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Recommended Hardware / Software for Coffee Crack Meter

Posted: Sat Jun 16, 2018 4:51 pm
by Algo
Hi, I am looking to use a Pi to monitor the rate of crack for a coffee roaster (think popcorn cooking), near the end of the roast it produces high pitched cracks the rate of which I would like to measure in real time as it's a good indicator of when the roast is done.

I'm familiar with Python but not sure where to start with the project, does anyone have any suggestions on extra hardware I'd need or software libraries out there that may might be best suited?

Thanks,

Re: Recommended Hardware / Software for Coffee Crack Meter

Posted: Sat Jun 16, 2018 6:52 pm
by ericcooper
Sounds like a great project. You'll need some way of getting audio input, either with an audio HAT or a USB audio device.

Then you'll need to do some signal processing on the input. I'd recommend prototyping your algorithm on a desktop or laptop, using pre-recorded audio of the coffee beans during different points of the roast. Then when it's working reliably, you can move it to the Pi and do it in real time.

I haven't used it, but it looks like the aubio library ( https://github.com/aubio/aubio ) might provide some useful algorithms for your problem.

Re: Recommended Hardware / Software for Coffee Crack Meter

Posted: Sun Jun 17, 2018 7:24 pm
by Algo
The pre-recorded idea makes a lot of sense, I will work on that then worry about the rest later.

Aubio looks good, could be just what I need.

Now to find a microphone that won't melt!

Re: Recommended Hardware / Software for Coffee Crack Meter

Posted: Fri Jul 13, 2018 9:07 am
by Yukon Cornelius
Algo wrote:
Sun Jun 17, 2018 7:24 pm
The pre-recorded idea makes a lot of sense, I will work on that then worry about the rest later.

Aubio looks good, could be just what I need.

Now to find a microphone that won't melt!
Sounds like a great project ( no pun intended ) ..... I love to see innovative stuff like this !

I can only offer a suggestion on the hardware side ....

Brüel & Kjær make superb specialist microphone capsules for use in harsh environments ( both physical and chemical )
Expensive kit though .... from memory , the custom-made 4144 modules I used were around $400 , and that was 20 years ago !
They will need a phantom voltage of course , probably a pre-amp , and a very well shielded audio path .

We started our research using electret mics sourced from hearing-aid manufacturers ..... at best they lasted for days ,
and at worst .... a few hours :)

Re: Recommended Hardware / Software for Coffee Crack Meter

Posted: Fri Jul 13, 2018 12:38 pm
by Algo
Thank you for the suggestion I will look them up, I wasn't getting very far.