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My Third Roaster
BenGeldreich
KK,

Thanks I had a quick email chat with the supplier of the thermocouples. Below are his thoughts.

1) It is very unlikely the grounding will cause the reading lower. Normally, if there is a grounding issue, the reading will be very unstable. The thermocouple signal is in micro volt level. The grounding noise is in the mv level or higher.

2) The problem is related the sensor used. The sensor you have is originally designed for measuring plastic injection mold temperature (solid metal). It will be slow to respond the air temp change. It will be significantly affected by the mounting base temperature. To measure air, you need a thin and long temperature probe. The thin probe makes the response faster because air has much lower thermal mass than solid metal. The long probe make the interference from the mounting site to be minimal. TC-K5 or TC-K3MM will do better job. If the TC-K3MM is too long, you can bend it to save the space.

3) The location of the sensor will affect its reading. Without knowing the heater location and how the heat flow, I can't comment on your system. Are you sure that the location of the sensor should have the same temperature as the coffee beans?

Seems fair and truly what I suspected. So I am going to purchase a K type long probe like my current ET and mount it inside the wooden box below my pot. THis will be an easy change as the holes are already in place I just need to mount the probe at the exact height so it just pokes up into the bean mass. I don't think the placement is a 50?F variance issue. THe current placement is right in the mix and can't imagine a bean not hitting the probe on every pass.

Not having an accurate BT reading is most likely the cause of my tipping issue so hopefully this "will kill two birds with one stone". Though I would never actually kill a bird.

Ben
Edited by BenGeldreich on 12/02/2011 10:35 PM
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Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
Koffee Kosmo
That is an excellent response and communication from that supplier

We will see what transpires when you get a more suitable probe

KK
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
BenGeldreich
I finally finished my TC4C project box and thought I'd post some pictures.

Big shout out to Jim and Jack for all there support!

I found the wooden box as a set of two in Michaels, which is a hobby store, for $2.99. I got the switches, and LED's from a local Radio Shack style shop. Most or the square wholes were drilled then filed to shape.
BenGeldreich attached the following image:
img_0541.jpg

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Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
BenGeldreich
Here's a shot of the back.

I was shaking a bit in these shots so you will have to excuse the camera shake.
BenGeldreich attached the following image:
img_0543.jpg

Edited by BenGeldreich on 12/22/2011 3:52 PM
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
BenGeldreich
The inside of the project box.
BenGeldreich attached the following image:
img_0545.jpg

--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
BenGeldreich
With all LED"s lit up and the lights down low. ;)
BenGeldreich attached the following image:
img_0544.jpg

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Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
JackH
Nice job with the enclosure Ben. It looks great! Clean wiring job too.

Have fun with the roaster.

--Jack
 
BenGeldreich
I have also recently mounted a new K-type thermocouple. I wasn't happy with the original BT thermocouple that I purchased. I mounted the probe to my motor mount assembly. I am hoping to get a faster response from this and a closer reading when hitting first crack.
BenGeldreich attached the following image:
img_0552.jpg

--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
BenGeldreich
Lastly I added a part of a thin silicon matt that I had lying around to the top of my wooden box. I did this to prevent the wood from getting the full force of the heat from the bottom of my pot and to keep the smoke grease off the wood and on to something I could clean if need be.
BenGeldreich attached the following image:
img_0548.jpg

--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
allenb
I vote Ben's TC4 case best and sexiest to date! This is stunning and I'm now ashamed of my little gray plastic box.

I'll bet this would fit in perfect with Jon's "D*&%nation" steampunk roaster design.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
 
Koffee Kosmo
Beautiful work on the TC4 & K type probe
Now that you have had the roaster up and running for a while!

How are the roasts ?

KK
I home roast and I like it. Designer of the KKTO
Roaster Build information
https://homeroast...ad_id=1142

https://docs.goog...lide=id.i0
Blog - http://koffeekosm...gspot.com/

Bezzera Strega, Mazzer Robur Grinder, Pullman Tamper Convex,
(KKTO) Turbo Oven Home Roaster.
 
seedlings
Wow, these are some of the sexiest roaster gut shots I've seen! Well done!

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
BenGeldreich
Thanks for the kind words on the TC4C project box!

KK,

You will be the first to know!

Ben
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
BenGeldreich
With the holidays behind I had a chance to roast yesterday!!! Woot Woot!

I am still having BT thermocouple issues!! With the new TC4C I was able to focus on RoR but soon discovered that I was getting a 60 F variance throughout the roast. I quickly changed to just watching the beans to try and save the roast.

