You probably remember Bilbo Baggins' sword Sting? It glows in the dark when evil orcs are around, but they are not yet visible.

There are people who believe that radio waves and radiation of any kind is harmful and would negatively affect body and mind, well - just like orks.

For these people, there is now WiFi Sting! If there is an evil wifi in the surrounding area, the magic crystal starts to glow. Isn't that wonderful?

Supplies

NodeMCU / Wemos D1 mini /ESP32 /ESP8266 or any other WiFi-Arduino

4+ LEDs (blue)

1 or 4 100Ohm resistors

white wire

9V battery + clip + switch

jar

transparent plastic film/gift wrap

wood, clay, … for the base

sandpaper

wire winder + shrink tube

Step 1: The Electronics

For the electronics, we need a wifi-enabled Arduino and a few LEDs. The Arduino searches for WiFi networks in the surrounding area. Depending on the number of wifi networks, the LEDs start to light up. The strength of the wifi connection is not measured.

I use blue LEDs with a clear body. This way they are a little camouflaged later in the plastic foil of the "crystal".

The + connections of the LEDs are connected to pins D5-D8 on a NodeMCU Amica. The - poles run to ground via a 100 Ohm resistor.

Alternative: If you give each LED its own resistor, the light will remain the same brightness, no matter how many LEDs are on.

For a quick fixing of the wires, I used a wire winder. This wraps the cables tightly around the connections. In addition, I fixed the whole thing with heat-shrink tubing.

The LEDs are sanded a little with fine sandpaper so that the light becomes more diffuse and is better spread in the plastic film.

(Of course, you can connect more LEDs. You just have to change/extend the software slightly.)

Step 2: The Software

I hope you know a little bit about Arduino IDE? There are a lot of good tutorials here at instructables.com, so I don't need to explain it here anymore.

Set IDE on your Arduino (ESP8266, ESP32, Wemos D1, ...) and transfer "WiFiSting.ino". That's it.

The Arduino scans for wifi networks every 5 seconds. Depending on how many networks are active, the LEDs light up accordingly. They also sparkle a little.

In a residential area, the crystal will light up brightly (indicating radio wave danger), in the forest you are probably safe from wifi but may be standing alone in the dark.

WiFiSting.ino
Download

Step 3: The Crystal

The crystal consists of a jam/cucumber/olive jar and heavily crumpled gift wrap.

Wrap each LED in a little foil and then add another layer. Put the package in the jar and make sure it is filled well.

Step 4: The Base

I made the base of the crystal out of oak wood. But you can also make it out of clay, Fimo modelling clay, plaster or plastic. The main thing is to have room for the Arduino and battery. The switch is attached to the underside in a small drill hole.

If necessary, fix everything a little with hot glue.