hi,
Please confirm that you have a 5V relay on the Temperature module.
I assume the Fans are 5Vdc.?
E
View attachment 208435

Yes, the fans will be 5V

 

Sorry, stats = bi-metal thermostats.

 

A simple Google of "bimetallic thermostat switch" will bring up plenty of explanations and illustrations. Normally PC fans are 12 volt but you can buy an 80mm 5 volt fan. Control can be as simple as ON/Off or speed control based on temperature simple to complex. Matter of fact computer parts houses sell fan controllers really inexpensive.

Ron

 

A simple Google of "bimetallic thermostat switch" will bring up plenty of explanations and illustrations. Normally PC fans are 12 volt but you can buy an 80mm 5 volt fan. Control can be as simple as ON/Off or speed control based on temperature simple to complex. Matter of fact computer parts houses sell fan controllers really inexpensive.

Ron

Thanks, studying it now.

 

Sorry, stats = bi-metal thermostats.

The idea of switching an electronic component for a mechanical device sounds great, makes for reliability and cost. Thanks again.

Few doubts though:

I need a probe. The thermostat will measure water temperature not air temperature. The product must stay above water level but the probe must be submerged. Can you add a probe to these thermostats?

I believe I found a similar thermostat to the one you showed but it seems to work outside the temperature range I need, which is 72-78º, I need it to be adjustable at least within this range:
https://newliteparts.en.alibaba.com...2213314/Adjustable_Bimetallic_Thermostat.html

The temperature selection dial must be user-friendly and adjustable without tools.

Those PC fan controllers look beautiful! But they are controlled by the motherboard right? They're also powered by it. I would need it to work with the thermostat and the 5V power.

Look at this aquarium heater I found, for instance. It has a thermostat with a hand adjusting dial, probably adjustable bi-metal. The main difference is that I believe I wouldn't need a 110v current to power two 5V fans, while a heater probably does. This is exactly what I want in its most simplest way, would you agree?

So, where the heck do I get one of these thermostats?

 

Look at this amazing product, its exactly what I had in mind in the beginning. Its even USB powered. Too bad the temperature range is not quite right.

Its not even expensive, though I would prefer to build my own rather than incorporate it. If he could do it and keep it sleek and cheap maybe I should stick with this concept, what do you guys think? I'm good with the mechanical version also.

https://www.acinfinity.com/componen...set-thermal-trigger-for-usb-fans-and-devices/

 

The temperature to which the thermostat will be set to will be within 72-78º Fahrenheit. In some rare occasions, people might set it as low as 60º, but I wouldn't need to guarantee it could lower the temp that much.

Now I am worried. Hopefully you know that a fan will not lower the temperature below the temperature of the air it is blowing. Since you seem to be right in the range of normal room temp, is this device going to be operating in a place cooler than that?

Bob

 

I need a probe. ••• Can you add a probe to these thermostats?

No. The bi-metalic strips measure ambient air temperature, not water.

Look at this aquarium heater I found, for instance.

Sorry, that's not likely going to work. Though I do believe the better ones use electronic temperature sensing.

Now I am worried. Hopefully you know that a fan will not lower the temperature below the temperature of the air it is blowing. Since you seem to be right in the range of normal room temp, is this device going to be operating in a place cooler than that?

Hadn't thought of that. This is a design consideration for sure. Blowing away warm air and replacing it with warm air does nothing to cool anything. To exchange heat you need a temperature difference. But I'll leave the design up to the thread starter (TS).

For small packaging requirements, a simple J or K type thermal sensor connected to a comparator with a variable preset should allow temperature control. Hysteresis will need to be built into the design so that the comparator isn't sitting on a knife edge trying to decide to activate the fan or not. Also a suitable transistor or MOSFET will be needed to act as the power switch for the fan(s) With a sufficient MOSFET you can easily control one or two fans at once. If you want to set two different temperature set points you'd need a dual comparator, again, with all the bells and whistles afore mentioned.

It's easily doable, but it depends on your understanding of electronics on a basic level. It's something even I could figure out - if I were so inclined to do so. But I'm convalescing (torn meniscus left knee) and am spending a lot of time with my leg elevated. Trying to avoid the need for surgery. But I do spend a few minutes here and there looking at AAC and responding from time to time.

Best of luck.

 

Now I am worried. Hopefully you know that a fan will not lower the temperature below the temperature of the air it is blowing. Since you seem to be right in the range of normal room temp, is this device going to be operating in a place cooler than that?

