Vermes
Advanced Member level 4
Assumptions:
- easily available and cheap components
- FFT analysis, measurement of frequency
- amplify, bandwidth control
Written in C, about 7kB. It was written optimally.
Hardware:
Hardware of this device is also fairly simple. It uses LCD from Nokia 3310 with copper pads.
Atlega8 + LCD + dual amplifier AD8092ARZ, three keys and a few capacitors and resistors. Atmega works on 16MHz quartz. There is also a hardware filter LP (approx. 20kHz) designed in PSPICE. It was programmed for popular values of passive elements.
Construction:
2-sided board, so the LCD pads were on the other side. Solder mask was hand-placed. A large amount of flux was used. Housing Z24A, the pins were cut inside for rolling the housing, because the whole does not fit. In return, snaps were added.
The device is powered by 3 batteries AAA.
It is not equipped with a stabilizer, works in the voltage range of 2,8-5V.
It also does not have any mechanical switch, turning on and off is done in software. The option turn off is in the menu. In order to turn on – hold the “OK” key.
While working, the device consumes less than 20mA.
Off switch – POWER DOWN mode, current consumption less than 1uA.
Input voltage range -10/+10V. It can be adjusted through selection of the voltage divider at the input.
Features:
- 64 points fast Fourier transform
- change of the band: 20kHz, 10kHz, 5kHz, 2kHz, 1kHz, 500Hz, 200Hz
- percent gain adjustment
- automatic measurement of the signal frequency (for max. power of spectrum)
- frequency measurement made using the cursor
- measurement of the attenuation 0-30dB relative to the max. value
- stopping the measurement
- saving option (useful for determining the characteristics of the filters, audio tracks, etc.)
Scheme:
Link to original thread (attachment) – Analizator widma akustycznego