After the roaster had cooled I ran the following test. I took the metal colander where the beans sit out and ran the TO with both the ET and BT exposed. When ET hit 300 F, BT was at 222 F! I think that the temps are too far apart for both thermocouples being exposed. It is to my understanding that a TO is convectional and in a convectional oven the airflows from the heater down the sides and back up the middle. If that is true my only thoughts are that a vertical BT thermocouple would not read the same as a horizontal thermocouple due to the airflow of the convectional TO.

My thoughts are to mount the BT probe right underneath my ET on the side so the tip slides into the side of the Bean mass as others have done.l I could use a wire bead type thermocouple and move it around the bottom holes till I find the sweet spot but mounting it and the possible long term damage to the tip is preventing me from trying that.

Ideas? Thoughts? Am I way off on this?

Ben
Edited by BenGeldreich on 12/30/2011 3:42 PM
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
lmclaren
Hi Ben, It is unclear from the photos, but where the thermocouples attach to the board, are you extending the cables to a socket on the back? If so, you will loose the cold end reference, the thermocouple wire / thermocouple socket should be directly attached the the board. Note sure if it would make that much difference though.

Have you tried putting both thermocouples together and immersing in boiling water and ice water to see if they agree with each other?

I had real problem with one of my thermocouples when I let the metal probe touch the metal of my roaster, the readings where all over the place. I ended up replacing the probe with a bead so it remained isolated from the metal work, it is now totally stable.

best regards

Lee
 
BenGeldreich
Lee,

Thanks for your reply!

Quote

lmclaren wrote:
Hi Ben, It is unclear from the photos, but where the thermocouples attach to the board, are you extending the cables to a socket on the back? If so, you will loose the cold end reference, the thermocouple wire / thermocouple socket should be directly attached the the board. Note sure if it would make that much difference though.


The thermocouples are attached to female sockets which use an extension of the same thermocouple wire to attach to the TC4C. From what I've read there may be a slight variance because the thermocouple aren't directly hooked up.

Quote


Have you tried putting both thermocouples together and immersing in boiling water and ice water to see if they agree with each other?


I tried the boiling water test last night! I added two thermometers one digital and one analogue. I discovered that the BT probe was always 2 degrees higher than the ET probe and both thermocouples were a couple degrees higher than my thermometers. There was never more than 8 F difference between all of them. I let everything sit for 10 minutes and upon my return everything had reach the same reading of 96 F.

Quote


I had real problem with one of my thermocouples when I let the metal probe touch the metal of my roaster, the readings where all over the place. I ended up replacing the probe with a bead so it remained isolated from the metal work, it is now totally stable.

best regards

Lee


I too feel like this had been the issue with my BT thermocouple attempts. Both BT thermocouples that I mounted have always been touching some type of metal which is part of the roaster. I'm still not sure if I'm getting an air reading or the metal hole where the probe sticks up into the bean mass.

My thoughts are to ask omega build me a 4" K-Type probe with an exposed tip like this. http://www.omega....E&Nav=

If my logic is correct an exposed tip would not touch any metal and would only take a reading from the air or items that are in direct contact with the tip. Right now I am using a grounded thermocouple. It is correct to say that a grounded thermocouple takes its reading from the outer casing of the probe and not just the tip?

I have also thought of a way to mount the probe on the side but would prefer to keep the BT mounted underneath.

Thanks for the help!!

Ben
Edited by BenGeldreich on 01/01/2012 2:58 PM
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
lmclaren
The fact that the sensors are not too far from each others readings is encoraging, I expect if you terminated onto the board the TC's should read the same, I find all my TC's are within .5C of each other.

I use just a bead on the end of the insulated cable to measure air, to measure beans, you could mount the thermocouple using an insulated holder, I have used porcelain insulators before and they work well.

http://www.jaycar.com.au/productView.asp?ID=HM3182&keywords=porcelain&form=KEYWORD


To measure bean temp, I now use:

http://www.instrumart.com/products/32275/micro-epsilon-cs-series-infrared-thermometer

I am using a fluid bed roaster and as the beans are in flight most of the time, I did not like the chances of reading the bean temp with a thermocouple, I can recommend the IR enough.
 
lmclaren

Quote

It is correct to say that a grounded thermocouple takes its reading from the outer casing of the probe and not just the tip?


No, the temp is measured at the TC junction, probably at the tip of the probe, the problem is that the TC wires are not insulated from the metal enclosure which means that any earth potential will also flow into the TC signal. TC signals are very very small.

I expect in commercial equipment the TC interfaces are floating and do not have the same problem, commercial interfaces are expensive to buy.

I think it will work well if you keep the probe away from metal.

Lee
 
lmclaren
But I expect you are also correct for another reason, the body of the probe will conduct heat, so while it is measured at the tip, the heat further down the probe will be conducted to the tip and affect the readings.

