FlytrapCare Carnivorous Plant Forums

Hey everyone,

I've crawled from under my rock since i have been traveling to the middle east for work a lot lately.

Some of you might remember my last terrarium build, it works quite well, BUT for my taste temperature drop reached by the evaporative cooling is to low (http://www.flytrapcare.com/phpBB3/helia ... 25177.html)

This is due to 3 issues:
-Lamps inside terrarium (even 10w leds give off quite some warmth over the time of the day)
-Poor insulation
- No active cooling
Due to the lamps inside the terrarium i cannot have more then 8 leds on at a time while it was designed for 16 leds, and with the ever expanding collection i'm running into the limits of the currently setup.
This has made me rethink my current design, and possible improvements, therefor i am planning on a v.2 of the automated terrarium build.

Structure:

Dimensions wise it will look similar to this:

Front will be dual layer plexiglass with air in between, all other walls will be 7,5cm thick and insulated, top and front will be hinged for easy access.

Cooling:
After experimenting with the peltier cooler (only reaching -4 to ambient) i decided to mod an portable airconditioner and use that for cooling the cooling water that will be circulating to the terrarium by a "pc water cooling setup"

Lighting:
Do be decided.

This topic, once finished will be updated and summarized on post 1, any tips and or recommendation are most welcome!

Parts list:
PC cooling kit - second hand(ebay, craigslist) - 50 euros
Airconditioner - second hand(ebay, craigslist) - 30 euros
MDF 12mm thick - hardware store - 10 euros
MDF 4mm thick -hardware store - 10 euros
Styrofoam sheets -hardware store - 10 euros
PU foam -hardware store - 5 euros

I'll throw some spaghetti at the wall for you. I would say get the LEDs out if they are generating heat. You could put a plexiglass (or glass) top on the terrarium area inside, a few inches below the actual (wood?) top. Then put the LEDs above the plexi and vent the 'attic' area above the inside top below the outside top and maybe put a fan on it.

Another thing you might try, if the peltier is cooling the water well enough but not the air, is use a water pump to spray a mist of the cooled water in front of a fan, or drip the water down a cloth in front of a fan to help air-to-water heat transfer and evaporation.

Or maybe in reverse you could make a deep narrow reservoir with an air pump and air stone to bubble air up through the cool water.

I'm not sure I read you correctly though, maybe the peltier is not cooling the water enough either? Or you're using it on the air directly?

At 100W the peltier sounds like a lot of power for a cooler though. I may not be up to date with the tech but I don't recall them being efficient at all and that's why they're still kind of a research/hobby thing.

If you went with a PC water cooler the wattage would be 1/5th that, or you could run 5 of them at 100W. I don't know if it would work better or worse but the PC coolers all use radiators with fans. That requires the area you're cooling to be hotter than where the radiator is though, radiators generally work better cooling very hot things since they rely on the ambient air temp to cool off the radiator. CPUs and GPUs generate small hot heat spots that get a lot hotter than room temp so a radiator works well for cooling that. It would be very hard to get the terrarium cooler than the room it's in, or even as cool, but a radiator could keep it from getting much hotter than the room. It might work well if the terrarium is well above room temp. But if the water in the radiator is the same temp as ambient air in the house it will cease to draw heat out of the terrarium. PC coolers are very very small too, I kind of doubt they would be good at cooling an area the size of your terrarium.

Portable AC units and fridges and whatnot use compressors with condense/evap coils. This is probably most effective and efficient, especially for cooling a small confined area down below the surrounding ambient temps. And since it's a sealed unit they can use exotic gasses like freon that are even better than water at heat exchange. I think perhaps peltier devices aren't that efficient or else you'd see people making refrigerators with them instead. The downside is then you have to accommodate an evaporator coil inside the terrarium, and condenser coil and a compressor outside. If you went that route probably compressor underneath and condenser coil on the back like a fridge. Maybe put the evaporator on the top since heat rises and cold sinks, and mount the LEDs below it somehow.

Maybe use something like this for the parts?

http://www.ebay.com/itm/Portable-Car-Co ... SwjVVVt147

Something very small should do it, 100W would be a very small refrigerator but it should be more effective than the peltier. Hard to find wattage info on refrigerators online nobody seems to list it. I would think go with the littlest thing you could find because almost any typical refrigeration equipment is going to be overkill.

