DIY Peltier "ICA" Chiller

[doncb]

pardon me for asking what may have been posted, but how do you attach the peltiers to the block? I've got 3 40mm peltiers that I picked up off of ebay for a song and I'd like to use them for my 2.5G that has major temperature swings. I was just going to glue them right to the tank glass and see if they had enough 'oomph' to chill the tank a couple degrees right through the glass, but your idea seems much more fun.

Chris uses Arctica Thermal Epoxy to bond the TEC to the heatsinks in the ICA's. Be aware that if you use that, it's there for good. If you're going to screw the 2 heat sinks together w/ the TEC in between,then a good thermal paste would be the thing to use.

 

revance is right in that you want to keep the hot side as cool as possible. If you've ever seen one of the little thermal coolers, they use masive heatsinks. The air blowing off my ICA runs over 100 degrees. Make sure you don't run the TEC w/o the fan on. It will burn up fast.

[revance]

Well, it looks like it is never going to get a test run in the tank. My wife decided this past weekend she doesn't like me telling her "no, you can't keep that under your lighting" and bought a MH pendant. So we are now going open top with a pendant on the nano-cube. I'm glad she decided this before I took the time to cut up the splash guard in the hood.

 

Kind of defeats the purpose of a nano cube, but oh well... its "her" tank.

[halfpint]

 

I was looking foreward to seeing how well it performed. You could send it to me and I'll test it for you!

[Perpetual98]

I think I'm going to build a small unit for my pico using the 3 peltiers I have laying around. Maybe it will be too much of a pain though and I'll just use 1 of them, we'll see. I still need to scrape up a heatsink. Here's a quick sketchup plan that I did for sandwiching some 1/4" acrylic together. It would probably make more sense to channel the water through the center two pieces, but I didn't feel like getting that in depth with sketchup. I should be able to cut the acrylic easy enough, I just need to find some heatsinks and figure out what size hole to drill to tap a john-guest fitting into each side.

 

Or maybe I'll do something totally different.

 

Eric

[bigbabich]

If you pay your own electric bill, this is going to cost you.

[revance]

The peltier and fan I had was pulling about 80w on the PS I was using. If you only run it when the lights are on you are looking about $1.50 a month, if you put it on a controller it will be even less. Obviously using multiple peltiers will cost more... personally I think using more than one is really overkill on a pico.

[Perpetual98]

You see "overkill" I see a DIY challenge. I would be using it on a controller most likely and that will probably be the biggest expense.

 

I can't imagine that the electric will be that much. It's a 40mm peltier that's hardly the size of a half-dollar coin. That's why I was thinking about using multiple ones. I can use just one, but what fun is that?

 

Eric

[halfpint]

Instead of having three together, why not make three seperate ones in series, that way you would have good contact guaranteed on all three. Maybe even install some baffles in the exchange area.

Edited July 11, 2006 by halfpint

[Perpetual98]

I was planning on doing that halfpint, but I was too lazy to draw it yesterday. I did a quick mockup this morning. How's this look?

[halfpint]

I like that a lot better. How large is the scale? It seems like your baffles are stealing a lot of contact space by being that thick.

[Perpetual98]

I wouldn't call any of that to scale. The holes on the top will provide contact with the peltiers. I'm sure that the "channels" will be tweaked a bit before it's finished. You also want the water to go as slow as possible through there.

 

On another note, I ordered some fans today with small heatsinks (ThermalTake) and I'll see how those look when I come in. I also ordered some more weld-on 16 because I ran out. I'll have to see what I have for scrap acrylic or run to HD to pick some up.

 

The hard part will probably be figuring out how large to drill and tap the holes for the JG fittings. Wonder where I could find that out?

[ccjung]

Hey Guys

 

Not trying to interject, or be snide, but I have lots of experience in this area. As a Mechanical Engineer, your primary role is to deal with energy transfer in some way, shape, form, be it mechanical, thermal, electrical, etc.

 

The limiting factors arent "contact area", dwell time, or anything else, they are:

 

1. Hot Side Heat Removal - The heatsink is the limiting factor in this system because as more current/voltage is applied, the thermal overhead will become pretty large. The more juice you add, the more heat you will generate on the hot side, so much to the point that if you dont move enough heat off the hot side, it will backfeed into the water.

