DC from 0 to about 30 volts, as well as AC directly from the Variac and from the main transformer before the rectifier. What's primitive by today's standard is that it is not voltage regulated;....
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This circuit is a bidirectional amplifier that can amplify both signals of a duplex telephone conversation. It uses the principle of negative resistance. Obviously, such an amplifier could easily be unstable; however, you can adjust Rl for maximum....
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The LED indicates the status of a remote telephone. The light is off if the phone is hung up. It shines steadily if the phone is off hook, and it flashes on and off while phone rings and for 5 seconds after ringing stops. The flashing oscillator operates....
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When the water level is low, the probe is out of the water and SCRl is triggered on. It conducts and imposes a heavy load on transformer Tl"s secondary winding. That load is reflected back into the primary, gating triac TRl on, which energizes the load. If....
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The 566 can be wired as a positive or negative ramp generator. In the positive ramp generator, the external transistor driven by the Pin 3 output rapidly discharges Cl at the end of the charging period so that charging can resume instantaneously. The pnp....
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Recently, most digital video equipments, such as video recorder, DVD player and TV game, have component video output. The component video signal is like RGB video signal, but it cannot connect to RGB monitor directly. Thus I designed and built YUV(YCrCb) to....
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This battery tester makes use of an LM3914 bar-graph driver IC. SI selects load on battery under test and programs the volta..
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The RS232 transceiver supports both RS232 and EIA-562
standards, whereas the RS485 transceiver supports both
RS485 and RS422 standards. The logic input (MODE) selects
between RS232 and RS485 modes. With three additional
control logic inputs (RXEN, DXEN....
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The old and omnipresent NE555 can be very good at something it was not meant for: driving relays or other loads up to 200 mA. The picture shows an example circuit: if the input level rises over 2/3 of the supply voltage - it will turn on the relay, and the....
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This buck-derived circuit provides up to 8 A at 5 Vdc operating off 24 to 32 Vdc. The two power MOSFETs in the circuit conduct alternately for equal periods. Switching frequency is 150 kHz, set by the PWM125 controller. Output of the two MOSFETs is....
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The usual method for using a current-feedback amplifier to drive a capacitive load isolates the loa..
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This project is probably the most ambitious so far, and can be expected to be very expensive. On the positive side, it is also capable of excellent performance, and can be tailored to suit your exact specifications. There are several different input modules....
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This circuit uses a single chip, IC BA3812L for realizing a 5 band graphic equalizer for use in hi-fi audio systems.The BA3812L is a five-point graphic equalizer that has all the required functions integrated onto one IC. The IC is comprised of the five tone....
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This reflex radio project was inspired by Robert Bazian 's design. His reflex radio is the "darndest" thing I have seen and his spectacular results inspired me to come up with my own version! These designs are similar to two-transistor circuits used in some....
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The quartz QZ1 of the preceding receivers which set the work frequency is not on the market any more. It is replaced
by a locking phase loop allowing the free choice of an unspecified frequency on the band used, either the 41, or the 72 MHz. The step....
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If you do not like the whip antenna on your car, you may try this alternative circuit. A one-turn loop is installed in the windscreen of the car, keeping possibly away from the metal structure of the car. This loop is terminated in a 6.5mm ring core suitable....
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The circuit shows the method of `mirror` current sensing a MOSFET. A fully conducting MOSFET is resistive and behaves exactly as a resistor. It therefore you limit the voltage across the MOSFET when it is conducting you automatically limit the current....
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This probe is useful for any low level RF work, and simply connects to your multimeter. The voltage shown will not be accurate, since this is a rectifier probe, but the measurements are good enough for you to be able to determine where the RF stops, or if a....
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Applications such as photoelectric control, temperature detection and moisture sensing require a circuit that can accurately detect a given resistance ratio. A simple technique that uses an op amp as a sensing element can provide 0,5% accuracy with low parts....
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This Project is used to control a single phase Motor from any where in the world through the telephone. The circuit consists of a DTMF tone detector and a powerful 8 bit Microcontroller AT89S52. The Microcontroller senses the DTMF signal through the DTMF....