If finding space for condenser and coils ends up being a problem, you could combine with the radiator system. Stick a small fridge in another room, use a water pump and a whole bunch of tubing, stick the radiator in the fridge. Then mist or drip the returning water. You'd have to run the water tube down the wall into the basement or crawlspace, or up into the attic, and back into another room. And then it would basically be 'built in' furniture and much harder to relocate the terrarium. It would eliminate having to put the equipment in or on the terrarium though, just a pump and some tubing to remote equipment. Or put the terrarium on a stand and shove a small fridge under it and just pipe water through a radiator in the fridge right below it.

Just spit balling here, I don't know if any of these ideas are even sane let alone good.

I don't know about you but for me, reconfiguring all the refrigerant piping and components off a fridge and rigging them to a terrarium would be kind of intimidating and seem like a lot of work and a learning experience. Mostly the copper pipe brazing and the freon venting and refilling I imagine it involves seems like a pain.

Room temp radiators to me seem slightly doubtful and peltiers I don't see as efficient enough to be effective unless you're willing to go huge watts on lots of peltiers and pay for the devices and the power usage. But I don't know much about them.

Air hoses and pumps or water hoses and pumps I am perfectly comfortable with so that seems a lot easier.

I've been looking at what I can find online for portable AC units or refrigerators, to see if I can find an off the shelf solution. Like a very small compressor unit. I think that's probably how I would go, one of two ways.

The smallest portable AC compressor unit I could find, they sell them for a couple to a few hundred bucks. Don't really list wattage but I'd guess around 800-1500W (but only when it's running). They're meant to cool whole small rooms. They have wide vents on them, but that's easy to fix up something like a funnel or a plug with a hole to make it have a tube output on the evaporator supply. It already has a tube on the condenser supply meant to go out the window. Might also need some modification on the evaporator return to add a tube. The condenser return could just suck room air. Since this thing should be such overkill, it would hardly have to run I think and it could just vent into the house too instead of out a window. Then it's just a matter of putting it somewhere, anywhere, and getting a couple of air hoses, supply and return on the evap coil, to the terrarium. Then you might have to think about some way of disabling the dehumidifier that's on most of them unless you can turn it off. Also, the tubes in question will be way too big really, the unit would be way oversized for a terrarium. You could just use smaller tubes but it would constrict the unit. Some futzing needed there. Or find a smaller unit than I've found. And you'd have to hack the thermostat on it to go in the terrarium.

Or, option 2, in the same price range, some kind of small dorm room refrigerator (or maybe something smaller like the 12VDC car cooler I linked which was cheaper) with a liquid cooled heatsink thermal pasted to the freezer evap coil. Or the refrigerator evap coil, freezer would cool faster in use but then the water would freeze in the pipe when not in use. Probably start with the fridge coil and see if it works... if it runs all the time and never stops then try the freezer coil. I think it would probably work though and not run constantly. Then stick that somewhere, anywhere, and it's a matter of getting 2 water hoses from there to the terrarium, a thermostat with a relay and 1 cheap fishtank water pump. Then you will have to drill 2 holes in the side of the fridge, to route the pipes in and into the heatsink, and seal the holes with the best insulating sealant you can on both sides. Most of the tiny fridge would also still be operable to keep beer or food in (or dormant plants and cold stratifying seeds) as a bonus.

Add an ultrasonic cold mist humidifier (or a mist spray nozzle or a drip over some mesh in front of a fan) to move the cold water around through the air and keep temps more even.

If I was trying to build something like this now, that's probably how I would go, the water pipe and fridge route with a liquid cooled heatsink as a radiator and maybe some silicone tubing coiled up in the fridge. You'll end up with more control I think, the fridge is meant to go from 30-50 and the pump will determine the volume of water you move, which you can control to control temps. With the AC air unit, it's meant to operate more like 50-70 or 60-80, the temps won't go as low, air doesn't cool as well, tubing is bigger, and the volume of air the unit is pushing is pretty much fixed being way way too oversized.

The longer the tubes/pipes are, either with air or water, the more important it would be to insulate the supply side tubing/piping. Under the stand probably wouldn't matter, down in the basement on the other side of the house it might be more important.

I have been messing around with evaporative cooling lately, and the way you set up your terrarium I am not surprised that it isn't helping that much. I'm sure you know this already, but the higher the humidity, the less amount of water that will evaporate, and therefor less cooling will occur. If you can acclimate your plants to lower humidity, the cooling will drop the temperatures a lot lower.

entropy81 wrote:I'll throw some spaghetti at the wall for you. I would say get the LEDs out if they are generating heat. You could put a plexiglass (or glass) top on the terrarium area inside, a few inches below the actual (wood?) top. Then put the LEDs above the plexi and vent the 'attic' area above the inside top below the outside top and maybe put a fan on it.

