Sound Operated Switch Circuit Schematic with explanation

Amplifier: TL081 Comparator: TL081 or CA3140

R can be almost any value greater than about 10k. Use a small (low impedance) loudspeaker as a microphone

This circuit must have a 5v regulated supply. This is provided by the 7805 regulator.

The circuit shown above should be sensitive enough to respond to a reasonably loud clap of the hands at a distance of about a metre from the microphone. If the microphone (loudspeaker) is not very close to the circuit board, use screened lead to connect it to the rest of the circuit. If you require greater sensitivity, you can add the simple pre-amp shown below.

The sensitivity of the circuit can be adjusted using the variable potential divider connected to the inverting input of the comparator. To set the sensitivity to maximum, connect a voltmeter to the output of the second amplifier and adjust the variable potential divider to the point which just takes the voltmeter reading to its lowest figure (zero for CA3140, about 1·5v for TL081).

Adding this pre-amp to the sound operated switch will make it very sensitive so keep all connecting wires as short as possible.

Source : http://www.saburchill.com/

Intersting DIP Switch

A series of tiny switches built into circuit boards. The housing for the switches, which has the same shape as a chip, is the DIP.

DIP switches enable you to configure a circuit board for a particular type of computer or application. The installation instructions should tell you how to set the switches. DIP switches are always toggle switches, which means they have two possible positions -- on or off. (Instead of on and off, you may see the numbers 1 and 0.)

One of the historic advantages of the Macintosh over the PC was that it allowed you to configure circuit boards by entering software commands instead of setting DIP switches. However, the new Plug & Play standard developed by Microsoft makes DIP switches obsolete for PC expansion cards too.

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Simple circuit work as dew sensetive switch

Here is a simple circuit that can be used to switch ON or OFF a device when the dew present in the surrounding atmosphere crosses a set value.The circuit uses a dew sensitive resistive element and a comparator based on LM 358 to perform the above said operation.

At normal condition the resistance of dew sensor element will be low and so the voltage drop across it.So the voltage at the non inverting pin of LM358 (IC1) will be less than the voltage at the inverting input of the LM358.So the output of the opamp will be low.This keeps the opto-coupler (MCT2E) deactivated.When the dew increases the resistance of the element increases and so do the voltage across it.Now the voltage at the non inverting pin of LM358 (IC1) will be higher than the voltage at the inverting input of the LM358.So the output of the op amp will be switched to high.This in turn activates the optocoupler.The LED glows to indicate it. As a result we get an optopcoupler activated and de activated according to the amount of dew in the atmosphere.The output pins of optocoupler pin (5&4) can be used to control the external device.

Diode D1 , resistors R6&R3 and capacitor C1 is employed here to derive the power for the circuit directly from mains.

• The dew sensor is hard to find in market.But it can be easily obtained from a old VCR.Also the type no of the sensor is not so important here.Try with any thing you get.I used one from a old Hitachi VCR.
• LM 358 is a dual opamp.Here only one opamp inside it is used.

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versatile remote controlled appliance switch

Here is a versatile remote controlled appliance switch that can ON or OFF any appliance connected to it using a TV remote.

IR remote sensor IC TSOP 1738 is used for recieving the signal. Normally when no signal is falling on IC3 the output of it will be high.This makes Q1 OFF.When a signal of 38 KHz from the TV remote falls on the IC3 its output goes low.This makes Q1 conduct and a negative pulse is obtained at pin 2 of IC 1 NE 555.Due to this IC1 wired as a monostable multivibrator produces a 4 Sec long high signal at its out put.This high out put is the clock for IC 2 which is wired as a Flipflop and of , its two outputs pin 3 goes low and pin 2 goes high.The high output at pin 2 is amplified to drive the relay .For the next signal the outputs of IC2 toggles state. Result, we get a relay toggling on each press on the remote.Any appliance connected to this circuit can be switched ON or OFF.

• Before wiring the circuit make sure that the carrier frequency of the TV remote you have is 38 KHz.For that wire the sensor part only ,point your remote to the TSOP1738 and press any switch.If out put of TSOP1738 goes low them ok, your remote is of 38Khz type.Nothing to worry almost all TV remote are of this type.
• You can use any switch because for any switch the code only changes,the carrier frequency remains same.We need this carrier frequency only.
• Assemble the circuit on a good quality PCB or common board.
• The appliance can be connected through NO or NC and contacts of the relay .

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Gate control switch (GCS)

As mentioned earlier, low-current drop out is the normal way in which the SCR is turned off. Gate-controlled switch is designed for easy opening with a reverse-biased trigger. A gate controlled switch (GCS) is closed by a positive trigger and opened by a negative trigger (or by low-current drop out). Gate-controlled switch circuit is shown in figure. Each positive trigger closes the GCS, and each negative trigger opens it. Thus a square-wave output is obtained, as shown in the figure.

The most obvious advantage of GCS over the SCR or SCS is the fact that it can be turned on or off by applying the proper pulse to the cathode gate (without the anode gate and associated circuitry required for the SCS). A second very important advantage of GCS is improved switching characteristics.