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This circuit give low level output, when exist enough lighting, that is a detector of light. It can give, say ,command turn on somebodies lights, when fall the dark. His exit is compatible with TTL level and it give low logic level, when phototransistor Q1,....
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The circuit in Figure 1 allows you to light any type of LED from a single cell whose voltage ranges from 1 to 1.5V. This range accommodates alkaline, carbon-zinc, NiCd, or NiMH single cells. The circuit`s principal application is in LED-based flashlights,....
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Mobile robots need simple and lightweight dc-motor-speed-control hardware that can work with low-power batteries. Flip-flop type navigation systems allow only one motor to operate at a time while the other motor remains off. Navigation direction changes....
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This circuit shows how to cascade counters and retain correct leading zero blanking. The NAND gate detects whether a digit is active since one of the two segments a or b is active on any unblanked number. The flip flop is clocked by the least significant....
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Though this setup can act as a cost-effective current source with an output accurate to 1%, the voltage offset will turn on the current source even when Vqq equals Vin. 2. Modifying the configuration of Figure 1 can rectify the problem of the current source....
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The Dremel drill fitted with a mini drill-chuck on a stand is a great setup for drilling circuit boards. The problem is that it does not do low speeds very well. My unit had a failed internal speed controller, so I just wired around it and connected it to a....
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A state-of-the-art silicon temperature sensor like MAX6577 measures a remote temperature far from
the host system. The temperature sensor converts this temperature into a square wave with a
frequency proportional to the absolute temperature of its package,....
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A power transistor can be used to provide a high powered zener voltage from a low wattage zener. A 400 mW zener can be used where a 10 watt zener is required or a 1 W zener can be used where a 50 to 80 watt zener is required by using appropriate transistors....
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This circuit consists of an amplifier and video detector with a second subcarrier detector for synch recovery purposes. A pulse-former circuit modulates the gain of the main channel increasing it during synch intervals. ..
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The baseband-audio input comes from the pole of switch Sl in the stereo decoder, and is coupled to IC1 (a CA3089) via a 78.6 kHz bandpass filter that consists of capacitors Cl and C2, and inductor Ll. IC1 is a combination i-f amplifier and quadrature....
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This circuit uses a Hall-effect sensor, consisting of an IC that resides in a small gap in a flux-collector torrid, to measure de current in the range of 0 to 40 A. You wrap the current-carrying wire through the toroid; the Hall voltage VH is then linearly....
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No description available...
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This simple circuit is started running by connecting a twelve volt battery across the terminals, causing the large diameter Light-Emitting Diode to light up. When the battery is removed, the LED stays lit up because the circuit has become self-powering.....
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This unit recieves DMX 512 data and Analogue (0- 10v) data and uses these to phase angle control mains output. Features: DMX 512 data Input. Analogue (0- 10v )DC Input. 4 Output channels. Remotley programmable Interally saved Presets. 3 Modes of operation....
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An ordinary automatic room power control circuit has only one light sensor. So when a person enters the room it gets one pulse and the lights come on. When the person goes out it gets another pulse and the lights go off. But what happens when two persons....
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The Tiny Audio Amplifier kit is a good choice for battery operation. It is based on LM386 IC. Power supply - 6 - 12 VDC. Output power - 1 W, 8 Ohm. The quiescent power drain is only 24 mW when operating from 6 VDC. Self-centering output quiescent voltage.....
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This simple inexpensive audio amplifier can be constructed using a couple of T0-220 monolithic Darlington transistors for the push-pull output stage. Frequency response is fiat within 1 dB from 30 Hz to 200 kHz with typical harmonic distortion below 0%. The....
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The above circuit can be useful to detect if the load of any battery charger or plug-in adaptor supply is not properly connected. The load can be a set of batteries to be charged or any other type of battery or low dc voltage operated device...
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Here`s how to make a good charger for a sealed lead-acid battery (this will NOT work with NiCad batteries) that`s faster (because it allows more current into the battery initially) and safer (because it uses lower voltage when the charging is finished). The....
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Charging is accomplished with a constant current of 60 mA for AA cells to a cutoff voltage of 2.4 V per cell at which point the charge must be terminated. The charging system shown is designed for multi-cell battery packs of 2 to 6 series-connected cells or....
