New Circuits Page 250
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This circuit adopts the rather unusual Bowes/White emitter coupled multivibrator circuit. The oscillation frequency is about 1Hz and is set by C1 value. The LED starts flashing when the photo resistor is scarcely illuminated. The onset of flashing can be set....
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The FM oscillator/modulator is a voltage-control led oscillator, which exhibits a nearly linear output frequency versus input voltage characteristic for a wide deviation. It provides a good FM source with a few inexpensive external parts..
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The microphone has high sensitivity in the audio range, but in the ultrasonic range, the sensitivity decreases rapidly. The receiver is very sensitive. To prevent overdriving and feedback due to the high sensitivity of the microphone in the audio range, the....
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This circuit was created for digital cameras. It's known the digital cameras have considerable power consumption. For example my camera Minolta E223 requires approximately 800 mA. In practice a mains power supply or high capacity NiMH accumulators....
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When an asterisk * is pressed on the touch-tone phone, TCI a DTMF decoder, controls on-hold logic. Audio from the FM receiver IC4 is.placed on the telephone line when a hold condition is present. RY2 is a DPDT 12-V relay. To place a caller on hold,..
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Here is a design that you can own, tailor to your specific
needs, layout on your circuit board and put on your bill of
materials. Finally, you will be in control of the black magic
(and high voltages) of ring-tone generation...
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This document presents an overview of the hardware design of the Handy Cricket...
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A `micro power solar engine` has been a goal since my introduction to BEAM Robotics. I believe that if there wasn`t one before, I there is one now. What I`m presenting to you looks very similar to one of the circuits found in Steven Bolt`s web pages.....
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Wilf Rigter simplified this circuit a bit, made it phototropic, and doubled it up to yield a photopopper design in a post later the same day. I`ve got this design written up elsewhere in the library...
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Battery run times for notebook computers and other
portable devices can be improved and acoustic noise
reduced by using Linear Technologys LTC®1695 to optimize
the operation of these products internal cooling
fans. The LTC1695 comes in a SOT-23 package....
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For SR AB763 driver replace: 25k pot, 0.1uF cap and 4k7 resistor with 100 ohm resistor to ground. 56k resistor with 820 to 4k7 resistor. ..
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The circuit provides unambiguous LED + or - bar readout with steps of 0.1%. The reference frequency is multiplied by the PLLIC1 and divider IC9 to output 64 ? F (ref) and this is then gated by dividing F (measure) by 32 in IC8 thus is F (ref) = (measure)....
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Q1 and Q2 form a voltage amplifier which has sufficient gain to be overdriven by a rela-tively low input, such as an electric guitar. The result is that the output from Q2 is a Squared-Off verson of the input, giving the required fuzz sound. RV1 adjusts the....
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The circuit comprises a 3-stage resistor-capacitor coupled amplifier. When ring button S2 is pressed, the amplifier circuit formed around transistors T1 and T2 gets converted into an asymmetrical astable multivib-rator generating ring signals. These ring....
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An input signal of less than 1 mA and 1V is required to switch on CS1. As long as this input -signal is maintained, CS1 will conduct during each positive half cycle of anode voltage, thereby energizing load LI with half-wave rectified dc. L2 remains....
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This is a simple and low cost 60W power amplifier. The optimal supply voltage is around 50V, but this amp can work from 30 to 60V. The maximum input voltage is around 0.8 - 1V. As you can see, in this design the components have a big tolerance, so you can....
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In this circuit, a 2-MHz clock is divided by eight in Ul, providing a stable 250-kHz carrier. Ql and Q2 buffer the clock and provide a low-impedance drive for op amp U4, which is a high-gain amplifier and integrator. U4 accepts audio inputs and converts the....
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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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A voltage divider consisting of Rl, R2, and R3 is used to set the input reference voltage below which the batteries are to be replaced. That reference voltage, at point A, is varied by Rl. With the voltage divider shown in Fig. 9-7, a range of 2 to 3.5 Vis....
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This voltage-regulator/cuiTent-liimter combination can be made from two 7805 regulators as shown. Rl, R2, and R3 shouldbe selected for a 5-V drop at the maximum allowable currant limit. SI selects one of the three current values. Do not forget that Ul....
