New Circuits Page 217
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Before using this or a similar device, their data sheet should be read carefully and any power supply recommendations should be followed to prevent false output pulses.
The receiver module used for this test worked very well under all levels of....
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A typical device that requires less than 5v and draws less than 25mA is an LED. A LED must be supplied with an exact voltage for it to operate correctly. Because it requires LESS than 5v, a dropper resistor (current limiting resistor) must be included in....
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The digital clock of circuit, has as base one IC, the MM5314N, in which are contained all the circuits that need. The IC1 collaborates with six Display of common anode, that are not critically as materials. You can select what dimension, you want it is....
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The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a....
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Here the popular 555 timing IC, is wired as a monostable. The timing period is precise and equivalent to:-
1.1 x R1 x C1
With component values shown this works out at approximately 1.1msec.The output duration is independant of the input trigger....
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This circuit provides a delayed visual indication when a door bell switch is pressed. In addition, a DPDT switch can be moved from within the house which will light a lamp in the door bell switch. The lamp can illuminate the words "Please Wait" for anyone....
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This analyst is, a sensitive instrument, in the frequency changes and width of a acoustic signal. Thus the brightness of LED that turns on each moment of is proportional signal width, while the colour of proportionally frequency. The circuit input....
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This is a 0 - 6 MHz DDS VFO controlled by a PIC16F84 (or `C84).
The VFO is separated into two modules, the DDS module and
the controller module. The PCB layout (double sided) for
the DDS module is included as two Postscript files
(scale 1:1). The .PS....
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This is an easy to build, but nevertheless very accurate and useful digital voltmeter. It has been designed as a panel meter and can be used in DC power supplies or anywhere else it is necessary to have an accurate indication of the voltage present. The....
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The modules described in this application note can be used
as stand-alone multiplexers for both NTSC/PAL broadcast
and any HDTV format applications. In addition, by virtue of
their size, their performance and the SIP pin outs, they may
be used to form....
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The GT4123 and GT4123A are the first dedicated single
device, two input video mixer ICs available to the professional
video and multimedia markets. Each input signal is applied to a conventional differential
amplifier (AMP A and AMP B). From the....
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In order to assist the video design engineer in using Gennum's
GX4201 video crosspoint, an AC equivalent circuit has been
created. A PSpice® netlist of the circuit has been generated
and is available on floppy disk.
The equivalent circuit is for AC....
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The GX434 is a high performance low cost monolithic 4x1
video multiplexer incorporating four bipolar switches with a
common output, a 2 to 4 address decoder and fast chip select
circuitry. The chip select input allows for multi-chip paralleled
operation....
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This inverter uses no special components such as the torodial transformer used in many inverters. Cost is kept low with the use of cheap, readily available components. Essentially, it is a power amplifier driven by an asta-ble multivibrator. The frequency is....
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By connecting this circuit to a logic device that"s under power, you can get an indication as to its status. If the circuit is ..
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This circuit is capable of driving filament lamps of nominal rating 200 mA at 60 V dc from a CMOS logic signal. The lamp or load is connected in series with the Darlington transistor TR1 and emitter resistor R5. The Zener diode ZD1 establishes a soft....
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The output devices are MJL4281A (NPN) and MJL4302A (PNP), and feature high bandwidth, excellent SOA (safe operating area), high linearity and high gain. Driver transistors are MJE15034 (NPN) and MJE15035 (PNP). All devices are rated at 350V, with the power....
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An electric guitar often has to be connected to a mixing panel, a tape deck or a portable studio. As far..
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This astable will trigger itself and run free as a multivibrator. The external capacitor charges through RA and RB and discharges through R8 only. Thus, the duty cycle is set by the ratio of these two resistors, and the capacitor charges and discharges....
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This very simple circuit uses a transformer ,two diodes , a capacitor and an ammeter.
To charge a battery just connect the + and - terminals of the circuit to the corresponding terminals of the battery.
When the battery is not charged, the ammeter reading....
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The security system application and program offers a simple demonstration of the BASIC Serial Interface. By adding only a few door and window switches, a transistor, a siren, (see schematic) and a few lines of BASIC program (see program listing) the....
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The Sun-Up Alarm can be used to provide a audible alarm for when the sun comes up or it can be used in a dark area and detect when a light comes on. It can also be used to detect a light beam, headlights etc. The circuit works as follows. The phototransistor....
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This circuit can be adapted for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply use two 12 Volt batteries in series and a 7815 regulator. There is a lot of flexibility in this circuit...
