New Circuits Page 245
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Suitable for amateur use, this 1.5-W transmitter runs on a 12-V supply. Ql is an oscillator using a surplus FT2..
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Two gates, U1A and U1B O/3 of a 4049 hex inveter), are connected in a VFO circuit. Components Rl, R3, and CI set the frequ..
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This circuit provides about 20 dB voltage gain with a frequency range from 0.5 to 50 MHz. You can extend tbe low-frequency response of this circuit by increasing tbe value of the 0.05-ILF capacitor- or try removing tbe capacitor. This circuit delivers a....
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In a single difference amplifier configuration, the AM-427 exhibits excellent common-mode rejection and spot nois..
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In many applications, a single on/off button switches the power supply on or off. Usually, the system switches off regardless of the processing function or workload the microcontroller or DSP circuit is currently handling. The small circuit in Figure 1 is....
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In this circuit the gain is provided by a FET type op-amp. I have used an LF351, which may be hard to obtain, but the TL071CN or TL081CN may be used and have a faster slewing rate than the LF351. The Maplin order codes are RA67X and RA70M respectively. The....
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Who would like to build a sidetone oscillator with a minimum amount of parts should try the NE567 integrated circuit. The NE567 is a PLL circuit with an internal VCO for a operating frequency less than 500 kHz and it is normally used as an audio tone....
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You can effectively double the sample rate of a DAC by interleaving two DACs into a single unit. Updating each DAC on an alternating basis and switching to the appropriate output double the effective throughput of the overall system. It is essential to....
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This is a fun and non-dangeros project for those people who like to throw projectiles magnetically. It simply works by placing a ferromagnetic projectile at one end of a coil and pulsing some power in it. The trick is to switch off power when the projectile....
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The SPC2 is a solar power center, it can be used to handle all of the power functions for small 12 Volt solar powered devices. It contains a photovoltaic charge controller and a low voltage load disconnect circuit. The low voltage disconnect has a load....
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Using four diode in an array allows using only one MOSPOWER transistor for analog switching. The current flow is controlled by keeping the source-base connection of the MOSFET towards the load. Be sure to use diodes capable of handling the load current....
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This circuit produces an output pulse when SW1 (pushbutton) is depressed. It also becomes a hysteresis ga..
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The 741 op amp integrator signal is fed into the Schmitt trigger input of an inverter. When the signal reaches the magnitude of the positive-going threshold voltage, the output of the inverter is switched to zero. The inverter output controls the FET....
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I've taken the classic Fuzz Face circuit and added optical temperature compensation. This ensures that the output stage is biased at half the supply voltage regardless of variations in the transistors, particularly those caused by temperature. Tweaks:....
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This circuit generates MIDI clocks and start/stop messages...
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A reverse-biased pn junction of a 2N2712 transistor is used as a noise generator. The second 2N2712 is an audio amplifier. The 005 µf capacitor across the amplifier output removes some high-frequency components to simulate pink noise more closely..
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Low-intensity ultrasonic sound waves in the 30-45 kHz frequency band repel insects and small rodents. The unit is designed to generate a swept square wave from 30 to 45 kHz. The LM555 IC is wired as an ultrasonic oscillator driving a piezoelectric speaker of....
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With this circuit we can create a altered sound of siren. The oscillator IC1a-b is constituted by two gates NAND, oscillating in very low frequency. This oscillation drive the IC2, that is a electronic switch, which opens and closes in the rythm of....
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The GX4201 is a wideband 1x1 video crosspoint implemented
in bipolar monolithic technology. The device is characterized
by excellent differential gain and phase in the enabled
state, and very high off-isolation in the disabled state. The
fully buffered....
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The programmable multiple output generator provides the control signals for data converter ATE. Major performance criteria are simple, interfaces to a number of microprocessor systems, low power consumption, stable output timing relationships combined with....
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Rear channel "ambience" can be added to an existing stereo system to extract a difference signal (R - L or L - R) which, when combined with some direct signal (R or L), adds fullness, or "concert hall realism" to the reproduction of recorded music. Very....
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? simple heart-beat transducer can be made from an infrared LED and an infrared phototransistor. ?t works because skin acts as a ref1ecti?e surface for infrared light. The lR ref1ecti?ity of one's skin depends ??? the density of blood in it. Blood density....
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Simplified logic checker. Logic voltage levels have the ability to display LED (Of course I (^_^;)." H "in the LED is green," L "and red LED lights, and so both the open and goes out .
But not only that was put on the ability to detect narrow pulses. In....
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Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and....
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The first 5 circuits described in the following sections were reverse
engineered from commercial HeNe power supplies. There may be errors in
transcription as well as interpretation. In many cases, the transformer
secondary voltage was not marked and....
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Door open alarms are used chiefly in automotive, industrial, and appliance applications. This type of circuit can sense the opening of a refrigerator door. When the door opens, a triac could be activated to control the inside light. The figure shows a door....
