New Circuits Page 247
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This circuit operates as an oscillator and a timer. The 2N6028 is normally on due to excess holding current through the 100 k resistor. When the switch is momentarily closed, the 10 µ¥ capacitor is charged to a full 15 volts and 2N2926 starts oscillating....
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A 15 watt amplifier made using discrete components. Sergio designed this circuit for his Electronics Level II course...
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For this radio, which I repaired for someone, I made this DIY VL1. Later I found the real tube...
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This small but useful circuit is a DC voltage convertor for using 6V devices with car battery voltage. The maximum output current is dependent if the T1 is covered with a proper heat sink or not. You can use the circuit to drive devices that they sink....
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The linear power supply, shown in the schematic, provides 0-30 volts, at 1 amp, maximum, using a discrete transistor regulator with op-amp feedback to control the output voltage. The supply was constructed in 1975 and has a constant current mode that is used....
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The UPS is basically an ac inverter that is powered by a 12-V, lead-acid automobile battery. During power outages, it can supply several minutes of power for an average personal computer. It incorporates a crystal-controlled 60 Hz time base, so that a....
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These controllers have an inhibit input and the effect of shorting this down to ground is to turn down the internal demand speed. So with the battery current limiter fitted, the internal demand speed can only ramp up to a value which engages the limit. Some....
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The windshield wiper interval circuit presented here is very compact and is noteworthy for its use of ..
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Because many amateur receivers are fitted with an S meter that functions far from logarithmically, the proposed circuit should be a welcome extension of such receivers. Although ICs such as the CA3089 or the CA3189 are not in common use anymore, they serve....
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Each and every time a phone on the same line or calling numberis taken off-hook, the circuit will be activated to control an external electronic circuit. If several extension telephones are used on one phone line, the circuit can be useful as a busy....
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The Infineon C16x Series of µCs use an internal 16-bit-register architecture. The architecture can also process byte-wide functions. The µC uses byte moves to implement library functions such as memset() or memcopy(). This process makes the library code....
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A four output Hall sensor combined with a few logic gates produce this digital compass. The NOR gates resolve the four Hall..
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This circuit produces the sound of a beeper like the one in pagers which produces a "beep-beep" sound. Basically the circuit consists of a 555 timer oscillator which is turned ON and OFF periodically.
The first IC(left) oscillates at about 1Hz. The second....
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This transmitter needs heatsink at 2N2219. With the C4 we regulate the frequency. With their C7, C8 we adapt the resistance of aerial (practically to them we regulate so that it is heard our voice in the radio as long as you become cleaner)...
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This stabilized voltage-to-frequency converter features 1 Hz -1.25 MHz operation, 0.05% linearity, and a temperature coefficient of typically 20 ppm/°C. This circuit runs from a single 5-V supply. The converter uses a charge feedback scheme to allow the....
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The circuit is built around an LM339 quad comparator, Ul, which forms the basis of a Schmitt trigger, timer circuit, and a window comparator. One comparator within the LM339 (pins 1, 7, 6), plus LDR1, R4, R5, R6 and R8, is used as a Schmitt trigger. The....
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Using a 555 timer to drive a CMOS counter, this device uses RCA CA3079 zero-voltage switch to control triacs TR1 through..
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Silicon controlled rectifiers (SCR) can easily oscillate if there is an inductor (a speaker coil in this case) which gives just enough extra voltage to completely switch off the sustain current. In this way a new cycle may start and oscillations set in. It....
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This circuit enables a single SCR to provide fullwave control of resistive loads. Resistor R3 should be chosen so that when potentiometer R2 is at its minimum setting, the current in the load is at the required minimum level..
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This FM transmitter (FM Tx) is about the simplest and most basic FM Tx it is possible to build and have a useful transmitting range. It is surprisingly powerful despite its small component count and 3V operating voltage. It will easily penetrate over three....
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This amp uses the basic circuitry of the 60W power amp (see Index), but modified for true Class-A operation - it should be pretty nice! This amp has been built by several readers, and the reports I have received have been very positive...