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This circuit prevents damage to the load due to incorrect phasing. The three power SSR's are only permitted to turn-on for a phase sequence of phase A leading phase B. If phase A lags phase the input currents will cancel, causing the SCR and the inhibit SSR....
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Suitable for monitoring an amateur band or a segment of the radio spectrum, this simple adaptor uses an NE602 mixer-oscillator chip to produce a 455-kHz IF signal, which U2 amplifies, then feeds to detector D2 and the Y axis of an oscilloscope. VT is used....
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The following is a method to allow day and night detection using Infrared/Visible light sensitive phototransistors and a simple LM339 voltage comparator circuit. A phototransistor is mounted between the rails so that it is covered by the train as it passes.....
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Humans have been using light and sound to achieve altered states of consciousness for thousands of years. Primitive cultures used flickering fires and rythmic drumming to induce these altered states. Today, you can choose from a wide variety of electronic....
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The basis ofthe beam splitter is a 555 timer connected as an astable multivibrator. Signals at the two inputs are alternately displayed on the oscilloscope with a clear separation between them..
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The circuit is simple, yet is capable of excellent performance. I designed it specifically for use as an amplifier for the digital sound card in my computer. Audio input can be from any two-channel line level device such as a television, CD player, or VCR.....
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The presented project is a function generator for sinusoidal and square signals production. The output frequency covers the range from 10 Hz to 100 KHz with a step of 2 Hz.
The waveform synthesis is based on the D.D.S. technique (Direct Digital Synthesis)....
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The LM117 series of adjustable 3-terminal positive voltage
regulators is capable of supplying in excess of 1.5A over a
1.2V to 37V output range. They are exceptionally easy to use
and require only two external resistors to set the output voltage. Further,....
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Uses a low cost CMOS IC to tum four LEDs on and off at a rate that is set by the values of R1, R2, Cl, and C2. The pulse rate for the component values given for R1 and R2 is about one cycle every four seconds. By lowering the values of Rl and R2 to 220 KO,....
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One leg of the photocell (Rl) is tied to the +15 volt supply and the other end is connected to ground through resistor R2, forming a voltage-divider network. The non-inverting input of the 741 op amp, IC1, is tied to the junction formed by Rl and R2, while....
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The VTG-01 is designed to display user defined text over a composite video signal. This is useful in a multitude of different applications such as adding titles to home movies and adding custom text to security videos. Text can be displayed in different....
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The HF/SW receiver preamplifier is comprised of a broadband toroidal transformer (LI-a and Ll-b), LC network (comprised of a 1600-kHz, high- pass filter-and a 32-MHz, low-pass filter), L2 and L3 (26 turns of #26 enameled wire wound on an Amidon Associates....
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The phototransistor and photodarlington couplers act as de relays in saturated switching at currents up to 5 mA and 50 mA, respectively. When higher currents or higher voltage capabilities are required, additional devices are required to buffer or amplify....
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The internal zener on pin 15 of the 4046B supplies a stable voltage to the 3140IC op amp. This amplifier modulates the 4046B V..
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The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery....
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In this circuit, a simple calculator, in conjunction with a COB (chip-on-board) from an analogue quartz clock, is used to make a telephone call meter. The calculator enables conversion of STD/ISD calls to local call equivalents and always displays current....
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This circuit uses a 15-kHz oscillator coil. Whan metal placed ixi the energy field is withdrawn, the oscillator voltage is rectified and compared to a reference. A drop in oscillator voltage therefore operates comparator IC2 and D4 (LED) extinguishes.
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This smartcard adapter follow exactly the specification ISO 7816. Also, the protocol is the "asynchronous half duplex T=0 protocol" with "active low reset" and "inverse convention" as defined in this standard.
The following description may be used in order....
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The purpose of this circuit is to control the water temperature in a hot-water heating system. What it does is to lower the boiler temperature as the outside air temperature increases. The op amp is used as a comparator. Thermistor TH2 and R2 form a voltage....
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In this mode, the timer functions as a one shot. The external capacitor is initially held discharged by a transistor internal to the timer. Applying a negative trigger pulse to pin 2 sets the flip-flop, driving the output high, and releasing the short....
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Here is one that uses a single IC (LM324 quad op amp)
and a handful of parts. This circuit is for detecting one of those 3.6khz..
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The 2N2222 circuitry is a three-element, phase-shift oscillator circuit, designed to yield a 1,000-Hz sine wave. The 1,000-Hz sine wave is then applied to the TCG-610 varactor diode, 6 pF at 4 V, which changes the tank capacitance, thus varying the rf....