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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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All vocal eliminators start with the assumption that the lead vocal in a recording is in the center of the stereo field - which means that it is equal amplitude and phase in both left and right channels. Subtracting one channel from the other removes this....
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Fan noise is becoming a significant issue as electronic equipment increasingly enters the office and the home. Noise is proportional to fan speed, and the airflowhence, fan speednecessary for cooling is less at low ambient temperatures. Because ambient....
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By varying either Rl or R2, the oscillator frequency can be adjusted over a narrow range. The R3/R4 ratio sets the second amplifier's gain to compensate for signal attenuation occurring in the phase shifters. The circuits can be driven from an external....
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The zener provides a constant voltage of 20 V to unijunction transistor Ql, except at the end of each half-cycle of the input when the line voltage drops to zero. Initially, the voltage across capacitor Cl is zero and capacitor C2 cannot charge to trigger....
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A monolithic phase locked loop for data communications. The IC contains a basic phase locked loop for tracking an input signal within the pass band, a quadrature phase detector which provided carrier detector and an FSK voltage comparator which provides FSK....
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This is a single gain-of-100 amplifier with a gain-bandwidth product of 20 MHz! The primary limitation in the performance is the low slew rate (0.3 VIJ1s) imposed by IoH charging CcoMP· The effects of slew rate and compensation are shown. A lower gain....
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This circuit produces a sound similar to a factory siren.
It makes use of a 555 timer Ic used as an astable multivibrator of a center frequency of about 300Hz.
The frequency is controlled by the pin 5 of the IC. When the supply is switched ON, the....
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Video-DVM is a very cheap DVM that shows how an output as complex as a videocomposite signal can be generated entirely in software: two I/O pins and three resistors are all the hardware required. Connected to any TV set it displays voltages, included max and....
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Cl, C2, and C3 are miniature ceramic or plastic trimmers- Tl (main winding) is 0.34 µ,. Use of 11 turns of no. 24 enameled wire on a T37-10 toroid core. The antenna winding has one turn, and Ql the source winding has three turns. T2 primary consists of 11....
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Rectifier circuits based on semiconductor diodes typically handle voltage levels that greatly exceed the diodes` forward-voltage drops, which generally don`t affect the accuracy of the rectification process. However, the rectified signal`s accuracy suffers....
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Such supplies are often realised with dedicated integrated circuits nowadays but it`s still interesting to give a look at old designs to understand the basics...
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The power supply section is the important one. It should deliver constant output regulated power supply for successful working of the project. A 0-12V/500 mA transformer is used for this purpose. The primary of this transformer is connected in to main supply....
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Here they exist two regulator circuits, that use the IC L200, as regulator of voltage and current, the company SGS-Thomson, which give these circuits. In circuit Fig.1, we can regulate the output voltage, with the RV1, while in the Fig.2, we can regulate....
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The function generator features two BNC outputs : one for the high speed [1 to 8 MHz] square signal (BNC1) and another for the DDS signal (BNC2). Offset and amplitude can be regulated by two potentiometers : offset in range of +5V to -5V (POT1) and amplitude....
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I found some similar circuits but aren't good enough for me. Some circuits measure the water's resistance to determine the level. That is dangerous for drinking water (contamination) or explosive liquids because electricity is in contact with water. The....
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At the heart of the Full-Cup Detector is a 555-oscillator/timer configured to produce a 15-Hz click, until ..
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A neon bulb and a CdS photocell enclosed in a light-tight enclosure form an optocoupler. A diac/triac combination is used to provide the snap- switch effect. A second CdS photocell acts as the main sensor. As darkness approaches, the resistance of K4 begins....
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When the driver depresses pushbutton switch S1, timing capacitor C1 charges to 12 V and turns on transistor Q1, which drives power transistor Q2 into conduction. This, in tum, energizes the relay which has its contacts connected in parallel with the....
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A resistive voltage divider is used to establish a bias voltage for the input (pins 2 and 3). The demodulated (multiplex) FM signal is fed to the input through a two-stage high-pass filter, both to effect capacitive coupling and to attenuate the strong....
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The power supplies for electronic flash and strobe equipment operate at extremely lethal voltage and current levels. The energy storage capacitors in even the smallest disposable camera flash operating from a 1.5 V AA battery can be deadly under the wrong....
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By using a circuit built with a single analog multiplier and five precision resistors, an output voltage (Ko) can be made to create a second- order polynomial. The circuit implements the quadratic shown. The input terminals of IC1 are connected to create a....
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This is a nice amplifier and very easy to make it. Its an 20W Audio Amplifier based on LM1875 IC...
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The above pictured schematic diagram is just a standard constant current model with a added current limiter, consisting of Q1, R1, and R4. The moment too much current is flowing biases Q1 and drops the output voltage. The output voltage is: 1.2 x....
