What’s inside S Pen – How S Pen work?

Did you ever wonder what’s inside S Pen and how it work? As Samsung advertised when they released Galaxy Note, S-Pen is an input tool that provides a similar feel to an actual pen by detecting the pressure applied on the screen with great accuracy.

What's inside S Pen - How S Pen work

To knowing more about S Pen, we are going to explore some theories and the details inside a Galaxy S Pen.

Basic Theory of S Pen

Samsung partnered with Wacom to develop the S Pen. The pen works on the principle of Electromagnetic Resonance (EMR). Devices utilizing EMR Technology do not require any cable or built-in battery-based power supply at all.

What's inside S Pen - How S Pen work

When you pull out S Pen from a Samsung Galaxy Note and write on the Screen, an electromagnetic field is generated from a circuit behind the screen. The S Pen picks this up and uses it to power itself and figure out its position relative to the screen. It sends this, along with information from the S Pen button and the nib at the end, back to the Note phone.

What’s inside S Pen

What's inside S Pen - How S Pen work
What’s inside S Pen

As the Picture show above, you can see some components on the PCB:

  • Coil Assembly Push Button/Pressure Sense: Starting from the tip we have the coil assembly consisting of a 0.22 mm dia (approx.) wire wound on a soft iron core which is not cylindrical. The tip is connected to a spring at the base of the assembly which appears to be some kind of switch or a variable capacitor. This assembly consisting of the spring deals with the pressure sensing, either by bringing the coil close to the display surface by compressing the spring or by using the contacts at the base of the assembly as a variable parallel plate capacitor.
  • Push Button and Potentiometers (Sens Adj): We have the Push Button that is usually used for the air command interface followed by two sensitivity adjustment potentiometers.
  • Capacitors Bank: A bunch of capacitors connected in parallel to the coil thereby forming an LC resonant circuit. The little solder blobs below each capacitor are jumper connections. Therefore as shown above, from left to right the first capacitor and the last capacitor are not connected in parallel with the coil.

So that all what’s inside S Pen and how a S Pen work. Amazing just how much technology is surrounding the Note. Even in places where you don’t immediately expect.

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