So I decided I really wanted a nano tank for my desk at work, and I figured I might as well make it computer controlled. Here's the list of features:
Definite:
3G Mr. Aqua rimless bowfront (don't have that yet)
TEC cooler/heater
water temperature sensor
DIY filter/pump
ambient temperature sensor
dimmable LED lighting w/color control
Maybe:
wireless
LED UV sterilization
after-heater temp sensing
turbidity measurement
Here's some of the materials I'll be starting with (Click for bigger pics)
The pump, scavenged from a cheapo desktop fountain. It's about 1" diameter.
Some acrylic, HDPE and aluminum for the filter case.
The peltier cooler (TEC). I picked this up from an electronics surplus place years ago because it looked cool. Finally a use for it...
The heatsink. When using the TEC as a cooler, you really need a good heatsink for the warm side of the cooler. .
So far I've managed to mill the case out of plastic (3.5" x 3.5" x 1"). The pump will fit inside and there will be an acrylic lid on one side to see what's going on, and the other side will be aluminum, heated/cooled by the TEC.
The aluminum cover. I think I'm going to cover the outside of this with a sheet of styrene to insulate it. Hard to get a sense of scale, but the screws are all 1" apart. The rest of the pics aren't this out of focus...
A microprocessor will control the following: pump speed, temperature, lighting, low water alarm, and UV sterilization as well as logging ambient temp and turbidity. Connecting to a PC will allow me to read the sensors and logs and adjust setpoints for the controls. I plan to have 24 hourly settings for everything so that I can have, for instance, orangish light in the morning, brighter bluish light mid-day with a slightly higher temp, and blue light with a lower temp and UV sterilization at night. I don't know if I'll need all of that flexibility, but it's the gadgets that make it fun for me.
I'd love to put in a ph sensor, but I have yet to find a decent diy probe and the commercial probes are too big and outside the budget. If you know of any way to build a small, cheap sensor I'd be happy to hear about it.
I will probably be using an ATMega128. I have one of the USB AVR modules (a Bumble-B) but I haven't learned the USB api or programming toolchain yet. It would be easier to stick with what I know.
Yes, I'm an avid fan and customer of Sparkfun also. Hmmm, I bet I could point this color sensor at a DIY drop checker and control some CO2...
On the build side, I did some testing and found I could heat 400mL from 62 F to 78 F in 20 minutes, but 20 minutes of cooling only got me from 78 F down to 74 F. Not good enough. Prototype 1 down. Ah, well, the pump was too noisy anyway, so I am designing a new pump from scratch, probably based on a brushless DC control scheme. More info after the weekend maybe...
The styrene "sweater" on the outside of the aluminum cover with a hole cut for the TEC. This should insulate the heat/cold from the air a bit. The black fittings along the top used to be an air line tee, that I sliced into thirds and glued into tight-fitting holes. I hope to use air line for the intake and exhaust.
The pump mounted in the frame. The white tube in the upper left is to direct the incoming water towards the aluminum for more efficient heat transfer. The intake for the pump is on the right end, just below the exhaust tube. I plan to put something inside to use as filter material, possibly the plastic-based pillow stuffing? I am assuming I want to stay away from anything organic, like wool.
My next action will be to close everything up and see what kind of GPH I can get from this thing. Is there a ratio I should be looking for, like the pump should turn over the entire tank 3 a minimum of 3 times every hour?
On a side note; I'm way too impatient to be using cheapo aquarium-safe silicone (I found Loctite brand at the Lowes down the street). Is there anything that cures faster?
Are you using bluetooth for wireless connection? That would be cool.... Wires are so 2009.
and you can use LED for lights. The heat output from that would be minimal so controlling tank temperature would be easy. And as for pumps, you can find a cheapo desktop pump for little fountains at hobby stores or petsmart.
If I go wireless, it will be this module. I just wrote control firmware for it last month, and I have several laying around.
I plan to get some white LEDs from Deal Extreme (maybe these 10W!) and throw in a few low power RGB LEDs to vary the color a bit.
The pump shown a few posts back was scavenged from a desktop fountain, but it was too slow at 3.3V and way too noisy at 5V. Time for a custom solution. I just finished writing the G-Code for the 1.7" diameter pump impeller:
Maybe I'll get a chance to cut one tomorrow night. I found a decent motor in my "motors" bin in the garage. Nice and quiet, with decent torque. I am planning a magnetic clutch drive so I don't have to fiddle with any rotating seals.
I'm also thinking, as long as I'm at it, I might as well build the tank, too. I'll pick up some glass once I get the pump & TEC figured out.
I had a change of plans and decided to concentrate on the cooler for now and buy the pump. I have a couple on the way, hopefully they will be here Monday.
