Shock-proof Remote Switch

Using this shock proof remote switch circuit, you can control any AC/DC appliance remotely through inexpensive, low-voltage cabling and a standard push switch. The circuit can easily support cable length up to 25 metres. The load is triggered by a low voltage signal that helps avoid electrical shock.

Remote switch circuit

The circuit is built around dual D-type flip-flop IC CD4013 (IC1), which contains two positive-edge-triggered D-type flip-flops. One flip-flop is wired in toggle mode, while the other is not used. The first flip-flop is clocked via its pin 3 once switch S1 is pressed. This causes its output at pin 1 to change state from low (off) to high (on), or vice versa.

Npn transistor T1 (BC548) is used to drive electromagnetic relay RL1 (12V, 1C/O). Depending on the AC/DC load voltage rating, connect the AC/DC power supply through relay contacts as shown in the figure. Resistors R1 and R2, diode D1 and capacitor C2 are used to eliminate the effect of switch-bouncing. The combination of resistor R3 and capacitor C3 provides power-‘on’ reset.

Shock-proof Remote Switch Circuit Diagram:

Working of the circuit is simple. Suppose you want to activate any AC load from some distance. Connect the load as indicated in the figure and provide the required power supply of 230V AC, 50Hz at the supply terminal. Extend switch S1 to the desired place through low voltage cable. When you press switch S1 momentarily, the load will turn on. On pressing switch S1 again, the load will turn off. Thus the cycle repeats.

The same circuit can be used to trigger high power loads (water pump, generator, etc) by replacing the relay by higher contact-current-rating relay.

In the circuit, push-to-on switch (S1) is used to activate/de-activate the load but the same design can be used with other triggering methods like IR, RF etc.

Construction & testing

Assemble the circuit on a general-purpose PCB and enclose in a suitable ABS cabinet. Ensure that all the mains wiring is done properly and it is completely isolated so that there is no possibility of accidental electrical contact with the low voltage side of the circuit. Push-to-on switch S1 can be connected using a two-core screened cable or something similar. Use a standard 230V AC to 12V DC adaptor for this toggle switch circuit. Alternatively, you can use a 12V battery.

Author by: T.K. Hareendran Copyright: EFY

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Relay Switch Activated by Tone and Signal

This is a simple project of Relay Switch Activated by Tone and Signal circuit diagram.The essence of the circuit is for the input of tone and signal to provide an activation for the relay switch.

• Relay – an electrically operated switch where the current flowing through the coil of the relay is creating a magnetic field which attracts a lever and changes the switch contacts, thereby making its state open or close
• BC214 – a complementary silicon planar epitaxial transistor used in AF small signal drivers and am1 as well as for low noise preamplifier applications due to its feature of good linearity of DC current gain
• LM741 – a general purpose single operational amplifier with features such as offset null, compensated internal freq uency, voltage range with high input, good stability of temperature, and protected from short circuit

The use of relay will allow the circuit to switch from one condition to another. It can also be referred to as a form of an electrical amplifier since it is able to control an output circuit of higher power than the input circuit. There are many types of relays being used in many electronic and electrical circuits, which include solid-state relay, Buchholz relay, overload protection relay, latching relay, forced-guided contacts relay, mercury-wetted relay, contactor relay, machine tool relay, reed relay, polarized relay, and solid state contactor relay.

Relay Switch Activated by Tone and Signal:

The circuit created is sensitive enough to the AC signals in the input stage, where the signals are ranging above 5 mV. It will also be sensitive to react with the human voice signals having a range of frequency from 50 Hz up to 3 KHz. The human voice is a part of the human sound produced primarily by the vocal cords or vocal folds which in turn produces a voice frequency that is used for the transmission of speech.

During the absence of an input signal, the state of the 12 V relay RL1 is at OFF condition as regulated by the 10K Ohms trimmer RV1. The circuit can be made to react with its sensitivity in points A, B, & C, where a negative feedback can be placed due to the addition of band pass filter. The filter will operate only in the 1 KHz range and the circuit will only correspond at this frequency.

The signal and tone activated relay switch were used in a wide range of fields which includes measuring instruments, audio systems, communications equipment, and factory-automation equipment. They can also be found on telephone subscriber circuits for the polarity reversing switch, testing, and ringing functions.

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9 Channels Sensor Switch

This 9 channels sensor switch circuit diagram is designed using CMOS components. This 9 channels sensor switch circuit consist of only three integrated circuits and some resistors.

