Simple Light Switch

Light switch is a simple circuit that can be used to control the LEDs based on surrounding light. Sensors used to detect the light on this circuit using LDR Light Switches. This circuit uses only three transistors and a few supporting components. As a contactor for Light Switches lamp circuit uses relay. To set the sensitivity of the exposure can be adjusted by adjusting R7. Light Switches circuit uses a source of DC voltage 9-12 Volt. For more details can be viewed directly from the following series of images.

Light Switches Series

Component List:

R LDR

R1 4.7 K

R2 1.2 K

R3 2.2 K

R4 1.2 K

R5 1.2 K

R6 2.7 K

R7 100 K

C1 10 uF/16V

TR1 BC107-BC108

TR2 BC107-BC108

TR3 BC557-BC558

D1 1N4148

RELAY 12V

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Green USB switch

According to the Energy Saving  Trust, if you add up all the current drawn in standby mode by items such as stereos, TVs, VCRs and DVDs over a year in the UK alone, it amounts to 3.1 million tonnes of CO2 released into the atmosphere.This is without factoring in the current drawn by all the PCs,laptops and their associated peripherals left in standby mode. 

Circuit diagram :

Green USB switch Circuit Diagram

It  is  not  necessary  to  spend  a  great deal of money or time to  make a difference on a personal  level. The circuit described here  is designed for use by laptop or  notebook computers. It will automatically switch off all mains  powered peripheral equipment  including monitor, printer, scanner, TV tuner and USB hub etc  when it detects that the notebook  is switched off. The circuit is quite  straightforward; in addition to an  optocoupler it requires a 12 V  double-pole  relay  with  mains  rated contacts and a small power  supply  for  the  optocoupler.  When the laptop is switched on  5 V appears at the USB socket,  activating the relay and switching  through  the  mains  supply  on K3 and K4. The notebook’s  USB socket is still available to be  used as normal but it’s worth remembering that the optocoupler  takes a few milliamps from the  USB supply and this may cause a  problem if a high-current device  is plugged into the USB socket.  In the case where the laptop has  more than enough USB sockets it may be worthwhile us-ing one of them solely for this  circuit, the extension USB connector K2 would then not be  required. 

The circuit is mounted into a  mains plug enclosure which  provides a socket where the  mains extension strip will be  plugged into. With any luck  there will be sufficient space  to fit the entire circuit into the  mains extension strip enclosure and save the need for a  separate enclosure. The slow-blow 6.3-A fuse (F1) protects  the equipment plugged into  the strip. 

In  addition  to  the  optocoupler  and relay the circuit also has a  ‘freewheel’ diode D1 and a relay  driver formed by T1 and its base  bias voltage divider network R2/ R4. The two ‘snubber’ networks  C1/R3 and C2/R5 reduce the  possibility of arcing which can  occur  when  the  relay  contacts  open (especially with inductive  loads). Capacitors C1 and C2  must be class X2 types which  can handle mains voltage plus any  spikes.  The  power  supply  consists of a small mains trans-former  (12 V,  50 mA),  bridge  rectifier and smoothing capacitor C3. 

The laptop’s mains adaptor itself  can also be switched by this circuit when the laptop is fitted with  its rechargeable battery which  allows the computer to boot up  without a mains supply. The en-tire USB switch circuit draws cur-rent even when it is off but this value  is  tiny  compared  to  the  combined standby current of all  the peripherals. 

Note that parts of this circuit are  connected to the (potentially lethal) mains supply voltage; it is  essential to provide protection  to ensure that nothing can accidentally make contact with these  parts of the circuit. It is also important to observe correct separation between parts of the circuit carrying low voltage and  those carrying the high volt-age. Please observe the electrical Electrical Safety guide-lines which are reprinted in  Elektor  Electronics  several  times a year. 

The  circuit  is  less  suitable  for use with desktop PCs be-cause  the  majority  of  these  machines supply 5 V over the  USB socket even though they  have been shut down via soft-ware. The only way to turn off  in this case is to reach around  the back of the machine and  switch off at the main switch.

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Simple Automatic Headlight Brightness Switch Circuit Diagram

Going by car the highway with your high-beam headlights can actually increase your visibility, but can be a blinding hazard for other drivers. This easy circuit can be connected into your headlight swap to provide automatic swaping between high and reduced beam headlights when there is oncoming traffic. It does this by feeling the lights of that traffic. In this way, you can propel securely with your high-beams on without blinding other drivers. 

 Automatic Headlight Brightness Switch Circuit Diagram

1. Q1 should me mounted in such a way so it points toward the front of the car with a clear line of site. 
2. Suitable places are on the dashboard, in the front grill, etc.
3. Adjust all the pots for proper response by testing on a deserted road.
4. S1 enables and disables the circuit.B1 is, obviously, in the car already.
5. Before you try to connect this circuit, get a wiring diagram for your car. 
6. Some auto manufacturers do weird things with wiring.
7. Connection A goes to the high beam circuit, B goes to the headlight switch common and C connects to the low beam circuit.
   

Part	Total Qty.	Description	Substitutions
R1	1	5K 1/4W Resistor
R2, R3, R4	3	5K Pot
Q1	1	NPN Phototransistor
Q2	1	2N3906 PNP Transistor
K1	1	Low Current 12V SPST Relay
K2	1	High Current 12V SPDT Relay
S1	1	SPST Switch
B1	1	Car Battery
MISC	1	Case, wire, board, knobs for pots

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Automatic light activated switch circuit

The circuit can be used for switching OFF a particular lamp or group of lamps in response to the varying ambient light levels. The unit once built can be used for switching OFF a lamp when dawn breaks and switching it ON when dusk sets in. The power supply is a standard transformer, bridge, capacitor network, which supplies a clean DC to the circuit for executing the proposed actions.

