Friday, December 9, 2011

Low Cost Capacitive Touch Switch II

In my previous post of capacitive touch switch, it gives the o/p as long as you touch it. Means it was only drive the load when you touch it, and when you remove your hand/finger then it was not able to drive the load. Tough that touch switch circuit can be used in various apps but does not meet my requirements. So by changing the circuit a little bit i am able to design a touch switch that behave like a normal switch i.e touch to on and touch to off.

For this i used CD4017 decade counter. Output of 40106 drives this counter and load is connected to the pin2 of the counter, and reset is to pin4. When you touch the touch plate (wire in my case) a pulse is provided to the counter and it increments its o/p. So as the load is connected to the Q1 of counter, the o/p is high to drive the load. Similarly if you want to switch off the load and again touch the plate; counter will increment again and reset itself and make Q0 high. As your load is not connected to this pin it will go off. That is all!.


Components Required:

R1------------------------------6.8k ohm
R2------------------------------10k ohm pot
R3------------------------------100k ohm
R4------------------------------10M ohm
R5,R6--------------------------10k ohm
R7------------------------------1M ohm
R8------------------------------1k ohm

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