$16 digital temperature control

[Paul Verizzo]

I might be reposting something already brought up.

In my health and diet endeavors, I came to this posting: http://wholehealthsource.blogspot.com/2015/03/build-your-own-yogurt-maker-sous-vide.html (A great site, BTW.)

Seems that the heart of this device costs only $16 at Amazon, a bit less on eBay. So, depending on what you have in the garage, and your own skills, it can cost from that to $40.

http://www.amazon.com/gp/product/B0...2&tag=whoheasou02d-20&linkId=LTBZ2M4UASFRG7TT

Allegedly +/- .1 degree accuracy, can control heating or cooling devices. Amazon review ratings are 4 1/2 stars.

Attach it to one of those coiled cup of coffee immersion heaters in an insulated water bath, there ya go.

 

[DREW WILEY]

+/- 0.1 deg Readout does not equate to 0.1 Accuracy, not for $16 to $40, not even for ten times that amount. To get that kind of dollar to performance ratio you need a very high BS Coefficient, which seems engineered in. So, "Allegedly" is an understatement.

 

[DREW WILEY]

Well I have owned, and currently own, a real thermoregulator that does keep temp inside +/- 0.1 deg F. And I assure you, even a hundred
bucks wouldn't even buy the empty shell of the housing for that thing. There's a bit more to it than just adding another zero to a readout LED.
Amazon ratings are about as professionally informed as a phD dissertation on flying a jetliner written by an armadillo.

 

[Paul Verizzo]

Well I have owned, and currently own, a real thermoregulator that does keep temp inside +/- 0.1 deg F. And I assure you, even a hundred
bucks wouldn't even buy the empty shell of the housing for that thing. There's a bit more to it than just adding another zero to a readout LED.
Amazon ratings are about as professionally informed as a phD dissertation on flying a jetliner written by an armadillo.

"Perfection is the enemy of good enough."

Sniff, nose held high...............

Whatever it is, it's a hell of a lot better than trying to work with a glass stick thermometer. And if it's off, all you have to do is learn the degree of error and compensate.

I remember when American car dealers derided that funny little German car. And then, those Japanese ones.

 

[Paul Verizzo]

(there was a url link here which no longer exists)

Thanks, there ya go. Not that I've figured out what a PID is.

In some experiments, I found that a small submersible pump adds enough energy to the water in small ice chest to raise the temperature pretty fast. Could be OK in a steel sink with heat loss.

 

[polyglot]

Yeah, it's a PID. It'll work for a while but those cheap ones have nasty cheap mechanical relays. The cycling rate (often around 2Hz) means the relay will die in extremely short order.

You typically need to spend about $50-$90 to get a decent one with a quality autotune and triac (SSR) output. Similar price but more quality buying used industrial control gear, if you know where and what to look for. Despite drew's sniffiness, the temperature accuracy and control stability has very little to do with the controller; it's all down to the dynamics of the system you're controlling, e.g. ratio of heater power to thermal mass it's responsible for and the magnitude of the load disturbances.

If you're willing to attach wires to a super-cheap controller like this that might catch fire, you should go one tiny step further and be better off with a $3 arduino clone, a semi-decent $20-$50 SSR and the Arduino PID library.

 

[welly]

I use one of these for a temperature controlled fridge as my other hobby, home brewing, requires a temperature controlled fermentation fridge. It's otherwise known as an STC-1000. I've been running it almost constantly for 7 months. It is absolutely brilliant and surprisingly accurate. These are highly renowned in the home brewing world. I've started using it in the last few months to cool water to 20c as I'm living up in Darwin, Australia, where the water from the tap comes out at around 27C. It is surprisingly accurate. It very rarely fluctuates and without fail every time I've taken water out of the tank I store in my fermentation fridge, it comes out dead on 20c, according to my highly accurate Thermopen thermometer.

There is absolutely nothing to worry about with this controller, home brewers have been using them for years now and there are few if any complaints about them. Do a search for STC-1000 review on Google and you'll see plenty of confirmation this is a solid piece of kit that is priced well below it's value.

 

[Chan Tran]

I have used numerous temperature controllers and I don't recall ever used anything that is accurate to within a couple of degrees F. Although if you only need 1 temperature there are some settings in the controller that allow you to get quite accurate at that one temperature. The problem with a tempering bath is that even if the bath temperature is exact the chemical temperature isn't. If you then pour the chemical into a drum and process outside of the tempering bath then the temperature would drop during the processing time. They all have display and set point that are in 0.1 degree. The one I used priced from $150 to $500 for a single channel temperature controller.