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Transistor Ql, a 2N3563, and its associated components form an oscillator circuit that will oscillate if, and only if, a good crystal is connected to the test clips. The output from the oscillator is then rectified by the two 1N4148 diodes and filtered by....
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In designing µC-based systems, you often face a situation in which the µC has to respond to an external event happening at an uncertain moment in time. One example is receiving an echo from an object in a pulse-range measuring system. In these situations,....
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The DS1602 and DS1603 from Dallas Semiconductor offer a simplified hardware solution for keeping time as well as tracking powered up time of a system. The DS1602 and DS1603 can be read and written directly by a microprocessor or microcontroller using simple....
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This article discusses application circuits for Maxim force/sense digital-to-analog converters (DACs). Applications include: selectable fixed-gain DAC, programmable gain DAC, photodiode bias control, amperometric sensor control, digitally programmable....
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The 20-MHz clock phase-locks to Apple"s Mac II 10-MHz NuBus clock. It uses a simple, inexpensive CMOS circuitry to generate 10-and 20-MHz square waves. The output duty cycle settings are insensitive to Vee variations. The input to the circuit is a NuBus....
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The VPP generator circuits shown here cover a range of
30mA to 240mA with 3.3V or 5V inputs as noted. Table 1
summarizes these circuits for quick reference...
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The 2400-bps modem in Figure 1 makes it easy to connect a Basic Stamp (Parallax Inc, www.parallaxinc.com) to a telephone modem. Using this circuit, you can call home via your PC and find out if the house is still there. The Basic Stamp2, BS2-IC, has the....
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This very simple circuit just uses a couple of resistors, a capacitor and the easily available 555 timer IC.
The 555 is setup as an astable multivibrator operating at a frequency of about 1kHz that produces a shrill noise when switched on. The frequency can....
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The HA-5033 is a unity gain monolithic lC designed for any
application requiring a fast wideband buffer. A voltage
follower by design, this product is optimized for high speed
50W and 75W coaxial cable driver applications common in
color video systems.....
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It's a great convenience that most modern cars come with a built in alarm, however it is nothing but noise pollution that the horn sounds when the alarm is armed. Disconnecting the alarm system from the horn relay will eliminate this, but prevent the horn....
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Most current microprocessors, DSPs, and field-programmable gate arrays integrate hardware and software resources that support either or both of two common interface standardsSPI (serial-peripheral interface) and I2C (inter-IC)/SMBus. Both two-wire-interface....
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The circuit of preamplifier use the 5533 chip and features a combination of controls balance and volume. Due to the nonlinearity of the human auditory system, low frequencies must be boosted at low listening levels.
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The circuit has a "floating" output, i.e., it behaves like an isolated transformer winding, with the output amplitude remaining unchanged whether the center or either end of the load is grounded. This is achieved by making Z-out, common mode, infinite. The....
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The frequency range of this amplifier is 1.8 to 54 MHz. The amount of RF drive required for full output is about 30 W...
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The circuit shows a simple yes/no gas detector. Three 1.5-V D cells are used as a power supply, with SI acting as an on/off switch. The heater is energized directly from the battery, while the electrodes are in series with a 10 k resistor. The voltage across....
This Design Idea presents a simplified ac high-voltage amplifier that uses complementary, cascaded NMOS and PMOS transistors (Figure 1). The OP07 op amp has low input-offset voltage, low input-bias current, and high open-loop gain...
This circuit consists of twin-T sine-wave oscillators. Each oscillator has a filter in the feedback loop. If the loop gain is greater than unity, the circuit will oscillate. Gain is adjusted to be just less than unity. Touching the touch plate starts the....
Two complementary MOSFETs are used to deliver 20 W into 8 . A TL071 op amp is used as an input amplifier. The MOSFETs should be heatsinked with a heatsink of better than 5C/W capability...
This basically the frequency meter section of the frequency meter/pulse generator based on the AT90S2313 described elsewhere on this site, combined with the 100 MHz RF interface described in the page about the RS-232 to 100 MHz RF desktop channel adapter.....
The ratio of capacitors Cl and C2 determines division. With a positive pulse applied to the base of Ql, assume that Cl = C2 and that Cl and C2 are discharged. When {31 turns off, both Cl and C2 charge to 10 volts each through R3. On the next pulse to the....
