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Index 345

SET_TIME_WINDOWS_WITHIN_A_CLOCK

Published:2009-6-22 22:49:00 Author:May

SET_TIME_WINDOWS_WITHIN_A_CLOCK
At times, it is necessary to produce pulses of adjustable width and whose start times might vaty with reference to a master clock. The input signal is inverted and buffered by U1A, while U1B and U1C reinvert the signal to produce square, buffered renditions of the input signal. Potentiometers R3 and R4 set references for the comparators.The input polarity of U2A keeps its output transistor tumed on until the voltage at the nonin-verting input exceeds the reference set by R4 (the rising edge adjustment). When this reference voltage is exceeded, the output transistor is turned off and the output signal is pulled up via R6.Meanwhile, the input polarity of U2B keeps its output transistor turned off until the voltage at the in-verting input exceeds the reference set by R3 (the falling edge adjustment). When this reference voltage is surpassed, the output transistor of U2B is turned on, pulling the output signal low through the wired-OR conftguration of U2. The output of U2 is then double-inverted and buffered by U1D and U1E. What results is a pulse whose start time (rising edge) can be adjusted by R4, and whose stop time (falling edge) can be adjusted by R3.The output of the comparators is pulled up to the input waveform through resistor R6 to U1C.This prevents the comparators from switching during the low cycle of the input waveform, regard-less of the positions of R3 and R4. This has the effect of locking out changes during the low period of the input signal, and would probably require additional logic if it were done strictly in the digital domain.The circuit, with the component values shown, works well between about 50 and 150 kHz.   (View)

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PROGRAMMABLE_RESISTOR_CIRCUIT

Published:2009-6-22 22:49:00 Author:May

PROGRAMMABLE_RESISTOR_CIRCUIT
IC1 CD4066 quad bilateral switchC1  0.1-μF capacitorRI 10-kΩ, 1/4-W 5% resistorR2 4.7-kΩ, 1/4-W 5% resistorR3 2.2-kΩ, 1/4-W 5% resistorR4 1-kΩ, 1/4-W 5% resistorR5 1-MΩ, 1/4-W 5% resistor A programmable resistor can replace a potentiometer or fixed resistor. Remember that the ON resistance of IC1 might have to be taken into account in some applications.   (View)

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PROGRAMMABLE_CAPCITOR_CIRCUIT

Published:2009-6-22 22:42:00 Author:May

PROGRAMMABLE_CAPCITOR_CIRCUIT
IC1 CD4066 quad bilateral switchG1 10-μF, 25-V capacitorC2 22-μF, 25-V capacitorC3 47-μF, 25-V capacitor04 100-μF,25-V capacitorC5 1-μF, 25-V capacitor06 0.1-μF, 25-V capacitorThe programmable capacitor can be very useful in circuits where you need to switch capacitance values. Remember that the ON resistance of IC1 appears in series with the capacitors and must be taken into account in some applications as it is not negligible.   (View)

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PHOTODIODE_ANIPLIFIEB

Published:2009-6-22 22:41:00 Author:May

PHOTODIODE_ANIPLIFIEB
A photodiode amplifier combined with a dc-restoration circuit will reject low-frequency ambient backgroud,easing measurement of a light signal.   (View)

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SUPPRESS_JITTER_WITH_HYSTERESIS

Published:2009-6-22 22:40:00 Author:May

SUPPRESS_JITTER_WITH_HYSTERESIS
When the comparator's output changes its state from low to high, the rising edge of the output pulse, differentiated by the C1/R1 chain, opens Q1. This blocks comparator M via its strobing input and sustains its output in the H state for a period of time, defined by the time constant R,Ct After C1 is charged by the current flowing through R1, Q1 is shut off and the comparator is released. When the comparator's output state changes from high to low, a similar process, involving elements R2, C2, and Q2, occurs. In many applications, the output transition in only one direction is of vital importance, and the elements, which provide temporal hysteresis for the opposite direction transition, can be omitted.   (View)

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10_MHz_FREQUENCY_STANDARD

Published:2009-6-22 22:39:00 Author:May

10_MHz_FREQUENCY_STANDARD
A Radio Shack 10-MHz receiver is used as a basis for this circuit. The L.O. and IF frequencies are added. When the receiver is tuned to 10 MHz(WWV), the sum of the L.O. and IF are used to phase lock a VCO to the 10-MHz signal. By using a divider in the Ioop, 2.5 or 5 MHz can be used as well.   (View)