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This converter enables a receiver that tunes 28 to 32 MHz to receive the 144- to 148-MHz amateur band. A BF981 dual-gate ..
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Getting the power from your 110 volt receptacle to a suitable foam cutting format presents several problems. A standard light dimmer can be successfully used to vary the heat, but it can`t heat the wire in a direct circuit. With a light dimmer powered by....
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This is design for a frequency meter based on AVR microcontrollers. Maximum input frequency is specified to be 30 MHz in the multi-chip configuration, and in single-chip configuration, there are both 5 MHz and 10 Mhz versions operating with 10 and 20 MHz....
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This circuit was designed for measuring the current from a set of power trackers on the Iowa State University Solar Car, the PrISUm Phoenix. The power trackers provide impedance matching between the solar array and the main electrical bus on the car. Because....
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This is a very simple, low cost, Hi-Fi quality power amplifier. You can build it 5 ways, like it?s shown in the table (from 20 W to 80 W RMS). The first thing that you must do, is to measure the end transistors (T3 and T4) amplifying coefficient, the hfe or....
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In this circuit exists a second designing proposal of preamplifier RIAA. The first stage uses discernible components and in second exist a opamp. [IC1]. In the negative feedback exist the correction RIAA filters. Certain points need certain discriminators:....
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Since the volume control is after the gain stage, the preamp can be easily overloaded. I tried to limit the input signal by mounting a 470 k resistor in series with the CD input. A voltage divider is formed by this resistor and R107, resulting in a greater....
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Three factors contribute to the output symmetry. The capacitor charges and discharges through the same external resistor. An internal resistive divider sets accurate switching thresholds within the chip, the bipolar types use dividers, as well. Most....
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The Project presented here waters your plants regularly when you are out for vocation. The circuit comprises sensor parts built using op-amp IC LM324. Op-amps are configured here as a comparator. Two stiff copper wires are inserted in the soil to sense the....
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A simple X-band radar detector is capable of indicating changes in rf radiation strength at levels down to 2 mW/cm2. Radiation falling on the detector diode, produces a voltage at the input of an amplifier whose gain may be adjusted to vary the range at....
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The probelike device in Figure 1 comes in handy as a quick go-no-go test for step-down power supplies. You can build it using a very bright surface-mount LED and an inductor of the same type as in the power supply, which in this case is 100 µH. Placing this....
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Many security-alarm systems require the use of a random number. A computer program uses this random number to create a sequence of random numbers to prevent unwanted visitors from gaining entry into a protected facility. You can use a "rolling-code....
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A relaxation oscillator is used to flash an LED in the base circuit. Cl is charged slowly through R1 by the power source, then discharged periodically through R3 and the LED by the UJT.
..
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The circuit in Figure 1 provides not only a complementary drive signal but also a deadtime delay on both rising and falling edges. The high-speed inverter gates use IC1, a 74HC04 CMOS circuit, and 1N5819 Schottky diodes D1 and D2. The 74HC04 inverter....
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The SX 28 internal oscillator Is not that fast so an external oscillator can be hooked up to the processor as shown in the diagram to increase the operation cycles per second...
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The circuit needs that the VGA card sends out the video signal the the RGB format compatible with PAL or NTSC standard video timings. This is accomplished with right VGA to TV driver...
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The first servo controller project at http://www.rentron.com/servo.htm had the com port fixed at com1. This new version will seek out the available com ports on your PC and then let you select the desired port and baud rates. It has 1 additional servo port....
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Typical circuit representative of those used in most light switch type digital timers. The timer module is normally a PIC or custom chip, and it syncs to the AC line so that a trigger pulse can be supplied at the right moment...
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This sound-operated switch will sense the ring of the phone and translate this to a lamp that will go on and off. The..
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When any particular key is pressed, its value will appear in BCD form at the outputs (A, B, C & D). It will remain there until another key is pressed. The 12 keys produce outputs up to "1011". Extended to 16 keys, the circuit will give the full HEX to....
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The Tesla coil described here can.generate 25,000 V. So, even though the output current is low, be very careful! The main component is a flyback transformer from a discarded TV. A new primary windin_g is needed. Begin by winding 5 turns of #18 wire on the....
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Arcing completes a circuit -- closes a system -- between two voltage potentials. When arcing occurs, two oppositely charged static voltage potentials can cancel each other out. The arcing problems that occur are usually between two electrically isolated....