Lee
 
BenGeldreich

Quote

lmclaren wrote:

No, the temp is measured at the TC junction, probably at the tip of the probe, the problem is that the TC wires are not insulated from the metal enclosure which means that any earth potential will also flow into the TC signal. TC signals are very very small.



Lee,

Thanks! Excuse the ignorance but when you say any "earth potential" are you referring to loose voltage trying to ground itself? If all the electrical equipment used in my roaster are grounded then why would there be any loose voltage? Or is there always fly aways! :)

Quote


I expect in commercial equipment the TC interfaces are floating and do not have the same problem, commercial interfaces are expensive to buy.

I think it will work well if you keep the probe away from metal.

Lee


Yeah the price is my only concern when looking at commercial TC's.

Ben
Edited by BenGeldreich on 01/01/2012 5:21 PM
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
lmclaren

Quote

Thanks! Excuse the ignorance but when you say any "earth potential" are you referring to loose voltage trying to ground itself? If all the electrical equipment used in my roaster are grounded then why would there be any loose voltage? Or is there always fly aways!


While the voltage on all the metal work is 0 when measured on a multimeter, there is in reality a very large voltage in thermcouple terms, eg

100F is only 1.521 mV or .0015V, wont get a reading on a multimeter!

http://www.omega.com/temperature/z/pdf/z218-220.pdf

As you can see, the voltages are very low, no problems as long as you dont introduce earth loops, eg earthing at multiple points.

Just keep it away from metal and it should be fine, you should be able to see the problem by just watching the readings while touching and untouching the probe on the metal.
 
lmclaren
More information than you could ever want about thermocouples:
http://www.omega.com/temperature/z/pdf/z021-032.pdf

Z-28 mentions earth loops.
 
JackH
Ben, I had similar issues with grounded type metal sheath probes. JimG said it might be a ground loop problem like you were describing. It is especially a problem with the two prong power packs we use to power the TC4 and the metal roasting pot.

My solution was to change the BT probe to a bead type. The response is much faster with the open bead too. My only concern is contamination of the probe from the oils and other stuff. I guess they are cheap enough to get spares.

He also suggested that you could also run a ground wire from a good ground to the TC4's ground pin.
Edited by JackH on 01/03/2012 12:13 PM
 
BenGeldreich

Quote

JackH wrote:
Ben, I had similar issues with grounded type metal sheath probes. JimG said it might be a ground loop problem like you were describing. It is especially a problem with the two prong power packs we use to power the TC4 and the metal roasting pot.

My solution was to change the BT probe to a bead type. The response is much faster with the open bead too. My only concern is contamination of the probe from the oils and other stuff. I guess they are cheap enough to get spares.

He also suggested that you could also run a ground wire from a good ground to the TC4's ground pin.


Thanks Jack!

I'm only running USB to power my TC4C. Not sure if that still applies?

I have narrowed down the issue to what I believe to be, air flow and my original BT placement. I am in the process of moving the BT to the side below my current ET probe to see if there is a difference. I'll post the results when it's done.

Ben
Edited by BenGeldreich on 01/04/2012 10:22 AM
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
BenGeldreich
Roasted 453g of Brazil last night. My goal was to see if the new BT location would give me a closer reading, using FC (395?F - 405?F) as my desired temperature reading. I've attached a pBourbon graph of my roast because I haven't yet experienced a roast quite like this.

I pre heated the roaster to 300?F and dropped in the beans. Once I dropped in the beans the temperature didn't drop all that much. I decided to keep the RoR low to slow down the drying process and prevent cooking the outside of the beans. Once I visually saw that the beans were yellow, I increased the voltage to ramp to FC, I got excited as my BT click over to 400?F but quickly faded when it past 415?F and still hadn't heard a snap. I finally started to hear snapping at 425?F but it sounded almost like a rapid second crack. I saw that ET was starting to get above 500?F and was trying to keep that below so I killed the roast.

Upon inspection of the beans, there is some tipping and some scorching but some of the beans look fantastic. Looking at the graph you can see that both ET and BT are not smooth and go up and down every second. I haven't seen this yet even when testing air flow. Anyone have any ideas on A.) Why the temperature isn't dropping when the beans are added and B.) Why the BT and ET go up and down every second on the graph?

I ended up with 390g of beans but haven't cupped it yet.

When pre heating I have been lifting the TO off the roaster, pouring in the beans and then immediately putting the TO back on the roaster. Is that the correct way to pre heat using a TO roaster?

Ben
BenGeldreich attached the following image:
120109roast2040.jpg

Edited by BenGeldreich on 01/10/2012 12:58 PM
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
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