Insulated-gate, field-effect transistor (IGFET), Q2 and silicon photo cell Zl form the heart of this circuit. Transformer T1 is an audio-output type, but it"s reversed in the circuit. A sudden flash from a photoflash unit detected by Zl sends a voltage pulse through the low-impedance winding of Tl via Rl. That voltage pulse is stepped-up in Tl"s 500-!l, primary winding before being rectified by Ql. Transistor Ql is used as a diode; its emitter lead was snipped off.....
The base of Ql is connected to the car`s ignition circuit; the easiest point to make that connection is at the ignition switch fuse in the car`s fuse panel. Also, one side of the piezoelectric buzzer is connected to the instrument-panel light fuse; when the headlights or parking lights are on, the instrument panel is lit, too. When the headlights are off, no current reaches the buzzer. Therefore, nothing happens. What happens when the headlights arc on depends on the.....
Many devices operate from a car"s 12-V electrical system. Some require 12 V; others require some lesser voltage. An automobile battery"s output can vary from 12 to 13.8 V under normal circumstances. The load requirements of the device might vary. This circuit maintains a constant voltage regardless of how those factors change. Simple circuit, A, uses a 7805 voltage regulator. ..
Most circuits that provide an electrical stimulus for research subjects are constant-voltage designs; this circuit is a constant-current design. Stimulator circuits must be isolated for two reasons: to ensure safety and to minimize interference. Isolated stimulators are essentially two-terminal devices; output currents can flow only between tbe two output terminals and can at no tiroe flow through any other path, such as the power ground. ..
This de adapter provides a regulated 9-V source for operating a Kenwood TR-2500 hand-held transceiver in the car. The LM317T"s mounting tab is electrically connected to its output pin, so take this into account as you construct your version of the adapter. ..
No electrical contact exists between the circuit and the conductor. The 7474 flip-flop is triggered by the output ..
This circuit is intended as a revolution control for small dc motors as fitted, for instance, in small electric drills (..
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..
A phototransistor senses daylight. At dusk, it ceases to conduct and Rl biases Q2, activates Kl, and ..
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. ..
The mercury-in-rubber strain gauge is the detector of breathing. In the model device, the strain gauge produced by Medimatic, Demark was used. The change in the length of the strain gauge wrapped around the chest during breathing causes a varying electrical resistance of about 0.2 0/cm. The constant current passing Rl, R rand R4 gives the constant component on the output of Ul differential amplifier. The change in the resistance of the strain gauge, which results from.....
The tester consists of a rectifier circuit and a multivibrator circuit. The ac voltage is half-wave rectified by diode D1 and stored in capacitor CI. Resistor Rl is used to limit the current through D1 to a safe value. The voltage stored across CI supplies ICi operating power. The IC, the versatile 555 timer, is configured to operate as a multivibration whose operating frequency is determined by C2, R2, and R3. The output of ICI, on pin 3, is coupled to a piezoelectric.....
This electronic motor-speed control circuit is designed to operate in an electrically noisy environment. The circuit includes an optoelectronic pickup device. whichis placed inside the motor housing to provide a speed feedback signal. The circuit automatically maintains the speed of the motor at the commanded value. The pickup device contains an infrared LED and a phototransistor. The radiation from the diode is chopped into pulses by the motor fan blades. which are.....
The dimming action is controlled by varying the amount of current passed through triac Q4 and, thus, the lamp plugged into ac receptacle SOL Unijunction transistor Q3 operates as a relaxation oscillator whose output pulse frequency depends on how fast capacitor C2 recharges after firing. Transistors Ql and Q2 furnish the charging current, with the R3/Cl and Rl/R2/Cl time-constant networks controlling the turn-on and turn-off times. Inside ICl is a LED, a detector, and.....
This little tester is useful for checking vehicle electrical circuits. Two LEDs indicate whether one of the cl..
A circuit stabilizes the current-transfer ratio (CTR) of an optically coupled isolator used as a linear transducer. The optocoupler produces a voltage output that is proportional to—but electrically isolated from—the voltage input. However, the output voltage is directly affected by changes in the CTR, and the CTR can change substantially with temperature and current. To a lesser extent the CTR changes with time over the life of the optocoupler. The circuit.....
Light filtering through the finger tip is detected by the cadmium sulphide photoresistor CD1 which forms the feedback network for transducer amplifier section ICA producing a weak signal which is further amplified by ICB. This signal is now compared against a user adjusted threshold, comparator ICD triggers gating on the piezoelectric buzzer PZ1. On each falligg edge of the comparator's output signal one-shot multivibrator ICD produces a 2 ^s pulse which is inverted by Ql.....
By repetitively charging and discharging a capacitor through the primary of an induction coil with a high voltage, an ultra high emf is induced in the secondary. Switching is performed by the triac, triggered by the disc at times set by Cl and Rl. With a 12 V car ignition coil for example, the length of sparkgap obtained is 12 mm of air for C2 = 0.1 µ¥. If the dielectric strength of air is assumed to be 3 kV/mm, this spark-gap length corresponds to 36 kV. ..
An electric guitar often has to be connected to a mixing panel, a tape deck or a portable studio. As far..
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 core. Then, twist a loop in the wire, and finish by winding five more turns. Wrap with electrical tape, but leave the loop exposed. A four-tum winding must be wound over the ten-turn winding that you"ve just finished. ..
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