Inexpensive Temperature Controller - Page 2

[jasonmolinari]

I don't know what i need it for, but i think i should buy one just in case.

[another_jim]

Hi Jim,
I missed this post somehow

here is a link to their page for the dual loop control http://www.love-controls.com/controls/32dz/32dz_frame.html

I will get a price today.

Sean

Thanks for the link

[cannonfodder]

I have it bench rigged and running, details in the lever forum, PID thread.

[another_jim]

I got mine yesterday, and rigged a temperorary box for it today. The unit works easily and well, just as advertised, so I won't go into the details except to say the relay contact is very quiet (no big clack, just a soft click).

How does this unit compare with a PID? On the Peppina, my PID control produces a 2F range of temperatures, as thermal currents disturb the set temperature and the unit compensates. The switch produces a 3F variation -- basically the 2F inherent in the boiler currents and the extra 1F for the deadband.

Based on this, I would say this unit is a good option for steam boiler control on HX machines, electroinc control on single boiler machines, and even on most older double boiler designs, where there is a few degrees inherent variation like on the Peppina. I wouldn't be surprised if units like this become fairly standard on espresso machines. They are cheap enough to replace conventional mechanical controls, and much more idiot proof than PID systems.

[miKe mcKoffee]

Based on this, I would say this unit is a good option for steam boiler control on HX machines, electroinc control on single boiler machines, and even on most older double boiler designs, where there is a few degrees inherent variation like on the Peppina. I wouldn't be surprised if units like this become fairly standard on espresso machines. They are cheap enough to replace conventional mechanical controls, and much more idiot proof than PID systems.

Or grouphead rope heater control on a Silvia. Sure, now I read this thread, after ordering another FUJI and SSR! But that's ok. May order one anyway and use the 2nd FUJI on the Bric' boiler somehow! Or just wait and see what the Monster Bric' project reveals next month.

[another_jim]

Or grouphead rope heater control on a Silvia. Sure, now I read this thread, after ordering another FUJI and SSR! But that's ok. May order one anyway and use the 2nd FUJI on the Bric' boiler somehow! Or just wait and see what the Monster Bric' project reveals next month.

On the rope heater, you want PID, since it's the final control element. The Silvia's boiler you can put on one of these suckers without affecting anything.

[miKe mcKoffee]

My one concern using its built-in relay would be the relay life expectancy versus SSR. This week talking to TTI about using the FUJI PXR3 relay option for the rope heater we estimated 1,000,000 switch life with its 100w pull. Based on 1sec cycle time and on twelve hours a day that only came out to 23 days! I know MTBFs are not even close to set in stone, but are an indicator of robustness for an application. Controlling boiler heater of course greater load which would mean lower life expectancy. However, this has a much heavier duty relay but switch life not noted in the PDF so can't calculate MTBF. IIRC the FUJI relay was only rated 2A compared to the Love's much beefier 15A so might be just fine even for the boiler.

[cannonfodder]

It is working good for me.

[another_jim]

Here's the red-eye, no sleep, follow up (cross-posted to alt.coffee):

After playing with it most of the night, I now have reservations on
how useful this is as a **final** temperature control on single or
double boiler espresso machines. I doubt what I say will affect it's
usefulness as a pstat replacement, although Ken's experience, see
below, may indicate that even here a PID may be better.

The problems is not the deadband and the consequent loss in accuracy,
but that it turns on and off for longer periods of time (i.e cycle
times around 1 minute, rather than the 1 second of an ssr or 1/60th
second of an SCR).

Here's what I found when I rigged the PF (this is neither Schomer nor
Scace, just a TC in the PF with some waterproof packing -- I use the
spring lever to blow the entire shot volume through in less than a
second and get the average shot temperture by taking the high
reading).

Using a PID or dimmer, the PF reading was always a fixed offset away
from the boiler reading -- so the boiler reading allowed one to know
average shot temperature within 1F at worst. Not so with the
temperature switch. The difference between its reading and the shot
temperature dependended on whether the heat was on or off. With the
sensor further away from the heater than the intake of the piston, the
'heater on' readings were too low, and 'heater off' readings too high
-- the shot temperatures, being closer to the heat source, swung more
dramatically. If the sensor was placed closer to the heat, the
opposite happened. Moreover, the closer to the heat the sensor is
placed, the more overshoot one reads.

When I finally found a spot for the TC that remained perfectly
correlated with the shot temperatures (within 1F), the performance of
the switch had degraded considerably-- set at 200F the actual
operating range ran from 198F to 204F. Hugely better than button
stats, and a little better than bulb stats and pstats, but not in the
same league as a well placed PID.

