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My Third Roaster
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
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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
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Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
jedovaty
Ben - I got the same ROR graph like you, with the up/down/up/down, try to adjust the filter setting in the code -- I forget exactly where it is, either in the pBourbon or aBourbon, but if you increase the number from the default of 85, it'll smoothen out (but add a bit of lag). I'm at 92 or 93, but think I need to go higher.

What TO do you have, what kind of wattage is it?

I'm getting the same bean temp stalling you are at what seems like FC. I'm running more tests, but I theorize if we want to stick below 500 ET, either we need more heat intensity (e.g. another heating element), or move the bean mass closer to the heat source, or combine one of these with a different amount of beans. Think of it like heating up a cup of water with ice cubes. The temp of the water will not change until all the ice cubes melt.

I want to go as far as saying that the variac is causing this (like my router control), you'd be better off with something like the SSR with potentiometer, as it will provide the full heat source to help raise the BT while keeping ET right. However, I see others using variacs with similar setups succesfully, so I don't know what's we're doing different.
Edited by jedovaty on 01/10/2012 3:38 PM
 
BenGeldreich

Quote

jedovaty wrote:
Ben - I got the same ROR graph like you, with the up/down/up/down, try to adjust the filter setting in the code -- I forget exactly where it is, either in the pBourbon or aBourbon, but if you increase the number from the default of 85, it'll smoothen out (but add a bit of lag). I'm at 92 or 93, but think I need to go higher.{/quote}

Thanks I will look into it.

[quote}
What TO do you have, what kind of wattage is it?


I am using a Galloping Gourmet model with 1470 Watts.

Quote


I'm getting the same bean temp stalling you are at what seems like FC. I'm running more tests, but I theorize if we want to stick below 500 ET, either we need more heat intensity (e.g. another heating element), or move the bean mass closer to the heat source, or combine one of these with a different amount of beans. Think of it like heating up a cup of water with ice cubes. The temp of the water will not change until all the ice cubes melt.


You can ignore the data on the graph after FC. I pulled the beans just forgot to hit the eject button and turn everything off. What I want to know is how people are pre heating when using a TO roaster. If you look at my graph when I added the beans the temperature only went down 40?. My goal is 5 minutes for drying or for the BT to reach 300?F / 5 minutes ramping to FC / and 3 - 5 Minutes finish depending on the bean and or the roast level I want. Because the BT only went down 40?F I had a RoR of 8?F for the first 5 minutes then increased it to ramp to FC. It is a very shallow RoR which is my main concern.

Having said that I haven't cupped it and will post an update when I do.

Quote


I want to go as far as saying that the variac is causing this (like my router control), you'd be better off with something like the SSR with potentiometer, as it will provide the full heat source to help raise the BT while keeping ET right. However, I see others using variacs with similar setups succesfully, so I don't know what's we're doing different.


I have had many successful roast with a Variac on my SCTO. I don't think it has anything to do with that at all. If anything it's me and how I am using the Variac. But this particular roaster is new(ish) so volume and the amount of beans I use have to change is I can't achieve the results I'm looking for.

Ben
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Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
jedovaty
Okay, then I will go back to my corner of inexperience, I tried :)

My roasts have yet to have a successful looking profile, however, they seem to hit 300F in about five minutes if I preheat to 375-400F ET; the probe for BT, which is a little lower, is around 380F. I preheat, lift the TO off with one hand, drop the beans in, then cover it; the BT probe reads a dropped temp of 150-160F. I hope it is helpful despite the issues I'm having.
 
JackH
I usually pre-heat to about 300F and let it run for 5 minutes adjusting the variac to maintain 300F. This is mainly to get the roaster pot all heated and stable in my cold garage. If I roast softer beans like sumatra or brazil I go lower pre-heat temp to prevent tipping or burning and keep the power lower during the roast.

I open the top and dump in the beans and close like Ben said. Then I raise the variac to full power. The BT and ET will drop. The BT drops to about 150F and then begins the "turning point" up. Then it is full power until just before 380-390F (which always seems to be first crack for me).

