Choosing a thermocouple for a La Peppina - Page 3

Recommendations for espresso equipment buyers and upgraders.
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Bluecold

#21: Post by Bluecold »

GreatDane wrote:Interesting thread. :shock: I don't understand why you would want to take something as simple as a La Pappina and complicate it with a PID. I have had mine for a week, and once the pot boils (nature's indicator) :D I just turn the heat off. With all of the hot water up their I have found the temperature to be very stable and I am pulling some very nice sweet shots. Besides the awesome shots, what I enjoy about a lever machine is the simplicity.

Les
I did it. Mainly because i can turn it on and it stays on just fine. I can pull a shot, walk away, drink my shot and decide 30min later i'd like another one. So i just walk back to the Peppina, grind my beans, dose, tamp and pull. Sometimes i leave it on a whole day. No waiting and turning off or counting schemes. And a PID isn't complicated on the user end. It's a complicated piece of electronics inside, but on the outside it's just the target value and the process value.
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."

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ddr
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#22: Post by ddr »

For posterity:

I found some more reference material at Omega.com which is very helpful. They say that stainless steel and Inconel are commonly used in the food industry, and their wire insulation document lists which insulations are appropriate for submerging. Here is a link:

http://www.omega.com/prodinfo/thermocouples.html

Look for the Thermocouple Info Links.
Dan
LMWDP #242

JimG

#23: Post by JimG »

Dan -

I have a few comments that you might find helpful:
  • Chances are very good that you can use a grounded thermocouple. Good quality controllers like the Fuji generally have "common mode rejection" circuitry that will ignore stray AC. Digital signal filtering is also available on this controller if there is residual noise.
  • The docs for the Fuji PXR3 suggest that your controller can be configured (set Pn-2 = 1) to accept a Pt100 RTD sensor. (I have a controller like yours and have confirmed that the controller will accept that value. But I have not actually tested with an RTD connected, so treat this information accordingly).
  • Despite the preceding statement, I think a grounded type T thermocouple is your best bet for this application. I would suggest either a washer-style for external sensing, or a 1/16" stainless sleeved sensor for internal sensing. I also suggest teflon/teflon (i.e. PFA/PFA) insulation on the leads.
Jim

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ddr
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#24: Post by ddr »

Thanks Jim,
I will look deeper into the docs regarding the RTD, it would be nice to have more flexibility, although I think I will stick with the Type T (as you suggested) unless I see an RTD real cheap. I am glad you pointed out the PXR3's ability to ignore noise as I can get faster response times with the grounded TC.

Thanks for the PFA/PFA suggestion, I was looking at those as they rate "good" for flexibility and "excellent" for water submersion.

So, cool. I am looking for:

Type T
1/16" stainless sheath (6" inch or shorter)
Teflon/Teflon insulation
grounded

Looks like the one Ian mentioned earlier (TTSS-116U-12) is a good one if I shrink it to 6" and decide on ungrounded or grounded.

What I will do is try to investigate whether or not there is an external spot on the boiler which tracks the water temp in the boiler (using the K Type TC provided with the PID). If there is no good spot I will probably order a TTSS-116G-6 (6" grounded).

Thanks again. I hope no one is bothered with me beating this topic into the ground; I am trying to make a proper decision and record the process for the next reader.
Dan
LMWDP #242

GreatDane

#25: Post by GreatDane »

Bluecold wrote:I did it. Mainly because i can turn it on and it stays on just fine. I can pull a shot, walk away, drink my shot and decide 30min later i'd like another one. So i just walk back to the Peppina, grind my beans, dose, tamp and pull. Sometimes i leave it on a whole day. No waiting and turning off or counting schemes. And a PID isn't complicated on the user end. It's a complicated piece of electronics inside, but on the outside it's just the target value and the process value.
Thank you for taking my question as an honest question, not as a smart remark. That makes sense! It would be nice to not have to mother the machine as much as I have done the last couple of days. I would love to see a picture of your setup. Now I am thinking about a PID for my La Peppina. It would be nice to have the convenience.

Les
LMWDP #079

GreatDane

#26: Post by GreatDane »

ddr,
I don't think you are beating this to death. I have done some reading on thermocouples and PIDs and am still in the fog, however there is at least light coming through now and I am not in the dark! I may follow your path with my La Peppina. Please keep us informed.

Les
LMWDP #079

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Bluecold

#27: Post by Bluecold »

GreatDane wrote:Thank you for taking my question as an honest question, not as a smart remark. That makes sense! It would be nice to not have to mother the machine as much as I have done the last couple of days. I would love to see a picture of your setup. Now I am thinking about a PID for my La Peppina. It would be nice to have the convenience.

Les
Image
The cigar box wasn't a good idea. Water leaked in (its a kitchen afterall) and i turned it on, not knowing it was wet. The controller blew up.
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."

User avatar
cafeIKE

#28: Post by cafeIKE »

ddr wrote:Thanks again. I hope no one is bothered with me beating this topic into the ground; I am trying to make a proper decision and record the process for the next reader.
You're more than welcome. When I did the PID on the Vibiemme HX, I did research for six months. Assembled all the bits, prefabbed the connections. Took only 60 minutes to install. Less Haste, More Speed.

Cupla points :
Measure the resistance between each power pin of the A/C cord to the chassis of the Peppina. If both pins are essentially open circuit, i.e. several megohms, an ungrounded TC is unnecessary.

Neatness counts, so consider TC location and whether / where you want a wire hanging about for several years.

Over size the SSR. 20A is good for 115v espresso machines. 30A is better.

Get an SSR with Zero cross operation. It generates less noise and is easier on the element.

Add a heatsink of adequate capacity for the SSR. Seat it with a non-hardening heat sink compound. Arctic Silver makes good stuff. [Stainless steel is a poor heat conductor.]

Use wire rated for the job. 105°C as a minimum. Auto shops usually carry it.

Use high quality connectors and a proper crimp tool.

Make sure all connections have drip loops.

When / If you auto-tune, start @ ~180°F or about 20-30° below set point.

JimG

#29: Post by JimG »

JimG wrote: The docs for the Fuji PXR3 suggest that your controller can be configured (set Pn-2 = 1) to accept a Pt100 RTD sensor. (I have a controller like yours and have confirmed that the controller will accept that value. But I have not actually tested with an RTD connected, so treat this information accordingly)
Just for the record, I have now tested my PXR3 with a 3-wire Pt100 RTD and found it to work just fine.

Jim

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ddr
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#30: Post by ddr »

Thanks Jim, can you post the part number on yours (if it is visible; don't bother removing it if it is mounted).
Dan
LMWDP #242