Last time I showed the final frequency response of Spectrum. I guess now I need to show the finished thing!
Minus a couple of tweaks, the circuit is basically finished. I just want to adjust the brightness of the LEDs and tune up the sensitivity of the comparators. I will follow with a video soon but I need to find a decent camera to capture the full effect.
With all of the sub-systems developed on a breadboard I moved to the next step of designing and ordering the circuit board that I would use for the final product. For now, I will skip over the design choices and jump straight to what happened when I received the board and what the mistakes were and how I have changed my design.
The system needs a way to listen to the sound around it and the natural way to do this is with an electret microphone. I will probably include a 3.5mm jack input to allow you to plug music straight in too.
As I said in the previous post, I want my filters to perform in the same way as the MSGEQ7. The frequency response of this chip is given in it’s datasheet.
From the datasheet I can see that, to replicate this response, I will need 7 bandpass filters at 63Hz, 160Hz, 400Hz, 1kHz, 2.5kHz, 6.25kHz and 16kHz. Each filter will need a quality factor of 6 (this basically sets the bandwidth of the filter).
It’s getting harder and harder to find spare time to work on projects. Firstly, the holidays at MIT are tiny compared to the holidays I get at Cambridge, and now that it’s finally Summer I am doing an internship which keeps me pretty busy 5 days a week, and I still want time to explore California and surrounding areas.
Anyway, I want to do a project that looks good and has some analogue electronics in it. I will build a system that listens to sound via a microphone, breaks the sound down into frequency bands and displays how loud each frequency band is using a strip of LEDs. It’s a similar idea to a Colour Organ but I want 7 frequency bands and 10 volume levels per frequency band (a total of 70 LEDs).