 

2. Power Supplys - DC power supplies arent cheap, and you really need to get one that will be LOW voltage/high current, enough to support your heatsink. This is why the basic ICAs we sell only run at 8.4 even though the Peltier can support as much as 15v.

 

Perpetual - we have talked a few times before offline and on the phone. To be honest. You will only need one Peltier to do the job of cooling that tank. Our ICA will keep a 5 gallon tank at 20F below ambient, and thats at 8.4v/2500mA. Try a simpler approach, like a single TEC, and you will have more cost/time benefits.

 

If you decide you still want to build this larger TEC, keep in mind that the heatsinks must be kept cool enough to be effective. Ideally, Peltier based devices are effective at under 100w because at higher wattages, the thermal overhead becomes too great.

 

Ie, you are going to use 200w to move 100w of heat, and that means you have to dissipate 300w to the environment via the heatsink, which needs to be large enough to carry the heat flux.

 

Regardless, this looks like a fun project. Im sure that if you can make the 3 TEC system work, you will be able to chill that tank to 20F.

 

Good Luck

 

Chris

Edited July 12, 2006 by ccjung

[Perpetual98]

I agree Chris, this is more of a "I wonder if this is possible" type project moreso than a "does this make sense to do it" project.

 

As far as power supplies go, I have several that I can possibly use at work for either cheap or free, depending on what I go with. There's a 12VDC one running at 2.5A that I have that I think I will use, or at least try. I have some 5V ones that run around 3.5A too, but I don't know if the voltage is high enough, maybe someone can answer that for me.

 

The controller is actually the part that I'm most concerned about. I'd like a dual-stage controller and I suppose I could even use a 2 peltier block and set it up to both heat and cool the tank (or a 1 peltier block creatively set up I guess) but I don't want to spend $100+ on a Ranco.

 

This is all just for fun anyway, and to see if I can burn my house down.

 

Later!

Eric

[ccjung]

Lol..

 

If you have access, try to hook it up to a variable voltage power supply to find the voltage/current the tec draws (we run a BK precision here at the shop), or even better, if you still have the auction/tec info, i can look it up for you.

 

I would go with the 5v, because the 12v will need to be up around 5A (depending on tec).

 

I have built some prototype controllers for the ICA, but its going to be part of our "nanocommander" system controller/datalogger. Let me know if you need some ideas on a controller, and ill shoot you over some plans.

 

 

Chris

[Perpetual98]

Would a computer power supply have enough "oomph" to it? Not sure what amperage they put out. I just found a 9.5V 2.7A power supply sitting on a shelf in my office too. That might work out well too. At least I can play around with them when I get the heatsinks in.

 

Chris, if you wouldn't mind sharing some contoller plans, I'd be game to look at them. Electronics aren't a strong point for me though, but I'd love to look at them and pretend I know what the heck they are.

 

PM me if you need my email addy.

 

Eric

[ccjung]

A computer supply would definately have enough "oomph" but again, im afraid of the heat on the hot side. Ideally, you could run any power supply in the world, if you were willing to cool the hot side with some water or a radiator.

 

In early development of the ICA, i toyed around with the idea of filling the hot side with water and letting it "boil" off. But then thought of the scenario where the user left or forgot, and the "inner lawyer" in me thought "lawsuit". Lol.

 

I would also look at oogies nc6 for some ideas on keeping the hot side of the TEC cool. I think he used a radiator to keep it cool and got tremendous pulldown.

 

PM me your email addy and ill see if i can throw together some plans for a temp controller. Personally, we will be running a Microcontroller based controller, so its mostly code. I do have some electronic/passive based temp control plans tho, so i'd be more than happy to share.

 

Chris

[Perpetual98]

Hmm, I'm starting to doubt those ThermalTake heatsinks and they're cooling capacity. I could always stack some peltiers and use a massive 8x6" aluminum heatsink that I have laying around at work. LOL

 

Sending PM to you Chris.