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This simple circuit mixes two or more channels into one channel (eg. stereo into mono). The circuit can mix as many or as few channels as you like and consumes very little power. The mixer is shown with two inputs, but you can add as many as you want by just....
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The circuit below provides the horizontal drive voltage. The supply voltage on one end, +135 to +165, is made variable for the horizontal position control...
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This project I made for my little daughter. It is 24 channel light illumination. The schematic is very simple ? 24 LED?s, 1 MCU and some additional components. The main principle is dynamic indication, which is usually implemented for control of 7-segment....
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The circuit presented on this page attemps to be an interface to convert pulses such as provided by a Basic Stamp or R/C receiver to a dual PWM(Pulse Width Modulation) signal required by an H-bridge. The simplest circuit would use a small microcontroller....
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By judging the rate at which a particular LED flashes, you`ll be able to estimate the resistance. The circuit consists of two IC`s (1 4011 CMOS quad 2-input, NAND gate, Ul; and a 4024 binary counter, U2), seven LEDs, and a handful of additional .components.....
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Reverse engineered circuit diagram of a commercial Electronic Bird. This one was built into a plastic christmas ornament and runs off a 9V battery. Note that L1 is actually just an audio transformer with an unused secondary winding...
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Converter consists of four quad bistable latches activated in the proper sequence by the digit strobe output of the LD110. The complemented outputs (Q) of the quad latch set reflects the state of the bit outputs when the digit strobe goes high...
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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...
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The described device is used to convert the digital signal format S / PDIF (AES3) to analog. It can be used for any device with uncompressed digital audio output (desktop CD or DVD, minidisk, sound card PC CD-ROM). Separate transmitter can improve the signal....
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This circuit was designed for testing fuel cells, but it could also be used for testing batteries under a constant current load. It provides a dynamic, constant current load, eliminating the need to manually adjust the load to maintain a constant load. For....
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Tesla's free-energy receiver was patented in 1901 as An Apparatus for the Utilization of Radiant Energy. The patent refers to "the Sun, as well as other sources of radiant energy, like cosmic rays." That the device works at night is explained in terms of the....
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This circuit works well in the range of 50 kHz to 500 kHz. Slight component modifications are needed for higher frequency operation..
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The common clock oscillator in Fig. 68-19A has two small problems: It might not, in fact, oscillate if the transition regions of its two gates differ. If it does oscillate, it might sometimes oscillate at a slightly lower frequency than its equation....
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A 2 Watt audio amplifier made from discrete components. This was one of the earliest circuits that I ever designed and built, in Spring 1982. At that time I had only an analogue meter and a calculator to work with. Although not perfect, this amplifier does....
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Based on the classic Baxendall tone control circuit, this provides a maximum cut and boost of around 10dB at 10K and 50Hz. The first BC109C transistor (left hand side) is acting as a buffer. It provides the circuit with a high input impedance, around 250k....
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This circuit is an AGC system for audio-frequency signals. AGC systems usually consist of three parts: an amplifier, rectifier, and controlled impedance. In this circuit the functions of an amplifier and a rectifier are performed by a single op amp. This....
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The circuit will find excellent usage in high frequency line driving systems that require wide-power bandwidths at high output current levels. (IC=HA2530) The bandwidth of the circuit is limited only by the single pole response of the feedback....
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This circuit employs a synchronous demodulator to separate a 1 KHz signal from noise and measures the amplitude of the 1 kHz signals once a second at about 60 microvolts per count then sends the measurements via an RS-232 interface for further processing or....
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U1 is configured to operate in the standard astable mode, providing a form of relaxation oscillator. When power is applied, C2 initially charges through Rl, R2 and R3 to two-thirds of the supply voltage. At that point, U1 senses that its threshold voltage at....
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This adaptor will capture plots or prints of your GPIB instrument to your PC through the serial port. It fills the need of anybody who has a test instrument with the GPIB port and likes to get the screen dump on his PC without any GPIB card. Project based on....
