Assume the correct phase sequence to be VA-VB-VC. The circuit terminals are connected such that Tl gets connected to phase A and T2 to phase B. The capacitor advances the voltage developed across R2 due to phase "B" by — 60°, while the voltages developed across it by phase "A" is in phase with VA as shown in Fig. 69-1. The net voltage developed across R2 ~ zero, the neon lamp is not energized, thereby signaling correct phase sequence. If terminal T2 gets.....
This circuit monitors the power-line (ac) voltage. When a power failure occurs, on restoration of power, the circuit a..
The PWM controller uses complementary half-H peripheral drivers SN75603 and SN75604, with totem-pole outputs rated at 40 V and 2.0 A. These drivers effectively place the motor in a full-bridge configuration, which has the ability to provide bidirectional control. Timer U1 operates in the astable mode at a frequency of 80Hz. The 100-0 discharge resistor results in an 8-p.s trigger pulse which is coupled to the trigger input of timer U2. Timer U2 serves as the PWM.....
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 Rl and Cl integrate the input square wave, producing a quasitriangular wave at the noninverting input of op amp IC1A. At this inverting input is a.....
For two simultaneous race-car sounds. ..
In this proximity detector an NE567 tone decoder provides a signal of about 100 kHz that is fed to one sensor. The senso..
Dc power can also be controlled via fiberoptics. The circuit provides an insulated speed control path for a small dc actuator motor (< Vn hp). Control logic is a self-contained module requiring about 300 mW at 12 V, which can be battery powered. The control module furnishes infrared pulses, at a rate of 160 Hz, with a duty cycle determined by the position of the speed adjust potentiometer. The programmable unijunction multivibrator provides approximately 10 mA pulses to.....
The resistor capacitor network R1-R2-C1 provides a ramp-type reference voltage superimposed on top of a dc voltage adjustable with the speed-setting potentiometer R2. This reference voltage appearing at the wiper of R2 is balanced against the residual counter emf of the motor through the SCR gate. As the motor slows down due to heavy loading, its counter emf falls, and the reference ramp triggers the SCR earlier in the ac cycle..
The modified power-factor controller, developed at the Marshall Space Flight Center, employs a phase detector for each of the three phase windings of a delta-connected induction motor. The phase-difference sum is the basis for control. ..
The relay which applies power to the wiper motor is actuated at periodic intervals by the timer circuit, closing the wiper motor contacts. Potentiometer R1 serves as the pulse rate control and potentiometer R5 as the pulse width control. ..
The control of both direction and of proportional motor speed is achieved by rotation of a single potentiometer. The motor driver is an SGS integrated circuit L293 which will drive up to 1 amp in either direction, depending on the logic state of input 1 and input 2 as per table. I/P 1 I/P 2 Function. High Low Motor turns one way. Low High Motor reverses. By applying a variable M/S ratio flip-flop to these inputs, both speed and direction will be controlled. With RV1 in its.....
This circuit gives a 3 phase square-wave output for a variable speed motor drive. Operation is straightforward, the 4017 counter is synchronously reset after six clock inputs. The she outputs are combined to give the required waveforms. It is interesting to note that although NOR gates are shown, OR gates will give effectively the same result...
This single time-constant circuit can be used as proportional speed control for induction motors such as shaded pole or permanent split-capacitor motors when the load is fixed..
This circuit is intended as a revolution control for small dc motors as fitted, for instance, in small electric drills (..
Digital ICs and opto-isolators provide the drive for this TMOS servo amplifier, resulting in fewer analog circuits and less drift. Fast and consistent turn-on and turn-off characteristics also enable accurate analog output results directly from the digital signal without the need for analog feedback. An "H" bridge configuration is employed for the servo amplifier, which obtains complementary PWM inputs from digital control circuits. The PWM inputs are applied via.....
Use this circuit to keep the fluid level of a liquid between two fixed points. Two modes, for filling or emptying are possible by simple reversing the contact connections of Kl. The loads can be either electric motors or solenoid operated valves, operating from ac power. Liquid level detection is accomplished by two metal probes, one measuring the high level and the other the low level..
The system shown consists of the HA-2542, a small 12-Vdc motor, and a position encoder. During operation, the encode..
This one-chip modulator requires some outboard circuitry..
The hexFET can swatch dc power to relays (as shown in A), motors, lamps, and numerous other-devices. That arrangement can even be used to switch resistors in and out of a circuit,..
The battery life and operating cost of an electric vehicle is severely affected by overdischarge of the battery. This circuit provides both warning and shutdown. An electronic switch is placed in series with the propulsion motor contactor coil. Three modes of operation are possible: When the propulsion power pack voltage is above the 63-V trip point, the electronic switch has no effect on operation. ..
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