 

Eric

[revance]

Something to keep in mind on the power supplies... make sure the PS is self limiting on the current rather than protected. Not sure why so many are "protected" as the components needed to do that are more expensive than the ones to just limit the current draw, but many that I tried were.

 

The problem I had was that my peltier pulled over 4A with 12v applied and my PS couldn't handle it and "protected itself" by turning off. I ended up settling on a 12v 4.5A power supply that only limited the current to 4.5A. So even if the peltier pulls more, it would limit to 4.5A rather than shutting off. For my particular peltier, 4.5A @12v was just about perfect and managed to produce a nice sheet of ice on the cold side (with stagnant water of course).

 

As for cost, all the PS I used were just old ones laying around.

 

 

I might have to hook it up to my NC anyway just to see how it does. Unfortunately, now going topless the peltier chiller looks worse than just a small clip on fan. This whole topless thing TOTALLY defeats the purpose of a nano-cube.

Edited July 12, 2006 by revance

[Perpetual98]

Ok, I brought some stuff to work to play around with. I'm going to prototype a single peltier chiller because I don't have a heck of a lot of scrap acrylic laying around. The only thing holding me back from jumping on the CNC machine this morning is finding an O-ring. I'll probably jam over to the hardware store at lunch and look for one, but by that time, I won't be able to get on the CNC until tomorrow or Monday probably seeing as that machine gets pretty busy in the afternoon. I'm still trying to talk my boss into getting a 35W laser.

 

I was going to come up with 3 heatsink ideas, but I can't find my big heatsink/fan at home so either I'll have to give up looking for it, or I'll try the two that I have and see which one works better.

 

Eric

[shookbrad]

If you have an Ace or true Value Hardware store near you go their and ask for their scrap acrylic. They have tones as they sell the acrylic in std sheet sizes and if the customer wants one cut the scrap peaces are put in the trash bin. I have gotten peaces as big as 8" X 32" for free.

 

This is what I am planning on doing on my DIY Peltier chiller. I am going to build a voltage regulator using an LM317 put it inline with the peltier and a DC power supply I picked up for about $15 that runs 12V 5Amps. I am going to us the idea of an acrylic block to pass the water over the peltier. I got a large heat sink W/Fan from Tigerdirect for about $5.00. I have a good contact that always gives me great deals. The only thing I will be missing is the Temp controller which I might experiment with some set temp switches since they are cheap. If the heat sink gets too hot I might add a closed loop on it to help disburse the heat. We will see. I am slowly getting the parts.

[Perpetual98]

Sounds like we're on the same page. I found a little gasket that will work perfectly on my peltier.

[Perpetual98]

Ok, I spend some time this morning and cut some acrylic pieces out, but I still don't have the Weld-on, so I can only play with the top piece. I mounted the peltier temporarily too it and wired it up with the heat-sink. Upside down it gets a tablespoon or so of water really cold. It would be cool if I could freeze the water (just to say that I can) but either I haven't found the right power supply yet, or this little peltier just can't handle it.

 

So far I've tried the 9.5V 2.7A power supply and without a thermometer, it seems to be about the same as the 12V 2.5A power supply that I tried. I might also try that 5V 3.5A power supply too. I'm looking to see if someone has one of those infrared thermometers so that I can do some more accurate tests.

 

If I get bored I'll sketchup what I did.

[Perpetual98]

Ok, I got bored and didn't feel like working.

[revance]

Get yourself a 12v 4.5A or greater PS and you will have yourself some ice

 

Wish I had a laser cutter... I'll have to remember you do. You know, since I gave you all the idea of sandwiching acrylic together to make a water block and all

[Perpetual98]

Oh I don't have a laser cutter yet either. Yet. I'm trying to talk my boss into getting on. Don't think I'll be able to slide a $15,000 expense past him without him knowing. This job would have went SUPER fast with the laser. I assume that a 35W laser could cut through 1/4 acrylic. When he was here demoing the unit he had a chunk of 1/2 or larger acrylic that he said he cut through using 3 passes.

 

I found a 12V 4A power supply that I'm trying now. Unfortunately, I can't keep that one, it belongs to something else. I'll keep looking around at work. That's the nice thing about working at an electrical distributor.