Relay Circuits

You can use that circuit to drive a relay of 12 V with a trigering signal of 5V. It uses 2 diodes 1N4002, 1 transistor 2N3904 and two resistors...

Audio operated relay

Ql and Q2 are general purpose transistors. The 10 K input pot is adjusted to a point just short of where Ql turns on as indicated by K pulling in. K is any 5 V reed relay. With the values shown for R (100 K) and C (47 Âµf), timing values from 5 to slightly over 5 seconds can be achieved..

Ir Reflection Proximity Switch

IR radiation from LED2 (modulated by a 1-kHz wave) is keyed by Ul, and Ql is radiated. Reflected IR energy i..

Ac-relay

When zero voltage switching is not required, methods of providing this function are illustrated. The lowest parts count version of a solid-state relay is an optoisolator, the triac driver HlU. Unfortunately, the ability of the Hll} to drive a load on a 60-Hz line is severely limited by its power dissipation and the dynamic characteristics of the detector. These factors limit applications to 30 -50 mA resistive loads on 120 Vac, and slightly higher values at lower.....

AUTO SELECTION OF ANY AVAILABLE PHASE, IN 3 PHASE SUPPLY SYSTEM

The project is designed to provide uninterrupted AC mains supply i.e., 230 volt to a single phase load. This is achieved by automatic changeover of the load from the missing phase to the next available phase in a 3 phase system. It is often noticed that power interruption in distribution system is about 70% for single phase faults while other two phases are in normal condition. Thus, in any commercial or domestic power supply system where 3 phase is available, it is.....

SCADA (SUPERVISORY CONTROL & DATA ACQUISITION) FOR REMOTE INDUSTRIAL PLANT

The main aim of the project is to process the real time data acquisition under supervisory control for large scale remote industrial environment. In large industrial establishments many processes go on, therefore it is essential to monitor all the processes and control the factors affecting them. Adapting a technology like SCADA (Supervisory Control and Data Acquisition) one can achieve the above mentioned objective effectively, and thus saving a lot of manpower......

Low-Consumption Monostable Relay

A monostable relay has two states: operative when a large enough current flows through its coil and quiesc..

ULTRA FAST ACTING ELECTRONIC CIRCUIT BREAKER

The project is designed to shut down the power supply when it is overloaded. Conventional circuit breaker like MCB based is on thermal bimetal lever trip mechanism. It is very slow and the trip time is dependent upon the percentage of overload. This project senses the current passing through a series element and the corresponding voltage drop is compared against the preset voltage proportional to the current by a level comparator to generate an output for the load to trip......

Triac relay-contact protection

This circuit can be used to prevent relay contact arcing for loads up to 50 amperes. There is some delay between the time a relay coil is energized and the time the contacts close. There is also a delay between the time the coil is de-energized and the time the contacts open. For the relay used in this circuit both times are about 15 ms. The TRIAC across the relay contacts will turn on as soon as sufficient gate current is present to fire it. This occurs after switch SI is.....

TIME DELAY BASED RELAY OPERATED LOAD

The project is designed to develop a time delay based switch to control any load. A 555 timer is used in monostable mode to drive a relay to switch ON/OFF a load for fixed time duration. A time delay based relay is a relay that stays on for a certain period of time once activated. This circuit is made up of a simple adjustable timer circuit which controls the actual relay. The time is adjustable from 0 to few seconds but can be increased by increasing the time.....

Sound-modulated light source

This circuit modulates a light beam with voice or music from the output of an amplifier. If the 10 K pot is adjusted to slightly less than the Vbe of the transistor, the circuit forms a peak detector..

Solid State Relay circuits

This dark-activated relay switch can be used to turn on walkway or other outdoor lighting at dusk. By using alternate connections to A and B, increasing illumination, ..

Solid-State Relay

A power MOSFET and a quad exclusive-OR oscillator makes an effective solid-state relay. Figure 75-5(a)"s capacitively iso..

DTMF BASED LOAD CONTROL SYSTEM

The project works on the principle of DTMF tone command so received from any phone to remotely switch any electrical load such as agricultural pump, domestic and industrial loads etc. In industries, the loads are spread over a large area and thus, operating these loads is a very tiresome and difficult task. In agricultural fields also, pumps and other loads are connected over a large area and hence it is difficult for the farmer to operate all the loads and similarly for.....

Normally-open-and-closed-relays

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 photocoupler output. The addition of hysteresis to provide fast switching and stable pick-up and drop-out points can be easily implemented simultaneously. ..

Variable Voltage Regulator

The op amp is wired as a 2 noninverting dc amplifier with a gain that is determined by the R3/R2 ratio. The inp..

POWER SAVER FOR INDUSTRIES & COMMERCIAL ESTABLISHMENTS

The project is designed to reduce the power loss in industries by power factor compensation through a number of shunt capacitors. This results in reduction in amount of electrical bill for industries and commercial establishments. Power factor is defined as the ratio of real power to apparent power. This definition is often mathematically represented as KW/KVA, where the numerator is the active (real) power and the denominator is the (active + reactive) or apparent.....

AUTO POWER SUPPLY CONTROL FROM 4 DIFFERENT SOURCES: SOLAR, MAINS, GENERATOR & INVERTER TO ENSURE NO BREAK POWER

The main objective of this project is to provide uninterrupted power supply to a load, by selecting the supply from any source out of 4 such as mains, generator, and inverter and solar automatically in the absence of any of the source. The demand for electricity is increasing every day and frequent power cuts is causing many problems in various areas like industries, hospitals and houses. An alternative arrangement for power source is a must. In this project uses four.....

Siren-space war-phasor gun

The one shot and decay functions could be added to make an ideal phasor..

AUTOMATIC STAR DELTA STARTER USING RELAYS AND ADJUSTABLE ELECTRONIC TIMER FOR INDUCTION MOTOR

The project is designed to provide low voltage start to induction motors. This is achieved by using star to delta conversion. Star/Delta starters are probably the most common reduced voltage starters in the 50Hz industrial motor world. Star delta is used in an attempt to reduce the start current applied to the motor. Thereafter, full load current is applied to the motor. The Star/Delta starter is generally manufactured from three contactors; and electromechanical timer and.....