The circuit uses the primary current of a small 6 volt filament transformer to actuate a triac and energize the load. When switch Si, in the six-volt secondary, of the transformer is open, a small "magnetizing" current flows through the primary winding. This....
A general purpose audio power amplifier is a must have for the electronics amateur. It's not a good thing to use your HiFi set for an experiment, when there's a risk of blowing it's transistor out. Amplifier for your experiments should be simple in....
The quad operational amplifier circuit yields full 0 to 100 percent pulse width control. The controller uses an LM3900 requires only a single supply voltage of 4-30 V. The pulse repetition frequency is set by a 1 kHz oscillator amplifier that integrates AI.....
Astable or free-running multivibrators have been used in home-built amateur radio equipment for many years. The basic circuit is a two stage amplifier with AC-coupled feedback from output to input. One transistor stage is on ( conducting current ) while the....
This project is basically what I use for a quick prototype, or for just mucking about with an idea. It is easy to make, and only needs a medium size sheet of un-etched printed circuit board (or possibly two). This can usually be obtained from electronics....
The fax mate separates the fax machine from the phorie line, rings the fax machine on command, connects equipment to incoming lines, and senses the end of the message. When a touch tone pound signal (#) is detected, it actuates a ring greater and driver for....
LED's are great display tools. Their prices have decreased to a point where they are replacing more conventional light sources. In one sense their characteristic need for low voltages is an advantage e.g compatibility with I.C drives, but this voltage....
The regenerative detector uses a field effect transistor (FET). Like with the better valve designs, feedback is controlled by a variable capacitor. A ferrite rod was used to allow reception of local stations without an external antenna. This FET stage forms....
This circuit senses the video from the VCR. When the VCR is turned on, video signal is amplified by U3A and to drive Ql, activating Kl. In this manner, it is not necessary to turn on and off two video devices every time. In many cases, this avoids the use....
The circuit below uses a CMOS dual D flip flop (CD4013) to toggle a relay or other load with a momentary push button. Several push buttons can be wired in parallel to control the relay from multiple locations...
The HllC supplies the de latching relay function and reverse polarity blocking, for currents up to 300 mA, depending on ambient temperature. For de use, the gate cathode resistor can be supplemented by a capacitor to minimize transient and dV/dt....
Ll, Ql, L2, and L3 compose an RF amplifier stage that feeds Ml, a doubly balanced mixer. Q4 is a l..
This circuit is intended to let the user turn off a lamp by means of a switch placed far from bed, allowing him enough time to lie down before the lamp really switches off. 15 seconds delayed switch-off A good idea for bedroom lamps. Obviously, users will....
You won't be disappointed with the performance of this sensitive ultrasonic receiver. It can let you listen to bugs, bats, engines, and virtually any other source of ultrasonic sounds. The circuit uses a piezo tweeter as an ultrasonic microphone, amplifier....
The 555 timer produces a rapid series of pulses whenever switch SI is open. These pulses are counted in groups of 16 and converted into binary form by the 7493 and applied to the 74154 (a l-of-16 decoder/demultiplexer) wired so that each of its 16 output....
Pretty nice design for a cheap consumer grade flashlight. The power switch was not exactly as shown since there was an option to have the lamp on solid...
The simple circuit transforms the steady beep of an audible-signal device, such as a Mallory sonalert, into a distinctive warble or chirp. The value of R, C2 determines just what tone color you"ll get. With 1k the 1-I"F value shown, the circuit produces....
This circuit extracts the sync pulses from a video signal over a wide range of amplitudes and operates a single +15 V supply. IC1 buffers and amplifies the incoming signal and applies it via C3 to the peak detector, consisting of D2 and C4. It is also....
The Above circuits are based on TEA2025 is a monolithic integrated audio amplifier in a 16-pin plastic dual in line package manufactured by UTC .Circuit has an Internal Thermal Protector. It is designed for portable cassette players and radios. You can also....
The protection circuit output amplifiers and speakers, has some interesting features such as isolating the speaker from the amplifier output when shown a continuous trend in output or when the temperature gets too much cooler while providing a time delay and....
