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This Laser Controlled ON/OFF switch circuit is built around a 555 timer using very few components. Since the circuit is very simple, even a novice can easily build it and use it as a controlling device. A laser pointer, now easily available in the market, can be used to operate this device. This circuit has been tested in operational conditions from a distance of 500 meters and was found to work satisfactorily,though it can be controlled from still longer distances. . Laser Controlled ON/OFF switch Circuit diagram : Laser Controlled ON/OFF Switch Circuit Diagram Aiming (aligning) the laser beam exactly on to the LDR is a practical problem. The circuit is very useful in switching on/off a fan at night without getting off the bed. It can also be used for controlling a variety of other devices like radio or music system. The limitation is that the circuit is operational only in dark or dull lit environments. By focusing the laser beam on LDR1 the connected gadget can be activated throug...

We are surrounded by battery operated equipment of all kinds, and this array is growing still. Manufacturers and designers lean over backwards to make sure that their equipment draws a small current and can thus be operated by a battery. This has its flip side, too. because even if the equipment in question draws only a small current, when it is not switched off, the battery is flat after a few days or weeks. The circuit presented here can prevent this happening. It may be added to all kinds of equipment operating from a 9 V battery and switches this off automatically one minute after a preset time has elapsed. The peak switching current is 20 mA, which is more than enough for most applications.   Circuit diagram: The switch is formed by a p-n-p darlington, T1, which is actuated by push-button switch S1. The very high amplification of the darlington enables it to be kept on fairly long with the aid of a relatively small-value capacitor, C1 (= 100 µF). Resistor R3 limits the chargin...

This circuit uses a NE555 timer and CD4020B. When +12 Vdc is applied to the circuit, the output of IC2 is set low via C2, which turns on the relay, and IC1, a pulse generator. Auto Turn-Off Alarm With 8-Minute Delay Circuit Schematic IC1 pulses counter IC2. After 8192 clocks, IC2 output (pin 3) goes high, cuts off Q2, and completes the cycle.

Simple Remote on-off Switch Circuit Diagram . This circuit provides power control without running line-voltage switch leads. The primary of a 6-volt filament transformer is connected between the gate and one of the main terminals of a triac.   Simple Remote on-off Switch Circuit Diagram The secondary is connected to the remote switch through ordinary low-voltage line. With switch open, transformer blocks gate current, prevents the triac from firing and applying power to the equipment. Closingthe switch short-circuits the secondary, causing the transformer to saturate and trigger the triac. Sourced By circuitsstream

This is a Simple Auto Turn-Off Alarm With 8-Minute Delay Circuit Project. This circuit uses a NE555 timer and CD4020B. When +12 Vdc is applied to the circuit, the output of IC2 is set low via C2, which turns on the relay, and IC1, a pulse generator. IC1 pulses counter IC2. After 8192 clocks, IC2 output (pin 3) goes high, cuts off Q2, and completes the cycle. Simple Auto Turn-Off Alarm With 8-Minute Delay Circuit Diagram

The power line fluctuations and cut-offs cause damages to electrical appliances connected to the line. It is more serious in the case of domestic appliances like fridge and air conditioners. If a fridge is operated on low voltage, excessive current flows through the motor, which heats up, and get damaged. The under/over voltage protection circuit with time delay presented here is a low cost and reliable circuit for protecting such equipments from damages. Whenever the power line is switched on it gets connected to the appliance only after a delay of a fixed time. If there is hi/low fluctuations beyond sets limits the appliance get disconnected. The system tries to connect the power back after the specific time delay, the delay being counted from the time of disconnection. If the power down time (time for which the voltage is beyond limits) is less than the delay time, the power resumes after the delay: If it is equal or more, then the power resumes directly. This circuit has been desig...

For a hobbyist, it has always been fun to activate or automate through a clap or a whistle . A whistle sometimes can act like a voice recognition actuator as the frequency varies from person to person. However, for this use the tuning is to be done around 1700 Hz, a pitch that is somewhere near to the middle C octave of the piano chords. A condenser microphone acts as the audio sensor and produces a few milli - volts of current to activate the electrical actuator like a relay. For this it has to be supported by a transistor or FET. Driving such a switch with the resultant milli-Volt from the condenser microphone is not possible. Hence an overall gain 4000 times larger is needed to be divided into two amplifier sections having gain values of 65 each. Resistors denoted by the values R1, R2 and R3 are responsible for the individual gain of the amplifiers and are 1.1K, 1.2K and 15K respectively. Thus we arrive at the formula given below  · R1 = Q/(G*C*2*Pi*F) = 8/(65*.01^-6*6.28*17...

This is a simple Turns ON-OFF Control Circuit Diagram , This simple circuit can be use circuit instead of a standard on-off switch. Switching is very gentle. Connect unused input pins to an appropriate logic level. Unused output pins *MUST* be left open!. First 'push' switches ON, another 'push' switches OFF. You can use 1/4 watt resistors if they are metal-film type. Any proper substitute will work for Q1, including the European Tun's. For C2, if you find the relay acts not fast enough, leave it out or change to a ceramic cap between 10 and 100nF.    Turns ON-OFF Control Circuit Diagram   Parts List All resistors are 1/2 Watt and 5% tolerance. R1 = 10K R2 = 100K R3 = 10K C1 = 0.1μF, Ceramic C2 = 1μF/16V, Electrolytic D1= 1N4001 Q1 = 2N4401 (ECG123AP, NTE123AP, etc.) IC1 = 4069, CMOS, Hex Inverter (14069), or equivalent S1 = Momentary on-switch