The gate-controlled switch is useful in counters, digital circuits, multivibrators, voltage regulators and other applications in which a negative trigger is available for turn-off.

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Characteristics and operation of SCS( Silicon Controlled Switch)

Operation of a Silicon Controlled Switch
The easiest way to understand how it operates is to realize it to be formed of two transistors Q₁ and Q₂ placed back-to-back, as shown in figure.b

In a two-transistor equivalent circuit shown in figure.c, it is seen that a negative pulse at the anode gate G₂ causes transistor Q₁ to switch on. Transistor Q₁ supplies base current to transistor Q₂, and both transistors switch-on. Similarly, a positive pulse at the cath­ode gate G₁ can switch the device on. Since only small currents are involved, the SCS may be switched off by an appropriate polarity pulse at one of the gates. At the cathode gate a negative pulse is required for switching-off while at the anode gate a positive pulse is needed.

Volt-Ampere Characteristic of SCS

The volt-ampere characteristic of an SCS is similar to that of an SCR and is shown in figure. With the increase in applied voltage, the current first increases slowly upto point A and then rapidly in the region AB, as shown in the figure. At point B, the product β₁β₂ exceeds unity and the device is suddenly switched on. In the on-state, the current increases enormously and is limited by the external series resistor. SCS also exhibits negative differential resistance in the on region similar to SCR. SCS gets switched on accidentally if the anode voltage gets applied suddenly. This is known as rate effect, which is caused by inter-electrode capacitance between elec­trodes G₁ and G₂, known as transition capacitance.

Advantages and Applications of SCS

An advantage of SCS over an SCR is the reduced turn-off time, typically within the range of 1 to 10 micro seconds for the SCS and 5 to 30 micro seconds for the SCR. Other advantages of the SCS over SCR are increased control and triggering sensitivity and a more predictable firing situation. However, the SCS is limited to low power, current, and voltage ratings (typical maximum anode currents range from 100 mA to 300 mA with dissipation rating of 100 to 500 mW).

A few of the more common areas of application of SCS include a variety of computer circuits (such as counters, registers, and timing circuits) voltage sensors, pulse generators, oscillators etc.

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Silicon controlled switch (SCS) with symbol

Silicon controlled switch (SCS), like the SCR, is a unilateral, four layer three junction P-N-P-N silicon device with four electrodes namely cathode C, cathode gate G_x, anode gate G₂ and the anode A, as shown in figure. Infact, the SCS is a low power device compared with the SCR. It handles currents in milli amperes rather than amperes. SCS differs from an SCR in the following aspects. It has an additional gate—the anode gate.It is physically smaller than SCR.It has smaller leakage and holding currents than SCR.It needs small triggering signals. It gives more uniform triggering characteristics from sample to sample.

The basic structure and schematic symbol of SCS are shown in the figures. It may be fabricated by using either the grown junction technique or the planar technique.

Basic magnetic proximity switch

Here is the circuit diagram of a magnetic proximity switch that finds a lot of applications in many fields.The circuit is based on a magnetic reed switch(S1) as the proximity sensor. A monostable multivibrator based on NE555 (IC1) and a toggle flip flop based on CD4013 (IC2) does the rest of the circuit.

When a magnet is reached in proximity of S1 it closes to give a negative trigger at pin 2 of IC1.The output of IC1 goes high for a time determines by R2 and C2.This clocks the IC2 wired as a toggle flip flop.The output (pin 1 ) of IC2 goes high and the transistor Q1 is biased to ON.The relay is activated and so do the equipment connected to the relay.The LED D1 glows when IC1 is triggered.

• Switch S1 can be a general purpose magnetic reed switch.
• The equipment to control can be connected using NC,NO and C points of the relay according to the application.
• Use a 12 regulated power supply for powering the circuit.

Opto-Thermo Control Relay Switch with IC 741 Circuit Opto-Thermo Control Relay Switch with IC 741

Circuit Opto-Thermo Control Relay Switch with IC 741

Infrared Remote Controller and Transmitter Circuit with IC4013

IR remote controller Circuit

I have a number of switch / out with an infrared remote control TV as a transmitter, which is great for me to work yet there is something that I add, or you must remove or change to better? 4013 is configured to switch on / off switch, namely the production will remain high until the clock is replaced by a high level, and will remain until replaced by another , then the output will go low, and so on. if the TV remote control is pressed, it sends the signal (pulse) to the receiver, making the CLK output transistors have to activate the double flip-flop IC, I, nor the 47uF capacitor, so if it is considered that the pulse is High input CLK, while the TV remote control is pressed when you press the remote (off), the pull-down resistor 10K, stream discharge capacitor and the output remains high until the process happens again, then the output remains low, and so on.

IR Remote Transmitter Circuit

4013, that the isolates from large voltages / currents. Inside the 3011 is an LED and a photo-transistor. The LED lights up when Q goes high, and in return the photo could transistor. Alternatively, the IC triggers a triac.

What I want to do is develop the setup to be triggered with the touch switches work or a facility managed by infrared.

Here is a diagram of the original circuit. I crossed the touch-switch on the top because they do not work properly. Now there are two resistors, capacitor, and a trigger for clock generation Schmit