The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840. The IRF series of power transistors are available in various voltage and power ratings. A single IRF840 can handle maximum power output of 125 watts. Since these....
Use CA3164A BiMOS detector/alarm system. For operation as smoke detector with electromechanical hom (Fig. 40-la), the output of driver at terminal 8 is used. Large npn transistor Q3,-with an active pull-up and transistor Q2 provide over 300 mA of drive....
R1 controls the trip-point of the circuit. adjust it accordingly. to reverse the logic (have the led light up when the battery has at least X amount of power,) connect the led to ground through R4...
As you know the AT90S1200 microcontroller include an internal RC oscillator that is disabled by default. If you want to change it (enable or disable) you must to program it with parallel mode. The most programmers working with serial mode and its not....
This circuit makes a very compact level indicator where a meter would be impractical or not justified due to cost. Resistor values will depend on type of LED used. For MV50 LEDs the resistors are 2 K for steps of approx 2 V and current drain with all three....
The circuit consists of 6 building blocks and the first is the inverter between pins 1 and 2. This forms a low frequency oscillator with a 1u and 1M + 2M2 resistor. It governs the overall timing of the ring by creating an ON and OFF time. When the output is....
Owing to the recent launching in Europe of Cranial Electrotherapy Stimulation (CES) portable sets, we have been "Electronically Stimulated" in designing a similar circuit for the sake of Hobbyists. CES is the most popular technique for electrically boosting....
The comparator has an output pull-up resistor RL and is connected up to operate as a Schmitt trigger using the single rail supply Vcc. The feedback resistors Rl and R2 give upper and lower threshold levels VT+, VWxw, respectively. VT+ is easily set by....
Pressing the pushbutton of the transmitter, a sound and/or light alert is activated in the receiver. The system uses no wiring or radio frequencies: the transmitted signal is conveyed into the mains supply line. It can be used at home, in any room from attic....
ICl, a 555 timer, is set up as an astable multivibrator to produce the signal that triggers IC2, a 7490 decade counter. That IC, in turn, produces a BCD output that is fed to IC3, a 7445 BCD-to-decimal decoder/driver. IC3"s output is inverted by two hex....
If you`re an effects builder or repairer, you know by now that it`s a good idea to protect the circuitry in the effect from the consequences of a reversed battery. While many older effects can withstand a momentary reversal, some more modern components can....
This is a simple servo tester which will comprehensively test the capabilities of almost any modern servo. It has two pushbuttons, CENTRE and SWEEP and a potentiometer which works as follows: - CENTRE Does exactly that, centers the servo, afterwards the....
Here exist a small collection from three generators, what using crystal for basic production of oscillations. Each generator uses different topology of circuit for the production of oscillations. ..
The Analog Interface Unit (AIU) is a simple circuit that connects to a PC parallel port, and allows you to sample and output 8-bit analog signals under software control...
The reason why I'm using a LCD display is because it allow me to display many characters and it doesn't need to be "refreshed" as 7-segment Led displays. Also, the interface requieres less I/O pins. For this project I used a 16x1 LCD Display with 4-bits....
Based on the classic Baxendall tone control circuit, this provides a maximum cut and boost of around 10dB at 10KHz and 50Hz. As the controls are passive, the first transistor, Q1, is configured as common-collector to act as a buffer stage. The last....
A piezoelectric detector (BZ1) is used in this circuit to detect a change in air pressure. BZ1 produces a volt..
A battery is a vital element of any battery-backed system. In many cases the battery is more expensive than the system it is backing up. Hence we need to adopt all practical measures to conserve battery life. As per manufacturer's data sheets, a 12V....
This power supply is able to deliver adjustable center-tapped DC from 0 to about 30 volts, as well as AC directly from the Variac and from the main transformer before the rectifier. What's primitive by today's standard is that it is not voltage regulated;....
This circuit is a bidirectional amplifier that can amplify both signals of a duplex telephone conversation. It uses the principle of negative resistance. Obviously, such an amplifier could easily be unstable; however, you can adjust Rl for maximum....
The LED indicates the status of a remote telephone. The light is off if the phone is hung up. It shines steadily if the phone is off hook, and it flashes on and off while phone rings and for 5 seconds after ringing stops. The flashing oscillator operates....
