Touch Switch assembling guidelines

Assembling guidelines

Procuring components

Since very few components are involved in the circuit design of this touch switch, it can be easily procured from the local electronics mart. IC, relays, resistors and capacitors listed in the parts list are easily available. There may not be any difficulty in procuring even in small towns as normally these types of components are familiar and in vogue. The components are low priced and can be purchased in a small amount.  Take the list to the shop and buy the items instantly. 

12 V DC power pack can be procured from the same place or one can use a 12 V DC battery pack if one desires portability. Dry cells can also be used with this circuit. 

PCB 

The circuit can be easily assembled on the ready-made PCB designed by me. A novice or a beginner will find the PCB useful for construction. Otherwise one can alternatively assemble the circuit on a general-purpose PCB available in the market. As the circuit is not complicated, a general-purpose board or even a hookup board may be helpful.  For demo purposes, one can even use an electronics breadboard for assembling the circuit provided the constructor is well aware of the breadboard usage. This saves the components and they can be reused as there is no soldering involved. 

IC 555

Here 8pin DIL pack of IC is used. The same may be procured and soldered directly to the board. If one desires to use a socket it is a good idea to get an 8 pin DIL socket and fix it on the board. The IC can be inserted into the circuit after finishing all the soldering work. Care must be taken to see that the pins of the IC are correctly inserted on the socket. Ensure the right pin on the right hole of the socket. 

The touch plate

The touch plate can be tin or metal foil for contact and it may be the size of one rupee coin for better performance. Sometimes part of the PCB track also can be made of a sensor touch plate. However, the contact surface should be clean and non-greasy for effective functioning. 

Relay

The relay may be SPST type of operating voltage 9V DC with less than 150 mA capacity. DPDT relay may be connected if the output performance is required for more than one function. Anyhow the relay may be selected for PCB mounting type for simplicity of construction and ease of operation. The relay gives isolation to the output circuit from the main PCB circuit. 

The relay may be dispensed with LED or driver transistor etc., based on how one wants the output to be performed. 

RC components

The relay gets energized for approximately 100 seconds and then it is de-energized after that automatically. The timing factor of energization depends upon the RC combination in the circuit. If one wants a longer duration of timing 100 MFD electrolytic capacitor may be replaced with 470 MFD or even 1000 MFD depending upon the delay time required. This can be selected only after the trial and error method. 

Alternatively one can use 1M ohm preset instead of the fixed value resistor. The preset can be adjusted such that the required time delay is achieved.  

To sum up

Always the assembling task should be a pleasurable one for happy construction and utility value. Build this circuit as you like with the above guidelines. Please put your comments and suggestions for the benefit of all.