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The unit is constructed around a balanced-bridge circuit. using both capacitance and inductance. The bridge consists of capacitors C2 and C3, and the center-tapped winding of Tl. One end of the bridge is coupled to ground by C4, while capacitance changes....
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The Digi-Tach contains a master-clock circuits (U6)v latch and reset pulse generators (U2-b-U2-d), input signal bonditioner (Ul, U2-a), pulse counter (U3), display and display drivers (DIS1, DIS2, U4, and U5), and a voltage regulator (U7)...
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This circuit exhibits a 10 V acquisition time of 900 ns to 0% accuracy and a droop rate of only 100 µ-V/ms at 25° C ambient condition. An even faster acquisition time can be obtained using a smaller value hold-capacitor. By decreasing the value from 1000....
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Many embedded-microcontroller applications require generation of analog signals. An integrated or stand-alone DAC fills the role. However, you can often use PWM signals for generating the required analog signals. You can use PWM signals to create both dc and....
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There are two switches: a memory disable switch and a pulse polarity switch. Memory disable is a push-button that resets the memory to the low state when depressed. Pulse polarity is a toggle switch that selects whether the probe responds to a high-level or....
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This is a simple microphone preamplifier circuit which you can use between your microphone and stereo amplifier. This circuit amplifier microphone suitable for use with normal home stereo amplifier line/CD/aux/tape inputs. This microphone preamplifier can....
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You can expect 100mA output from LT1303 based circuits
and 300mA from the LT1372 circuit without modification.
All of the circuits feature output disconnect; in shutdown
the outputs fall to 0V...
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In this application, an AD652IC is used in a synchronized V/F converter that derives its input from th..
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This circuit gives an early warning of the discharge of batteries. Zener diode Dl is chosen for the voltage below which an indication is required (9 V). Should the supply drop to below 7 V, Dl will cease conducting causing Ql to shut off...
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This circuit shows a simple method of achieving a voltage reference which can be trimmed using an 8bit DAC with an on-chip voltage reference. The analogue output from the DAC drives the trim pin of the ZNREF025 via a resistor, R,. When Rs = 0, this circuit....
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The MC74HC04 IC is a low cost CMOS Hex Inverter. I used this type mainly because, it is what I have, although you can use LS type but, with a little modification or exemptions....
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In perfect discharge the batteries of lead acid, exists the fear they are destroyed. This circuit makes the work, this detection of discharge, protecting the batteries from destruction. At the discharge the polar voltage of batteries 12V of Lead acid, is not....
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The transistor is connected as an audio oscillator, using an audio transformer in the collector. The secondary goes to a linear pot...
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This project Digital gated Emulator using Microcontroller is used to emulate the basic gates such us NOT, OR, AND. The system has the selector switch by which we can select any gate. The system has two inputs and one output. We use two SPDT switches for the....
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The accurate, high-side, current-sense circuit in Figure 1 does not use a dedicated, isolated supply voltage, as some schemes do. Only the selected transistors limit the common-mode range. The circuit measures the voltage across a small current-sense....
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When the turn signal switch SI is closed, lamp #1 will be activated and capacitor Cl will charge to the triggered voltage of Ql. As soon as the anode voltage on Ql exceeds its gate voltage by 0 V, Ql will switch into the low resistance mode, thereby....
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This circuit is used to slowly illuminate and fade a pair of red LEDs (light emitting diodes). The fading LEDs could be installed as 'eyes' in a small pumpkin or skull as a Halloween attraction, or mounted in a Christmas tree ornament. Or, they might be used....
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This reference design is a high efficiency, high power factor, digital dimming electronic ballast designed to drive
rapid start fluorescent lamp types. The design contains an active power factor correction circuit for universal
voltage input as well as a....
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The block diagram in Figure 1 represents a complete remote-temperature-sensing and fan-control system. The system uses an Analog Devices temperature-monitor and fan-control ASIC and a PIC16C84 µC from Microchip Technology. The ADM1022 allows you to measure....
