Touch Switch Circuit using 555 Timer

The modern mechanic switches are improved concern of old technology. We however need to check current greater than the durability of certain switches or simply we need something with modern appearance. The project for ON and OFF switch is build around a 555 timer configured in such a way that latch is on one state and some action is required to change that state. Image below details with a conventional touch switch sensor :

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Fig. 1: Image Showing Conventional Touch Switch Sensor

In this project, when power is supplied to the touch switch circuit, the devices connected to it remain ideal as voltage at pin2 is zero. When the switch is turned ON, trigger pin (pin2) receives trigger signal. The output pin (pin 3) receives a high output due to which transistor gets turned ON. Simultaneously relay connected to it also receives high signal due to this the device connected to it gets turned ON. Voltage at pin6 should be zero at this stage. When the switch is turned OFF similar action takes place. In this type of switches, relays are latched ON with push of a button and with another push, latch is released. The working is similar to flip flop.

Touch pad can also be used on place of switches. As soon as the switch is pressed ON, the device gets turned on and as the switch is pressed OFF the device gets turned off. When looked at the touch plates of the old toys it was found that some are light touch buttons. They consist of small carbon block which is mounted in silicon rubber. As the button is pressed, it touches the pad and resistance gets reduced between the two interleaved tracks. These pads are already protected against corrosion and have a good design for detecting finger. When finger is applied, the resistance between the tracks changes between 150K to 850K depending upon the pressure applied and the moisture of the finger.