Published:2009/7/8 5:08:00 Author:May
This motor driver circuit uses a μA759 power amplifter to drive a two-phase servomotor. (View)
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Published:2009/7/8 5:07:00 Author:May
The NE5561 provides pulse-proportional drive and speed control based on dc tachometer feedback. This simple switching circuit consists of transistor 2N4920 pnp with a commutation diode used to deliver programmed pulse energy to the motor. A frequency of approximately 20 kHz is used to eliminate audio noise. The dc tach delivers 2.7V/1000 RPM. Negative feedback occurs when this voltage is applied to the error amplifier of the NE5561. The duty cycle varies directly with load torque demand. The no-load current is≈ 0.3 A and full load is 0.6 A. (View)
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Published:2009/7/8 4:56:00 Author:May
Temperature-to-frequency converter drives digital display providing0 .001°C resolution with 0.15°C absolute accuracy, Linearized thermistor network biases inverting input of AD521J instrumentation amplifier, while noninverting input is driven from same reference. Output can be fed directly to analog strip-chart recorder or computer, in addition to providing 0-10 V feed (for 0-100°C) to voltage-to-frequency circuit that drives display.Readout is updated at 2-s intervals.-J. Wil-Iiams, Designer's Guide to: Temperature Measurement, EDN Magazine, May 20, 1977, p 71-77.
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Published:2009/7/8 4:55:00 Author:May
This transmitter consists of a keyed crystal oscillatoridriver and a high efficiency final, each with a TMOS Power FET as the active element. The total parts cost less than $20, and no special construction skills or circuit boards are required.The Pierce oscillator is unique because the high CRSS of the final amplifier power FET, 700 - 1200 pF, is used as part of the capacitive feedback network. In fact, the oscillator will not work without Q2 installed. The MPF910 is a good choice for this circuit because the transistor is capable of driving the final amplifier in a switching mode, while still retaining enough gain for oscillation. To minimize cost, a readily-available color burst TV crystal is used as the frequency-determining element for Q1.An unusual 84% output efficiency is possible with this transmitter. Such high efficiency is achieved because of the TMOS power FET's characteristics, along with modification of the usual algorithm for determining output matching. (View)
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Published:2009/7/8 4:54:00 Author:May
The controller circuit can reduce a fan's noise, power consumption, and wear, particularly in the presence of a low, fluctuating ambient temperature. Mount a temperature sensor in the fan's airstream, and the circuit will adjust the fan speed as necessary to maintain a relatively constant sensor temperature.Input components R1 and C1 integrate the input square wave, producing a quasitriangular wave at the noninverting input of op amp IC1A. At this inverting input is a reference voltage that decreases as temperature increases. The two-terminal sensor produces 1 μA/°K. The result is a rectangular wave at the output of IC1A with a duty cycle proportional to absolute temperature. Thus, a rise in temperature triggers a counter acting cooling effect by delivering more power to the fan. To calibrate the system with the sensor at room temperature, simply adjust R2 for a 50% duty cycle at V1. The fan will switch off at approximately 0℃ and will be fully on at 44℃. (View)
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Published:2009/7/8 4:52:00 Author:May
Uses MC1357 quadrature detector after ceramic filter to give IF bandwidth required for good stereo reproduction.Sensitivityis 18 μV for 3% total harmonic distortion.-''Integrated Circuit IF Amplifiers forAM/FM and FM Radios,'' Motorola,Phoenix,AZ,1975,AN-543A,p 6. (View)
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Published:2009/7/8 4:52:00 Author:May
The timed two-voltage circuit can start and run a small dc motoror 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 With input voltage VIN initially applied to the input,and capacitor C1 in a discharged state,the LM393 comparator's open-collector output circuit is open-circuited,Then the higher start-up output voltage is:
VOUT=1.25[1+(R3/240)]
At a time t after start-up,when:
t=-R1C1Ln[R4/(R4+R5)]or:
t=-R1C1,if R5=1.72R4
the comparator output decreases.At that time,the output voltage switches to a lower value to run thedevice at its proper operating level. (View)
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Published:2009/7/8 4:51:00 Author:May
Thermistor for desired temperature range is one leg of Wheatstone bridge driving microammeter through transistor to provide direct indication of temperature. Can also be used for control purposes if suitable amplifier and relay are used in place of meter. Thermistor cable can be or-dinary parallel or twisted wires. To calibrate, immerse thermistor in water at various tem-peratures and measure water temperature with conventional high-accuracy thermometer. Cal-ibration graph can then be prepared as guidefor marking meter scale.-F. M. Mims, Transistor Projects, Vol. 1, Radio Shack, Fort Worth, TX, 1977, 2nd Ed., p 86-93. (View)
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Published:2009/7/8 22:48:00 Author:Jessie
This circuit provides emergency lighting during a power outage. The phototransistor should be positioned to maximize coupling of both neon light and ambient light into the pellet, without allowing self-illumination from the 6-V lamp. Many circuits of this type also use line voltage to charge the battery.
