jannus wrote:There was this post some time ago on the same subject..

RoastLearner for Artisan: train Artisan to listen to your roast

I've never tried it but it seems very practical? Either way it speaks to artisan as well!

intersting, I wonder if it also works on a hot air roaster like the Genecafe, the air flow may cause loads of noise.

Take your new spare cap, and make a 1 inch round hole in it. Attach aluminum foil OVER the hole (make air tight). Mount a tube over the foil (round end of the tube aligned with the round piece of foil). Place a more typical microphone in the tube about 3 inches from the foil tympanum... when you get a pop, this will cause the foil to vibrate and send sound up the tube (which is not in the air flow). If you cap the end of the tube (furthest away from the roaster), this will make it perform better and pick up fewer "gene cafe noises".

This design allows your microphone to stay cool, and gives a good pathway for sound. I have a Gene Cafe as well, and hearing the pops can be difficult, especially with peaberry beans.

I am considering doing something very similar, as holding a carboard tube cupped against my ear for a couple minutes at a time is a bit of a drag. It makes it hard to watch the roast, while my head is turned sidewards. I roast outside, so venting smoke is not an issue for me.

Marcelnl wrote:great idea, that is in a Bullit I assume?
Not sure if the Genecafe has a trier...but the principle may be adaptable.

Yes an Aillio Bullet.

You could try using something like my RadioShack Mini Amplifier-Speaker (cat. no. 277-1008C) which I use for setting the beat on pendulum clocks. It's about the size of a pack of cigarettes and uses a probe that consists of an alligator clip connected to a wire that plugs into the amplifier. You can attach the clip to any part of the roaster that's connected to the roast chamber. Freq response is 100Hz to 10kHz. RadioShack went out of business but you should be able to find a similar gadget elsewhere.

[edit: the alligator clip probe I use is specially made for use in amplifying the clicks and other sounds made by clock mechanisms, like the following example: https://www.ebay.com/itm/332952590176?m ... olid=10050 ]

I just tried using the RadioShack audio amplifier with the alligator-clip pickup clipped onto the lip of the hood on my Sweet Maria's Popper and it does a great job of making the first and second cracks audible above the noise of this very noisy roaster. The amplifier and transducer used to amplify the sound of clock ticks really does selectively accentuate the snapping sound of bean cracks while roasting, making them more audible above the background roaster noise.

When thinking about a sensor appropriate for use in hot, harsh environments that that can reliably detect impulsive noise, an automotive knock sensor comes to mind. Here's a dev board that might facilitate getting started: https://www.ti.com/tool/TPIC8101EVM#included

Phil

Forgive me for playing the devil's advocate here, but when I had my Gene difficulty hearing first crack seemed like the least of its problems. From a quality of roast standpoint it seems to me that the major lack is the inability to measure actual bean temperature. Given that, trying to improve the ability to detect first crack seems like a fun mod but not one I'd spend a lot of money on.

I can't argue with your concerns about bean temperature. This is why hearing first and second crack are so important, as they act as a temperature benchmarks in lieue of actual bean temperature measurments. I also use the changing from full yellow to light browning as another temperature benchmark. I think a lot of Gene Cafe users read profile postings from other Gene Cafe users and duplicate the steps and times for the same bean (or in some cases, the family of beans).

Obviously, this is not a precise as having better metrics. It does prevent the users from drowning in a sea of information, as some newbies experience with better instrumented roasters. I have recently started using an optical pyrometer pointed at a specific area of the glass which has the maximum contact with the beans. Keep in mind the optical pyrometers only measure the first surface they "see". The glass drum on the Gene Cafe is heated by inside air, but cooled by outside air. However, the glass is reliably 340 F at first crack. This is a valuable thing to know with beans that are much more quiet during first crack, like peaberries and decaf coffees.

The Gene Cafe also forces you to pay attention to the appearance of the bean itself (seam spread, puffy-ness, cracks, color). You pay more attention to smell and smoke. The smell certainly changes throughout the roast, and offer a strong indication of what stage the roast is at. Time to Yellow beans, and Time to first crack gives a coarse Rate of Rise. The change in temperature seems to be pretty gentle, as the drum is not heated by anything other than the hot air blown through the drum. This tends to cause less large exagerations in the temperature curve.

Disclaimer: I make no claim of being a pro with the Gene; I am still very much learning. I will say that most books are written from the perspective of a metal drum roaster with heat applied to the drum for roasting. This means all of the great books require interpretation and adaptation to assist understanding a Gene Cafe roast process.

I tried the suggested alligator clip microphone on the Gene Cafe, and the machine noise burried the sound of the first crack. I could hear first crack with the cardboard tube to the ear method, but never heard it come out of the amplified speaker the microphone was attached to.

I use this https://www.amazon.com/Lisle-52500-Mech ... SQYSM?th=1. A mechanics stethoscope is used to pinpoint noises that are hard to find in a cars engine. I put the end where the exhaust exits the roast chamber. It is inexpensive and works great. There are some that are less expensive, some that are more expensive.
Curly