• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer
Build Electronic Circuits

Build Electronic Circuits

Electronics explained in a simple way

  • Start Learning
    • Basic Electronics
    • Digital Electronics
    • Circuits
    • Practical Skills
      • Printed Circuit Boards
    • Microcontrollers
      • Arduino
    • Maker Lifestyle
      • Podcast
  • About Me
  • Blog
  • Products
  • Contact
You are here: Home / Mail Archive / How to make a simple touch sensor

How to make a simple touch sensor

September 25, 2017 By Øyvind Nydal Dahl 20 Comments

Touch Sensor Circuit DiagramYou only need 3 components.

A transistor, a resistor and an LED.

See the video below to see how I connected it. Or skip the video if you prefer to read how to connect it.

Connect the resistor and LED in series from the positive supply to the collector of the transistor. Choose a resistor that sets the current of your LED to around 20 mA.

Connect the emitter of the transistor to the negative terminal of the supply.

Now, create two wires with exposed ends – so you can see the metal.

One goes to the positive supply. The other goes to the base of the transistor.

This is all it takes.

Now, try to touch these two wires with your finger – and the LED lights up!

The reason is that your finger acts as a resistor and will give enough current to the base of the transistor to turn it on.

This is one of the circuits you will build in «Getting Started With Electronics». Along with other fun and simple circuits, to get you started in electronics. Get it here:

https://www.build-electronic-circuits.com/products/ebook-2nd-edition/

Keep on Soldering!
Oyvind

Filed Under: Mail Archive

Reader Interactions

Comments


  1. StarDust says

    March 17, 2015

    That’s more clearly even I know how to build it.

    Reply

  2. victor says

    March 25, 2015

    Pls explained the it wel ..I have never use vero board before so create a video on how to link components on vero board …pls that just i need for now…thanks

    Reply

    • admin says

      March 26, 2015

      Veroboard is the same as a stripboard – check out this: https://www.build-electronic-circuits.com/stripboard/

      Cheers!
      Oyvind

      Reply

    • jsrobson10 says

      January 16, 2018

      It’s nearly the same as a stripboard, just a little different.
      https://goo.gl/images/ALQmeh
      This image shows the breadboard and the black lines show where it conducts the electricity.

      Reply

  3. calvin says

    March 26, 2015

    good i wanna try it

    Reply

  4. joyce says

    November 22, 2015

    If i touch a wire with my right hand and the other with my left does the LED turns on?

    Reply

    • admin says

      November 23, 2015

      Exactly =)

      Reply

  5. TR pooja says

    January 5, 2016

    I tried it in a breadboard but it doesn’t work .
    Can u pls explain.

    Reply

    • admin says

      January 8, 2016

      Hi,

      It could have something to do with the LED and the resistor you use. Try a lower resistor value for R1, such as 100 Ohm.

      Best Regards,
      Oyvind

      Reply

  6. Hari says

    April 5, 2017

    Sir, please explain the application &use

    Reply

  7. N V S Akhil says

    July 21, 2017

    hello plz could u help me to build a simple touch circuit

    Reply

  8. Vishy the Fishy says

    September 18, 2017

    hey buddy ty for the idea

    Reply

  9. Rohan Indurkar says

    October 13, 2017

    Sir I need your help I want your email ID please mail it to me

    Reply

  10. Faseeh Haider says

    December 19, 2017

    SIR PLEASE GIVE ME ITS PLACEMENT ON PCB ,, I NEED IT BADLY

    Reply

  11. simo says

    March 7, 2018

    Hi thank you for your post. I would like to make a variation of your circuit to apply it to a problem I am currently working on: I want circuit A to send a signal when I switch it on by touching with my left hand, and circuit B when I touch it with my right hand. Now, those circuits have a common ground and in order to close circuit A for example I have to touch the common ground and the other branch of the circuit with my left hand. However when I tested it I detect a cross talk that I am not sure how to get rid of. Do you have any suggestions on how to make it work?

    Reply

  12. Axel says

    January 24, 2019

    Thanks for this fun little project. Took me a while to find a transistor that could do the job, but in the end I used an old BC237 that I had laying around.

    The circuit is fun as I can see the led intensity change based on the wetness of my finger, ie how the base current controls the collector to emittor current.

    Reply

  13. samantha says

    February 17, 2019

    In your other transistor tutorial you use a battery to supply current to the base to turn the led on and off which makes sense to me. However I am still confused about how your finger is supplying the current. Is it because you are completing a seperate path for the electrons to flow from negative to positive? Thank you!

    Reply

    • admin says

      February 19, 2019

      The current flows through my finger from plus to minus. Without the finger, there’s no path for the current to flow through the base. The finger acts as a resistor, allowing some current to flow from plus, through the finger, through the base and down to minus/gnd.

      Reply

  14. Martine Akida says

    January 21, 2020

    Sir, where to apply this

    Reply

  15. Sarah says

    September 12, 2020

    Which type of touch sensor is this ….?

    Reply

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Primary Sidebar

Search:

Footer

Topics

  • Basic Electronics
  • Digital Electronics
  • Circuits
  • Practical Skills
  • Microcontrollers
  • Maker Lifestyle
  • Newsletter Archive

Social:

  • Facebook
  • Twitter
  • YouTube

Copyright © 2021 · Ohmify AS · Terms and Conditions · Privacy Policy