Another thing you might try, if the peltier is cooling the water well enough but not the air, is use a water pump to spray a mist of the cooled water in front of a fan, or drip the water down a cloth in front of a fan to help air-to-water heat transfer and evaporation.

Or maybe in reverse you could make a deep narrow reservoir with an air pump and air stone to bubble air up through the cool water.

This was exactly the plan for the new terrarium, mount the leds outside of the tank (in the lid, and fan the air between glass top inside and leds.
As for cooling the water, its sufficient (-10 ambient, 600ml of water, not insulated), so my thought was the same as yours: transfer the heavy water to the air of the terrarium. I thought about using the ultrasonic humidifier for this purpose.

entropy81 wrote: I'm not sure I read you correctly though, maybe the peltier is not cooling the water enough either? Or you're using it on the air directly?

At 100W the peltier sounds like a lot of power for a cooler though. I may not be up to date with the tech but I don't recall them being efficient at all and that's why they're still kind of a research/hobby thing.

If you went with a PC water cooler the wattage would be 1/5th that, or you could run 5 of them at 100W. I don't know if it would work better or worse but the PC coolers all use radiators with fans. That requires the area you're cooling to be hotter than where the radiator is though, radiators generally work better cooling very hot things since they rely on the ambient air temp to cool off the radiator. CPUs and GPUs generate small hot heat spots that get a lot hotter than room temp so a radiator works well for cooling that. It would be very hard to get the terrarium cooler than the room it's in, or even as cool, but a radiator could keep it from getting much hotter than the room. It might work well if the terrarium is well above room temp. But if the water in the radiator is the same temp as ambient air in the house it will cease to draw heat out of the terrarium. PC coolers are very very small too, I kind of doubt they would be good at cooling an area the size of your terrarium.

The Peltiers are considered inefficient, i agree with you on that. But depending on the temperature difference it can be more effective than most people think (have to do some tests to prove this haha). The positive side is that its small, does not need maintenance, i have seen a lot of people use them and fail due to the size and insulation of the terrarium as well as the way of using it. I don't think you got the plan as far as the PC cooling works, i again agree with you on all the points you made, but i will have the radiator inside the terrarium, with the peltier cool side on the "CPU" block outside the terrarium.

entropy81 wrote: Portable AC units and fridges and whatnot use compressors with condense/evap coils. This is probably most effective and efficient, especially for cooling a small confined area down below the surrounding ambient temps. And since it's a sealed unit they can use exotic gasses like freon that are even better than water at heat exchange. I think perhaps peltier devices aren't that efficient or else you'd see people making refrigerators with them instead. The downside is then you have to accommodate an evaporator coil inside the terrarium, and condenser coil and a compressor outside. If you went that route probably compressor underneath and condenser coil on the back like a fridge. Maybe put the evaporator on the top since heat rises and cold sinks, and mount the LEDs below it somehow.

Maybe use something like this for the parts?

http://www.ebay.com/itm/Portable-Car-Co ... SwjVVVt147

Compressor fridges are a lot more energy efficient, but also big and bulky, and difficult to repair/replace (this is an issue for me since i dont want to wreck the terrarium once its build). My thought at first was buying a small desk fridge (220v) and take that appart, but again, this will be a lot more chalenging. The portable cooler u posted is a peltier based cooler btw

entropy81 wrote: Something very small should do it, 100W would be a very small refrigerator but it should be more effective than the peltier. Hard to find wattage info on refrigerators online nobody seems to list it. I would think go with the littlest thing you could find because almost any typical refrigeration equipment is going to be overkill.

If finding space for condenser and coils ends up being a problem, you could combine with the radiator system. Stick a small fridge in another room, use a water pump and a whole bunch of tubing, stick the radiator in the fridge. Then mist or drip the returning water. You'd have to run the water tube down the wall into the basement or crawlspace, or up into the attic, and back into another room. And then it would basically be 'built in' furniture and much harder to relocate the terrarium. It would eliminate having to put the equipment in or on the terrarium though, just a pump and some tubing to remote equipment. Or put the terrarium on a stand and shove a small fridge under it and just pipe water through a radiator in the fridge right below it.

Just spit balling here, I don't know if any of these ideas are even sane let alone good.

I have considered buying a cheap fridge/freezer and fill it with the largest radiator i can find and run-as short as possible- from and to that radiator. This would be a serious option if i wanted to build a ultra highland tank, but as energy prices here are quite high (not to mention enviromental impact) i would rather have something that turns on when needed (e.a. at +20 degrees C).

