A simple touch sensor switch circuit can be built using a single IC 4017 and a few other passive components, the procedure is explained in the following article.
Using a 4017 IC for the Relay Touch Activation
Referring to the below given circuit diagram for the proposed simple touch activated relay circuit, we can see that the entire design is built around the IC 4017 which is a 10 step johnson's decade counter divider chip.
The IC basically consists of 10 outputs, starting from its pin#3 and randomly ending at pin#11, constituting 10 outputs which are designed to produce a sequencing or shifting high logics across these output pins in response to every single positive pulse applied at its pin#14.
The sequencing does not need to finish at the last pin#11, rather could be assigned to stop at any desired intermediate pinout, and revert to the first pin#3 to initiate the cycle afresh.
This is simply done by connecting the end sequence pinout with the reset pin#15 of the IC. This makes sure that whenever the sequence reaches this pinout, the cycle stops here and reverts to pin#3 which is the initial pinout for enabling a repeat cycling of the sequence in the same order.
For example in our design pin#4 which is the third pinout in the sequence can be seen attached to pin#15 of the IC, implies that as the sequence jumps from pin#3 to the next pin#2, and then to pin#4 it instantly reverts or flips back to pin#3 to enable the cycle again.
How it Works
This cycling is induced by touching the indicated touch plate which causes a positive pulse to appear at pin#14 of the IC each time it's touched.
Let's assume at power switch ON the high logic is at pin#3, this pin is not connected anywhere and is unused, while pin#2 can be seen connected with the relay driver stage, therefore at this moment the relay stays switched OFF.
As soon as the touch plate is tapped, the positive pulse at pin#14 of the IC toggles the output sequence which now jumps from pin#3 to pin#2 enabling the relay to switch ON.
The position is held fixed at this point, with the relay in the switched ON position and the connected load activated.
However as soon as the touch plate is touched again, the sequence is forced to jump from pin#2 to pin#4, which in turn prompts the IC to revert the logic back to pin#3, shutting of the relay and the load and enabling the IC back to its standby condition.
Modified Design
The above touch operated flip flop bistable circuit might show some oscillation in response to finger contact, leading to relay chattering. To eliminate this issue, the circuit should be modified as given in the following diagram.
Or you may also follow the diagram which is shown in the video.
Sir thanks for quick reply and it works great.
Thanks Janak, I am glad it's working!
Sir i tried it using 1000mf cap with 1m resistor and also diode. but now it works only if switch is in off state. suppose before power goes if switch is off and power comes it remains off but if switch is ON and power goes and when power comes back it is off. Sir is there any other way to keep same state of switch even if main power goes and come it remains in previous state.
circuit description for two touch switch.
Ic used cd 4013. Two output taken from this Ic 1st output from pin 1 and 2nd from pin 13.Input given through M397 TTP223 Capacitive Touch Switch Button Self-Lock Moduleto both input pins 3 & 11 with 2k resistor to I/O of touch module other end of resistor goes to pin 3 of ic 4013 and one more resistor of 100k from pin 3 goes to ground. . short pins of Ic 2 with 5, 4 with 6&7, 12 with 9 and 10 with 8 which is then shorted to 7 as ground & 14 is vcc.
output of this Ic given to ULN2004 ic and output through this ic is given to relay circuit. Input supply is 5v
sir pls let me know if any other modification to be done so that switch remain in same previous state even if power goes and come.
Janak, please refer to the last diagram of the following article:
https://homemade-circuits.com/2012/05/make-this-easiest-flip-flop-circuit.html
did you connect the parts in the indicated manner?
Sir I made a touch switch using 4013 ic and its works fine but suppose if switch is OFF and main power goes and when power comes back again switch turns ON (vice versa). How can I avoid this. or how to keep the same state of switch when power goes OFF or comes ON.
Janak, to rectify the issue you can connect a high value capacitor across the ICs suply terminals via a 1M resistor, and also make sure to connect a 1N4148 from the supply to the (+) of the capacitor, that is at the junction of 1M and capacitor positive, cathode will go at this point, and the anode to the supply positive.
Dear sir,
Can this circuit may be used for fence for detecting intruder. If nor what changes needed in above circuit.
Abbas
Dear Abbas, no it cannot be used for fence, since the fence could act like an antenna and cause stray pick ups and spurious relay operations
The number of pin which is on the left of pin15 is not written. Is it pin16?
yes it's pin#16
Ok it worked..thank you…Is there simple touch on/off circuit working by 220V? Or can't we,for example, add bridge diode and condenser..? Have you got any simple/easy such circuit?
a capacitive power supply can be dangerous and lethal, so it's not recommended
what is that touch plate..is it an ordinary metallic plate to which base of transister is connected..sir im new to these type of circuits thats why i asked
it can be any metal end, even a small 1 inch stripped wire will do.
this wire should be as small as possible, longer wires might produce erratic results due to stray disturbance pick up
Sir good morning Hope you fine. I requested u to design a circuit for boost the heart beat sound from stethoscope via condensor mic to 8" speaker.Is there any chance to design.
Thank you
Sridhar
Sridhar, it is in my draft and I will post it soon, there's one article in the queue, next to that I will publish your article
Thank you sir,I will wait.
Sridhar, I think I already have this circuit in this website, you can see it here:
https://homemade-circuits.com/2016/01/electronic-stethescope-amplifier-circuit.html
alternatively you can try the following preamplifier circuit and use it with your STK amp circuit for amplifying the heart beats:
http://www.ti.com/lit/ug/tidu765/tidu765.pdf
it works perfectly u a great SWAGATAM, thanks
Thank you Davis! It's my Pleasure!
your welcome!!
sir
is there any progress in my request
can you tell me how to buy parts for making these projects online individually..i dont want bulk quantity.can you tell me any site..this ia because nowadays all parts are not available in my nearby electronic shops..please help me
NvD, can you please repeat your request, I have it my draft but it would be easier if you could say it again.
Parts can be purchased by placing an order through any online component dealer and by paying through your debit card or netbanking…the parts will reach the destination within the stipulated date.
OK, I think I have recently posted it here:
https://homemade-circuits.com/2016/07/simple-touch-sensor-switch-circuit.html
sorry the correct link is given below:
https://homemade-circuits.com/2016/07/touch-free-faucet-circuit.html
circuit it not working. im hooking up a simple LED to the relay and it wont turn on
remove the relay and check by connecting the LED across pin#2 and ground via resistor 1K…first confirm this.
Does the touch plate work when it is placed under a glass panel? LIke if we touch the particular area on the glass which is placed above the touch plate, the relay should response.
No, it needs to be touched physically to actuate…
for your application you can try the IC 555 capacitive switch circuit from this site