9 channels sensor switch circuit Diagram: 

Due to high input impedance, 74HC147 allows to use of 4.7 M resistors to create a logic level "high" to sensor inputs. When one sensor is touched, the resulting low resistance to ground circuit causes IC1 to read a logical level L. If several sensors are touched simultaneously, priority encoder delivers 4-bit code corresponding to the sensor with the highest number.

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Simple Voltage Comparator Switch

This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2. The limits are adjustable and the circuit made to trigger from the adjustable "window".

Circuit Diagram:

Notes:
This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2. The supply voltage, Vcc must be higher than the highest input voltage by at least 2 volts. One application here is to monitor a 12V car battery. V1 could be set to 14V and V2 to 11V thus giving an indication of over charge or a weak battery.

Please Note. Only pins 7 and 4 (power supply), pin 6 (output) and pins 2 and 3 (inverting and non-inverting inputs) are used. All other pins are not connected. The pinout for the CA3140 is shown below.

The op-amps used here are MOSFET CA3140. They are used to advantage as they have very little output offset voltage and can switch down to near 0 volts. If any other op-amp is used such as LF351 or CA741 then it will be necessary to have an offset null control. This is just a 10k preset contacted between pins 1 and 5, the wiper connected to the negative supply rail or op-amp pin 4. With this circuit either op-amp will light the LED if the input voltage goes out of limits, the two 1N4148 diodes forming an "AND"-gate at the output. The input voltage to be monitored is fed via a series 10k resistor to inputs of both op-amps. If the input voltage is greater than the limit set by V1 then the CA3140 will swing its output to almost the full supply voltage and light the LED. Similarly, if the input voltage is less than the limit defined by V2 then this op-amp will swing towards Vcc and light the LED.

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Simple Sound Operated Switch

Here is very simple and easy build a sound operated switch electronic circuit project. A sound operated switch with a relay driver.

Simple Sound Operated Switch Circuit Diagram:

Notes:
This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electret (ECM) microphone. If an ECM is used then R1 (shown dotted) will need to be included. A suitable value would be between 2.2k and 10kohms.

The two BC109C transistors form an audio preamp, the gain of which is controlled by the 10k preset. The output is further amplified by a BC182B transistor. To prevent instability the preamp is decoupled with a 100u capacitor and 1k resistor. The audio voltage at the collector of the BC182B is rectified by the two 1N4148 diodes and 4.7u capacitor. This dc voltage will directly drive the BC212B transistor and operate the relay and LED. It should be noted that this circuit does not "latch". The relay and LED operate momentarily in response to audio peaks.

The gain of the circuit and sensitivity is controlled by the 10k variable resistor on the emitter of the first (left hand side) transistor. A preset may be used if gain is fixed, a potentiometer should be used to trigger at different sound levels.

The relay contacts close and then open (momentary action) in response to audio peaks, these can be used to switch other circuit. The diode across the relay is the usual back emf diode and a 1N4003 or 1N4004 will work well here, preventing damage to the transistor.

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Voltage Controlled Switch using the 555

This electronic voltage controlled switch circuit diagram project make a very easy. In this electronic project circuit the 555 timer is used in a novel way, as a voltage controlled switch. 

Voltage Controlled Switch Circuit Diagram:

Notes:
The old and omnipresent NE555 can be very good at something it was not meant for: driving relays or other loads up to 200 mA. The picture shows an example circuit: if the input level rises over 2/3 of the supply voltage - it will turn on the relay, and the relay will stay on until the level at the input drops below one third of the supply voltage.

If the relay and D1 were connected between pin 3 and ground, the relay would be activated when the input voltage drops below one third, and deactivated when the input voltage goes over two thirds of the supply voltage.

It is also a nice advantage that the input requires only about 1 uA, which is something bipolar transistors can't compete with. (This high impedance input must not be left open.) A large hysteresis makes the circuit immune to noise. The output (pin 3) can only be either high or low (voltage-wise), and it changes its state almost instantenously, regardless of the input signal shape.

The voltage drop across the NE555's output stage (at 35-100 mA) is 0.3-2.0 V, depending on the way the relay is connected and the exact current it draws. D1 is absolutely vital to the safety of the integrated circuit.

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Simple Latch Switch

Here is a very simple electronic circuit diagram project of simple latch switch. In this circuit a non-locking push switch is used to activate a load. The load remains switched on until power is removed from the circuit.

Simple Latch Switch Circuit Diagram:

Circuit Notes:
The load is represented by R5 and D1, but could be a lamp, a relay or another circuit. S2 breaks power to the circuit but could be omitted altogether. If S2 is left out, then reset would be by disconnecting the power; this would mean unplugging the battery if battery powered or disconnecting from the electrical outlet.

