Hot Air Popcorn Popper - which probe length?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
ste
Posts: 35
Joined: 3 years ago

#1: Post by ste »

Hello all and thanks again for helping me out in my roasting journey.

Before I get hold of a proper roaster, can you please help me with my popcorn popper?

If the roasting chamber has a diameter of 7cm, would a 2cm long probe work well to detect been temperature, or is it too short?
K-type, 3mm thickness.

I would drill it inside the chamber.

Alternatively, I could go for a no brainer solution of using a Bosch Infrared Thermometer (gun) - not sure how accurate that would be though.

Thanks!

Stefano

marcism
Posts: 131
Joined: 11 years ago

#2: Post by marcism »

On my set up I actually run a naked probe to about an inch above the bean mass when it's off and then it's submerged at the top of the mass when they are roasting (expansion + movement).

I read somewhere here that having that set up means you're getting the reading of the bean mass heat as it leaves the chamber, as opposed to too low where you'll get the heated air messing with your readinngs. Works well for me and I adjusted the offset in Artisan to give me readings in line with what I expected (offset was only like 1 degree C anyway!).

With sheathed probes, you might see a bit of a slowed response, which I didn't want. I tried both but preferred the naked probes. I drilled into the top collar of my roaster at a 45 degree angle and then inserted the probe so the entry point was a cm or so above the metal "roasting chamber".

Here's some photos:



The probes run down to a plastic container that contains all my arduino, fan booster, stuff like that. That second probe? That is a naked probe that runs down the side and I bent open one of the air inlets to push it through, then bent the metal back to hold it in place. It is about 0.5cm away from the inlet and records the ET (enviromental temp) from the fan+heater!

Here's what the profiles look like in artisan (red is ET and blue is BT):

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ste (original poster)
Posts: 35
Joined: 3 years ago

#3: Post by ste (original poster) »

marcism wrote:On my set up I actually run a naked probe to about an inch above the bean mass when it's off and then it's submerged at the top of the mass when they are roasting (expansion + movement).

I read somewhere here that having that set up means you're getting the reading of the bean mass heat as it leaves the chamber, as opposed to too low where you'll get the heated air messing with your readinngs. Works well for me and I adjusted the offset in Artisan to give me readings in line with what I expected (offset was only like 1 degree C anyway!).

With sheathed probes, you might see a bit of a slowed response, which I didn't want. I tried both but preferred the naked probes. I drilled into the top collar of my roaster at a 45 degree angle and then inserted the probe so the entry point was a cm or so above the metal "roasting chamber".

Here's some photos:
image
image

The probes run down to a plastic container that contains all my arduino, fan booster, stuff like that. That second probe? That is a naked probe that runs down the side and I bent open one of the air inlets to push it through, then bent the metal back to hold it in place. It is about 0.5cm away from the inlet and records the ET (enviromental temp) from the fan+heater!

Here's what the profiles look like in artisan (red is ET and blue is BT):

image
Thank you very much for the photos and the great explanation! And very cool setup! I will definitely consider that !

1) Does your probe gets submerged as soon as the airflow starts?

2) May I know thickness and length of your BT probe?

3) I understood the probe should not move, but I guess in your case it does oscillate right ? Doesn't seem to affect your readings

4) how did you cut that bottom of that moka pot piece?
5) is that a Severin or a Poppery ? Just out of curiosity

marcism
Posts: 131
Joined: 11 years ago

#4: Post by marcism »

ste wrote:Thank you very much for the photos and the great explanation! And very cool setup! I will definitely consider that !

1) Does your probe gets submerged as soon as the airflow starts?
It sits just above the beans before it starts, and I'd say it touches the beans as the airflow gets going.

2) May I know thickness and length of your BT probe?
It is naked so there's no probe on the end. Probes work as a sheath that covers the two wires that are soldered together at the end like a little bead. The wire is probably 0.5mm thick or so.

3) I understood the probe should not move, but I guess in your case it does oscillate right ? Doesn't seem to affect your readings
It does not as far as I can tell, and if it does it must be almost nothing. This is due to the wire being VERY sturdy. It was a concern of mine too but that wire is quite rigid indeed.

4) how did you cut that bottom of that moka pot piece?
Simply unscrew the Moka from it's bottom piece, remove screen etc, and then I took a drill to it punching holes around the perimeter. Finished it off with a file. Works very well :)

5) is that a Severin or a Poppery ? Just out of curiosity
Keen eye! Severin. Over here in DE there's a lot of them on hand and there's a fantastic guide you can follow when it comes to modding the severin. I used this guide for the mechanical side, and then Lukas Grasse's guide + help from Ira on the board here for the software.

ste (original poster)
Posts: 35
Joined: 3 years ago

#5: Post by ste (original poster) »

marcism wrote:
Thanks a lot!!!

I have a Severin too, a colleague got it for me from Germany :)

Do you mind sending me a link to your thermocouple so I can see how it looks like with more clarity ? How could I search for it?

I would like add one probe like you did. And I will get someone to join my voltage regulator to the heating element!

Meanwhile I got a Bosch Universal Temp at special price since I work for them. I will use it till it instal the thermocouple !

Thanks again

Stefano

marcism
Posts: 131
Joined: 11 years ago

#6: Post by marcism »

Search for MAX6675 on eBay and you'll find a lot of them. This was used with my Arduino.

The Severin was great and easily does 125g with good control. I did boost the fan a bit from 24v to 28v.

ste (original poster)
Posts: 35
Joined: 3 years ago

#7: Post by ste (original poster) replying to marcism »

Thanks! So that silver color wire which I see is rather sturdy and won't move much! And I can see you removed the stealth from it!

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marcism
Posts: 131
Joined: 11 years ago

#8: Post by marcism »

You got it! I just used a pair of pliers to "unpinch" the cover and slid the cover off the wire. Worked well and honestly they are so cheap it's not a huge deal if you mess it up.

ste (original poster)
Posts: 35
Joined: 3 years ago

#9: Post by ste (original poster) replying to marcism »

Thank you so much for your help!!!

kina2
Posts: 9
Joined: 4 years ago

#10: Post by kina2 »

marcism wrote:Here's what the profiles look like in artisan (red is ET and blue is BT):image
Hey Marc,
So pleased to see how you manage to make those probes that come bunded with the MAX6675 boards useful!

Your roast profile in post #2 above includes power settings during the roast. I assume that is the heater power on your popper, rather than the fan power that is increasing :) Are you using sliders in Artisan to do that adjustment manually, or have you set multiple alarms to control the heater adjustments? And then if so, what does your PID do?

Just wondering if one could have a PID controlling one parameter (eg heater) while one also adjusts another during the roast.

Currently, I use a Severin popper with manual controls; dimmer for the heater and adjustable voltage power supply for my fan. Im about to start a second popper project to add artisan with PID as described in the Instructible that you linked to in post #4 above. As an IT-illiterate, I have been trying to get my head around the scripts, Artisan etc off and on over the past few months. I found your link to the power issues that Ira helped with very useful; Inconsistent Power Scaling with Arduino Control

My imperfect roast routine is to pre-set the heater power (about 7.x out of 10 on the dimmer) and control the roast by reducing the fan speed (25V down to 20V) in steps every 30seconds. This works as the beans are getting lighter and easier to move as the roast progresses but my fixed heater setting is dependent on the ambient temperature... :roll:

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