When the water level is low, the probe is out of the water and SCRl is triggered on. It conducts and imposes a heavy load on transformer Tl"s secondary winding. That load is reflected back into the primary, gating triac TRl on, which energizes the load. If....
The 566 can be wired as a positive or negative ramp generator. In the positive ramp generator, the external transistor driven by the Pin 3 output rapidly discharges Cl at the end of the charging period so that charging can resume instantaneously. The pnp....
Recently, most digital video equipments, such as video recorder, DVD player and TV game, have component video output. The component video signal is like RGB video signal, but it cannot connect to RGB monitor directly. Thus I designed and built YUV(YCrCb) to....
This battery tester makes use of an LM3914 bar-graph driver IC. SI selects load on battery under test and programs the volta..
The old and omnipresent NE555 can be very good at something it was not meant for: driving relays or other loads up to 200 mA. The picture shows an example circuit: if the input level rises over 2/3 of the supply voltage - it will turn on the relay, and the....
This buck-derived circuit provides up to 8 A at 5 Vdc operating off 24 to 32 Vdc. The two power MOSFETs in the circuit conduct alternately for equal periods. Switching frequency is 150 kHz, set by the PWM125 controller. Output of the two MOSFETs is....
The usual method for using a current-feedback amplifier to drive a capacitive load isolates the loa..
This project is probably the most ambitious so far, and can be expected to be very expensive. On the positive side, it is also capable of excellent performance, and can be tailored to suit your exact specifications. There are several different input modules....
This circuit uses a single chip, IC BA3812L for realizing a 5 band graphic equalizer for use in hi-fi audio systems.The BA3812L is a five-point graphic equalizer that has all the required functions integrated onto one IC. The IC is comprised of the five tone....
This reflex radio project was inspired by Robert Bazian 's design. His reflex radio is the "darndest" thing I have seen and his spectacular results inspired me to come up with my own version! These designs are similar to two-transistor circuits used in some....
The quartz QZ1 of the preceding receivers which set the work frequency is not on the market any more. It is replaced by a locking phase loop allowing the free choice of an unspecified frequency on the band used, either the 41, or the 72 MHz. The step....
If you do not like the whip antenna on your car, you may try this alternative circuit. A one-turn loop is installed in the windscreen of the car, keeping possibly away from the metal structure of the car. This loop is terminated in a 6.5mm ring core suitable....
The circuit shows the method of `mirror` current sensing a MOSFET. A fully conducting MOSFET is resistive and behaves exactly as a resistor. It therefore you limit the voltage across the MOSFET when it is conducting you automatically limit the current....
This probe is useful for any low level RF work, and simply connects to your multimeter. The voltage shown will not be accurate, since this is a rectifier probe, but the measurements are good enough for you to be able to determine where the RF stops, or if a....
Applications such as photoelectric control, temperature detection and moisture sensing require a circuit that can accurately detect a given resistance ratio. A simple technique that uses an op amp as a sensing element can provide 0,5% accuracy with low parts....
This Project is used to control a single phase Motor from any where in the world through the telephone. The circuit consists of a DTMF tone detector and a powerful 8 bit Microcontroller AT89S52. The Microcontroller senses the DTMF signal through the DTMF....
This circuit give low level output, when exist enough lighting, that is a detector of light. It can give, say ,command turn on somebodies lights, when fall the dark. His exit is compatible with TTL level and it give low logic level, when phototransistor Q1,....
This circuit shows how to cascade counters and retain correct leading zero blanking. The NAND gate detects whether a digit is active since one of the two segments a or b is active on any unblanked number. The flip flop is clocked by the least significant....
Though this setup can act as a cost-effective current source with an output accurate to 1%, the voltage offset will turn on the current source even when Vqq equals Vin. 2. Modifying the configuration of Figure 1 can rectify the problem of the current source....
The Dremel drill fitted with a mini drill-chuck on a stand is a great setup for drilling circuit boards. The problem is that it does not do low speeds very well. My unit had a failed internal speed controller, so I just wired around it and connected it to a....
A power transistor can be used to provide a high powered zener voltage from a low wattage zener. A 400 mW zener can be used where a 10 watt zener is required or a 1 W zener can be used where a 50 to 80 watt zener is required by using appropriate transistors....