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The filter should provide adjustable gain to maximize SNR at the audio processor's first stage. The filter's frequency response should also include a notch at 19 kHz to achieve maximum attenuation at the FM-subcarrier pilot-tone frequency and thus minimize....
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High Quality very simple unit -- No need for a preamplifier
Can be directly connected to CD players, tuners and tape recorders.
Don`t exceed 23 + 23V supply.
Q3 and Q4 must be mounted on heatsink.
D1 must be in thermal contact with Q1.....
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This simple tone control can be used in may audio applications. It can be added to amplifers, used as a stand alone control module, or even built into new and exciting instruments. It`s one IC construction makes it a very compact circuit, as only a few....
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Laptop computers often use large-screen LCDs, which require a variable and a negative supply to ensure maxi..
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The instrument used to measure battery capacity. The battery may be charged to any current in the range 0-3 A. The load current may be constant, may change over time or even break off completely. Unloading stops when the battery voltage drops below the set....
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This circuit will allow you to place a phone call on hold and if you wish to have them listen to music while they are on hold. The circuit operates as follows: The RED wire from the phone jack is typically positive and the GREEN wire is negative or ground.....
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To calibrate the gauge, connect the battery and press the probes gently into a pot containing a plant that is just on the verge of needing water (stick it in so that only an inch of the probe is left visible at the top). Turn the potentiometer until the "OK"....
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ome games are easier to play with digital joystick instead of analogue type. Unfortunately PC has only analogue joystick connector, which makes it impossible to connect normal digital joystick to it. But with a little adapter circuit, it is possible to use....
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The circuit allows a precision regulated drive current to be set to drive an LED, and in response to a TTL level signal, the LED is switched on and off with rise and fall times of less than 500 nanoseconds and less than 7% overshoot. This was designed for....
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Shortly after the 2002 WCRG, Ori Barbut started tinkering with Ben Hitchcock`s FRED SE. His aim was to create a simple, solar-powered, light-seeking head design (and in particular, to create a head design that could be based on a FRED photopopper kit with....
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The VFC (voltage-to-frequency-converter) circuit in Figure 1 achieves a wider dynamic range and a higher full-scale output frequency100 MHz with 10% overrange to 110 MHzby a factor of 10 over any commercially available converter...
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The input consists of two comparators that operate with different reference voltages supplied by separate potential dividers. ..
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The circuit in Figure 1 shows the versatility of the
LTC2418. A combination of single-ended, differential,
unipolar and bipolar input sources are simultaneously
applied to the LTC2418...
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This high-performance switching controller for a low-power de servo motor uses a symmetrical complementary- transistor bridge. The bridge acts as a reversing switch between the motor and a single-ended power supply. Since the transistors operate either....
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The circuit in Figure 1 is a keypad interface that solves this problem by using an ultralow-power microcontroller. The circuit typically consumes 100 nA while awaiting a key press and consumes a maximum of only 2 µA if all keys are stuck or held down. An....
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The circuit is designed to operate at 25 kHz. The data stream turns the 2N4401 hard on or off depending upon the coded state. This in turn switches the series infrared LEDs on and off. The receiver circuit consists of a three stage amplifier with photo....
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This approach uses a Hip-Hop, a shift register, and two gates (A). Before the one-shot pulse, the output of the NOR gate is 0. Consequently, the data input of the D-type flip-flop is equivalent to the trigger. When a trigger pulse is present, the flip-flop....
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This version sports a 2nd audio amplifier stage at Q3. The output level with this version is sufficient to drive a crystal headphone to a comfortable volume. The "crystal" headphone is like those used on ye olde crystal radios. A "Walkman" type headphone is....
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This circuit is an FM 88-108 MHz reciever...
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The circuit devised by Phil Allison still has some input voltage limitations, since it is based on a FET. Junction FET VCAs also create considerable distortion, with the worst of it appearing when the signal is attenuated by 6dB. The common way to fix this....
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Using the principle of capacitance between two plates this circuit senses when more than one sheet of paper goes betwee..
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A 5.1-V zener diode clamps positive-going transients, and a Schottky rectifier clamps negative-going transients. Th..
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Finally, white LED`s are bright enough to use in a practical stroboscope. This circuit can operate as a bench-top stroboscope that, in conjunction with an oscilloscope or frequency meter and bench top power supply can accurately measure rotational speeds, or....
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Excellent clock generator to drive 4017 type cmos circuits. R1 = 10K to 10M, C1 = 100pF to 47uF. Fo is ±1Kz when R1=100K and C1=10nF. Input voltage can be from 5 to 15V...
