Wiring Schematic Diagram

The touch sensor can be constructed using a small piece of a printed circuit board ( two small tracks with a 2 mm distance between each other ) . This circuit is powered using a 12 volts DC power supply , so the relay used for this project must be a 12 volts relay . This circuit is working very simple , when both plates of the sensor are touched the skin resistance will activate the circuit .

The following circuit shows about Water Switch Sensor circuit based on the S201S02 IC. Features: two closely spaced metal rings are used as the water sensor mechanism.

water circuit switch sensor can be used as applications for: rain alarm, watertap leak detectors, water level sensors for bathroom water heaters, wetness checker for flower pots and more.

Working principle of this circuit is very simple. When the sensor rings are bridged by water, an isolated electric switch turns on to activate the load (an alarm, for instance) connected through its switching contacts. Here, the renowned S201S02 solid-state relay (IC1) is wired as the electronic switch.

This following circuit shows a Long Delay Timer Circuit Diagram. This circuit designed mainly to switch off a portable radio after some time:

A very long time constant is provided by R1 and C1. C1 discharges and the near zero voltage at its positive lead is applied to the high impedance inputs of the four gates of IC1 wired in parallel when P2 is momentarily closed. The battery voltage is available at Q1 Emitter since the four paralleled gate outputs of the IC go therefore to the high state.

The circuit will start if P2 is pushed for 1 to 5 second and will switch off after about 35 minutes. The time delay can be varied depends on values of R1 and/or C1. If required, P1 will stop the timer. LED D1 is optional. When the load is placed far from the time, LED D1 can be useful to signal relay operation

R1   : 10M
R2   : 4K7
R3   : 1K
C1   : 220µF/25V
D1   : LED any type
D2   : 1N4148
IC1  : 4011 Quad 2 Input NAND Gate CMos IC
Q1   : BC337
P1,P2: SPST Pushbuttons
RL1  : 12V Relay Switch 

This is a delayed turn-on relay driver and can produce time delays for up to several minutes with reasonable accuracy. The 4001 CMOS gate here is configured as a simple digital inverter. Its output is fed to the base of a regular 2N3906 transistor, Q1, at the junction of resistor R5 and capacitor C2. The input to IC1 is taken from the junction of the time-controlled potential divider formed by R2 and C1. Before power is applied to the circuit, C1 is fully discharged. Therefore, the inverter input is grounded, and its output equals the positive supply rail; Q1 and RY1 are both off under this circuit condition. When power is applied to the circuit, C1 charges through R2, and the exponentially rising voltage is applied to the input of the CMOS inverter gate. After a time delay determined by the RC time constant values of C1 and R2, this voltage rises to the threshold value of the CMOS inverter gate.

The gate's output then falls toward zero volts and drives Q1 and relay RY1 'ON'. The relay then remains automatic turn-off relay driveron until power is removed from the circuit. When that occurs, capacitor C1 discharges rapidly through diode D1 and R1, completing the sequence. The time delay can be controlled by different values for C1 and R2. The delay is approximately 0.5 seconds for every µF as value for C1. The delay can further be made variable by replacing R2 with a fixed and a variable resistor equal to that of the value of R2. Taken the value for R2 of 680K, it would be a combination of 180K for the fixed resistor in series with a 500K variable trim pot. The fixed resistor is necessary.

This crcuit from:  www.sentex.net

Sound Activated relay. The relay remains dormant until the op-amp activates upon sound via the electret-microphone. The input stage is a regular off-the-shelf 741 operational amplifier and connected as a non-inverting follower audio amplifier. Gain is approximately 100 which you can raise by increasing the value of R2. The amplified signal is rectified and filtered via C3, D1/D2, and R4 to an acceptable DC level. Potentiometer R5 is used to set the audio level to a desired sensitivity value to activate the relay via transistor Q1. Diode D3 is mounted over the relay coil to absorb sparks. The op-amp configuration in this particular drawing needs a dual voltage power supply which can be made from two 9-volt batteries. 

This crcuit from:  www.sentex.net

Here is a circuit that allows you to control a relay in response to sound from a non-amplified sound source (computer, CD player, or my Digital Sound Recorder board).

This circuit accepts audio input from any non-amplified sound source and when the volume reaches a certain level, it actuates a relay. This relay can be used to switch another device (light bulb, etc.) on and off in sync with the volume of the input.

The circuit can work from any 5–12 VDC regulated power supply provided a relay with the suitable coil voltage is used. When you first connect the supply voltage to the sound activated switch circuit, the relay will be energised because of the effect of capacitor C2. Allow a few seconds for the relay to be switched off. You can increase or decrease the ‘on’ period by changing the value of C2. A higher value results in a longer ‘on’ period, and vice versa. Do not use a value greater than 47 μ F.

Biasing resistor R1 determines to a large extent the microphone sensitivity. An electret microphone usually has one internal FET inside which requires a bias voltage to operate. The optimum bias level for response to sound has to be found by trial and error.

This is a circuit which built to one of my audio amplifier projects to control the speaker output relay. The purpose of this circuit is to control the relay which turns on the speaker output relay in the audio amplifier.

Turn On Relay Delay Circuit for power amplifier

The idea of the circuit is wait around 5 seconds ofter the power up until the speakers are switched to the amplifier output to avoid annoying "thump" sound from the speakers. Another feature of this circuit is that is disconnects the speaker immediately when the power in the amplifier is cut off, so avoiding sometimes nasty sounds when you turn the equipments off.