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The circuit shown here is used to switch on a lamp when the tele- phone rings, if the ambient light is insufficient. The circuit uses only two ICs and it can be implemented very easily. A light dependent resistance (LDR), with about 5 kilo-ohms resistance in....
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Modern high-performance transmitters require accurate monitoring of RF power, because most cellular standards depend on strict power- transmission levels to maintain an effective network. Regulation of transmitted-signal strength also lets you build lower....
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Three CD4007 A IC packages perform the switch function using a 10-V logic level. A single 15-V supply provides a positive bus for the follower amplifier and feeds the CA3085 voltage regulator. The scale adjust function is provided by the regulator output....
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Have an old hard drive that no longer works? As long as it still spins up chances are you could build a clock out of your old hard drive! You will need some electronic knowledge, some common electronic components and a bit of patience. The clock that is....
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The accuracy of direct linear coupling of analog current signals via an optocoupler is determined by the coupler linearity and its temperature coefficient. Use of an additional coupler for feedback can provide linearity only if the two couplers are perfectly....
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As with the Electronic sel. 8 we also have here a circuit with a choice of 8 different sources. The difference is that only two of the switches are used and the movement of commands is Up-Down in series. We have evidence of activity at each entrance by the....
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The transducer circuit can be operated as either a tone encoder or decoder by changing the position of Sl. The operating frequency of that dual-purpose circuit is determined by C3 and R2. Capacitors Cl and C2 are not critical and can be of almost any....
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A high-input-resistance op-amp, a bridge rectifier, a microammeter, and a few other discrete components are all that are required to realise this versatile circuit. This circuit can be used for measurement of dc, ac rms, ac peak, or ac peak-to-peak voltage....
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The MK50398 is one modern decimal counter up/down of six tens, with control of screen LED of seven segments and flip-flop of storage. Counter it can measure additive and abstractively. The IC MK50398 is ideal for manufacture frequency counter as the....
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The circuit can use any general-purpose, low-offset, low-drift op amp, such as the OP-07. The differential signal from the bridge feeds an amplifier that drives an ordinary, rugged ±50-p.A meter. Near the null point, however, the drastically reduced....
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This Transmitter can be powered by a battery 9V (not more than 12V). You can connect your music source where the microphone is or use a simple condenser microphone. The range of signal can reach 400 meters in open air. The wide range of frequency is up to....
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The circuit above above makes use of the CMOS 4017 decade counter IC. Each depression of a switch steps the output through 0 - 9. By coupling the output via an AND gate to the next IC, a predefined code has to be input to create the output. Each PBS switch....
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The 5 volt regulated power supply for TTL and 74LS series integrated circuits, has to be very precise and tolerant of voltage transients. These IC`s are easily damaged by short voltage spikes. A fuse will blow when its current rating is exceeded, but....
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This is the lowest cost dialing alarm on the market and shows what can be done with an 8-pin microcontroller. The complete circuit is shown below. You cannot see all the features of this project by looking at the circuit - most of them are contained in the....
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This add-on device for telephones can be connected in parallel to the telephone instrument.
The circuit provides audio-visual indication of on-hook, off-hook, and ringing modes. It can also be used to connect the telephone to a cid (caller identification....
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IC4, C1, R1 and R2 are used for the clock pulse which is fed to both the counters IC2 and IC3 Pin 14. IC1 is a Flip Flop and is used as a switch to enable ether IC2 or IC3 at pin 13. IC7a detects when ether IC2 or IC3 has reached Q9 of the counter pin 11.....
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There have described the involvement benefited LM3909 circuit, which is quite expensive. That's why I prefer to use a much cheaper known timer 555th.Involvement of the tree is a very simple scheme is to figure 2 . It is based on several multivibrator used as....
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Symmetry of the square-wave output is maintained by connecting the right side of R2 through resistor R3 to the output of the third amplifier stage. This changes the charging current to the capacitors in proportion to the setting of frequency-adjusting....