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The timed two-voltage circuit can start and run a small de motor or solenoid. The input voltage to the LM317 three-terminal regulator ranges from 5 to 40 V, and the output voltage can range from 2 to 36 V. ..
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Pure A class is the most simple topology for designing an amplifier! The tube or the power transistor is loaded directly by the speaker (often thru a transformer, fro impedance matching!), and is biaised at the current necessary for full modulation (that....
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The decoder`s operation is more complicated than that of the encoder. A behavioral simulation (Figure 2) shows the internal signals that are involved in the decoding process. Note that the spike on the "cd" signal is not a true spike; it appears only in the....
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One of the main features of the regulated power supply circuit being presented is that though fixed-voltage regulator LM7805 is used in the circuit, its output voltage is variable. This is achieved by connecting a potentiometer between common terminal of....
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This application note uses a timer IC (ICL7555), CMOS logic and discrete transistors to automatically control the conversion the MAX190 12-bit SAR analog-to-digital converter (ADC). The delay between conversions can be programed using a resistor. Logic....
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The NE602, U1, contains oscillator and mixer stages. The mixer combines the oscillator signal with the input rf signal to produce signals whose frequencies are the sum and difference of the input frequencies. For example, a 7.5-MHz signal is picked up by....
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This amplifier is useful for applications where a 10- to 15-W peak-envelope-power (PEP) signal is needed i..
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The charger is built around a single LTC®1541,
which contains a voltage reference, op amp and comparator.
The high accuracy voltage reference (±0.4%) regulates
the battery float voltage to ±1.2%, as required by most
Lithium-Ion battery manufacturers...
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817V The outputs in this circuit are independently variable and can be loaded unsymmetrically. The output voltage remains constant, irrespective of load and changes. By varying potentiometers R2 or R6, the output voltages can be conveniently set.....
Before using this or a similar device, their data sheet should be read carefully and any power supply recommendations should be followed to prevent false output pulses. The receiver module used for this test worked very well under all levels of....
A typical device that requires less than 5v and draws less than 25mA is an LED. A LED must be supplied with an exact voltage for it to operate correctly. Because it requires LESS than 5v, a dropper resistor (current limiting resistor) must be included in....
The digital clock of circuit, has as base one IC, the MM5314N, in which are contained all the circuits that need. The IC1 collaborates with six Display of common anode, that are not critically as materials. You can select what dimension, you want it is....
The pitch of the tone is dependent upon the resistance under test. The tester will respond to resistance of hundreds of kilohms, yet it is possible to distinguish differences of just a few tens of ohms in low-resistance circuits. Ql and Q2 form a....
Here the popular 555 timing IC, is wired as a monostable. The timing period is precise and equivalent to:- 1.1 x R1 x C1 With component values shown this works out at approximately 1.1msec.The output duration is independant of the input trigger....
This circuit provides a delayed visual indication when a door bell switch is pressed. In addition, a DPDT switch can be moved from within the house which will light a lamp in the door bell switch. The lamp can illuminate the words "Please Wait" for anyone....
This analyst is, a sensitive instrument, in the frequency changes and width of a acoustic signal. Thus the brightness of LED that turns on each moment of is proportional signal width, while the colour of proportionally frequency. The circuit input....
This is a 0 - 6 MHz DDS VFO controlled by a PIC16F84 (or `C84). The VFO is separated into two modules, the DDS module and the controller module. The PCB layout (double sided) for the DDS module is included as two Postscript files (scale 1:1). The .PS....
This is an easy to build, but nevertheless very accurate and useful digital voltmeter. It has been designed as a panel meter and can be used in DC power supplies or anywhere else it is necessary to have an accurate indication of the voltage present. The....
The modules described in this application note can be used as stand-alone multiplexers for both NTSC/PAL broadcast and any HDTV format applications. In addition, by virtue of their size, their performance and the SIP pin outs, they may be used to form....
This inverter uses no special components such as the torodial transformer used in many inverters. Cost is kept low with the use of cheap, readily available components. Essentially, it is a power amplifier driven by an asta-ble multivibrator. The frequency is....
By connecting this circuit to a logic device that"s under power, you can get an indication as to its status. If the circuit is ..
This circuit is capable of driving filament lamps of nominal rating 200 mA at 60 V dc from a CMOS logic signal. The lamp or load is connected in series with the Darlington transistor TR1 and emitter resistor R5. The Zener diode ZD1 establishes a soft....