I reduce power to try and get a RoR of 8-10 degrees per minute before 390F so it does not go into second crack too fast. A balancing act of time, timing and temperature. I try and keep the ET below 500F. I read somewhere that temperatures above 500F and total roast times longer than 15-16 minutes are not good. Could depend on roaster type.

On my roaster, I have a chaff ejector that is a piece of spring steel covering a square slot in the spacer ring that I open when I see the chaff satellites. This usually helps drops the temp down.

This seems to works for me and my roaster. No expert here. I haven't been doing this very long either.
Edited by JackH on 01/11/2012 4:18 AM
 
BenGeldreich
Thanks guys!

The fact that both of you pre heat the same way as I do, and both of your thermocouples indicate that the BT drops to 150 aprox then the only thing left for me to do is to invest in a better thermocouple. Unless the amount of beans I'm using could cause the temperature to only drop 40 degrees.

Thoughts?

Ben
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
jedovaty
Hi Ben, take with a metric cube of salt with my no-experience. I do 400g batches, which are ~50g off yours, not that much difference. I use 24ga for ET and BT:
http://www.omega....t/5TC.html

They're not very expensive. Also, how are you making the connection between TC and the Arduino? Are you using all the TC wiring, or do you have any "normal" wires in the mix?
Edited by jedovaty on 01/11/2012 2:19 PM
 
BenGeldreich
Jano,

Quote

jedovaty wrote:
Hi Ben, take with a metric cube of salt with my no-experience.


I have been roasting coffee for less then a year so I fall into the rookie category as well!! Any ideas are always welcome :)

Quote


I do 400g batches, which are ~50g off yours, not that much difference. I use 24ga for ET and BT: http://www.omega....t/5TC.html They're not very expensive.


Thanks I am in the process right now of building two exposed probes with Omega.

BT: NB1-CA-SS-18-E-4RP-TT48
ET: TJ48-CASS-18E-3

It will most likely cost me $95 with shipping which is way more than i wanted to spend but I here nothing but great things about there probes. To be honest if $95 gives me the readings that I can trust then it's worth the investment. LOL!

Quote


Also, how are you making the connection between TC and the Arduino? Are you using all the TC wiring, or do you have any "normal" wires in the mix?


The probes are currently connected to a mini female connector in the project box (see previous pictures of my TC4C project box for details) and then the same thermocouple wire is used to connect the female connectors to the board.

Ben
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
BenGeldreich
I cupped the Brazil coffee this morning and it's FANTASTIC!!! I am a fan of Brazilian coffee but it is by far the best roast I have tasted with my new roaster.

Ben
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
jedovaty
Ben, I did a similar thing, had some expensive thermocouples in my basket. For ET, I chose a 6" exposed: KMTSS-020E-6. I forget what it was for BT.

However, decided I'd just go the cheap route as the bead type are relatively cheap ($7/pop) and so you can replace them without second thought in case they get covered in gunk. I got the fine-enough gauge ones were response time is around 1 second. The only drawback so far, the bean probe has become a bit frayed because of how I installed it. But it works fine :)

Just another opinion, but get what you are most comfortable with!

Good news on the brazil. Did you cup alongside another coffee, or just straight up? As one very new-newbie, I've learned that doing it together with other coffees is VERY helpful (after a few days rest, I ask the gf to switch them around, too, so I can do it blind).
Edited by jedovaty on 01/11/2012 5:16 PM
 
BenGeldreich
So after a few months of roasting and modifying I thought I share some changes I've made that have proven to be quite successful.

