Introduction: Credit Card Sized Contactless Voltage Detector (555)

The idea came looking at other Instructable:

I have chose the design with the 555 because I had several 555 around and I like build small projects, like this other credit card sized project.

Step 1: The Circuit and Components

This is a screenshot from the project of :

The Component are:

  • 555 Timer
  • Credit card
  • battery holders (recycled)
  • 2032 coin batteries
  • 10 kΩ resistor
  • 220 Ω resistor
  • 4,7 μF electrolytic capacitor
  • buzzer
  • led
  • switch
  • copper tape (antenna)
  • epoxidic glue (few drops)


  • solder
  • cutter

Step 2: First Prototype

As you can see in the photo, pretty ugly.

But it was working, so I started to work to the final version.

Step 3: Final Version

As you can see in the video it is working and with good sensitivity, actually I had to keep the antenna very short due to the high sensitivity.

I used a 1kΩ resistor instead of 220Ωto reduce the sound of the buzzer .

Pocket Sized Contest

Participated in the
Pocket Sized Contest