The output devices are MJL4281A (NPN) and MJL4302A (PNP), and feature high bandwidth, excellent SOA (safe operating area), high linearity and high gain. Driver transistors are MJE15034 (NPN) and MJE15035 (PNP). All devices are rated at 350V, with the power....
An electric guitar often has to be connected to a mixing panel, a tape deck or a portable studio. As far..
This astable will trigger itself and run free as a multivibrator. The external capacitor charges through RA and RB and discharges through R8 only. Thus, the duty cycle is set by the ratio of these two resistors, and the capacitor charges and discharges....
This very simple circuit uses a transformer ,two diodes , a capacitor and an ammeter. To charge a battery just connect the + and - terminals of the circuit to the corresponding terminals of the battery. When the battery is not charged, the ammeter reading....
The security system application and program offers a simple demonstration of the BASIC Serial Interface. By adding only a few door and window switches, a transistor, a siren, (see schematic) and a few lines of BASIC program (see program listing) the....
The Sun-Up Alarm can be used to provide a audible alarm for when the sun comes up or it can be used in a dark area and detect when a light comes on. It can also be used to detect a light beam, headlights etc. The circuit works as follows. The phototransistor....
This circuit can be adapted for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply use two 12 Volt batteries in series and a 7815 regulator. There is a lot of flexibility in this circuit...
This circuit prevents damage to the load due to incorrect phasing. The three power SSR's are only permitted to turn-on for a phase sequence of phase A leading phase B. If phase A lags phase the input currents will cancel, causing the SCR and the inhibit SSR....
Suitable for monitoring an amateur band or a segment of the radio spectrum, this simple adaptor uses an NE602 mixer-oscillator chip to produce a 455-kHz IF signal, which U2 amplifies, then feeds to detector D2 and the Y axis of an oscilloscope. VT is used....
The following is a method to allow day and night detection using Infrared/Visible light sensitive phototransistors and a simple LM339 voltage comparator circuit. A phototransistor is mounted between the rails so that it is covered by the train as it passes.....
Humans have been using light and sound to achieve altered states of consciousness for thousands of years. Primitive cultures used flickering fires and rythmic drumming to induce these altered states. Today, you can choose from a wide variety of electronic....
The basis ofthe beam splitter is a 555 timer connected as an astable multivibrator. Signals at the two inputs are alternately displayed on the oscilloscope with a clear separation between them..
The circuit is simple, yet is capable of excellent performance. I designed it specifically for use as an amplifier for the digital sound card in my computer. Audio input can be from any two-channel line level device such as a television, CD player, or VCR.....
The LM117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in excess of 1.5A over a 1.2V to 37V output range. They are exceptionally easy to use and require only two external resistors to set the output voltage. Further,....
Uses a low cost CMOS IC to tum four LEDs on and off at a rate that is set by the values of R1, R2, Cl, and C2. The pulse rate for the component values given for R1 and R2 is about one cycle every four seconds. By lowering the values of Rl and R2 to 220 KO,....
One leg of the photocell (Rl) is tied to the +15 volt supply and the other end is connected to ground through resistor R2, forming a voltage-divider network. The non-inverting input of the 741 op amp, IC1, is tied to the junction formed by Rl and R2, while....
The VTG-01 is designed to display user defined text over a composite video signal. This is useful in a multitude of different applications such as adding titles to home movies and adding custom text to security videos. Text can be displayed in different....
The HF/SW receiver preamplifier is comprised of a broadband toroidal transformer (LI-a and Ll-b), LC network (comprised of a 1600-kHz, high- pass filter-and a 32-MHz, low-pass filter), L2 and L3 (26 turns of #26 enameled wire wound on an Amidon Associates....
The phototransistor and photodarlington couplers act as de relays in saturated switching at currents up to 5 mA and 50 mA, respectively. When higher currents or higher voltage capabilities are required, additional devices are required to buffer or amplify....
The internal zener on pin 15 of the 4046B supplies a stable voltage to the 3140IC op amp. This amplifier modulates the 4046B V..
The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery....
In this circuit, a simple calculator, in conjunction with a COB (chip-on-board) from an analogue quartz clock, is used to make a telephone call meter. The calculator enables conversion of STD/ISD calls to local call equivalents and always displays current....
This circuit uses a 15-kHz oscillator coil. Whan metal placed ixi the energy field is withdrawn, the oscillator voltage is rectified and compared to a reference. A drop in oscillator voltage therefore operates comparator IC2 and D4 (LED) extinguishes. ..