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The sound card for a PC generally has a microphone input, speaker output and sometimes line inputs and outputs. The mic input is designed for dynamic microphones only in impedance range of 200 to 600 ohms. Lazar has adapted the sound card to use a common....
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Controlling a small dc motor without speed control sounds like a trivial task; a switch or a relay should suffice. However, several problems accompany this approach. For one, the switch, because of the inductive load and the low starting resistance of the....
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Figure 2 is a diagram of the control circuit
built on a 1.45 X 1.8 inch PC board. IC1 is
an LMC555 CMOS timer that generates a
200 microsecond wide clock pulses to step
the motor and control its speed. The speed
can be varied by changing the pulse....
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The transceiver is composed by three single sided printed boards 100x70 mm, theese may be
stacked so as to reduce the overall size of the metal cabinet. I suggest to employ small size
components (1/4 W resistors, 2,5 mm capacitors, ) wich should fit....
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The output voltage is = 0.707 x Vin, at the center posititon. The output voltage is = Vin, at either extreme position...
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This type of design can produce a very high amperage current for a faction a second that can used to do some useful work if properly harnessed.
A point to remember is that Paul Baumann built his first device in prison and as such did not have access to....
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This application uses the timer connected for astable (free-running) operation, with a modulating signal again applied to the control voltage terminal. ..
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This is the basic fm trasmitter that I built. In theory, according to electronics, it shouldn't work but works fine and is very sensitive. It can transmit the signal up to 45 yards (about 40 meters) . A sensitive FM radio can pick up the signal up to 100....
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This design was born of frustration with the mic preamp in my Sony R91. It clips at ridiculously low levels, basically it has 28mV of headroom to deal with an input that could be as high as 1800mV (depending on mic & volume), so this design attempts to cure....
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If your amplifier is fitted with two level controls, it actually offers you a balance control and a level control. A draw..
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The trip point is set half way between the supplies by Rl and R2; R3 provides over 200 mV of hysteresis to increase noise immunity. Maximum frequency of operation is about 300 kHz. If response to TTL levels is desired, change R2 to 39 K..
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Wien bridge sine-wave oscillator using two RCA CA3140 op amps cover» 30 Hz to 100 kHz with less than 0 percent total harmonic distortion. The 10k pot is adjusted for the best waveform..
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There is little to be said about this circuit. All the work is done by the regulator. The 78S09 can deliver up to 2 amps continuous output whilst maintaining a low noise and very well regulated supply. The circuit will work without the extra components, but....
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This circuit above uses a 13 volt zener diode, D2 which provides the voltage regulation. Aprroximately 0.7 Volts are dropped across the transistors b-e junction, leaving a higher current 12.3 Volt output supply. This circuit can supply loads of up to 500 mA.....
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The compact 5 pin L165 IC general a stabilized symmetrical power supply from a single asymmetrical power supply. The output voltage is however, half of the input voltage. One needs to add the ripple filter capacitors C1, C2, C3 and C4 and some resistors for....
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When using a regulated power supply to reduce a supply voltage, there is always the danger that component failure in the power supply might lead to a severe overvoltage condition across the load. To cope with overvoltage situations, the circuit is designed....
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This circuit was designed on request, to remotely monitor when a couple of electric heaters have been left on. Its sensor must be placed in contact with the feeder to be able to monitor when the power cable is drawing current, thus causing the circuit to....
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This circuit will automatically switch on several mains-powered "slave" loads when a "master" load is turned on. For example, it will switch on the amplifier and CD player in a stereo system when the receiver is turned on. It works by sensing the current....
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Circuits to interlace the Si7135 directly with two popular microprocessors are shown in Figs. 18-2a and b. The 8080/8048 and the MC6800 families with 8-bit words need to have polarity, overrange, and underrange multiplexed onto the digit 5 word. In each....
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The two circuits below illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button. The circuit on the left can be used for long time periods where the push button can be pressed and released....