When first plugged in (or S2 is operated) C1 charges via the base emitter junction of Q1 and hence a brief positive pulse is applied. Q1 will switch on and be saturated, its collector emitter voltage being close to zero volts. Q2 is therefore off, and the full supply voltage is applied to Q1 base via D1, R5 and R1. The circuit is now in a permanent off state.

If S1 is momentarily pressed, a high voltage is applied to Q1 collector and also Q2 base via R3. Q2 now becomes saturated and the full power to the load is applied. At the same time Q2 collector voltage is now low, and so the volatge at Q1 base, applied via R1 is also low and Q1 switches off. As Q1 is off, bias for Q2 is obtained via R2 and R3 and the circuit is now permanently latched on. Even if S1 is pressed again, this has no effect. The only way to reset is to use S2 (if fitted) or remove power source.

The transistor choice depends on the load. For low currents up to 100mA QN2222 transistors or any other general purpose transistor.

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Light Sensitive and Differential Temperature Switch

This is a very simple electronic circuit project of light sensitive and differential temperature switch circuit.

 

In Fig. 1 see a precision light- sensitive switch that activates when the sensed quantities go above or below pre-set values. The LDR can be any cadmium – sulfide unit that has a resistance in the range 500R to 20k at the required trip level. The RV1 adjust LDR at normal light level. In Fig. 2 see a differential temperature switch circuit using ordinary silicon diodes as temperature – sensing elements and responding to differentials of a fraction of degree. RV2 can be used to apply an effective offset of several degrees to the two diodes.

To adjust the circuit, apply the required differential temperature to the diodes and then adjust RV2 so that the relay just turns on. The circuit responds to the relative temperatures, rather than the absolute temperatures, of the two diodes.

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Simple Pushbutton Switch

Here is a Simple Electronic Circuit Project of Simple Pushbutton Switch This circuit acts like a two-position switch but is operated using a pushbutton. After power has been applied, the circuit is in the following initial state: the bases of T1 and T2 are at the positive supply potential and the base of T3 is at ground potential. All transistors are cut off. The other contact of the pushbutton is at ground potential. No current flows through the relay coil and the status LED is off.

Pushbutton Switch Circuit Diagram:

 
If the pushbutton is pressed, T2 and (after a slight delay due the RC network) T3 switch on. The collector of T3 is now nearly at ground potential, so current flows through the relay coil and the function LED is illuminated. T1 can also switch on. This situation is stable, since ground potential can reach the base of T2 via R1, so nothing changes when the pushbutton is released. C1 is charged via R3 to cause a positive potential to be present at the pushbutton. If the pushbutton is now pressed again, it connects a positive potential to the base of T2 instead of the ground potential. This causes everything to toggle back into the initial state.

Similar operation can be obtained using a thyristor circuit, and in fact T2 and T3 form a sort of thyristor. However, the circuit shown here is largely independent of the voltage and current demands of the connected load. The relay coil should be suit-able for the supply voltage (5–12 V) and should not draw more than 250 mA, since otherwise T3 will go up in smoke. With our lab prototype, we measured a current consumption of 70 mA in the ‘on’ state and less than 0.1 mA in the ‘off’ state.

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Simple But Automatic Load Sensing Power Switch

This circuit will automatically switch on several mains-powered "slave" loads when a "master" load is turned on. For example, it will switch on the amplifier and CD player in a stereo system when the receiver is turned on. It works by sensing the current draw of the "master" device through a low value high wattage resistor using a comparator. The output of that comparator then switches on the "slave" relay. The circuit can be built into a power bar, extension cord or power center to provide a convenient set of "smart" outlets that switch on when the master appliance is powered (turn on the computer monitor and the computer, printer and other peripherals come on as well).

Automatic Load Sensing Power Switch Circuit Diagram

Parts List:

Notes:

• This circuit is designed for 120V operation. For 240V operation, resistors R2 and R6 will need to be changed.
• A maximum of 5A can be used as the master unless the wattage of R1 is increased S1 provides a manual bypass switch.
• This circuit is not isolated from the mains supply. Because of this, you must exercise extreme caution when working around the circuit if it is plugged in.

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Sound Operated Switch

This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electret (ECM) microphone. If an ECM is used then R1 (shown dotted) will need to be included. A suitable value would be between 2.2k and 10kohms.

Sound Operated Switch Circuit diagram

The two BC109C transitors form an audio preamp, the gain of which is controlled by the 10k preset.  The output is further amplified by a BC182B transistor. To prevent instability the preamp is decoupled with a 100u capacitor and 1k resistor. The audio voltage at the collector of the BC182B is rectified by the two 1N4148 diodes and 4.7u capacitor. This dc voltage will directly drive the BC212B transistor and operate the relay and LED.