This circuit is not the most accurate and elegant design, but it has worked nicely in my small home-built PA amplifier. This circuit can be also used in many other applications where a turn on delay of few seconds is needed. The delay time can be increased by using bigger C2 and decreased by using a smaller C2 value. Note that the delay is not very accurate because of simplicity of this circuit and large tolerance of typical electrolytic capacitors.

This circuit energizes the relay when the temperature rises above the preset level. The value of the thermistor is not critical. The important thing is the voltage on pins 5 & 6. Any value thermistor should work satisfactorily. But you may need to change the value of R1 - to achieve the desired range of adjustment.

This is a LDR switch or light activated relay circuit. This circuit will let you make a switch that will be activated by light falling on a sensor. It is a very useful device and can be used in automatism’s, security systems, counters, remote controls etc. It is very sensitive, fast acting and reliable. The circuit uses a Light Dependent Resistor (LDR) as a sensor and IC LM311 to amplify the signals from the LDR and transistor 2N2222 to drive the relay which does the switching.

Normally the resistance of an LDR is very high, sometimes as high as 1000 Kohms, but when they are illuminated with light resistance drops dramatically. The relay on when LDR uncoverd and relay off when LDR covered. Adjust VR1 for light sensitive.LED will turn on at the same time with relay

This is a simple 220V light dimmer circuit based triac can be used to adjust the brightness of mains lights about 350 watts. It also can be used to adjust the speed of AC motors. It uses a triac, diac and has a radio-frequency interference (RFI) noise suppression circuit built into it as well. Please note that this circuit cannot be used with fluorescent lights.

R1     : 50K Pot
R2     : 15K 1/2W Resistor
C1, C2 : 0.068 250V Capacitor
L1     : Lamp To Be Controlled (up to 350 watts)
L2     : Neon Lamp
TR1    : 40502 TRIAC 
 

Note: 

This is a circuit of electrnic on-off Touch switch controller using IC CD 4011 that is connected as a FLIP-FLOP. He is simple in the manufacture and the materials that use they exist everywhere. This based in the known CD 4011, which drives a relay of which the contacts play the role of switch. The metal surfaces can have what form we want, but it should they are clean and near in the circuit. In order to it changes situation it suffices touch soft somebody from the two plates.

This high sensitivity of the circuit makes the touch switch  operation possible. The two gates are held at logic state «1» continuously by means of the two resistors R1 and R3 that connect them to the positive supply rail. These resistors have a very large resistance of 10 Mohm. If we now touch a set of contacts the skin resistance closes the circuit between the corresponding gate and the negative supply rail. The skin resistance for small areas of the skin is normally much lower than 10 Mohm and the gate is effectively brought to logic condition «0» which makes the FLIP-FLOP change state. For any given state of the FLIP-FLOP touching the corresponding set of contacts will make the circuit to reverse its state of balance and in effect toggle the switch. As a switch is used a relay driven by a transistor which is driven from the out put of the FLIP-FLOP.

R1  : 10MOhm 1/4 W
R2  : 10MOhm 1/4 W
R3  : 1KOhm 1/4 W
D1  : Led red
D2  : 1N4148 diode
TR1 : BC558 PNP Transistor – BC327
IC1 : CD4011 CMOS IC
RL1 : 12V relay rated at 250 V / 2A 

This is a simple Light / Dark Activated Relay  circuit with the base of the LDR. The voltage divider has two resistors. The first is the 100K potentiometer plus the protective 1K resistor. the second resistor is the LDR.

As light falls on the surface of the LDR, the LDR changes it's resistance. The more the light, the less the resistance of the LDR, the less the resistance, the less the voltage drop across it. The less the light, the more the resistance and thus the more the voltage drop across it.

As the voltage drop increases, so does the VB of the 2N2222 transistor and therefore the ICE increases accordingly, until the time that the current is enough to actuate the relay.

The amount of light needed to actuate the relay can be changed by changing the 100K potentiometer. Basically, any change to the potentiometer will have an effect to the voltage drop of the LDR, as they are both members of the voltage divider described above.

The 1N4001 diode is used to eliminate any back voltage when the relay is disarmed. It is very important to have this diode because without it, the transistor may be damaged.

A simple electronic touch switch can be constructed using this circuit diagram . This electronic touch switch circuit is based on 2-transistors an can activate a relay. Putting a finger on the touch pads turns the top transistor ON and this transistor turns on the bottom transistor. When the finger is removed, the circuit consumes less than a microamp.

The touch sensor can be constructed using a small piece of a printed circuit board ( two small tracks with a 2 mm distance between each other ) . This circuit is powered using a 12 volts DC power supply , so the relay used for this project must be a 12 volts relay . This circuit is working very simple , when both plates of the sensor are touched the skin resistance will activate the circuit.

The 555 can be used to create a Touch Switch. The only problem with this is the 555 consumes about 8mA, at all times when the supply is connected. This circuit is a simple touch plate controller which when touched on the touch plate operates the relay for a preset time then turns off automatically. This circuit has got applications in common equipments like touch operated doorbells, toys, buzzers etc. See below for an ON-OFF touch switch using a 555.

The trigger pin of NE 555 has high input impedance. This property is exploited in this circuit in such a way that human body induced voltage is used for triggering this IC. When this IC is triggered, its output goes to high for a time duration determined by resistor R1 and capacitor C1. The relay used here is driven by a transistor. This relay contact is utilized here to drive loads like bell, lights, motor etc.

Note: To setup the circuit connect to power supply and adjust R1 while keeping touching on the touch plate and stop at the point where relay activates.