Digital Touch Sensor Using LM358

Sensors are the best thing to work around with DIY electronics and this is the second instructable of a series of Instructables which creates different sensors compatible with various microcontrollers. In the previous instructable, I showed you how to build a digital tilt sensor. In this instructable, I'm going to show you how to build a Touch Sensor. This has various applications such as Touch Controlled switches, doorbells, etc.

This instructable will require soldering skills it is easy to learn to solder and there are various YouTube videos that show you how to do that.

Here is a list of what you need to get started with this instructable.

• LM358 IC
• 10K Pot
• LED
• 330 Ohm Resistor
• PCB (Optional)
• Connecting Wires
• 5v Power Supply
• Breadboard
• Soldering Iron
• Soldering Wire
• Soldering Flux
• Multimeter (Optional)

The Circuit is quite simple, the heart of the circuit is an LM358 IC, this IC is used to detect when the copper plate is touched. The copper plate is a small block of PCB which is used for etching out circuits. The LM358 has a voltage range of 3V to 32V, which can be easily powered with most microcontrollers.

The 10K pot can be used to change the sensitivity of the circuit, if the led remains ON even without touching the plate vary the pot until the LED turns off.

If the LED doesn't stick to the Copperplate, use sandpaper or a file to make the surface rough and then flux to stick the soldering wire onto the board.

After you have tested out the circuit on a breadboard next you can build a PCB out of it, there are two ways you can do that one would be to build Arduino shield and another would be to make tiny PCBs that could plug into a breadboard Arduino prototype shield.

If you have any queries, feel free to leave a comment below or PM me and I would try to help you.