In this article we are going to construct a capacitive touch switch circuit with 10 channel output, the state of the each channel can be turned ON and OFF sequentially by touching acoin sized metal plate.
Capacitive touch is very commonly used in our smartphones, tablets or any gadgets which have touch screen. The term “capacitive” means charge, any smartphone or any gadgets say the term capacitive touch; it works by detecting charges around the screen.
When we touch any part of the screen there will be change in electrostatic charge, this information is processed by the microprocessor inside your smartphone.
Before the smartphone era most of us would have used a phone with touch screen which is much harder to navigate through the user interface (UI) and we have to apply force to select an item.
This type of touch screens is called resistive touch. They don’t work as smooth as capacitive touch.
They have two layers whichare coated with conductive material.When two layers come in contact a touch is registered and the microprocessor will receive this information and executes rest of the process.
In this 10 channel capacitive touch switch circuit project we are dealing with touch switch which operate similar to capacitive touch.
In capacitive touch the change in electrostatic charges are used to detect touch, but in our project, charges from the surrounding are injected into the circuitthrough our hand and this register a touch.
Initially pin#3 will be high and rest of the pins are low.When we touch the touch plate, pin#2 turns high and rest of the pins to low and touching it again turns pin#4 highand rest of the pins to low and so on (Q0 to Q9) sequentially .
The transistor detects the injected charge and amplifies. The touch signal is fed to IC 555 which is configured in mono stable mode. The IC555 generate clock pulses necessary to change the state of 10 pins in IC 4017.
You can connect MOSFETs or transistor or any other peripherals according to your customized needs.