EMR technical resources

General resources

• Electronics

  • Sabins - Understanding Inductors

  • Lesics - The beauty of LC Oscillations!

  • The Organic Chemistry Tutor - LC Oscillator Tank Circuit

• Drawing tablets

  • Digital Art Tablet Guides - The Insides of Some Tablet Pens!

  • rukozhop - This video shows the internals of a Huion PW100 pen

  • Satoshi Uchino, et al - A full integration of electromagnetic resonance sensor and capacitive touch sensor into LCD

  • https://junyichen083.commons.gc.cuny.edu/technical-description/

Wacom resources

• Wacom Digitizer Implementation Guide: https://fcc.report/FCC-ID/GKR-TP00062BWD/2506839.pdf (archived link)

• Wacom: EMR Stylus (Electro-magnetic Resonance): How Wacom Pens work https://community.wacom.com/us/emr-stylus-electro-magnetic-resonance-how-wacom-pens-work/

• Wacom: EMR (Electro-Magnetic Resonance) Technology https://archive.is/mhHkP

• Wacom: How the Wacom cordless, batteryless pen work https://quietpc.sk/instructions/wacom/tech_bam_en.pdf

• Wacom Patents https://patents.google.com/patent/US4786765A/en https://patents.google.com/patent/US4878553B1/en

• Wacom: Wacom feel EMR https://wcm-cdn.wacom.com/-/media/graveyard/wacomdotcom/archived%20images/enterprise/technology-solutions/2015-12-21/f_emr_datasheet_12192015.pdf?la=en&rev=5973a6a064ce4f57b20a049410aed106&hash=A479EA340EE48BD510113192CCC3D271

Scanlime resources

• The Scanlime videos are the deepest examination on drawing tablet tech I have found.

• Scanlime: Your Wacom pen is an Electric Pendulum (https://youtu.be/oKVCwPn6OPI)

  • 1:10 a tuned LC circuit can act as an EMR pen

• Scanlime 013: Graphics Tablet Primer for Hackers (https://youtu.be/nPab7pbOhBY)

  • Accompanying write up: https://scanlime.org/2016/08/scanlime013-wacom-teardown-and-schematic/
  • This video shows an Huion H610PRO tablet and Huion PEN80 (rechargable) battery-powered pen.

  • Key points at around 24:20

    • 24:22 buttons lower the frequency of the oscillation

    • 24:41 the nib is plastic and does not affect the inductance of the coil

    • 24:44 the nib moves a small ferrite core that changes the inductance of the coil.

    • 24:50 Pressure decreases inductance which decreases energy stored in the magnetic field and slightly increases the oscillation

  • Other points

    • 25:35 Shielding freom electromagnetic interference

• Scanlime: Wacom Teardown and Schematic - (https://youtu.be/j4AKwJERxOw)
• What’s Inside those Wacoms, And How Can You Use Them In Projects?(https://makezine.com/article/maker-news/whats-inside-wacoms-can-use-projects/) (archive: https://archive.is/wip/wr9mn)
• Key points:

  • "At this point the Wacom and Huion designs diverge. Huion’s pen [PEN80] is a single-transistor oscillator. Pressure on the nib changes the frequency from 255 to 266kHz by tuning the inductor, and the two buttons switch to 235 or 245kHz with additional capacitors. The simplest Wacom pen would be a resonant LC circuit tuned to 750kHz. To transmit button and pressure status, an additional digital circuit modulates the resonant damping to send out individual bits of sensor data on each carrier burst."