I was wondering if there were any recommendations for a roaster data logger that uses a thermocouple inside the bean mass as it's turning? I'm not interested in PIDing it, just accurately getting repeatable bean temps. Even if it is not measuring the internal temperature of the bean, that might be ok if it was consistent.

The ones I looked at online seem pretty expensive.

thanks,

dan

You could try this:

http://roasterthing.com/?q=Logging

I make it and it only works with my software but it's reasonable.

Ira

That looks very interesting and useful. Do I have to buy thermocouples? What sort should I get?

You're really done a lot of work --

Regards,

dan

It uses type K thermocouples. You can but them from Omega, eBay or other places I don't know of. They seem to range from $2.00 or so to $20 or a bit more. I'm currently using $2.00 ones in my Behmor. Using my board BT automatically logs 2 temperatures. It also displays them on the next roast if you want to match the profile.

There are some not very good screen captures here:

http://roasterthing.com/?q=RoastCoffeeMenu

Ira

You can get a variate of them from eBay. The type K loggers are the most common and least expensive. Most of the inexpensive units have a large tolerance but for what you are doing it is not that big of a deal. I use a Fluke 54II two channel logger, it does a half dozen different thermocouple types. If you ever want to use something like a Scace you will need more robust logger. You can also get type K bead TC's relatively inexpensive off the bay as well. They are not calibrated/certified but again, for what you are doing, you do not need 0.01F accuracy. You can even make your own if you happen to have a TIG welder

Dave or anyone else,

Do you end your roast "by the numbers"? Currently I use an IR hand held thermometer, but really only use it to monitor and control (manually) heat rise. I know it is not accurate, but it does tell me when the bean mass is getting hotter. I kind of do a mental average, since it can be plus or minus 15 degrees. I shoot 3-4 times and so it's not a problem. If the rate of heat rise is too slow, I increase the propane and vice versa.

What I want to get is a measurement that will tell me what I'm guessing at right now:

When to pull the beans right before they go into 2d crack?.

I was thinking if I found a temperature and it was repeatable (accurate is important, repeatable is) it might help.

Any suggestions/advice on this matter?

Thanks

dan

DJR wrote:What I want to get is a measurement that will tell me what I'm guessing at right now:

When to pull the beans right before they go into 2d crack?.

Hi.

The second crack depends on the internal temperature of the beans. And a BT probe only reads the surface temperature of the beans (not the inside). That means that as long as you keep the same Rate of Rise (RoR aka as delta BT) then the temperature of the second crack will be approximately the same (assuming same load, same beans, consistent roaster, etc). But if you were to do a different finish phase (ie. with different RoR) then the second crack temperature will show up with a different BT surface temperature. For example, a faster RoR will make the second crack appear at a higher BT surface temperature. If the profiles are identical, and everything else identical, then you can do what you are after but with some margin error.

There was a recent thread about picking meters here:

Choosing thermometry equipment for home roasting

Cheers

The onset of second crack (and 1st) will vary by bean and a dozen other variables. One good indicator is smell and smoke. Just before second crack the aroma will turn heavier and you will get a big jump in smoke output. 30 or so seconds after that second crack usually starts. I rairly go to second crack. city+/full city is about as dark as I will roast but some beans will do good roasted to the onset of second. Brazils as a general rule, will not. They go ashy well before second where a Sumatran and Yemen will often take the heavier roast.

That's been my experience as well, but I was wondering if there was an actual magic number the numerically inclined have found. I guess not. So I'll continue to refine my nose. My problem is that recently I've been roasting about 3.5 pounds at a time. Before that, about 2 pounds. At 3.5 the roast seems to be able to take on a life of its own and generate heat faster towards the end of the roast than I am applying to it.

At least that's been my experience. I've found that taking the hood off the roaster right after 1st crack seems to slow things down and keep them from getting out of hand.