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Stepping motors find wide use in disk drives and machine control. MOSPOWER transistors are ideal motor drivers because of their freedom from second breakdown. Note that snubbing networks are not used because load line shaping is not necessary with MOSPOWER....
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The schematic shows a valve / tube audio power amplifier and a type 390 Rectron B eliminator...
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The problem of setting any one of four modes of a µC-operated process has a straightforward solution: Have the µC check the states of some 4 bits of a µC register or an input port and then execute one of the four predetermined subroutines according to the....
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This circuit is a two-channel baseband video switcher. Buffer amps Ul/Ql, U4/Q4, and associated components produce a b..
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This circuit has a rate multiplier using a 4093 Schmitt trigger as an oscillator, driving a 4017 decade counter. When a pulse p..
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This circuit is used to measure the voltage on a 12V (nominal) lead acid rechargeable battery system. It was specifically designed for use in solar powered systems, but is general enough that it can be used for automotive or other 12V systems. Lead acid....
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The Jammer is a very small circuit and can fit inside a small plastic box with 9V battery inside. It can be very illegal if you attach an external antenna so don't. adjust frequency by turning trimmer. It is intended only as a practical joke device. The....
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This in-depth article covers the theory behind a Delta-Sigma analog-to-digital converter (ADC). It specifically focuses on the difficult to understand key digital concepts of over-sampling, noise shaping, and decimation filtering. A description of new....
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This circuit was specifically designed to recharge alkaline cells. The unusual connection of the transistor in each charging unit will cause it to oscillate, on and off, thus transferring the charge accumulated in the capacitor to the cell. The orange LED....
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The software sample is written in C for a specific application. A general purpose interface is not available at this time but is planned for the future. The information detailed here should provide the basic framework for designing and implementing your I2C....
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This project uses a four-point resistance measurement process also known as the Kelvin method. This procedure uses a current source to determine the value of an unidentified resistance. A constant current flows through the unknown resistance and the voltage....
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The capacitor charges until the PNP transistor (here shown as a 2N3906, but you could also use a BC327) receives base current through the Zener and turns on. Then the NPN transistor (here shown as a 2N3904, but you could also use a BC337) turns on and....
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The three major types of current-limit-protection mechanisms are constant, foldback, and hiccup. Hiccup current limit performs the best of the three types; however, the implementation is rather complex. In this scheme, upon detection of an overcurrent event,....
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Transistor Q1 acts as an amplifier for condenser microphone MIC1. The output of Q1 is applied to the base of transistor Q2 through a 4. 7 -I"F capacitor. C2 and 11 form an LC tank circuit. which is used to set the frequency at which the transmitter....
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Continuing with the thermocouple interface concept, the next step is to amplify the TC's millivolt signal into a more readable analog voltage, on the order of 0 to 5VDC. This simple circuit fits the bill. The LM358N is a dual op-amp IC. I'm quite sure any....
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The ' 'zero voltage switching'' technique is widely used to modulate heating and similar types of ac loads where the time constant associated with the load (tens of seconds to minutes) is sufficiently long to allow smooth proportional modulation by time....
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The basic die circuit is given. A 555 timer, ICl, is connected as an astable multivibrator. This feeds clock pulses to divide-by-six counter IC2 tbe outputs of which are decoded by gates Nl to N6 to drive an array of LEDs in the familiar die pattern. When....
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The automatic fader drops at the background music while the narration is in place. The control input through RIO, a preset audio level control, into an emitter-follower buffer stage CQI). The buffer provides high input impedance and ensures that the source....
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IC2 forms a stable oscillator whose frequency and pulse width is determined by the values of R4, R5, R6, and C4. R4 is made adjustable for precise frequency setting. The output of IC2 is pin 3, which is capacitively coupled to the base of Ql. Ll acts as a....
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The oscillator is a standard UHF design which delivers about 10 mW at 1.2 GHz. R1 and R2 bias the base of Q1 to 1.2 V via 12. Collector current is set by R3 to about 30 mA. C2 couples the base of Q1 to the stripline circuit. Tuning is provided by CVl, and....