I ended up punting -- I put the dimmer back in series with the unit,
and set it down after warmup, so the heat remains on for long periods
as it traverses the 199 to 200 interval. This reduces the subsequent
overshoot back to 201. However, it's a concession of defeat for the
concept of using this for very tight control, since with the added
dimmer cost, one may as well get a proportional controller.

Adding a PID to Ken's Junior boiler improved the inter-shot stability
of the Cimbali considerably when starting after an idle. I always
thought with all the buffering between boiler and brewhead, the effect
of an on/off control is minimized. However, a pstat looks a lot better
than it may be -- by recording pressure, it's reading an average
temperature for the enitre boiler -- a very stable figure. The HX
itself may be much more influenced by the heater or other local
conditions in the boiler. In other words, the 2- 3C swing read by the
pstat may be concealing much larger ones at the HX itself; just as the
nice readings I had last night concealed much larger swings at the
intake of the Peppina's piston/cylinder.

This opens up one of the problems of espresso machine control in
general. The sensors for control do not read shot temperature, but
something upstream. The obvious solution is to find the spot that
correlates best with shot temperature over the entire heating cycle
for on-off control, or the full wave-length of a PID controller (the %
output values on these mostly graph out as decaying amplitude
sinewaves with fixed wavelengths).

The peppina makes this easy since there's no refill, and the cylinder
isolates one shot's worth for measurement. I think the same can be
done with pump machines by putting a sensor in a blind filter. Run
this to get an idea of what's going on at the head for different
sensor placements.

[cannonfodder]

I am positive that my unit does not cycle (heat) for one minute. It is more like 20 seconds. My Factory is much easier to manage with the controller than with the units Pstat. As you stated, there is a bit of overrun in the temp using the controller. Once the heater kicks off I get another 3 degrees of overrun. I also have my TC running up through the bottom of the boiler right in the center of the heating element. The probe length places the TC tip about a half inch below the grouphead water pickup.

One observation I had was in regard to steaming power. With the controller adjusting based on water temp and not boiler pressure, I get a greater drop in steam before the heater kicks on.

I attribute that to the large mass of water in the boiler. While pressure and temperature are directly related, that is within a sealed container. I may have my boiler set to 238 (about.9 on the pressure gauge), once I crack the valve the pressure starts to drop. With the Pstat, the heater would immediately kick back in. With this controller, the pressure slowly reduces to about .6 bar before the water masses temperature has decreased to the point the controller kicks on.

I would have reservations about replacing the Pstat on my Isomac with this, but on my lever machine, I get much better control than the factory Pstat. I also have the adjustability.

I explained my reasons to Dan using an analogy with a Rancilio Silvia. With my pstat controlled lever machine, I essentially had a Silvia with only a steam switch. I got 211F water out of the portafilter spout, flashed boiled espresso. Getting anything that was not bitter and burnt was a trick.

By adding the controller, I can set the temp down to .5 bar for brewing. The Pavoni style machines need pressure to operate, .5 bar was the minimum usable pressure for me. I have not metered the exiting water temp yet, busy week, but the shots immediately improved. Prior to the controller, I had to work the power switch on and off to keep the temp in that range, major pain.

Once finished with my shot, I up the temp to 238 (about .9 bar) and steam. One nice point, using the controller I can leave the machine set at 190F all day. Bump the temp up from standby, one minute later it is ready to pull shots instead of the 15 it took from a cold start. Once finished, I can set the temp back down and go back to work.

On a single boiler espresso machine, this controller would give you more flexibility and stability. On a higher end HX machine, or dual boiler, you may actually take a step backwards. However, for my intended application, it works much better than the OEM system.

[slithy]

Has anone installed one of these in a Silvia yet? I've been watching this thread with interest, hoping for a less expensive alternative to a PID. It seems like is would be helpful - the ability to set a target temp, and use the display to know where you are in the overshoot cycle would be an improvement over temp surfing.

[miKe mcKoffee]

Hi Jim,
I missed this post somehow

here is a link to their page for the dual loop control http://www.love-controls.com/controls/32dz/32dz_frame.html

I will get a price today.

Sean

How do you find the price on that site or do you have to call? (I didn't see the price mentioned later in the thread) That looks like could be a perfect controller for the likes of Silvia. Control boiler and grouphead from same unit. Too late for me, but not for future Silvia modders. Unless its price is more than a couple FUJIs!

[barry]

http://www.dwyer-inst.com/htdocs/...eries32DZPrice.cfm