Knock sensor to listen for bean crack

Is it possible to add a knock sensor (generally used in the car engine) to listen for bean crack (first and second)?

Well volunteered sir :wink:

If you can get something like that to work…we’re “all ears”. :sunglasses:

There are thumps and sounds that the beans create just from tumbling and lodging between the front edge of the drum and door. So, a solution to pick “cracks” would need to listen for a range of crack sounds and eliminate the other non-crack related noises.

Here’s a thread where discussed other technical and non-techy solutions to hearing cracks:
Speaker/sound feature

I’m coming over from the car world. If you are involve in tuning car engine, Motec is definitely on the top of the list.

Motec has this device called the standalone knock control module Motec Knock Module, you can attached a knocked sensor Bosch knock sensor and listen to all the “noises”.

If you think it’s noisy in a coffee roster drum? think how noisy it is in a car engine with piston and valve slapping at metal @ thousands of rpm. This knock sensor has the ability to withstand high heat while listening to all sort of noise.

The approach is to listen to all noises and record them especially during the first crack and second crack and pick a frequency range that provide the highest signal to noise ratio.

I’m not saying that it’s easy, but I’m offering a solution which has been successfully implemented in the auto industry for decades.

There are many other tech which are currently been widely utilize in the auto industry that the espresso machine industry should pick up and I think this knock sensor would be the one for roasting industry.

NOW, even better is that I have a couple of these motec knock module sitting around which I’m happy to lend one to Aillio for experiment. (Unless they are willing to send me a bullet which I can mod it on!) :wink:

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Here is the link to the pdf file for the knock module link

This is a hell of an idea! Maybe we can also adjust the timing to smooth out our curves…

Maybe they were testing a knock sensor on that torched Bullet that Tom at Sweet Maria’s showed off in a recent YouTube video and took the car engine idea a little too far…

I can’t imagine letting my Bullet get into that bad of shape. Your comments are right on the mark.

There’s a piece of software that someone developed about 5 years ago called Roast Learner that does just this using a $9 USB microphone and Artisan.

I think that project died and last I read was no longer working with Artisan either…there was some thread on home-barista.com I think…

Do you know how the knock sensor actually work? Is it some piezo microphone?
I could not find any datasheet for the bosch sensor.