 

[DREW WILEY]

A helluva lot worse than a stick glass thermometer. Of course, if you expect something for nothing in that dept too, then all bets are off.
Sure, someone can stick a Leica logo on a plastic Holga camera; but that won't make them equal. Having "your nose held high" is more likely of having money to burn wasting lots film, paper, and time due to poor process control. Go out an buy a good used Kodak Process Thermometer for fifty bucks. They were $250 new and worth every cent. A new thermoregulator which ACTUALLY hold temp +/- 1/10th will
cost you around $2500 for a small unit. But there are all kinds of fussy tricks using even these. And unless you're doing something relatively estoric like matched color separations and masks (like I sometimes do), the whole concept is ridiculous overkill. A plain water bath and decent thermometer is plenty good for conventional black and white work. I've tried piles of devices - expensive water temp valves, electronic thermometers, blah blah. You don't get something for nothing. Two blocks away there was a warehouse that sold nothing
but thermometers. There was a market for them here in the University and Biotech/Pharmaceutical R&D town. Probably nothing in the whole place under $200, even in plain glass. A few things in the tens of thousands of bucks. Cheap camera store thermometers are like
camera store spotting brushes - not worth even looking at. You'd be better off with a drugstore medical thermometer. Certified scientific
thermometers cost way more. And as far as true thermoregulators go, the average home darkroom doesn't even have sufficient wattage
to run them. If you're getting into color printing, you do need to keep you developer within a couple of degrees of so, ideally. Otherwise,
no big deal.

 

[fotch]

 

[Paul Verizzo]

If the naysayers will step forth with comparative evidence, I'll listen. Until then, its just pretentiousness and dismissal. Even if not nuclear lab calibrated, just like any photo process, adjust to get what's needed.

BTW, fotch, it's obvious that some of the reviewers very accomplished electronic experts.

 

[MattKing]

As best as I can tell, this item is just a controller.

What would one actually hook this up to in order to actually warm or cool the chemicals?

 

[Joe VanCleave]

PID = Proportional Integral Derivative. Three different temperature control feedback methods, based on how close or far away the actual temperature is to the set point. Prevents oscillations and hunting around a set point when trying to control temperature using a feedback system.

~Joe

 

[Paul Verizzo]

PID = Proportional Integral Derivative. Three different temperature control feedback methods, based on how close or far away the actual temperature is to the set point. Prevents oscillations and hunting around a set point when trying to control temperature using a feedback system.

~Joe

Thanks for that, Joe! I wondered what PID means. Not exactly your simple on-off thermostat.

Matt, a heating element. Like those cup of coffee coils.

 

[polyglot]

As best as I can tell, this item is just a controller.

What would one actually hook this up to in order to actually warm or cool the chemicals?

Typically these are provided with a thermocouple input (of selectable type) and relay output and you program them for heating or cooling. For a typical water-warming scenario, the output relay will control the current to a big resistive heater, e.g. a submersible element of some sort. You will also want a circulation pump to keep the temp uniform; it will also improve the system transient response and improve control stability (prevent oscillations).

To make warm water, basically you need: a thermocouple (often included), immersion heater and aquarium pump. Maybe a bigger or solid-state relay if you don't trust the relay in the controller.

 

[Paul Verizzo]

FYI, the submersible fountain pump I have raised the temperature rather rapidly within a couple of gallons of water in a small ice chest. So, even those few watts can raise the temperature, and it's not controlled. If one is shooting for the classic high C-41 temperature, shouldn't be a problem, I would guess that normal cooling losses would exceed that. But if not going that high, could be a problem.

 

[Paul Verizzo]

I bought one of these units.

I have a Kodak glass stick thermometer, and this unit agrees to within the half degree F.

Not sure of the claimed Kodak accuracy, but I'd say that's as well enough as needed for photo processing, even color.

 

[BetterSense]

These STC1000 controllers are legendary among brewers. I have 2 of them driving my fermentation fridge. As previously mentioned, control has as much to do with the system as it does the controller. These offer thermostatic control with programmable calibration offset, deadband, and compressor delay, which is all you need in 99.9% of process control applications, certainly for photography.

 

[mweintraub]

Thanks for that, Joe! I wondered what PID means. Not exactly your simple on-off thermostat.

Matt, a heating element. Like those cup of coffee coils.

Or you can use a crock pot. and plug it directly into the unit's AC socket.

 

[Paul Verizzo]

These STC1000 controllers are legendary among brewers. I have 2 of them driving my fermentation fridge. As previously mentioned, control has as much to do with the system as it does the controller. These offer thermostatic control with programmable calibration offset, deadband, and compressor delay, which is all you need in 99.9% of process control applications, certainly for photography.

Might have to justify the purchase by taking up brewing. (I did make beer a few times, long, long ago. Sometimes OK, sometimes not. No temperature control other than "basement."

 

[Paul Verizzo]

Or you can use a crock pot. and plug it directly into the unit's AC socket.

I would think that would be pretty high wattage just to kick the temperature up a degree or something. And a hell of a lot of thermal inertia with all that ceramic. Would overshoot greatly, I think.