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During the development of systems that include small motors, a simple, bidirectional motor controller with speed adjustment may be helpful. Figure 1 shows such a controller. The circuit uses everyday components whose tolerances and ratings are unimportant as....
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This circuit is particularly applicable to digitally-controlled systems in robotic and X-Y positioning applications. By functioning from the 5-V logic supply, it eliminates additional motor-drive supplies. The tachless feedback saves additional space and....
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The whistle switch allows you to turn on, or off, an appliance by whistling at it. I originally built the whistle switch in 1974. Do not attempt to duplicate it from the schematic below, but instead, understand the functions and duplicate these functions....
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You may be familiar with this effect. You switch audio equipment such as an amplifier to a different input and there is a loud click or "thump" in the speaker system. Not all equipment is affected. Some high end audio systems never suffer, but intercoms....
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In this circuit Ql, Q2, Rl, and CI form a multivibrator. The square wave that results from the oscillation..
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This circuit uses a small microphone to capture the sound and some transistors to generate radio waves that can be picked up by a FM receiver like a car stereo. The first part is the microphone and some resistors to get it working. Next we have a capacitor....
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In this circuit, the input from IC2 optocoupler is fed to the comparator input of the AD..
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The LTC1392 is
designed to be used for PC board temperature and supply
voltage/current monitoring or as a remote temperature
and voltage sensor for monitoring almost any kind of
system. It is available in SO-8 and DIP packages allowing
it to fit onto....
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This page provides basic information about voltage comparator integrated circuits and is to act as reference material for other circuits. The circuits shown are based on the LM339 Quad Voltage Comparator chip or the LM393 Dual Voltage Comparator chip. These....
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I leave it to the reader to supply their own power supply. I am using a supply from an old external SCSI drive. My cutter runs from the five volt supply and 25cm of nichrome wire pulls about 900mA or 4.5 watts. That is actually running a little hot and I....
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Pin 3 defines the Display type: Common Cathode or Common Anode. Connect this pin to GROUND if you are using common cathode 7-segment led displays. To use common anode displays, connect it to VCC (positive)
Pin 4 is the signal input, you can use optical....
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The circuit is so simple that there is little to say about it, but it gives very good results. Tr1 is operated in grounded base mode with input to its emitter to give low impedance input. The values shown give correct operation from 9v. If operating from....
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It many times happens, we want erase or decrease in a musical song, the voice of singer or some other sound that usually is written in same level and in the two channels. If we remove between them two signals of channels, we can take in the output a mono....
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Hand and body motions in proximity to the sensing antennas produce frequency changes in a Hartley oscillator operating at approximately 750kHz. The signal from this variable oscillator is mixed with a constant reference frequency in a ring modulator and the....
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The peak detector tracks and holds, using the charge-storing ability of a capacitor, the highest output voltage from a transducer. Initially, the voltage on the inverting input of the comparator is at ground level. As a small voltage (0-5 V) is captured by....
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This circuit relies upon the minute current between two conductive probes suspended in a washer fluid reservoir..
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This board is designed specifically to control the 5-motor Robot Arm sold by Baycom Technologies. It has no input facilities, but it is less expensive than combining the I/O Board with the Relay sub-Board. If you need lots of relays and no input, this is the....
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Very often when enjoying music or watching TV at high audio level, we may not be able to hear a telephone ring and thus miss an important incoming phone call. To overcome this situation, the circuit presented here can be used. The circuit would....
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The transmitter is built around two CMOS 555 timer ICs (TLC 555s). The transmitter generates a modulated 35-kHz ..
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This circuit shows an active antenna that can be used for AM, FM, and shortwave (SW). On the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. This circuit is designed to be used on receivers that use untuned wire antennas,....
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If you wish to take a picture of a fleeting event which generates a sound, you can do it with this sound activated trigger. It does not require any power supply: it feeds on the high voltage available on the flash trigger terminal. Any economic ceramic....