This smartcard adapter follow exactly the specification ISO 7816. Also, the protocol is the "asynchronous half duplex T=0 protocol" with "active low reset" and "inverse convention" as defined in this standard. The following description may be used in order....
The purpose of this circuit is to control the water temperature in a hot-water heating system. What it does is to lower the boiler temperature as the outside air temperature increases. The op amp is used as a comparator. Thermistor TH2 and R2 form a voltage....
In this mode, the timer functions as a one shot. The external capacitor is initially held discharged by a transistor internal to the timer. Applying a negative trigger pulse to pin 2 sets the flip-flop, driving the output high, and releasing the short....
The 2N2222 circuitry is a three-element, phase-shift oscillator circuit, designed to yield a 1,000-Hz sine wave. The 1,000-Hz sine wave is then applied to the TCG-610 varactor diode, 6 pF at 4 V, which changes the tank capacitance, thus varying the rf....
This converter enables a receiver that tunes 28 to 32 MHz to receive the 144- to 148-MHz amateur band. A BF981 dual-gate ..
This is design for a frequency meter based on AVR microcontrollers. Maximum input frequency is specified to be 30 MHz in the multi-chip configuration, and in single-chip configuration, there are both 5 MHz and 10 Mhz versions operating with 10 and 20 MHz....
This is a very simple, low cost, Hi-Fi quality power amplifier. You can build it 5 ways, like it?s shown in the table (from 20 W to 80 W RMS). The first thing that you must do, is to measure the end transistors (T3 and T4) amplifying coefficient, the hfe or....
In this circuit exists a second designing proposal of preamplifier RIAA. The first stage uses discernible components and in second exist a opamp. [IC1]. In the negative feedback exist the correction RIAA filters. Certain points need certain discriminators:....
Since the volume control is after the gain stage, the preamp can be easily overloaded. I tried to limit the input signal by mounting a 470 k resistor in series with the CD input. A voltage divider is formed by this resistor and R107, resulting in a greater....
Three factors contribute to the output symmetry. The capacitor charges and discharges through the same external resistor. An internal resistive divider sets accurate switching thresholds within the chip, the bipolar types use dividers, as well. Most....
The Project presented here waters your plants regularly when you are out for vocation. The circuit comprises sensor parts built using op-amp IC LM324. Op-amps are configured here as a comparator. Two stiff copper wires are inserted in the soil to sense the....
A simple X-band radar detector is capable of indicating changes in rf radiation strength at levels down to 2 mW/cm2. Radiation falling on the detector diode, produces a voltage at the input of an amplifier whose gain may be adjusted to vary the range at....
A relaxation oscillator is used to flash an LED in the base circuit. Cl is charged slowly through R1 by the power source, then discharged periodically through R3 and the LED by the UJT. ..
The SX 28 internal oscillator Is not that fast so an external oscillator can be hooked up to the processor as shown in the diagram to increase the operation cycles per second...
The circuit needs that the VGA card sends out the video signal the the RGB format compatible with PAL or NTSC standard video timings. This is accomplished with right VGA to TV driver...
The first servo controller project at http://www.rentron.com/servo.htm had the com port fixed at com1. This new version will seek out the available com ports on your PC and then let you select the desired port and baud rates. It has 1 additional servo port....
Typical circuit representative of those used in most light switch type digital timers. The timer module is normally a PIC or custom chip, and it syncs to the AC line so that a trigger pulse can be supplied at the right moment...
This sound-operated switch will sense the ring of the phone and translate this to a lamp that will go on and off. The..
When any particular key is pressed, its value will appear in BCD form at the outputs (A, B, C & D). It will remain there until another key is pressed. The 12 keys produce outputs up to "1011". Extended to 16 keys, the circuit will give the full HEX to....
The Tesla coil described here can.generate 25,000 V. So, even though the output current is low, be very careful! The main component is a flyback transformer from a discarded TV. A new primary windin_g is needed. Begin by winding 5 turns of #18 wire on the....
Arcing completes a circuit -- closes a system -- between two voltage potentials. When arcing occurs, two oppositely charged static voltage potentials can cancel each other out. The arcing problems that occur are usually between two electrically isolated....
The filter should provide adjustable gain to maximize SNR at the audio processor's first stage. The filter's frequency response should also include a notch at 19 kHz to achieve maximum attenuation at the FM-subcarrier pilot-tone frequency and thus minimize....
High Quality very simple unit -- No need for a preamplifier Can be directly connected to CD players, tuners and tape recorders. Don`t exceed 23 + 23V supply. Q3 and Q4 must be mounted on heatsink. D1 must be in thermal contact with Q1.....
