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Old 08-15-2012, 12:46 AM   #31
TimpanogosSlim
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Again, I apologize. I was in a bad way. Doing poorly. Off my meds, as it were. Far more embittered than usual.

But i do have an aesthetic objection to using luddite methods to circumvent shortcomings in high-tech solutions.

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Old 08-15-2012, 04:39 PM   #32
BetterSense
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Just to be annoying I want to point out that you can implement PID control in systems that are only 'fully on' or 'fully off', if the frequency of the switching is somewhat higher than the lag time of your system. I work with industrial furnaces that are only fully on/fully off, but they are controlled proportionally with PID because they use PWM that switches a few times per second. Your proportional variable is the duty cycle of the furnace element in this case.

This is irrelevant for freezers because you can't cycle the compressor quickly. You could use PID over very long time scales, though.

And I still fail to see any way in which changing the programming is superior or inferior to adding 'thermal mass' to the sensor. It's totally a six-of-one, half-dozen of the other situation.

 
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Old 08-15-2012, 04:49 PM   #33
zachattack
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No disagreements from me. That's why I mentioned that you can use PID for something with a variable or simulated variable output (duty cycle like you pointed out).

 
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Old 08-16-2012, 12:25 AM   #34
cwi
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Quote:
Originally Posted by TimpanogosSlim View Post
Again, I apologize. I was in a bad way. Doing poorly. Off my meds, as it were. Far more embittered than usual.

But i do have an aesthetic objection to using luddite methods to circumvent shortcomings in high-tech solutions.
Nice passive/aggressive apology.

Exactly what luddite methods are you talking about?

The high tech solution is to use the ASD provided by modern digital controllers (except for Ranco) for guaranteed hot start protection, instead of the wish and a prayer method most home freezers use.

The other modern solution is to specialize the system by using control inputs that directly sense the thing being controlled, instead of some secondary indicator. Since the thing we want to control is thermally massive, this is a win/win- tighter, easier temp control, and fewer cycles (which was the whole point of this thread). There is no amount of software in an off the shelf controller that can replace this approach.

Most digital controllers have <1F temp differential resolution. If tighter control than that is desired, it would most likely require something besides a home fridge/freezer with a fixed speed compressor.

 
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Old 08-16-2012, 12:28 AM   #35
cwi
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Quote:
Originally Posted by zachattack View Post
Also, the word traceable means traceable, nothing more. A traceable thermometer is one with a traceable calibration, it says nothing about how/if it averages data.

If you're going to rant, criticize and complain, at least have some clue what you're talking about.
Glad you were the one to stick it to him about that one. I was tempted when I saw it, but already catch enough grief for the reaming I do.

 
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Old 08-16-2012, 04:47 AM   #36
TimpanogosSlim
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Quote:
Originally Posted by cwi View Post
Nice passive/aggressive apology.

Exactly what luddite methods are you talking about?
How is it passive/aggressive when I'm just stating my opinion?

I'm serious when i say i was not myself when i made those posts. But i am also serious that i have an aesthetic -- not technical -- objection to having to result to a physical solution to a software problem.

Sticking a thermistor inside a container of water - to use the water as a physical buffer against temperature change - can be observed and characterized and expressed as a hysteresis. I can already program a hysteresis into my $13 ebay aquarium controller.

 
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Old 08-16-2012, 06:30 PM   #37
cwi
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Quote:
Originally Posted by TimpanogosSlim View Post
How is it passive/aggressive when I'm just stating my opinion?
When you apologize for a previous comment, then make the essentially the same comment again that calls everyone a cretan that chooses to place their sensor on their beer.

Quote:
Originally Posted by TimpanogosSlim View Post
I'm serious when i say i was not myself when i made those posts. But i am also serious that i have an aesthetic -- not technical -- objection to having to result to a physical solution to a software problem.

Sticking a thermistor inside a container of water - to use the water as a physical buffer against temperature change - can be observed and characterized and expressed as a hysteresis. I can already program a hysteresis into my $13 ebay aquarium controller.
I have an aesthetic AND a technical objection to resorting to a software solution for a physical problem, especially when there is no software solution for the given physical problem.

Your argument has already been debunked- several times. This is not a software/controller problem, and without also including a sensor input for the object being controlled, there is no way for any software to both decrease cycling AND maintain temps of the beer.

For a single sensor controller, the best way to reduce cycling and maintain temps is to put the sensor on the smallest mass being controlled (a bottle, a keg, or a facsimile), then use the temp diff to balance temperature control vs. cycling. They go hand in hand. This has been explained many times.

Measuring air temps, or some other mass smaller than that being controlled, it is possible to use a temp setting and temp diff that would result in the desired balance of temp control and cycling. To do this, you could either spend a couple of weeks tuning it manually; spend a few days (or more) writing some code to do it for you (with an additional sensor, and many tuning cycles for the code to converge on the proper settings); or you could simply put the probe on the thing being controlled, set your controller for your maximum temp tolerance, and have everything be automatically optimized.

RE: Hystersis- More than likely, that is not a true 'hysteresis' setting on your ebay controller, it is temp differential. Hysteresis is an oft mis-applied term as demonstrated by both of your inaccurate applications of it. The subject is too boring to go into here, especially since it is not relevant.

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Old 08-19-2012, 02:17 PM   #38
franks160
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Can you replace an old thermostat with the stc1000? If so how do you do it? Thanks

 
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Old 08-19-2012, 02:55 PM   #39
rifraf
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Quote:
Originally Posted by franks160
Can you replace an old thermostat with the stc1000? If so how do you do it? Thanks
You don't replace the old one. The stc-1000 gets wired into an outlet that you plug the freezer into and it basically controls whether or not the outlet provides power to the freezer.

Here is the build I used: super easy.

http://www.homebrewtalk.com/f51/ebay...-parts-261506/
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