emr

2 Articles

An Open Source Electromagnetic Resonance Tablet

January 14, 2026 by 23 Comments

Drawing tablets have been a favorite computer peripheral of artists since its inception in the 1980s. If you have ever used a drawing tablet of this nature, you may have wondered, how it works, and if you can make one. Well, wonder no longer as [Yukidama] has demonstrated an open source electromagnetic resonance (EMR) drawing tablet build!

The principle of simple EMR tablets is quite straight forward. A coil in the tablet oscillates from around 400 kHz to 600 kHz. This induces a current inside a coil within the pen at its resonant frequency. This in turn, results in a voltage spike within the tablet around the pen’s resonant frequency. For pressure sensing, a simple circuit within the pen can shift its resonant frequency, which likewise is picked up within the tablet. The tablet’s input buttons work in similar ways!

But this is merely one dimensional. To sample two dimensions, two arrays of coils are needed. One to sample the horizontal axis, and one the vertical. The driver circuit simply sweeps over the array and samples every coil at any arbitrary speed the driver can achieve.

Finally, [Yukidama] made a last demo by refining the driver board, designed to drive a flexible circuit containing the coils. This then sits behind the screen of a Panasonic RZ series laptop, turning the device into a rather effective drawing tablet!

If tablets aren’t your style, check out this drawing pen. 

Continue reading “An Open Source Electromagnetic Resonance Tablet” →

On 5G And The Fear Of Radiation

April 8, 2020 by 178 Comments

The world around us is a scary place, with a lot of visible and invisible dangers. Some of those invisible dangers are pretty obvious, such as that of an electrical shock from exposed wiring. Some are less obvious, for example the dangers of UV radiation to one’s skin and eyes commonly known, but also heavily underestimated by many until it’s too late. In the US alone, skin cancer ends up affecting about one in every five people.

Perhaps ironically, while the danger from something like UV radiation is often underestimated, other types of electromagnetic radiation are heavily overestimated. All too often, the distinction between what is and isn’t considered to be harmful appears to be made purely on basis of whether it is ‘natural’ radiation or not. The Sun is ‘natural’, ergo UV radiation cannot be harmful, but the EM radiation from a microwave or 5G wireless transceiver is human-made, and therefore harmful. This is, of course, backwards.

Rather than dismissing such irrational fears of radiation, let’s have a look at both the science behind radiation and the way humans classify ‘danger’, such as in the case of 5G cell towers. Continue reading “On 5G And The Fear Of Radiation” →