It should be noted that this circuit does not "latch". The relay and LED operate momentarily in response to audio peaks.

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10 Channels Sensor Switch

A touch sensor switch circuit that works with 10 channels can be designed using electronic scheme in the figure below. If one of the 10 sensors is touched, the corresponding output goes in a logical state 1, the other inputs are in logic state 0.

10 Channels Sensor Switch Circuit Diagram

This 10 channel sensor switch is built using 4017 CMOS decimal counter which provides "decoded" signals. A second oscillator realized with CMOS logic gates produces clock signal. The counter is working until it achieved the desired position of the switch.

The switch can be supplied with a DC voltage between 3 and 15 volts DC.

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CMOS Toggle Flip Flop Using Push Button

The circuit below uses a CMOS dual D flip flop (CD4013) to toggle a relay or other load with a momentary push button. Several push buttons can be wired in parallel to control the relay from multiple locations.A high level from the push button is coupled to the set line through a small (0.1uF) capacitor. The high level from the Q output is inverted by the upper transistor and supplies a low reset level to the reset line for about 400 mS, after which time the reset line returns to a high state and resets the flip flop. The lower flip flop section is configured for toggle operation and changes state on the rising edge of the clock line or at the same time as the upper flip flop moves to the set condition. The switch is debounced due to the short duration of the set signal relative to the long duration before the circuit is reset.

CMOS Toggle Flip Flop Using Push Button Circuit Diagram

 The Q or Qbar outputs will only supply about 2 mA of current, so a buffer transistor or power MOSFET is needed to drive a relay coil, or lamp, or other load. A 2N3904 or most any small signal NPN transistor can be used for relay coil resistances of 250 ohms or more. A 2N3053 or medium power (500 mA) transistor should be used for coil resistances below 250 ohms. The 47 ohm resistor and 10uF capacitor serve to decouple the circuit from the power supply and filter out any short duration noise signals that may be present. The RC network (.1/47K) at the SET line (pin 8) serves as a power-on reset to ensure the relay is denergized when circuit power is first applied. The reset idea was suggested by Terry Pinnell who used the circuit to control a shed light from multiple locations.

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Latch Switch 2

This circuit uses a Silcon Controlled Rectifier (SCR) as a latch switch. Once enabled it can only be turned off by pressing S2 or power is removed from the circuit.

Latch Switch 2 Circuit Diagram

Circuit Notes:
The load is represented by the 1k resistor and orange LED, although the C106D can handle much larger loads. Once the On switch is pressed, the SCR receives a voltage on its gate terminal and goes into forward conduction and conducts current through its anode and cathode terminals. This current remains to flow even when the on switch is released, so the LED remains lit.

The load can only be turned off by pressing the Reset switch which is a Push-to-Break non-latching push switch. Note that reset switch must be able to handle the full load currents and voltage.

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Parking Light Switch

This is a simple parking light switch. The idea is that you drive your car towards your garage. You shine your headlights at the sensor, which switches on an external light . If you don't have a garage the sensor can be placed on a wall or post, and the external light will illuminate the area while you park and leave your vehicle. The circuit also has manual on and off controls.

Parking Light Switch Circuit Diagram

Notes:
This is a very simple light switching circuit using a single transistor and relay to control an external mains powered light. Relay RLA is drawn with two changeover contacts, but a relay with two make contacts can also be used. The contacts MUST be rated at 240V AC and at least 3 Amp (or higher) to safely switch loads of up to 500 Watts. Once energized the relay latches through contacts RLA1 and the external lamp is switched via contact RLA2.

Setting Up:
Wait until darkness and shine your vehicles headlights at the ORP12 Photocell. Adjust the 100k potentiometer until the relay triggers. Turn off the headlights and press S2 to turn off the relay. The external light should go off. It may be necessary to place a plastic tube of about 1 inch in length so that only light emitted by a cars headlights reaches the photocell. This will prevent unwanted triggering.

The light can also be manually controlled by pressing S1 which will latch the circuit, and S2 will turn off the lamp again.

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Schematic 10 Way Electronic Switch

This is a 10 way electronic latching switch using just two switches. Each output can be latched on and off independently.

10 Way Electronic Switch Circuit Diagram

Notes
The schematic is shown above, and two switches S1 and S2 are used to control the outputs. The main work is done by U2 a CMOS4017 decade counter divider IC. At switch on, C1 is quickly charged by R4 and a brief reset pulse is applied to to the reset pins of both U1 and U2. This results in U1, a 7 segment display display driver and decade counter showing "zero" on the 7 segment display and pin 3 (which is the output zero) of the 4017 becoming high.

