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'Sound Kit' electronics kit
'Sound Kit' is an electronics kit aimed at young people. Correctly soldering the components onto the included printed circuit board (PCB) creates a badge that visualizes the volume and frequency (the pitch) of sound via the microphone. As a bonus, the badge also creates a light scanner like used for example used by Kitt in the Knight Rider series.
Er is ook een pagina in het Nederlands aanwezig.
The front and back of a ready built Sound Kit.
You can send your questions about the Sound Kit project to pa1ivo [atsign] xs4all.nl.
Ronald PA5RB, Ivo PA1IVO and Leo PA0LEZ.
The building instructions can be found in a colour PDF file. When printing the manual, use a colour printer in order to see the red lines in the pictures. The instructions are only available in Dutch, but the manual will be useful for everyone due to the graphical presentation.
In the manual you can find all the information you need to know to operate the Sound Kit, however in Dutch only. 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.
Spectrum mode testing
By playing the special .wav file, the spectrum mode of your Sound Kit can be tested. Hold your Sound Kit close to the speaker: the .wav file plays first eight tones that will light the leds one-by-one and second four dual tones that light two leds simultaneously.
The .wavfile plays the following tones:
500 - 750 - 1000 - 1250 - 1500 - 1750 - 2000 - 2250 - 500+1500 - 750+1750 - 1000+2000 - 1250+2250 Hz.
Schematic of the Sound Kit electrical circuit.
- SW1: Spectrum mode
- SW2: Volume mode
- SW3: On/Off
- SW4: Disco mode
- TP1: See Auto calibration below
|Part & reference
||Name / value
|| Manufacturer part number
||Supplier & order code
||2.7 kΩ 1%
||33 kΩ 1%
||15 kΩ 1%
|Resistors R8 ... R16
||1 kΩ 1%
||1.5 nF (pitch 2.54 mm)
||4.7 µF (6.3 x 11 mm)
||RS Pro 711-1784
||10 nF (pitch 5.08 mm)
|Leds D1 ... D8
||5 mm red 120°
|Switches SW1 ... SW4
||Tactile Switch off-(on)
|Reichelt MCE 100
|IC socket U1
||28 pins (2 x 14) 7.62mm spacing
||ASSMANN WSW AR 28 HZL/7-TT
|IC socket U2
||8 pins (2 x 4) 7.62mm spacing
||ASSMANN WSW AR 08 HZL-TT
|Op Amp U2
||Low-Power Op Amp
||Battery holder 2 x AAA
||Keystone Electronics 2468
||2 x 1,5 Volt AAA
Electronic parts Sound Kit.
The PCB layout is available as:
The PCBs are manufactured at Safe-PCB.
The microcontroller (ATmega88, device signature 0x1E930A) firmware is available as .hex file. The fuse bits settings are: 0xF9, 0xD6, 0xE2 (extended, high, low).
The microcontroller uses the internal RC oscillator as clock base, which is factory calibrated. To check and possibly improve the factory calibration, the auto calibration function is available in the Sound Kit. For determining the sound frequencies in the 'Spectrum mode' it is important that the clock runs at the correct frequency of 8 MHz (the clock is not divided by 8 by means of the CKDIV8 fuse).
For pre packed kits the auto calibration has already been done, so it only needs to be performed when you are programming the microcontroller yourself.
The auto calibration uses an external signal as an reference:
Auto calibration procedure:
- Frequency: 1 kHz
- Amplitude: 3 V (signal low 0 V, signal high 3 V)
- Shape: square wave
Pin 14 (PB0 / TP1) outputs a square wave signal which (at an exact internal clock frequency of 8 MHz) toggles every 64 µs, and thus provides a 7.8125 kHz square wave. By monitoring this point the calibration can be checked. During the auto calibration you can monitoring the 'search algorithm' for the correct calibration value.
- Remove the power from the PCB.
- Connect the external 1 kHz signal between pin 9 (PB6) and ground at pin 8 (GND).
- Connect pin 10 (PB7) to ground somewhere (for example pin 8 or pin 22 or another ground on the PCB).
- Supply the power (3 V) to the PCB again.
- The Sound Kit will now perform the auto calibration for about 15 seconds. The calibration found will be stored in EEPROM so it will also be available after a power loss.
- When the auto calibration is ready, the "disco mode" will start automatically.
- Remove the external signal from pin 9 and the connection on pin 10.
© 2018 by Ivo Klinkert, PA1IVO - Contact