When I last posted I was having trouble getting accurate BT with my probe. I decided to purchase a 5 pack of k-type beaded thermocouples from Omega (5TC-KK-K-24-72) http://www.omega....amp;flag=1 along with a standard protection tube (SS-316-6OPEN) http://www.omega....amp;flag=1 and a OMEGAlok compression fitting (SSLK-316-18) http://www.omega....amp;flag=1. I mounted the tube underneath my roaster, where the probe used to sit, and fead the thermocouple through it. I now hit FC at 400? every time!! :)

farm8.staticflickr.com/7181/6775487584_9f007c0d4c.jpg

farm8.staticflickr.com/7196/6921601521_0c065fb952.jpg

farm8.staticflickr.com/7053/6921597483_33337ba9f2.jpg

While watching the roast's, I noticed that the stirring arms weren't flipping the beans that were caught near the centre but agitation was much higher near the outside. Using the same theory that some SCTO builds have done I decided to make a centre cap to keep the beans out of the stirring assembly. I found an oil cap at a local hardware store that was the perfect diameter. Modified the cap to and voila! Now the beans don't get trapped and the agitation is much better than before. :)

farm8.staticflickr.com/7184/6921597135_6328da8f82.jpg

Inspecting the roasts I am still getting some tipping (no more scorching) but I'm currently playing with the volume of beans to see if I can find the sweet spot.
Edited by BenGeldreich on 02/22/2012 4:44 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

Quote

Inspecting the roasts I am still getting some tipping (no more scorching) but I'm currently playing with the volume of beans to see if I can find the sweet spot.


Regarding tipping
Its the amount of agitation your roaster set up is doing

I found that the mid level of the bean mass needs good agitation
So you may need to alter or add to your agitator arms so by its action, will agitate to both the lower and higher parts of the bean mass
You have seen my agitation test videos

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

Quote

Koffee Kosmo wrote:

Regarding tipping
Its the amount of agitation your roaster set up is doing

I found that the mid level of the bean mass needs good agitation
So you may need to alter or add to your agitator arms so by its action, will agitate to both the lower and higher parts of the bean mass
You have seen my agitation test videos

KK


Yes I have seen your agitation videos!

I am going to wait and see what difference this oil cap makes as my last roast had very little tipping. I have been roasting 455g batches and am going to try half of that working my way back up to 455 and see if it make any difference. I am also struggling with keeping ET below 500? which may also be the cause. My suspicion is the overall volume of my roaster is a little to high. But I'll keep playing with it cause I'm getting closer every roast!
Edited by BenGeldreich on 02/22/2012 9:03 PM
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Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
jedovaty
Hi Ben, seeing as we've kind of been on similar build tracks, I'll chime in with what I've learned on my roaster.

When I keep my ET (measured slightly above the bean mass halfway between the center and side of the colander) below 500 (I shoot for max 475), I have no tipping or scorching - give that a shot if you can!

Changing batch size and increasing my agitation speed only led to a more even roast (my sweet spot is 350g and agitation speed increased by adding two more arms since I'm not sure how to overclock a window wiper motor).

I like the idea of the center cap, I'm going to work on adding one as well since I get a few straggler beans just getting pushed around the center. Thank you for sharing that! :)
Edited by jedovaty on 02/22/2012 9:45 PM
 
BenGeldreich

Quote

jedovaty wrote:
When I keep my ET (measured slightly above the bean mass halfway between the center and side of the colander) below 500 (I shoot for max 475), I have no tipping or scorching - give that a shot if you can!


Thanks for the advice! I am planning to use a beaded type thermocouple for ET on my next roast but I will try and get it right above the bean mass and see what my ET readings are like.

Quote

jedovaty wrote:
Changing batch size and increasing my agitation speed only led to a more even roast (my sweet spot is 350g and agitation speed increased by adding two more arms since I'm not sure how to overclock a window wiper motor).


I read that you had added two more arms and that you lowered your batch size which helped you find the sweet spot. I'm glad you shared that information it started me thinking about agitation and batch size. I don't recall you posting any photos of your new stirring arms on your thread.