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An RF isolator is a seemingly magic device that allows signals to pass in only one direction. Signals applied to the input port are sent to the test port and signals coming into the test port can only go to the output port. This one-way property is usually....
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This circuit is a small +5V power supply, which is useful when experimenting with digital electronics. Small inexpensive wall tranformers with variable output voltage are available from any electronics shop and supermarket. Those transformers are easily....
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A high voltage step-up DC power supply using adjustable flyback conversion...
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The diagram is a power supply circuit using the isolated feedback capabilities of the TL3103 for both current and voltage sensing. This supply is powered fromthe ac power line and has an output of 5 Vat 1.5 A. Both output voltage and current are sensed and....
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Because the power controller is powered from the vehicle`s accessory switch, the load can receive power only when the ignition key is on. Using half of a dual flip-flop (CD4013), a load of up to 10 A is controlled by a momentary pushbutton. This circuit was....
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When the telephone rings. or when the handset is lifted, ~the night light is turned on and remains on while the conversation takes place. When the handset is replaced in the cradle, the light remains on for about 11 s. During standby conditions, the -28 V....
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The Electronic Cash Register (ECR) keeps track of sales transactions quickly and effectively. An abundance of PLUs (Price Look Ups) and department keys accommodate a variety of merchandise items. This means a faster, more accurate check out process and the....
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Here is a simple circuit which can be used for decoration purposes or as an indicator. Flashing or dancing speed of LEDs can be adjusted and various dancing patterns of lights can be formed.
The circuit consists of two astable multivibrators. One....
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This unit provide 2 way IR communications using a numeric keypad and an LCD display. Data is sent and recieved in ASCII with no regard to what the data means to any particular device. The ASCII data still needs some form of encoding. For this I chose....
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This oscillator uses two transistors and operates the crystal in the fundamental mode. CT and C2 should..
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Well, it's pretty much a PAiA preamp - usual input circuity followed by one half of dual op-amp rigged in fixed 20dB amplification circuity, followed by second stage which is adjustable for up to 40dB amplification, for up to 60dB total. The power supply is....
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The circuit uses fast transimpedance amps, "floated" at 70V. Two "virtual-zener" circuits step down the high-voltage signals for subsequent processing in a ground-referred differential-amplifier stage (Figure 1). The circuit drops exactly 65.58V dc with the....
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An LMX1601 Phase locked loop, a discreet FET VCO, and an AVR micro controller combine to make a stable, easy to use monophonic FM transmitter that includes a an audio activated switch that turns the transmitter on only when its being used. The common....
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Compression and expansion ratios other than 2: 1 can be achieved by the circuit shown. Rotation of the dual potentiometer causes the circuit hook-up to change from a basic compressor to a basic expander. In the center of rotation, the circuit is 1:1, has....
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The DVM gives a direct indication of the temperature of the sensor in degrees Centigrade. The temperature sensor IC1 gives a nominal 1 µ per degree Kelvin which is converted to 10 mV per degree Kelvin by Rl and VR1. IC2 is a micropower, low input drift op....
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This circuit is able to take you to the world of the Wild West. For this it uses the integrated 18-pin IT82207 (IC1) of Holtek, which literally takes care of everything. You have to do is add a few accessories, including a loudspeaker and six selector....
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Here are two FM generators for low frequency, less than 0.5 MHz center frequency, applications. Each uses a 566 function generator as a modulation generator and a second 566 as the carrier generator. Capacitor Cl selects the modulation frequency adjustment....
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This counter makes direct readout of frequency-generating equipment very easy when a 1-H..
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The FM broadcast band was moved immediately after World War II from its original spot just below 50 Mc to the present 88-108 Mc band. Hallicrafters was one company to offer receiving converters for those who had the old FM radio sets. The offerings....
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This receptor is born of our annoyance against the irritating problem of Quartz: With the RX21, completed research of cut crystal for your personal rating, you have with him, access to ALL band frequencies, in steps of 5 kHz ! Desiring to make this universal....
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This structure is an amplifier RF, covering the range of UHF and intended for small TV transmitters, working in the channel UHF. The amplifier can enhance any video signal to the region UHF (450-800MHz). The circuit operates in class A and uses the known....