Automatic light activated switch circuit schematic

The LDR must be placed outside the box, meaning its sensing surface should be exposed toward the ambient area from where the light level is required to be sensed. The circuit can be used as an automatic street light controller system or a simple light activated switch.

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TOUCH SWITCH Diagram

TOUCH SWITCH

This circuit detects the skin resistance of a finger to deliver a very small current to the super-alpha pair of transistors to turn the circuit ON. The output of the "super transistor" turns on the BC 557 transistor. The voltage on the top of the globe is passed to the front of the circuit via the 4M7 to take the place of your finger and the circuit remains ON.

To turn the circuit OFF, a finger on the OFF pads will activate the first transistor and this will rob the "super transistor" of voltage and the circuit will turn OFF.

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Low Voltage Remote Mains Switch

This circuit allows a 240V mains appliance to be controlled remotely via low-voltage cabling and a pushbutton switch. The mains appliance (in this case, a light bulb) is switched with a suitably-rated relay. All of the electronics is housed in an ABS box located in proximity to the appliance. The pushbutton switch and plugpack are located remotely and can be wired up with 3-core alarm cable or similar. Cable lengths of 20m or more are feasible with this arrangement. When the switch (S1) is pressed, the input (pin 8) of IC1c is briefly pulled low via the 10mF capacitor, which is initially discharged. Low-Voltage Remote Mains Switch Circuit diagram:

Low-Voltage Remote Mains Switch Circuit Diagram

The output (pin 10) immediately goes high and this is inverted and fed back to the second input (pin 9) via another gate in the quad NAND package (IC1d). In conjunction with the 1MW resistor and 470nF capacitor, IC1d eliminates the effects of contact "bounce" by ensuring that IC1c’s output remains high for a predetermined period. The output from IC1c drives the clock input of a 4013 D-type flip-flop (IC2). The flipflop is wired for a "toggle" function by virtue of the Q-bar connection back to the D input. A 2.2MW resistor and 100nF capacitor improve circuit noise immunity. Each time the switch is pressed, the flipflop output (pin 13) toggles, switching the transistor (Q1) and relay on or off. Note that all mains wiring must be properly installed and completely insulated so that there is no possibility of it contacting the low-voltage side of the circuit.

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Electronic DPDT Switch

Switch It should be appreciated that the output impedance of the switch is fairly high and so for low signal distortion, a load greater than 10kS2 is necessary.
Using a high supply voltage (1 0-1 5V) also helps to achieve this end. The gates will pass signals above the 10MHz mark but as the frequency becomes higher, crosstalk between the switchesand distortion will inevitably increase.

A simple electronic DPDT switch circuit through a single trigger input

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Simple Switch Debouncer Wiring diagram Schematic

 This is a Simple Switch Debouncer Circuit Diagram. Switch debouncing is one of those things you generally have to live with when playing with switches and digital diagram. In this schema uses TTL inverter 74LS14 has an internal 16-Kohm, pull-up resistor that pulls the gate input high when the switch is open. As you close the switch, the 4.7uF capacitor discharges on the first contact.

 Simple Switch Debouncer Circuit Diagram

If the switch contacts bounce open, the internal resistor limits the capacitor`s recharge to a rate sufficiently slow to prevent an undesired gate transition before the contacts again close. 

Note 

That the schema correctly debounces the switch for both opening and closing. If you add an external pull-up resistor, you can use a CMOS Schmitt-trigger gate, 74HC14, and a smaller, 0.1uF, capacitor.

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Touch Switch II

This schema uses a 555 timer as the bases of the touch switch. You can learn more about 555 timers in the Learning section on my site. When the plate is touched the 555 timer is triggered and the output on pin 3 goes high turning on the LED and the buzzer for a certain period of time. The time that the LED and the buzzer is on is based on the values of the capacitor and resistor connected to pin 6 & 7. The 10M resistor on pin 2 causes the the schema to be very sensitive to the touch.

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Mat Switch Wiring diagram Schematic

This simple schema produces a warning beep when somebody crosses a protected area in your home or office. The switch, hidden be-low the floor mat, triggers the alarm when the person walks over it.

The schema uses a conductive foam as the switch. It can be two small pieces of conductive pads usually used to pack sensitive ICs as antistatic cover. Alternatively, you can make the switch by coating conducting carbon ink on two small pieces of a copper-clad board.

Simple Mat Switch Circuit Diagram

When the schema is in standby mode, transistor T1 does not conduct, since its base is floating. When the person walks, the switch is pressed and current flows through R1 and the switch to provide positive bias to transistor T1. Transistor T1 conducts and its collector voltage drops, which acts as a negative trigger input for the monostable wired around IC NE555 (IC1).

IC1 outputs a pulse of fifty-seconds duration with preset values of R4 and C3. This pulse is applied to the buzzer through transistor T2. The buzzer sounds a warning beep on unauthorised entry. The pulse duration can be changed to the desired value by changing the values of R4 and C3. Resistor R2 in the schema makes the trigger pin of IC1 high to prevent false triggering.

Assemble the schema on a general-purpose PCB and enclose in a plastic case. Use a 9V battery to power the schema. Connect the touchpad switch with the PCB and hide under the mat at the entrance. The PCB can be mounted on the nearby wall.

Make the switch carefully using conducting foam or copper clad coated with conducting ink. Place the two pieces with their conducting surface facing each other. Solder carefully a thin copper electric wire and ensure that it makes contact when the two plates touch together on pressing. Provide two 1cm rubber tabs between the plates to avoid touch in the standby mode.

http://streampowers.blogspot.com/2012/06/simple-mat-switch-schema.html 

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