Not sure if you seen these links but this is where i pulled all my info on wiper motor and wiring them.

http://www.scary-...wipmtr.htm
http://www.scary-...ipmtr2.htm

Quote

jedovaty wrote:
I like the idea of the center cap, I'm going to work on adding one as well since I get a few straggler beans just getting pushed around the center. Thank you for sharing that! :)


The centre cap really improved overall agitation in my roaster. I will say that cutting the cap to allow the arms to go through had to pretty precise to allow the cap to stay down without lifting up durning a roast. If it lifts off the insert, beans start getting trapped underneath. I measured three times and cut once to find my first attempt very accurate. I played around with some magnets as well but found it was to mush strain on the motor.
Edited by BenGeldreich on 02/23/2012 3:03 PM
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Ben

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

Quote

Koffee Kosmo wrote:

Quote

Inspecting the roasts I am still getting some tipping (no more scorching) but I'm currently playing with the volume of beans to see if I can find the sweet spot.


Regarding tipping
Its the amount of agitation your roaster set up is doing

I found that the mid level of the bean mass needs good agitation
So you may need to alter or add to your agitator arms so by its action, will agitate to both the lower and higher parts of the bean mass
You have seen my agitation test videos

KK


This is a video of my current agitation with the new centre cap. I added some red beans to see the agitation in action. Do you think it's enough or should I look into adding a few more arms.


Edited by BenGeldreich on 02/23/2012 11:06 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
What I see is the red beans in relatively one position, they appear to circumnavigate the pot & bob up and down like a cork on water

From experience I would recommend that the beans need a more through mixing

This is a quote form my blog

Quote

Q. Explain how the roaster agitates the beans?
A. I have spent countless hours fine tuning the agitator to have a complete mixing action rather than to push a mass of coffee beans around the roasting bowl
The main purpose of the agitator shape is to mix the beans in a specific way that is to move the beans from the centre out and back to the centre again
The action also cycles the beans from top to bottom in a helix pattern while also allowing the beans some intermittent rest time.


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
More updates!

I've added two new arms and modified my original spring arms to help with agitation. I added two pieces of steel strappings to agitate the middle / top of the bean mass, while the spring arms now act as bottom feeders.

The steel strapping is very easy to bend and manipulate so changing angles is easy but finding the perfect one has been more of a challenge. After a couple weeks of testing I think I found an angle that works well for a pound of beans. I have shaped the new strapping like a small smile or smirk. High point on both the inner and outer edges and low point in the centre. I angled the strapping in the centre slightly downwards so the beans squeeze out either side of the centre.

Here is a youtube video of the new arms and agitation.



On another note I have finally found a better solution then silicone to hold my BT in place. I was finding that after a couple roasts that I would have to re apply high temp silicone to my BT tube and wire to keep it from falling though. Looking through my hardware bin and came across a small collet for my Dremel tool.

farm8.staticflickr.com/7205/6816537622_dabb473dc4.jpg

I cut off the tapered end. Filed the freshly cut end down so the 4 pieces reach a point. This point acts as a compression fitting. I filed enough off as to not pinch to hard on the wire but enough so it won't fall through the tube. A light but firm compression. I put the wire through the collet and held the the BT wire in my desired position and then snapped the collet into the tube. The collet snaps into the tube because to the groves on the top.

farm8.staticflickr.com/7176/6798639892_c59c304e45.jpg
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
Koffee Kosmo
Thats a great agitation action Ben

It should also equate to better more even 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.
 
BenGeldreich
And here is a shot of 434g of Rwanda that i just finished roasting.

farm8.staticflickr.com/7055/6816807910_87d64be409.jpg

No sign of tipping or scorching and the roast is very even.

Here is a copy of my pBourbon graph of the roast.

farm8.staticflickr.com/7058/6962972655_d68ec09dd8.jpg

Notice that I still went above 500?F. So my question now is if I increase the volume of beans to 500g or 600g should I see the ET lower? My methodology is the more beans = less air movement = bean mass retains heat better. Am I way off? IF so then I may need to make a false bottom to lower my overall volume of the roaster.
--------

Ben

Turbo Oven Roaster w/ Variac, TC4Cw/ Bourbon | Bezzera Strega | Baratza Vario Grinder | Yama 5 Cup Syphon | Aeropress
 
Koffee Kosmo
Do you have a false bottom now ?

If not and you decide to install a false bottom, you should have by volume 7 to 9 litres for best results

This is also a good opportunity to add insulation for better heat stability
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.
 
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