decibel meter with LCD screen

here is the circuit i have so far but i dont know how to write the code i am really stuck and have to finish it by monday please help!!!!

here is the schematic please help http://www.dfrobot.com/image/data/DFR0034/DFR0034_SoundSensor_SC.pdf

Firstly that circuit is an opamp based amplifier with a gain of 100. Capacitor C2 means it output will be centred around ground rather than 2.5V which is a problem - the output signal will be driving input pin protection diodes and won't really be meaningful if you want to measure sound levels.

To measure decibel levels you may need to do some signal processing (filtering) to modify the frequency response and then take the root-mean value over a suitable period of time and take the logarithm. This is not trivial - you also need to compensate for the frequency response of the microphone and calibrate the thing.

But the first issue is that C2 - it needs bypassing.

dbA weighting or dbC weighting? Or both? :grin:

here is the circuit i have so far but i dont know how to write the code i am really stuck and have to finish it by monday please help!!!!

You have a copy of the assignment and you don't know how to do it, but you want us to do the assignment without even seeing it. Good luck.

Don

i have bypassed capacitor C2 now, i need it for dba weighting. i dont have an assignment sheet, i was asked to make a decibel meter and that there was plenty of information on the internet, so i found this circuit online and haved wired it like in the schematic i posted.

100x Gain, so a 50mV will give the ADC the maximum 5v that it can handle, thats a small signal for sure, or a pretty big gain..

jay90: i have bypassed capacitor C2 now, i need it for dba weighting. i dont have an assignment sheet, i was asked to make a decibel meter and that there was plenty of information on the internet, so i found this circuit online and haved wired it like in the schematic i posted.

Who asked you to do, and WHY did you take the project you can't do? That must be interesting story, wait, I go get some popcorn...

BTW, where is the rest of the circuit? I don't see LCD?

Cheers, Kari

I made an SPL meter with my Arduino when I first got it, with an LCD and frequency feedback as well.

Hopefully I posted the code in the thread I had made on this forum…maybe there’s something you can use.

(note it was designed to measure low frequency, high output stuff so I never tested it on anything above 100Hz or so…)

can you put the link to your thread please i dont know how to find it. thanks

Hello

I am searching for a solution about make an decibel meter based on arduino, and I found the circuit of Philips- NXT: AN 1991, that is an Audio decibel level detector with meter driver. I would like your opinion about it.

Link: http://ics.nxp.com/support/documents/interface/pdf/an1991.pdf