As you might have noticed, there are a lot of pros and cons for each setup, both in ease/tidiness of installation, replacing parts, size and (energy) efficiency, but any discussion is a good one and i rather make some mistakes in assumptions or looking over things then spending unneeded money!

I will get my PC cooling this weekend, and will run some tests with my peltier on them with my current tank to get some numbers.

entropy81 wrote:I don't know about you but for me, reconfiguring all the refrigerant piping and components off a fridge and rigging them to a terrarium would be kind of intimidating and seem like a lot of work and a learning experience. Mostly the copper pipe brazing and the freon venting and refilling I imagine it involves seems like a pain.

...

The longer the tubes/pipes are, either with air or water, the more important it would be to insulate the supply side tubing/piping. Under the stand probably wouldn't matter, down in the basement on the other side of the house it might be more important.

U are on the right path!
If you have a spare evening, this is an interresting read: http://www.terraforums.com/forums/green ... em-15.html

Leathal_Traps wrote:I have been messing around with evaporative cooling lately, and the way you set up your terrarium I am not surprised that it isn't helping that much. I'm sure you know this already, but the higher the humidity, the less amount of water that will evaporate, and therefor less cooling will occur. If you can acclimate your plants to lower humidity, the cooling will drop the temperatures a lot lower.

This is indeed a mistake i made while designing the terrarium i have now, all i accomplish at the moment is bringing down the temperatures to ambient (e.a. removing the heat from the lamps)
Since the RTC in the arduino keeps failing on me(on average 4 per year ), i cannot control the relais anymore with the arduino so i have no options of controlling the fan/humidifier. Once i'm done with the new terrarium i'll experiment with drilling some more holes in the V1 terrarium.

Ahh. Yeah I had the way you were planning to use the PC cooler radiator backwards. And some other things too.

I was thinking how you could include a compressor unit because I thought maybe you were saying the peltier device didn't cut it. I'll freely admit I've only read a bit about them and haven't used one. If the device is powerful enough for the cooling you need, then so it is and you don't need to go compressor route. Stick with the peltier you've already got.

Give some thought to the ultrasonic mist humidifier for the V1 terrarium. With cool water, the way you are currently doing it, atomizing the water into little droplets spread around the terrarium will probably be very helpful in controlling air temps. They sell little ultrasonic disc humidifiers for very cheap, about $10-20.

But with the PC cooler route, V2 terrarium, correct me if I am wrong but you will be cooling the air then right not the water? Because the fan will blow air across the radiator, and the water in the radiator and pipes to the peltier will not be connected to the water in the reservoir for the plants?

If it works it works. Let us know how it goes. I was sour on the PC cooler idea but I didn't know you were planning to hook the peltier up to it as well, which will make a huge difference.

I was kind of rambling last night and thinking of things as I was typing them. But this will be very helpful if I ever need to build another heli terrarium because cooling it somehow is probably the hardest part. I'm lucky in that I have a room in the basement that is just naturally in the right temp range so I can keep my heli with very low tech.

entropy81 wrote:Ahh. Yeah I had the way you were planning to use the PC cooler radiator backwards. And some other things too.

I was thinking how you could include a compressor unit because I thought maybe you were saying the peltier device didn't cut it. I'll freely admit I've only read a bit about them and haven't used one. If the device is powerful enough for the cooling you need, then so it is and you don't need to go compressor route. Stick with the peltier you've already got.

Give some thought to the ultrasonic mist humidifier for the V1 terrarium. With cool water, the way you are currently doing it, atomizing the water into little droplets spread around the terrarium will probably be very helpful in controlling air temps. They sell little ultrasonic disc humidifiers for very cheap, about $10-20.

But with the PC cooler route, V2 terrarium, correct me if I am wrong but you will be cooling the air then right not the water? Because the fan will blow air across the radiator, and the water in the radiator and pipes to the peltier will not be connected to the water in the reservoir for the plants?

If it works it works. Let us know how it goes. I was sour on the PC cooler idea but I didn't know you were planning to hook the peltier up to it as well, which will make a huge difference.

I was kind of rambling last night and thinking of things as I was typing them. But this will be very helpful if I ever need to build another heli terrarium because cooling it somehow is probably the hardest part. I'm lucky in that I have a room in the basement that is just naturally in the right temp range so I can keep my heli with very low tech.

For the V1 its working, however the cooling effect is most effective if the air droplets can evaporate (which "costs" energy thus reducing temperature) as mentioned by lethal trap, however it is an efficient and cheap way of cooling terrarium to ambient.