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TELEPHONE_VOICE_MAIL_ALERT

Published:2009-6-22 22:36:00 Author:May

TELEPHONE_VOICE_MAIL_ALERT
The circuit is built around a couple of low-cost ICs: an H11C4 optoisolator/coupler with an SCR output (U1) and an LM3909 LED flasher (U2). It is connected to the phone line in the same manner as any extension phone. A ring signal on the telephone activates the optoisolator/SCR, and causes U2 to flash LED1. This flash signifies that a ring signal has been received.   (View)

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WHEATSTONE_BRIDGE

Published:2009-6-22 22:35:00 Author:May

WHEATSTONE_BRIDGE
WHEATSTONE_BRIDGE

This circuit can be used to measure resistances. R7 is calibrated and fitted with an indicator dial, Lhen: A frequency of 1 kHz for the audio oscillator is usually used.   (View)

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PULSED_DOUBLE_HETEROSTRUCTURE_LASER_DRIVER

Published:2009-6-22 22:34:00 Author:May

PULSED_DOUBLE_HETEROSTRUCTURE_LASER_DRIVER
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IC_LASER_DIODE_DRIVER

Published:2009-6-22 22:33:00 Author:May

IC_LASER_DIODE_DRIVER
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MUSIC_ON_HOLD_BOX

Published:2009-6-22 22:28:00 Author:May

MUSIC_ON_HOLD_BOX
U1, an LS3404 melody chip is activated when hold S1 is pressed, which causes SCRI to con-cluct and hold the telephone line via T1, R1, and LED1. The voltage across R1 and LED1 is used to activate the melody chip. Q1 and Q2 form a restart circuit to keep the melody chip going during hold.   (View)

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LIGHT_BEAM_RECEIVER_AND_SOUND_EFFECTS_GENERATOR_FOR_LASER_PISTOLS

Published:2009-6-22 22:27:00 Author:May

LIGHT_BEAM_RECEIVER_AND_SOUND_EFFECTS_GENERATOR_FOR_LASER_PISTOLS
Schematic diagram for light, beam amplifier and sound-effects generator (using a 555 timer IC and speaker). The light striking Q1 generates a siren-like sound.   (View)

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12_V_HIGH_VOLTAGE_SUPPLY_FOR_HE_NE_LASER

Published:2009-6-22 22:25:00 Author:May

12_V_HIGH_VOLTAGE_SUPPLY_FOR_HE_NE_LASER
T1 is a 6-V:330-V dc/dc inverter transforlrter with a 57.4:1 turn ratio, rated at 7W.R1 270-Ω resistorR2 180-kΩ resistor, 3 to 5 W C1 22-μF electrolytic capacitorC2 1-μF electrolytic capacitorC3-C6 0.02-μF capacitor,1 kV or moreD1 1N4001 diodeD2-D5 High-voltage diode(3 kV or more)Q1 TIP 140 power transistor T1 High-voltage dc-to-dc converter transformer; see text for speciftcattons All resistors are 5 to 10% tolerance, 1/4 W, unless otherwise indicated. All capacitors are 10 to 20% tolerance, rated 35 V or more, unless otherwise indicated.   (View)

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EMERGENCY_TELEPHONE_DIALER

Published:2009-6-22 22:22:00 Author:May

EMERGENCY_TELEPHONE_DIALER
This system will alert you or anyone chosen by automatically dialing a programmed phone num-ber. This is accomplished by monitoring an open-loop or closed-loop sensor switch located in the protected area. When the sensor detects a problem (such as a break-in, fire, heating system failure, flood, etc.), Teleguard dials whatever telephone number has been programmed into its memory. When the phone is taken off the hook, Teleguard emits an unusual tone to alert the party on the re-ceiving end that something is amiss.The circuit is not hampered by busy signals when a call is placed; it automatically redials the number again and again (about once a minute) until it gets through. In addition, Teleguard can also automatically dial a number in the event of a medical emergency; for instance, where a mobility-im-paired person is unable to dial the telephone. That can be accomplished by adding a panic switch to the circuit.   (View)