Bob

Hi Bob,

your doubt is logic.

But air can actually cool water with evaporative cooling. Water chills when it evaporates, if you evaporate enough water fast enough it will lower the water temp. Although if room temp is too high it will defeat the cooling effect, but this body of water would sit somewhere within normal room temp. The fans will be blowing the surface of the water.

Anyway, its only supposed to keep the temperature from getting too high, not actually cooling below room temp. What happens is that sometimes water can get a couple of degrees F above room temp, so you just need a little evaporative cooling to bring it down a little bit. Of course the larger the body of water the more wind you'll need.

This fan will be operating on and off according to the water temp, which is influenced by room temp. You could turn the AC on and achieve the same results, but that is far more expensive.

 

Those PC fan controllers look beautiful! But they are controlled by the motherboard right? They're also powered by it. I would need it to work with the thermostat and the 5V power.

No, they are powered by 12 VDC and are stand alone. They normally include sensors, mostly thermistors which with a few drops of nail polish or epoxy are easily water proofed. Could easily be powered by a 12 volt DC wall wart. Just remember you want an automatic and not manual. That or roll your own but knowing now this will be submerged changes things as now you need a sensor made to be submerged. Rhere anything else we should know?

Ron

 

Here's what I know about evaporative cooling: And this is not going to be the "Be All - End All" of the story, but as far as I know, water evaporating cools the air. And the way water evaporates is if the humidity is low. High humidity is poor for evaporative cooling. This I know because I live in Utah; a typically dry climate. A few days ago we had higher than normal humidity and the swamp cooler (evaporative cooler, or "Swamper") didn't offer much relief. But with the dryer weather the swamper works great at cooling the air.

I don't know if the water is cooled too, it probably is. But that's because the water is flowing over a medium that creates more surface area for the water to evaporate. The reason why evaporation cools is because it takes energy. Energy right out of the air. Leaving the air at a lower energy level. And if you remember science class, hotter air has molecules moving faster and at higher energy levels than at colder temperatures. So when you trade off energy for evaporation you get cooler air. But I don't think you're going to get much cooling just blowing air over the surface of the water.

That's my 2¢. I'm sure there's another 98¢ to the story but I can't speak with any authority on that subject.

As far as cooling the water - if there's a heat pipe (thermally conductive pipe) in the water and the fan is blowing colder air over the warmer pipe then it will cool the water. Think "Radiator". But then again, I'm short a buck.

 

I think a design similar to this one may suit your needs. I would suggest using an LM393 (Comparator.) instead of the of the LM741 (op amp) an you could probably use a smaller transistor than the 2N3055. You have not said what the application is for this device so we have no idea how accurate you need the temperature control and weather you need any hysteresis about the set point. If you yse the fan shown which has a rated current of 150 mA then a small transistor such as as a BC337 would probably be OK.

Les.

 

In High School, myself and a couple of friends built an evaporative cooler for a salt water aquarium. Two acrylic tubes were drilled to appear glass capillary tubes. A cotton cloth was then woven through the c tubes. This device was put in series with the filter pump, one a tube was placed in the water and water was drawn up the cotton cloth by capillary action. A fan blew across the cloth surface. We dropped the temperature of the aquarium water by almost 10 degrees.

 

No, they are powered by 12 VDC and are stand alone. They normally include sensors, mostly thermistors which with a few drops of nail polish or epoxy are easily water proofed. Could easily be powered by a 12 volt DC wall wart. Just remember you want an automatic and not manual. That or roll your own but knowing now this will be submerged changes things as now you need a sensor made to be submerged. Rhere anything else we should know?

Ron

Sorry, Ron, dont want to give you guys the run around at all, in fact just the opposite. I just dont want to fully disclose the product itself but I believe I can give you all the information you need.

I made another sketch that might help narrow it all down:

 

In High School, myself and a couple of friends built an evaporative cooler for a salt water aquarium. Two acrylic tubes were drilled to appear glass capillary tubes. A cotton cloth was then woven through the c tubes. This device was put in series with the filter pump, one a tube was placed in the water and water was drawn up the cotton cloth by capillary action. A fan blew across the cloth surface. We dropped the temperature of the aquarium water by almost 10 degrees.