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One way to charge Ni-Cad batteries rapidly without abuse is to measure cell temperature and taper the charge accordingly. The circuit uses a thermocouple for this function. A second thermocouple nulls out the effects of ambient temperature. The temperature....
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This simple circuit is a good solution to the powering a dual supply op amp from a single battery problem. The circuit simply takes a positive voltage and inverts it. It uses only one 555 timer and a few other passive components, so it doesn`t add much in....
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The circuit provides for accurate half-wave rectification of the incoming signal. For positive signals, the gain is 0; for negative signals, the gain is -1. By reversing both diodes, the polarity can be inverted. This circuit provides an accurate output, but....
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This project provides an simple F1 motor racing style 5 light race start sequence with a random delay that you can use on a real race track, kart circuit or even your slot-car circuit.
Operation is simple; when the start button is pressed all the LED....
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This electronic ignition circuit is intended to be inserted into a car"s conventional ignition system. In effect, it re..
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The general (and very basic) principle of operation is shown in Figure 1. The test signal is simply derived from the mains, and is a sinewave at 50 or 60Hz. In most locations, the sinewave will be distorted, but this barely matters. With nothing connected to....
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In this circuit, the ringing voltage on a telephone line causes NE-1 to break over, triggering SCR1, which ..
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The alarm is built around two audio oscillators, each using two NAND gates. The detection oscillator is gated on by a pair of remote probes. One of the probes is connected to the battery supply, the other to the input of one of the gates. When water flows....
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This is a simple, cheap device that can be connected to any serial port to control most components that have infrared remote controls. I designed and built it (on a solderless breadboard) in 1991. In 1992 I wrote a lengthy description of it for an....
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A simple level of power meter can be arranged to give a bar or dot display for a hi-fi system. Use green LEDs for 0 to 7; yellow for 8 and red for 9 to indicate peak power. The gain control is provided to enable calibration on the equipment with which the....
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With the advent of high speed HCMOS circuits, it is possible to build systems with clock rates of greater than 30 MHz. The familiar gate oscillator circuits used at low frequencies work well at higher frequencies and either LC or crystal resonators maybe....
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The design is simple, tuneable, but no longer terribly useful (I include it here just for purposes of education and folks` historical interest). This design has a number of weaknesses; courtesy of Wilf Rigter, here are a few:..
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This amplifier can transfer dc-to 5-MHz signals across a potential difference of 25 000 V. This circu..
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In Fig. 104-3(a), when Vin is between reference voltages Vi and Vu, output Vout goes low. If Vin> Vl, IC2 produces a low..
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The RF oscillator using the inverter N2 and 10.7Mhz ceramic filter is driving the parallel combination of N4 to N6 through N3.Since these inverters are in parallel the output impedance will be low so that it can directly drive an aerial of 1/4th wavelength.....
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This simple and symmetrical free-running generator has a 50- output impedance, a pulse width of 100 ns..
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The input is ac coupled to the amplifier through C2, which blocks de signals that might also be present at the input. The Rl/Cl combination forms a low-pass filter, which eliminates unwanted high-frequency signals by bypassing them to ground when they....
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Most audio amplifier systems must have preamplifiers with many different characteristics. These include high-gain linear response for magnetic microphones, low-gain linear response for tuners, and high-gain RIAA equalization for magnetic phone cartridges. To....
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The heart of the clock is a PIC 16f628A microcontroller (PDF). This microcontroller has an internal oscillator however an external 20MHz crystal oscillator is being used since it will have to accurately keep track of time for weeks and months. The....
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By combining the responses of an Analog Devices (www.analog.com) AD590 temperature sensor and a Humirel (www.humirel.com) HS1101 humidity sensor, you can generate a single TTL-level signal containing information from both sensors (Figure 1). This design uses....
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Here is a teleremote circuit which enables switching on and off of appliances through telephone lines. It can be used to switch appliances from any distance, overcoming the limited range of infrared and radio remote controls.
The circuit described here can....
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Various embodiments of the BB metal detector have been published, and it has been widely described in the press as a new genre. Instead of using a search and a reference oscillator as with BFO, or Tx and Rx coils as with IB, it uses two transmitters or....
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This circuit will light a lamp at a remote location when the doorbell switch is pressed. This circuit should only be used with the solenoid type doorbells, the electronic type that play tunes will not work here. It is quite easy to miss the sound of a....
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The NE555 is connected in the astable mode and uses only three timing components (RA, RB, and Ct. A 0.01-/aF bypass ..
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A digital camera can be a handy substitute for an oscilloscope camera for older scopes that cannot output hard copy or digital data. A digital camera provides instant results and allows you to easily enhance the image and then add it to reports or Web pages...