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21_GAME

Published:2009-6-22 22:21:00 Author:May

21_GAME
21_GAME
21_GAME

Two 2N2647 unijunction transistors serve as the Clock generators for the two 4017 ICs,A single“deal”push-button switch,S1,operates both Clock generators at the same time,Diodes D1 and D2 isolate the two Clock circuits,allowing S1 to operate both.The 4017 counter/readout circuits are identical In circuitry and operation As long as Clockpulses enter pin 14 of each 4017,the ICs count from 1 to 10 over and over until the clock pulses stopWhen S1 is released,the clock pulses stop and one LED from each IC remalns on to indicate a cardwith a number value of 1(1 or 11) to 10.The position of switches S2 and S3 determines whether the number 1 (“Ace”)output of the 4017s count as an 11 or a 1,Both S2 and S3 can be switched in either position before or after thecards are played.The cards can be played either face up OI face down,When switches S4 and S5 are in the position shown in the figure,the cards are dealt face down,Transistors Q3 and Q4 are turned off in thisposition and no current can flow through the LEDs Pressing S6 turns both transistors on,lightingthe LEDs.   (View)

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MUSIC_ON_HOLD

Published:2009-6-22 22:14:00 Author:May

MUSIC_ON_HOLD
When an asterisk * is pressed on the touch-tone phone, IC1 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, press the asterisk button on the touch-tone phone and hang up the handset.   (View)

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TELEPHONE_RINGER

Published:2009-6-22 22:10:00 Author:May

TELEPHONE_RINGER
Using an AMI chip P/N S2561, this telephone ringer can be powered line. Audio output is about 50 mW when powered from a 10-V source.   (View)

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HIGH_CURRENT_DRIVE_CIRCUIT_FOR_SINGLE_HETEROSTRUCTURE_LASER_DIODES

Published:2009-6-22 18:01:00 Author:May

HIGH_CURRENT_DRIVE_CIRCUIT_FOR_SINGLE_HETEROSTRUCTURE_LASER_DIODES
HIGH_CURRENT_DRIVE_CIRCUIT_FOR_SINGLE_HETEROSTRUCTURE_LASER_DIODES
HIGH_CURRENT_DRIVE_CIRCUIT_FOR_SINGLE_HETEROSTRUCTURE_LASER_DIODES
HIGH_CURRENT_DRIVE_CIRCUIT_FOR_SINGLE_HETEROSTRUCTURE_LASER_DIODES

The transistor is operated in the avalanche mode. You might need to try several 2N2222 devices before finding one that oscillates. R2 is adjusted for optimum oscillation. This supply provides pulse of 10 to 20 amps at about 50 ns.   (View)

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SIMPLE_HARMONIC_DISTORTION_ANALYZER

Published:2009-6-22 17:54:00 Author:May

SIMPLE_HARMONIC_DISTORTION_ANALYZER
SIMPLE_HARMONIC_DISTORTION_ANALYZER
SIMPLE_HARMONIC_DISTORTION_ANALYZER
SIMPLE_HARMONIC_DISTORTION_ANALYZER

This simple circuit lets you accurately measure the total harmonic distortion(THD)using your true-RMS voltmeter.This THD circuit is somewhat different from the usual types: it can operate at the standard fre-quency of 1000 Hz, but it also is tunable from 970 Hz to 1030 Hz, and has an adjustable Q factor of 0.3 to over 50. Op-amp UI, a TLC272 CMOS unit, contains the two voltage-followers required to buffer the input to the bootstrapped twin-T notch filter. Tuning is accomplished by R1, R2, and R3, which are standard linear-taper slide pots ganged together by mounting them side-by-side and glu-ing their sliders together.The only other intportant construction hint is to use twisted pair at the cir-cuit's input and output.To calibrate the circuit, input a 1000-V RMS signal at 2000 Hz, set 51 to TEST, and adjust R7 for a reading of 0.99-V RMS on a true-RMS voltmeter at the output.To use the circuit, set 51 to TUNE, input a 1000-Hz sine-wave signal to the amplifier under test, and set the amplifier's output to the THD adapter and tune R1/R2/R3 for the lowest output signal.Then, set 51 to TEST and read the RMS voltage. To calculate the percent THD use:   (View)

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Color TV pincushion correction circuit diagram 1

Published:2011-7-21 1:42:00 Author:Ecco | Keyword: Color TV , pincushion correction

Color TV pincushion correction circuit diagram 1
Field excitation pulses is applied directly to the pin 13 of N402 (TA8859) to trigger monostable trigger, then it generates a constant field frequency pulse-width pulse, which can control field sawtooth wave generating circuit after shaping, the N402 (15) pin is connected externally C418 capacitor with constant current charging to form a sawtooth wave current. Sawtooth amplitude and charging speed is controlled by the AGC circuit of N402, which can meet the needs of 50Hz/60Hz. Sawtooth wave produced by the field sawtooth wave circuit is made a series of linear correction by the N402, then pin (8) will output field excitation pulse.   (View)

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