Each time S1 is pressed the clock input of U2 is incremented, by one count and the display and 4017 will cycle through all 10 outputs. A separate reset switch is not provided as the display reads the currently selected output.

When the 4017 is on a particular output, for example zero, then the controlled circuit can be turned on or off using switch S2. To latch the output a type JK flip-flop is used at each of the ten outputs. This works as follows. When the 4017 is at output zero, pin 3 will be high. This enables both JK inputs of the flip flop (U4A at output zero) and the circuit can then be toggled via pulses applied from switch S2. The 'Q' output of each flip-flop drives and NPN transistor and then a small relay. The NPN transistors can be any general purpose type, e.g. 2N2222, BC108, BC548 etc. The relay allows external loads of different voltage and current to this circuit to be controlled.

For clarity, the schematic is drawn with outputs, zero, six and nine shown only. The pinouts for the CMOS IC's 4017 and 4026 can be found in the practical section.

The CMOS 4026 is available at ESR Electronics in the UK.

If required, the external circuits power supply can be used to power the driver transistor and relay. This is shown on output 6, the dotted lines representing the power coming from an external battery. The only other requirement here is that the external circuits common negative terminal is tied to this circuits common chassis (negative) terminal.

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Automatic Switch for Batteries

Nowadays the batteries are gaining more and more power, being the only components that fail to provide energy for portable electronic devices. The evolution is rapid, leading manufacturers electronic equipment to attempt to minimize the consumption of their products so that they can operate for several hours using simple batteries trade. In spite of the efforts of manufacturers, the device will absorb a zero power not yet invented. Thus, both small and if the current device is mathematically certain that at some point, after a few hours, days or ethdomades, the battery-drain .

 Automatic Switch for Batteries  Circuit diagram

The purpose of the circuit will describe below, is to keep 'alive' batteries for the maximum time, minimizing unnecessary consumption. Taking a brief look at the circuit, you notice that the few parts that are can be integrated into any device powered by a battery of 9 V. The main trait is that allows current to flow to the load for a minute, since you pressed the switch S1. After this time automatically cuts off the battery connection. The peak current during switching is 20 mA, price satisfactory for most devices that work with batteries, this nominal voltage.

The heart of the construction is a Darlington type transistor PNP (T1), which is driven in a state of conduction through the pressing switch S1. The small current thaoio, which is due to the high rate of aid, makes able to remain in this condition even for relatively small values ??of the capacity of capacitor C 1 (Around 100 MF). The resistance A3 limits the charge current of the capacitor, thus ensuring long life pressing the switch.

Resistance A1 and A2, in conjunction with the capacitor C 1, determine the period allowed to flow, flow to the load. After this time, the T1 is driven in the state cutoff, a condition ensured by R1. In this design, the placement of a diode to protect from any reverse polarity would be an unnecessary luxury, since the maximum reverse voltage that can accept darlington between thasis and emitter (UBE) is equal to 10 V.

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12V Touch Switch Exciter

This circuit is designed to generate a 20KHz pseudo sine wave signal that can power about 50 remote touch activated switch circuits.  It can support a cable length of about 2500 feet.  A typical remote switch circuit is also shown as well as a receiver circuit for those switches.

12V Touch Switch Exciter Circuit diagram:

 Source: discovercircuits

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Touch Sensor Switch Using Inverters

This touch sensor switch can is designed using inverters (N1, N2)and some common electronic components. In standby state at the entrances of N1 there is a signal produced by oscillator N3/N4. At the touch sensor hand capacity forms a bridge to the ground for the 1MHz signal so that the voltage signal at the entrance of N1 decreases more (at the exit of N2 is logical 1). After the release of contact, a signal charge C4 through D1 Mhz, so the output of N2 is 0 logic after short time.

Touch Sensor Switch Using Inverters Circuit Diagram

Installation can be powered with a DC voltage between 3 and 15 volts (maximum current of 2 mA is absorbed).

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9 Channels Sensor Switch

This sensor switch circuit diagram is designed using CMOS components. This sensor switch circuit has nine channels and consist of only three integrated circuits and some resistors. Due to high input impedance, 74HC147 allows to use of 4.7 M resistors to create a logic level "high" to sensor inputs. When one sensor is touched, the resulting low resistance to ground circuit causes IC1 to read a logical level L.

9 Channels Sensor Switch Circuit Diagram

If several sensors are touched simultaneously, priority encoder delivers 4-bit code corresponding to the sensor with the highest number.

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