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Published:2009/7/20 20:53:00 Author:Jessie
Two-terminal -10 volt reference (courtesy Analog Devices, Inc.). (View)
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Published:2009/7/20 20:52:00 Author:Jessie
High-gail amplifier-microphone combination detects pulse beats and feeds them through shaper circuit to hold-relays that lock pressure gages at systolic and diastolic blood-pressure readings.-R. J. Roy and M. Weiss, Inexpensive Monitor Reads Blood Pressure Automatically, Electronics, 35:47, p 40-41. (View)
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Published:2009/7/20 20:52:00 Author:Jessie
15-/20-/25-/35-/50-/60-watt AF power amplifier with AC-coupled output (courtesy Motorola Semiconductor Products Inc.). (View)
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Published:2009/7/20 20:52:00 Author:Jessie
Two-component precision current limiter (courtesy Analog Devices, Inc.). (View)
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Published:2009/7/20 20:52:00 Author:Jessie
Uses drift transistor as efficient, highly sensitive oscillating linear-slope detector, injection-locked by one stage sound driver. A-m rejection is uniformly high over full detector bandwidth. Audio output is constant, independent of carrier strength.-M. Meth, Tv Sound Detector Uses Drift Transistor, Electronics, 32:8, p 62-64. (View)
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Published:2009/7/20 20:52:00 Author:Jessie
Negative voltage regulators for 5, 6, 12, or 15 volts using the ECG9XX series. Ratings for the three-terminal ECG9XX negative voltage regulators are as follows: ECG961, 5 volts; ECG963, 6 volts; ECG967, 12 volts; ECG969, 15 volts. A common is required between the input and output voltages. The input must remain 2 volts more negative than the output even during the high point on the input ripple voltage. These devices will handle up to 1 ampere without any heat sink. The input capacitor should be 0.33 μF if a tantalum or Mylar type is used. If an aluminum capacitor is used it should be 1.0 μF or larger (courtesy GTE Sylvania Incorporated). (View)
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Published:2009/7/20 20:51:00 Author:Jessie
Coded pulse train controls teleprinter. When negative pulses are applied to grid of V2, line relays open in correspondence to pulse pattern.-R. L. Thomas, R. Howat, and N. H. Mackworth, Tv Tracker Records Eye Focus Points, Electronics, 33:17, p 57-59. (View)
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Published:2009/7/20 20:51:00 Author:Jessie
Costs less than ratio derector sound system. Uses discriminator circuit with triode operating us power detector, with cancellation of undesired aim fundamental.-R. B. Dome, Inexpensive Sound for Television Receivers, Electronics, 32:9, p 66-68. (View)
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Published:2009/7/20 20:51:00 Author:Jessie
Drives ultrasonic transducer at odd harmonically related frequencies in 900 kc to 5 Mc optimum range, for neurosurgery, al power levels within 1 db of any prescribed level between 0.05 and 100 acoustic walls, without correction of amplitude after radiation has begun.-B. J. Cosman and T. F.Hueler, Instrumentation for Ultrasonic Neuro-surgery, Electronics, 32:200, p 53-57. (View)
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Published:2009/7/20 20:50:00 Author:Jessie
Negative switching regulator (15 volts) using an ECG915 or ECG915D IC. For a ±5% fixed output R1 is 3.65 ohms and R2 is 11.5 ohms. in metal can applications where Vz is required, connect a 6.2-volt zener in series with the regulated output.L1 is forty turns of AWG #20 enameled copper wire wound on Ferroxcube P36/22-387 pot core or equivalent with 0.009-inch air gap (courtesy GTE Sylvania Incorporated). (View)
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Published:2009/7/20 20:50:00 Author:Jessie
Produces variable-size rectangles in any desired position on tv screen, including horizontal or vertical white lines, for emphasizing particular part of picture during educational tv broadcast.-G. Southworth, Outline Generator for Educational Television, Electronics, 32:14, p 52-53. (View)
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