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'Wave Lights' electronics kit

'Wave Lights' is an electronics kit aimed at young people. Correctly soldering the components onto the included printed circuit board (PCB) creates a badge that visualizes strong radio signals (e.g. signals from mobile phones, WiFi routers or hand held radios). As a bonus, the badge also creates many fun light patterns.

Er is ook een pagina in het Nederlands aanwezig.

Main functionality

First, the badge can receive strong radio signals. The stronger the radio signal, the more LEDs will light up. You can for example detect if your mobile phone is currently transmitting, the strength of your home WiFi router signal. The badge is also able to detect hand held radios and other strong signals. In the manual it is described which two modes are available and what they mean (also see radio signal reception section below).

Second, the badge is able to display nice light patterns with the five LEDs. Seven different patterns are available, which can be selected via a button on the badge. The button can be used to move to the next pattern by using a short press, or back to the previous pattern by using a long press.

The following seven LED patterns are available:

Knight Rider
Bouncing ball
Alarm
Bubbles
Bit disco
Pulse
Highway

Availability

There are no Wave Lights badges in stock any more. But in the February 2017 issue of the VERON Electron magazine, an article about the Wave Lights was published (in Dutch) where all details about the badge are discussed in detail, so the badge can be built yourself. Also the PCB layout and the software is is available.

Contact

You can send your questions about the Wave Lights project to ivo [atsign] digiterraan.nl.

About the engineers

This electronics project was designed and implemented by Leo PA0LEZ and Ivo PA1IVO, with Leo mainly handling the electronics design and Ivo focussing on the IC software. Marianne helped a lot during the project, and Ronald PA5RB helped with the RF part of the electronic circuit. Thanks to Emco Electronics for supplying the means to make this project possible, and thanks to Mark KD7DTS for help with the English texts.

Building Wave Lights badges at the many places was made possible with the help of Koos PA3BJV, Benno PA3FBX, Paul PA0STE, Cees PA0CRB, Wouter PA3WEG, Wim PA3AKK, Dick PA0DFN, Berend PD1BK, Luc, Marianne and Linda.

Manual

In the manual you can find all the information you need to know to operate the badge. It is a PDF file in A4-format, containing two A5 columns of text. By double-side printing the A4 and cutting it exactly into two equal parts, you get two manuals in A5 format.

Building instructions

The building instructions can be found in a colour PDF file (1 MByte in size). When printing the manual, use a colour printer in order to see the red lines in the pictures. At the moment the instructions are only available in Dutch, but the instructions will be useful for everyone due to the graphical presentation.

PCB layout

The PCB layout is available as a set of Gerber files (zip file).

Software

The microcontroller program is available as .hex file. The fuse bits settings are: 0xFF, 0x56, 0x62 (extended, high, low).

As the external-reset-disabled fuse is enabled, an ISP programmer cannot be used after the fuse bits are programmed (so first download the hex file). An HVSP programmer (like the AVR Dragon) is required to program after the fuse has been set.

Pre-programmed ATtiny85V ICs are also available from Emco Electronics.

Schematic

Schematic of the Wave Lights electrical circuit.

Three of the LEDs (1, 2 and 5) can glow up very weakly when a button is pressed. This is caused by the fact that three I/O pins of the IC are both used as an output for a LED as well as an input for the push buttons.

Radio signal reception (technical details)

RF signals are received by the red wire of the badge (the handle) and rectified by diode D1 and capacitors C2 and C3. The amplitude of this rectified signal is measured by the ADC of the AVR microcontroller ATtiny85V.

The default length of the antenna wire is 35 cm which is sufficiently long to detect RF signal of 144 MHz and up (144 MHz works pretty well, 435 normal). Mobile telephones can be detected pretty well when they have a bad reception, but when they are in the close proximity of a base station it is hard to detect them with the badge. 2.4 GHz WiFi signal can also be detected, but here it is important to measure at the correct point along the antenna.

If measuring lower frequencies is desired, try using a longer antenna wire and experiment a bit. The highest frequency which can be detected mainly depends on the Schottky diode D1 (BAT81S). Measurements show that the sensitivity drops very fast above 2.5 GHz.

The badge can only detect 'strong' RF signals, namely those more that the voltage threshold of the Schottky diode (a bit more than 0.3 Volt). The ADC input of the AVR measures this voltage in a range between 0 Volts and the supply voltage (around 3 Volts), which is transformed into a value between 0 and 1023 The software in the AVR determines the relation between this measured value and the number of LEDs which will light up, see table 1 below.

'Normal':
LED lights at ADC value 'Linear':
LED lights at ADC value

LED 1 > 0 > 0

LED 2 > 5 > 250

LED 3 > 15 > 500

LED 4 > 30 > 750

LED 5 > 50 > 1000

	'Normal': LED lights at ADC value	'Linear': LED lights at ADC value
LED 1	> 0	> 0
LED 2	> 5	> 250
LED 3	> 15	> 500
LED 4	> 30	> 750
LED 5	> 50	> 1000

Table 1: Relation between the ADC signal of the antenna and the number of LEDs that will light up.

Current consumption

Table 2 below shows the current consumption of the badge measured at a supply voltage of 3 Volt. The last column mentions how long the batteries will last if you are using 2000 mAh batteries and the badge is used continuously in that condition.

Situation Current consumption Time [2000 mAh]

On - all LEDs on 5.8 mA 2 weeks

On - all LEDs off 0.8 mA 3.5 months

On - standby reception 0.85 mA 3 months

Off 19 µA 12 year