This simple tone control can be used in may audio applications. It can be added to amplifers, used as a stand alone control module, or even built into new and exciting instruments. It`s one IC construction makes it a very compact circuit, as only a few....
Laptop computers often use large-screen LCDs, which require a variable and a negative supply to ensure maxi..
The instrument used to measure battery capacity. The battery may be charged to any current in the range 0-3 A. The load current may be constant, may change over time or even break off completely. Unloading stops when the battery voltage drops below the set....
This circuit will allow you to place a phone call on hold and if you wish to have them listen to music while they are on hold. The circuit operates as follows: The RED wire from the phone jack is typically positive and the GREEN wire is negative or ground.....
To calibrate the gauge, connect the battery and press the probes gently into a pot containing a plant that is just on the verge of needing water (stick it in so that only an inch of the probe is left visible at the top). Turn the potentiometer until the "OK"....
ome games are easier to play with digital joystick instead of analogue type. Unfortunately PC has only analogue joystick connector, which makes it impossible to connect normal digital joystick to it. But with a little adapter circuit, it is possible to use....
The circuit allows a precision regulated drive current to be set to drive an LED, and in response to a TTL level signal, the LED is switched on and off with rise and fall times of less than 500 nanoseconds and less than 7% overshoot. This was designed for....
Shortly after the 2002 WCRG, Ori Barbut started tinkering with Ben Hitchcock`s FRED SE. His aim was to create a simple, solar-powered, light-seeking head design (and in particular, to create a head design that could be based on a FRED photopopper kit with....
The input consists of two comparators that operate with different reference voltages supplied by separate potential dividers. ..
This high-performance switching controller for a low-power de servo motor uses a symmetrical complementary- transistor bridge. The bridge acts as a reversing switch between the motor and a single-ended power supply. Since the transistors operate either....
The circuit is designed to operate at 25 kHz. The data stream turns the 2N4401 hard on or off depending upon the coded state. This in turn switches the series infrared LEDs on and off. The receiver circuit consists of a three stage amplifier with photo....
This approach uses a Hip-Hop, a shift register, and two gates (A). Before the one-shot pulse, the output of the NOR gate is 0. Consequently, the data input of the D-type flip-flop is equivalent to the trigger. When a trigger pulse is present, the flip-flop....
This version sports a 2nd audio amplifier stage at Q3. The output level with this version is sufficient to drive a crystal headphone to a comfortable volume. The "crystal" headphone is like those used on ye olde crystal radios. A "Walkman" type headphone is....
The circuit devised by Phil Allison still has some input voltage limitations, since it is based on a FET. Junction FET VCAs also create considerable distortion, with the worst of it appearing when the signal is attenuated by 6dB. The common way to fix this....
Using the principle of capacitance between two plates this circuit senses when more than one sheet of paper goes betwee..
A 5.1-V zener diode clamps positive-going transients, and a Schottky rectifier clamps negative-going transients. Th..
Finally, white LED`s are bright enough to use in a practical stroboscope. This circuit can operate as a bench-top stroboscope that, in conjunction with an oscilloscope or frequency meter and bench top power supply can accurately measure rotational speeds, or....
Excellent clock generator to drive 4017 type cmos circuits. R1 = 10K to 10M, C1 = 100pF to 47uF. Fo is ±1Kz when R1=100K and C1=10nF. Input voltage can be from 5 to 15V...
The timed two-voltage circuit can start and run a small de motor or solenoid. The input voltage to the LM317 three-terminal regulator ranges from 5 to 40 V, and the output voltage can range from 2 to 36 V. ..
Pure A class is the most simple topology for designing an amplifier! The tube or the power transistor is loaded directly by the speaker (often thru a transformer, fro impedance matching!), and is biaised at the current necessary for full modulation (that....
One of the main features of the regulated power supply circuit being presented is that though fixed-voltage regulator LM7805 is used in the circuit, its output voltage is variable. This is achieved by connecting a potentiometer between common terminal of....
The NE602, U1, contains oscillator and mixer stages. The mixer combines the oscillator signal with the input rf signal to produce signals whose frequencies are the sum and difference of the input frequencies. For example, a 7.5-MHz signal is picked up by....
This amplifier is useful for applications where a 10- to 15-W peak-envelope-power (PEP) signal is needed i..
817V The outputs in this circuit are independently variable and can be loaded unsymmetrically. The output voltage remains constant, irrespective of load and changes. By varying potentiometers R2 or R6, the output voltages can be conveniently set.....