With the PC cooler route i plan on cooling the water with the peltier then pump it to the radiator to dissipate the cold over there (inside the terrarium), i tested the temperature of the peltier in air, and it got to -10 degrees C in ambient air, and 600ml of water by 10 degrees C below ambient, so for the amount of water in the cooling system i'm expecting a drop of 10-15 degrees below ambient.

This weekend will prove if this is a viable option or not.

Ok i got my (second hand) rig and it needed some serious cleaning...

But here it is, even managed to fabricate a simple test setup holder.




Thermal glue is in place, once done ill try and see if i can get some testing done (might need longer hoses).

Edit:
Testing was done today, lowered the radiator in a cardboard box (72L) and poked a temperature sensor in there, so far only -3 below ambient, while ill leave the setup run for some more time, im off to scavenge an A/C unit.
End result: -4.3 degrees below ambient.

So an update regarding the AC, i bought a second hand portable AC that i will try to mod into a cooler.
This will be done by using the cooling radiator of the AC for cooling the water going to the terrarium (this way i have less issues with a drop in humidity, a more gradual decrease in temperature as well as the ability to use it for multiple terraria if ever needed).

The AC; an analog controlled 9000 BTU portable airconditioner (you want it to turn on when powered)


Remove all covers and disconnect controls and power supply (remember to take a picture how everything was connected!)


Remove the "cold air blower fan" and copper piping isolation.




Here comes the difficult part: Gently bent the copper piping, i did this manually and had enough bends to increase the length. Any kinks in the copper piping and you can start again.


To do:
Saw off "cold air blower fan" driveshaft and isolate bottom.
Make a box that will hold the coolant and the radiator, and again: isolate.

Wow, you are ambitious. Taking apart the AC unit and messing with the copper tubes. I would have just tubed it into a mini fridge I think but I have no doubt what you are doing will end up nicer. I'm sure you can get that to work, you have overkill equipment now, it's just a matter of getting it hooked up somehow which I am sure you will.

What was that clear cylinder on the PC cooler? A reservoir?

entropy81 wrote:Wow, you are ambitious. Taking apart the AC unit and messing with the copper tubes. I would have just tubed it into a mini fridge I think but I have no doubt what you are doing will end up nicer. I'm sure you can get that to work, you have overkill equipment now, it's just a matter of getting it hooked up somehow which I am sure you will.

What was that clear cylinder on the PC cooler? A reservoir?

Haha! Thanks, the copper tubing was not as hard as i imagined.
Before you spend all your savings on a mini fridge, be aware that a mini fridge often works with a peltier, and if they are compressor based, they are not ment to run continuously for a few hours at a time. Yes, it might be overkill

And it is indeed a cooling water reservoir, however i wont use it with the ac unit cooling.

already made a waterproof box for the radiator, now doing the insulating.

I'll be following this build. I read through your last build and it gave me the idea to consolidate a couple of my grow areas into one cabinet with multiple sealed chambers. One for a Heli area with cooling, and one for Drosera and germinating seed. Your last build looks incredible by the way! Beautiful craftsmanship, and it's functional! Something definitely worthy of being a show piece in the living room!

You have inspired me! Thank you!

Keep up the good work!






Sent from my SM-G930V using Tapatalk

boarderlib wrote:I'll be following this build. I read through your last build and it gave me the idea to consolidate a couple of my grow areas into one cabinet with multiple sealed chambers. One for a Heli area with cooling, and one for Drosera and germinating seed. Your last build looks incredible by the way! Beautiful craftsmanship, and it's functional! Something definitely worthy of being a show piece in the living room!

You have inspired me! Thank you!

Keep up the good work!

Sent from my SM-G930V using Tapatalk

Thank you for the kind words.
Using this setup i am convinced you can connect multiple large terraria to the main cooler due to the overkill of cooling power.

Got some more work done today

Remove some of the structural steel to make it possible to fit a single sheet of MDF


Sheets of MDF attached and controls installed on the front.


And the backside.

I also tested it with water, and it is waterproof

The benefit to overkill equipment with a well insulated terrarium is it won't have to run constantly, you can probably put it on a thermostat and it may kick on 5 minutes every hour.

Then if you ever want you can just lower the thermostat and make it ultra-highland.

And its finished, all i have to do now is connect the tubing/pump/radiator and wiring, i also added some screens for the heating radiators (bottom) which are not shown in the picture yet.



I just tested it out, it reaches -4 degrees C (at 21 ambient) within 5 minutes.
That is gonna be a really cold terrarium, i might have to add a fan speed control on the radiator fans.