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The first circuit was designed for the situation where a hijacker forces the driver from the vehicle. If a door is opened while the ignition is switched on - the circuit will trip. After a few minutes delay - when the thief is at a safe distance - the alarm....
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I didn't realize till the other day that I have never shown a circuit for a standard power supply. Shown below is a supply that will use any of the LM78XX series of voltage regulators. The transformer in the circuit will vary depending on which regulator you....
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VU (Volume Unit) meters used to be the mainstay of audio metering systems, but they have been replaced by LED metering in a great many mixers and other applications. Even in software, the most common level meter is made to look like an LED meter. The Peak....
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This circuit puts out a pulse when an object on the conveyor belt blocks the light source. The light source keeps the phototran-sistor turned on. This produces a high-logic-level voltage at the Schmitt-trigger inverter and a TTL-compatible low logic level at....
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This circuit provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light....
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This project shows you how to build a relay controller using the Basic Stamp I interfaced to the PC serial port. The Visual Basic 5 software developed for the interface lets you interact with the Basic Stamp to turn ON/OFF up to (2) relays attached to the....
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This circuit uses two quad op-amps to form an eight LED audio level meter. The op-amp used in this particular circuit is the LM324. It is a popular IC and should be available from many parts stores. The 1K resistors in the circuit are essential so that the....
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When a gate voltage is applied, Ql is turned on and capacitor C is charged via the attack pot in series with the 1 K resistor varying this pot, attact time constant. A fast attack gives a percussive sound, a slow attack the affect of "backward" sounds. When....
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The circuit consists of two parts: The LM335 and its adjustment. The output of the LM335 is 10 millivolts per degree C, with 25 degrees C corresponding to 2.982 VDC. A reference circuit provides a zero reference voltage. It is adjusted to (2.982 volts - (25....
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Two 741 operational amplifiers are used for the active element in this Wien bridge oscillator. (The 1458 is the dual version of the 741.) Frequencies of the two oscillators were chosen to fit standard component values. Other frequencies between 500 and 2000....
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Two comparators and a summing amplifier that generate differential harmonic spectra comprise a simple frequency multiplier. The resulting circuit can extract harmonics from a sine, triangle, sawtooth, or any other sloping-sided waveform. With a....
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This circuit uses a high quality audio amplifier IC in a 5-pin TO220 package that does not require insulating washers between the metal tab and heatsink in single rail supply applications. The amp can provide 32 watt rms into 4ohm load and 25 watt rms into....
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This preamp and tone control uses the JFET to its best advantage; as a low noise high input impedance device. All device parameters are noncritical, yet the circuit achieves harmonic distortion levels of less than 0.05% with a S/N ratio of over 85 dB. ..
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The circuit protects a solid-state relay from overloads. The circuit limits current, automatically disconnects the load after ..
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The I.F. amplifier is similar to the one used in the 80M receiver project . The original design has been modified by putting a couple of LED`s in the source circuit of each Mosfet. The voltage drop across the LED`s keeps the source voltage at about two....
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his circuit can be used as an Infrared beam barrier as well as a proximity detector.
The circuit uses the very popular Sharp IR module (Vishay module can also be used). The pin nos. shown in the circuit are for the Sharp & VIshay modules. For other modules....
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The tracer, consisting of both a transmitter and receiver, is designed to follow a closed-loop wire or cable system. It follows an induced voltage path created by feeding a low-current, audio-frequency signal through the cable. When the pick-up coils....
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This tiny pH-meter is very tiny: 11cm2 including the PSU circuit! I built it for the College Saint Pierre a few years ago. It is based on a circuit developped at the Facultes Notre-Dame de la Paix, Namur, Belgium. I modified several components to allow a....
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The circuit is light seeking; it will follow a flashlight around a darkened room. A pair of photocells determine the direction in which the robot will move. Each photocell is connected to an op amp configured as a comparator. When sufficient light falls on....
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This unit has a single column of LEDs that are spinning in a left to right motion, as it spins a microcontroller keeps track of the exact position of the board. Words are written in the air by flashing the correct bit pattern in the correct location. The....