Heat resistant microphone to attach to the Gene Cafe?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.

#1: Post by boren »

I just ordered an extra chaff collector cap and plan to drill a hole into it to attach a microphone inside the chaff collector (and maybe also a thermocouple at a later stage). Now I just need to find a suitable microphone. Any recommendations for one that can withstand high temperature?

Note that I cannot place the microphone (or my ear) close to the chaff collector exist because it connects to a pretty long exhaust pipe, that leads the smoke out of the window.

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BaristaBoy E61

#2: Post by BaristaBoy E61 »

I would start with a search high-temperature transducers, perhaps piezo or maybe even electret.

A guitar pickup might be an inductive pickup that would be at risk of having the varnish insulating the delicately wound wires of melting at high temperature and shorting making the device useless.

These wires are extremely thin and delicate, like human hair and measured in thickness in the 1000th of an inch like the wires in a phono cartridge. OK, I just dated myself. :mrgreen:

https://piezotechnologies.com/high-temp ... ansducers/
"You didn't buy an Espresso Machine - You bought a Chemistry Set!"


#3: Post by rmongiovi »

I'm not sure what you're trying to accomplish with a microphone, but is it really necessary to insert it into the hot air stream? I'd expect the Gene's chaff collector to be a pretty good resonating chamber. It's rigid plastic, after all. It still gets plenty hot, of course, but you could just attach a microphone to the outside and pick up sound by conduction. That might not be quite as stressful as inserting a microphone directly into the hot air.

boren (original poster)

#4: Post by boren (original poster) »

What I'm trying to achieve is to be able to hear first crack. It's quite difficult with the Gene Cafe, especially since I have an exhaust pipe attached to it.

And yes, I may not have to drill through the cap if I can find a microphone that's sensitive enough once attached to the outside of the chaff collector. Using a self-adhesive acoustic guitar pickup does look promising, thanks for suggesting this direction. If the adhesive doesn't last due to heat I can probably attach it more permanently using a bit of heat-resistant kapton tape.

Among those two metal-only pickups, which one do you think would be more suitable for this purpose:


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#5: Post by Marcelnl »

a simple accelerometer? Not sure if the noise results in enough vibration to be picked up but these things are pretty sensitive. (probably an acoustic guitar pickup is an accelerometer)
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boren (original poster)

#6: Post by boren (original poster) »

How would an accelerometer help with sound when it's intended to measure acceleration/movement?

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#7: Post by Marcelnl » replying to boren »

it measures acceleration, thus it can measure vibration...if you have a baseline vibration level during roasting I suspect that first crack will cause an increase above that baseline level.
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#8: Post by Marcelnl »

basically what BaristaBoy posted is an accelerometer, a piezo electric crystal will generate an electrical pulse when its compressed, using that principle you can measure acceleration/vibration/movement, it's amazing how precise and versatile these things are!
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#9: Post by Ken5 »

I don't know anything about roasting, or accelerometer in detail, but I use one in my banjo and it is amazing how accurate and sound isolating it is!!! Wonder how it would work in this instance though as the pickup does not pickup sound at all, it feels the vibration though it's clamp. I could scream into the tuner and it will not register a reading. Plus, the shorter and higher a note is the harder it is to pick out the sound.

Not saying it won't work, just wondering if it won't.

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#10: Post by ira »

A piece of tubing makes a decent conductor of sound. Putting a Tee in the chamber and putting the microphone in the end of a foot or two of tubing might work fine to keep it from overheating and still let it hear the sounds.