Inexpensive Temperature Controller

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another_jim
Team HB

Postby another_jim » Nov 19, 2005, 2:30 pm

I posted this to a lever thread, but thought I should give a heads up here.

Dwyer Instruments (Love division) is manufacturing and selling a thermocouple temperature switch (similar to the Brewtus stock controller) for $50. This is a simple on/off control with programmable hysteresis (e.g. turn boiler on at 122C, off at 124C). The really nice feature is that it includes a 16 amp rated contact, enough to drive most home espresso machine heaters comfortably, therefore does not require a separate SSR.

Info: http://www.dwyer-inst.com/htdocs/PDFFILES/iom/temperature/TCS_iom.pdf

To buy: http://www.dwyer-inst.com/htdocs/temperature/SeriesTCSPrice.cfm

For many applications, one wants easily settable reasonably tight temperature control, but the final shot temperature has so many other factors that PID is overkill. Steam boilers on dual boiler, lever or HX machines, as well as the boilers on smaller machines like the Silvia, come to mind. This unit could cut the cost to 1/4 of a PID, and simplify installation.

I've bought one to use with my Peppina. I will also assess whether it's useful for the Tea's steam boiler and for an ultra secret temperature control scheme I'm contemplating.

OK, you've twisted my arm. See my post in Knockbox.

lennoncs

Postby lennoncs » Nov 19, 2005, 3:15 pm

They also make a dual PID in 1/32 DIN format.
Nice company to deal with, they return calls and will actually give you an opinion.

Sean

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barry

Postby barry » Nov 19, 2005, 6:35 pm

fwiw, i've been evaluating these as low-cost displays for real-time brew temperature readouts. they're pretty nice, but are not a standard DIN size (no big deal), and are only 3 digit so you can only deal in whole degrees. i've got one hooked to my home marzocco right now. btw, i'm also going to get a couple for roaster control/display.

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another_jim
Team HB

Postby another_jim » Nov 20, 2005, 2:58 am

lennoncs wrote:They also make a dual PID in 1/32 DIN format.
Nice company to deal with, they return calls and will actually give you an opinion.

Sean


Cool? How much? I'm looking for a dual loop cascade controller for my roaster.

snoboy

Postby snoboy » Nov 20, 2005, 5:24 pm

Sounds like a good item for preheaters and the like. I've been thinking about adding a thermoblock to Silvia, but wondering what to use for the temperature control.

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cannonfodder
Team HB

Postby cannonfodder » Nov 21, 2005, 12:57 pm

I have ordered one unit to use as a temp controller on my lever machine, but I got to thinking (be afraid, be very afraid) would the thermocouple unit make an acceptable replacement for the good old pressurestat?

I looked at the specs, but not being an EE, I was unsure of some of the specifics. It looks like you have a ± of 1 degree on the accuracy, I can live with that. But my question, what is the dead band on the unit? It looks like you can set the time between heating sequences as well as the threshold. So if I were to order another unit, mount it in the front of my Isomac (like the brut) could I gain a tighter temperature control on the boiler? I would be mounting the type K TC in the boiler via an omega lock fitting.
Dave Stephens

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another_jim
Team HB

Postby another_jim » replying to cannonfodder » Nov 21, 2005, 2:37 pm

Way I read the PDF, one can set the deadband by 1C or 1F steps. Commercial pressurestats translate to about a 2C to 3C deadband; there's a new Mater or Ceme tight deadband model that is down to 0.1 bar, or just under 1C. In an HX machine, with all the intermediate buffering, the major advantage of a pressure switch is that you can set it easily and repeatedly. However, the benefit of such quick changes is unclear to me, since the final brew temp has so many intervening variables. I'm more inclined to use one as a grouphead temperature controller.

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cannonfodder
Team HB

Postby cannonfodder » Nov 21, 2005, 3:07 pm

I know my pstat has a dead band adjustment, I just have not played with it. Right now it is running about .2 bar, on at 1.1 off at 1.3. With a HX machine, I do not think I would really be gaining much other than the gee whiz looks cool factor. I could make quick boiler adjustments, but with an E61 group that is almost counter productive unless you used it on the thermosyphen loop to regulate GH temp, as you suggested. If I entertained it may be helpful, I could run the temp up for steaming a lot of milk, but it is just me.

Maybe if my pressurestat goes bad one day, or I just get real bored, I might give it a try. I have the stock Ceme in it (I believe that is the one I have) but I do not know if it is the tight band unit. The machine is about 8 months old. I am going to play with it more this week during the holiday. I want to change my boiler and HX preheat loop insulation.
Dave Stephens

skyryders90

Postby skyryders90 » Nov 21, 2005, 4:39 pm

another_jim wrote:there's a new Mater or Ceme tight deadband model that is down to 0.1 bar, or just under 1C.


Where might one acquire one of these?

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malachi

Postby malachi » Nov 21, 2005, 4:45 pm

Espresso Parts NW I believe has them.
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