Brilliant

 

Here's what I know about evaporative cooling: And this is not going to be the "Be All - End All" of the story, but as far as I know, water evaporating cools the air. And the way water evaporates is if the humidity is low. High humidity is poor for evaporative cooling. This I know because I live in Utah; a typically dry climate. A few days ago we had higher than normal humidity and the swamp cooler (evaporative cooler, or "Swamper") didn't offer much relief. But with the dryer weather the swamper works great at cooling the air.

I don't know if the water is cooled too, it probably is. But that's because the water is flowing over a medium that creates more surface area for the water to evaporate. The reason why evaporation cools is because it takes energy. Energy right out of the air. Leaving the air at a lower energy level. And if you remember science class, hotter air has molecules moving faster and at higher energy levels than at colder temperatures. So when you trade off energy for evaporation you get cooler air. But I don't think you're going to get much cooling just blowing air over the surface of the water.

That's my 2¢. I'm sure there's another 98¢ to the story but I can't speak with any authority on that subject.

As far as cooling the water - if there's a heat pipe (thermally conductive pipe) in the water and the fan is blowing colder air over the warmer pipe then it will cool the water. Think "Radiator". But then again, I'm short a buck.

When water evaporates it cools the surface it's evaporating from. The air also? Sure, due to the transfer of heat between the cooled surface and the air. Thats why wind is so cooling after exercising, when you're drenched with sweat.

Check out djsfantasi post #33

Humidity does plays a major factor to efficiency. The higher the humidity the less evaporation, and so the product will be more or less efficient considering this variable. But remember, I only need a couple degrees of deviation from room temp, it doesnt need to be the most efficient cooling method. I must consider size, reliability, aesthetics, power, user-friendl, etc... It also doesnt have to be immediate, it can take a while. In fact, it has to be slow.

It will indeed depend on the volume of water to be cooled. The user can add another unit if needed.

I though about many other more efficient ways of cooling water like you said, radiators, cooling fluid, heatsinks, fans, refrigerating units, but having to consider many other aspects like I mentioned and the fact that it doesnt have to be the most efficient cooling system, but a blend of trading one thing for the other enough to balance it to a very satisfactory result. If that makes sense.

In fact, this product I have in mind already exists! Meaning its been proven to be efficient enough and achieves a satisfactory cost/benefit. Exactly as I described (two fans, 5V), I'm just trying to add a thermostat so you dont have to keep monitoring the temperature and pushing the on/off switch all the time.

 

Sorry, Ron, dont want to give you guys the run around at all, in fact just the opposite. I just dont want to fully disclose the product itself but I believe I can give you all the information you need.

I made another sketch that might help narrow it all down:

No problem at all. I used similar rack mounted fan systems in test stands. Anyway if all you want is simple On/Off based on a set point temperature look at some of the temp controllers which use a thermistor. You are looking at a narrow range of temperature and if you can do with +/- a few degrees and there are cheap boards off the boat like this one.

This or roll your own with a few parts. There is not much to what you seem to want but it would require some basic skills to fabricate.

Ron

 

Can you clarify if you want to build the thermostat or are you looking for a ready made device. In terms of a ready made device I thought of a module that Maplin (Now ceased trading) used to sell It was had an LCD display and buttons to set the temperature at which the output switched. I had used these in the past to control the temperature of a seed propagator. I had a look on ebay to see if they were being sold there but could not find them. I did find this device that may meet your needs.

Les.

 

If all you want to do is keep the water from going above a settable temperature then the circuit need be little more than a waterproof thermistor probe, a potentiometer, a comparator with little hysteresis, and a switching device (relay or transistor). No display or fancy calibration procedure required: put the probe in water at the 'right' temperature and twiddle the potentiometer until the fan just cuts in/out.

 

So, where the heck do I get one of these thermostats?

View attachment 208470

When I kept tropical fish in North American I used these to maintain water temperature. It is very simple inside a bi-metallic switch connected to a knob so the temperature can be set, connected in series with the heater, which was probably nichrome so it would have low resistance.

It would be a simple matter to connect one of these as a thermostat -simply put 5 or a little more across the power line going into the heater. When the resistance is low, the fan should go off and the fan should run when the resistance is high.

You should be able to get these anywhere you can buy tropical fish and accessories if you live in a place where it gets cool during parts of the year.


eBay: about US$ 3. https://www.ebay.com/itm/Aquarium-F...hash=item3649e68d05:m:m6CFdK9lnE0U61yKIkafaeQ

Alibaba: about the same price. https://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=fishtank+heater

And I am sure plenty of other places on the internet.