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To avoid grief when using 12-V power supplies with mobile transceivers, especially when there is a short -circuit failure of the series pass transistor, crowbar circuits provide protection by clamping the power line and blowing the fuse within microseconds....
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This is a low-cost project for 20 or 40 watt fluorescent tubes. However the most efficient is to use a 40 watt tube (or two 20 watt tubes in series). It's a circuit you can put together from junk box components or build from a kit. It's very simple to build....
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During the first half-cycle (Fig. 99-5(a)), Dl conducts, D2 cuts off, CI changes to 170 V peak, and C2 discharges through ..
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As shown, three ICs are used to produce the sounds. ICl is a 555 timer that generates clock pulses. It is configured as an astable multivibrator. The frequency of the clock pulses is set by trim: mer potentiometer PI. These clock pulses are coupled to the....
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Hackers listen up. Everyone understands and enjoys the utilitarian benefits that GPS has brought to our lives but what if it didn’t work any more? I suppose you could build some sort of surface to space missile robot that would systematically seek and....
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Tendency of entry: 220V AC. Tendency of expense: 5V DC. Current of expense: 1A..
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The supply receives -20 V from the rectifier/filter which is fed to the collector of the Darlington pnp pass transistor, a TIP105. The base drive to the TIP105 is supplied through resistor R5. The base of the TIP105 is driven from Vz terminal at pin 9,....
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This tester can be used to check IC printed circuit boards. Two 4 K resistors and the transistors connected to them prevent current flow through the operational amplifier until the probe circuit is completed..
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The following text describes construction, testing and use of an electronic telephone line simulator of my own design. This self-build project can simulate a telephone call / connection between any two local telephone devices. This for a fraction of the....
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The Pocket Programmer is a stand alone serial programmer that can program most of the PICmicro®MCU range of microprocessors. (12C6xx, 16Cxxx, 16Fxxx, 18Cxxx) It works from a single 18VDC supply or with 2 X 9 volt batteries. Combine this with 64K of on board....
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The circuit has negative feedback only for positive signals. The inverting input can only get some feedback when diode Dl is forward biased and only occurs when the input is positive. With a positive input signal, the output of the op amp rises until the....
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A speaker system can be protected against amplifier failure when dc voltages (on speaker line a-b) arc sensed by the circuit. Either positive or negative dc voltages are sensed. A relay opens in this case, removing the dc from the speakers...
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This circuit controls the level of a tank using a bang-bang controlled electrical pump. The actual level of liquid is measured by a capacitive level-meter. The first inverter performs as a capacitance to frequency converter. It is a Schmitt oscillator and....
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The dual-channel PCA9540 I2C multiplexer often breaks up an I2C or SM bus or allows you to use devices with the same addresses on the same bus. When the PCA9540 initially powers up, it comes up in a state in which both channels are deselected. The I2C- or....
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This circuit is effective for lamp and heater loads. Some circuits driving reactive loads require integral cycling and zero-voltage switching-when an identical number of positive and negative half cycles of voltage are applied to the load during a power....
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This circuit takes as an input a signal from a 5-V CMOS logic circuit and outputs a high voltage of the same polarity. The high-voltage supply can be varied from ±30 V to ±150 V without the need to change circuit components. The input voltage is applied....
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The PC board has been designed to accept either a PIC16F84A or PIC16F628. With the introduction of the`628 to the world market, it has taken over from the PIC16F84A and we will be ceasing to design projects for the `F84 and concentrating on the cheaper....
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The circuit consists of separate amplifiers—one for each station—rather than a single amplifier and a time sharing arrangement. Ul and U2 are low-voltage audio amplifiers, each of which operates as separate entities with switches at either station....
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A simple circuit, High-Pass filter, variable between frequencies 20HZ until 200HZ, useful in a lot of cases elaboration of sound signals. The regulation is achieved with the double potesometer 47K? and the frequency response in his two extreme places,....
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is circuit was requested from an email. It will allow your car headlights to flash on and off at the same time or it will cause them to flash alternately. The circuit is based on the 555 timer. It is used in the astable mode. The 555 timer output will go....
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This circuit adds a VLF AM component to an audio signal. This effect is widely used in musical instruments. U1C, a phase-sh..
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Using a Motorola MC2833 one-chip FM transmitter, a few support components, and an MPF6660 FET RF amp, this transmitter delivers about 3 W into a 50- load...
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No description available...
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This is a series regulator with Q900 being the control ele-
ment, Q901 a driver, and Q902 an error amp. ZD900 forms
the emitter reference voltage source. Since the generated
high voltage and other voltages are linked by means of
the magnetic field of....
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A 3-x -3-inch piece of circuit board, or similar size metal object which functions as the pick-up sensor, is connected to the gate of Ql. A 100-MD resistor, R2, isolates Ql"s gate from Rl, allowing the input iropedance to remain very high. If a 100MO....