This circuit consists of an amplifier and video detector with a second subcarrier detector for synch recovery purposes. A pulse-former circuit modulates the gain of the main channel increasing it during synch intervals. ..
The baseband-audio input comes from the pole of switch Sl in the stereo decoder, and is coupled to IC1 (a CA3089) via a 78.6 kHz bandpass filter that consists of capacitors Cl and C2, and inductor Ll. IC1 is a combination i-f amplifier and quadrature....
This circuit uses a Hall-effect sensor, consisting of an IC that resides in a small gap in a flux-collector torrid, to measure de current in the range of 0 to 40 A. You wrap the current-carrying wire through the toroid; the Hall voltage VH is then linearly....
This simple circuit is started running by connecting a twelve volt battery across the terminals, causing the large diameter Light-Emitting Diode to light up. When the battery is removed, the LED stays lit up because the circuit has become self-powering.....
This unit recieves DMX 512 data and Analogue (0- 10v) data and uses these to phase angle control mains output. Features: DMX 512 data Input. Analogue (0- 10v )DC Input. 4 Output channels. Remotley programmable Interally saved Presets. 3 Modes of operation....
An ordinary automatic room power control circuit has only one light sensor. So when a person enters the room it gets one pulse and the lights come on. When the person goes out it gets another pulse and the lights go off. But what happens when two persons....
The Tiny Audio Amplifier kit is a good choice for battery operation. It is based on LM386 IC. Power supply - 6 - 12 VDC. Output power - 1 W, 8 Ohm. The quiescent power drain is only 24 mW when operating from 6 VDC. Self-centering output quiescent voltage.....
This simple inexpensive audio amplifier can be constructed using a couple of T0-220 monolithic Darlington transistors for the push-pull output stage. Frequency response is fiat within 1 dB from 30 Hz to 200 kHz with typical harmonic distortion below 0%. The....
The above circuit can be useful to detect if the load of any battery charger or plug-in adaptor supply is not properly connected. The load can be a set of batteries to be charged or any other type of battery or low dc voltage operated device...
Here`s how to make a good charger for a sealed lead-acid battery (this will NOT work with NiCad batteries) that`s faster (because it allows more current into the battery initially) and safer (because it uses lower voltage when the charging is finished). The....
Charging is accomplished with a constant current of 60 mA for AA cells to a cutoff voltage of 2.4 V per cell at which point the charge must be terminated. The charging system shown is designed for multi-cell battery packs of 2 to 6 series-connected cells or....
Transistor Ql, a 2N3563, and its associated components form an oscillator circuit that will oscillate if, and only if, a good crystal is connected to the test clips. The output from the oscillator is then rectified by the two 1N4148 diodes and filtered by....
The 20-MHz clock phase-locks to Apple"s Mac II 10-MHz NuBus clock. It uses a simple, inexpensive CMOS circuitry to generate 10-and 20-MHz square waves. The output duty cycle settings are insensitive to Vee variations. The input to the circuit is a NuBus....
This very simple circuit just uses a couple of resistors, a capacitor and the easily available 555 timer IC. The 555 is setup as an astable multivibrator operating at a frequency of about 1kHz that produces a shrill noise when switched on. The frequency can....
It's a great convenience that most modern cars come with a built in alarm, however it is nothing but noise pollution that the horn sounds when the alarm is armed. Disconnecting the alarm system from the horn relay will eliminate this, but prevent the horn....
The circuit of preamplifier use the 5533 chip and features a combination of controls balance and volume. Due to the nonlinearity of the human auditory system, low frequencies must be boosted at low listening levels. ..
The circuit has a "floating" output, i.e., it behaves like an isolated transformer winding, with the output amplitude remaining unchanged whether the center or either end of the load is grounded. This is achieved by making Z-out, common mode, infinite. The....
The frequency range of this amplifier is 1.8 to 54 MHz. The amount of RF drive required for full output is about 30 W...
The circuit shows a simple yes/no gas detector. Three 1.5-V D cells are used as a power supply, with SI acting as an on/off switch. The heater is energized directly from the battery, while the electrodes are in series with a 10 k resistor. The voltage across....