Almost all water blocks used for CPU cooling are copper (since the thermal conductivity of copper is twice that of aluminum) but I know that copper is bad for fish, so I milled a channel in a small piece of aluminum and sealed it against a piece of acrylic with some silicone. I also made my own airline fittings that could thread into the acrylic:
Then bolted on the TEC, a heastsink and a fan:
For testing, I used the little fountain pump to push water through the block, while I measured the temp of the 500mL reservoir at 5 minute intervals:
This shows that I can get at least 10 degrees below ambient with this setup, which should let me keep a small tank safe in the office when temperatures hit around 90-95F.
I have two really nice Gamoto motor controllers (the guy who makes them is a friend of mine) that I will use to drive the pump and TEC.
I plan to keep triops (and plants) in the tank. Since the life cycle of the triops is short (20-40 days), and the gravel needs to be dried between each generation, I am thinking of building a basket that holds the gravel and plants. Then I can lift that out of the tank when it's time to swap substrate.
Do you have actual tank water running through that aluminum block? If so, I am unsure if you want to do that.
What are the environmental effects of aluminum in water?
Aluminum may negatively affect terrestrial and aquatic life in different ways. Regular aluminum concentrations in groundwater are about 0.4 ppm, because it is present in soils as water insoluble hydroxide. At pH values below 4.5 solubility rapidly increases, causing aluminum concentrations to rise above 5 ppm. This may also occur at very high pH values.
Dissolved Al3+-ions are toxic to plants; these affect roots and decrease phosphate intake. As was mentioned above, when pH values increase aluminum dissolves. This explains the correlation between acid rains and soil aluminum concentrations. At increasing nitrate deposition the aluminum amount increases, whereas it decreases under large heather and agricultural surfaces. In forest soils it increases.
Aluminum is not a dietary requirement for plants, but it may positively influence growth in some species. It is taken up by all plants because of its wide distribution in soils. Grass species may accumulate aluminum concentrations of above 1% dry mass.
Acid rain dissolves minerals in soils, and transports these to water sources. This may cause aluminum concentrations in rivers and lakes to rise.
Aluminum naturally occurs in waters in very low concentrations. Higher concentrations derived from mining waste may negatively affect aquatic biocoenosis. Aluminum is toxic to fish in acidic, unbuffered waters starting at a concentration of 0.1 mg/L. Simultaneous electrolyte shortages influence gull permeability, and damage surface gull cells. Aluminum is mainly toxic to fish at pH values 5.0-5.5. Aluminum ions accumulate on the gulls and clog these with a slimy layer, which limits breathing. When pH values decrease, aluminum ions influence gull permeability regulation by calcium. This increases sodium losses. Calcium and aluminum are antagonistic, but adding calcium cannot limit electrolyte loss. This mainly concerns young animals. An aluminum concentration of 1.5 mg/L turned out to be fatal to trout. The element also influences growth of freshwater bony fish.
Phytoplankton contains approximately 40-400 ppm aluminum (dry mass), which leads to a bioconcentration factor of 104-105 compared to seawater.
Terrestrial organisms also contain some aluminum. Examples: mosquito larvae 7-33 ppm, springtails 36-424 ppm (dry mass). Together, pH values and aluminum concentrations determine larvae mortality.
A number of LD50 values for rats are known for aluminum. For oral intake this is 420 mg/kg for aluminum chloride, and 3671 mg/kg for aluminum nonahydrate. The mechanism of toxicity is mainly based on enzyme inhibition.
Only one non-radioactive aluminum isotope occurs naturally. There are eight instable isotopes.
I think the better question is "why not?" This is a hobby, and the more effort, the better if you ask me
Also, a lot of the aspects that the OP wants to solve here are already solved in commercially available options for larger tanks...
trackhazard: Yes the water is running through the aluminum, but I think that as long as the pH levels stay around 7, I should be OK. Also, I am only putting triops and plants in it, so at least I wouldn't be killin' any fish.
ikuzo: mistergreen and regloh pretty much covered it, plus I like small (take a look at my robots to see proof). Also, this is for my desk at work, so smaller is better.
Update, no pics tonight, sorry...
1. The pumps showed up today. The small one (6-12V dc brush motor) is really loud, so fail on that one. The larger one (6-12V brushless) is really quiet so I'll probably use that one. It pulls 800mA @12VDC and pumps 6.5 Liters per minute. Whoosh! Since it's brushless, I won't be able to vary the speed with a standard motor controller, but I'm sure I can figure something out. Pulling the water through the water block will slow things down quite a bit, and I can install another valve, but I hope it doesn't overheat if the throughput is too low.
2. I picked up a Triops kit at the local hobby store Saturday. I only put about 8 eggs in the container, and I now have 2 teeny(!) triops swimming around. I also ordered a couple of refill kits of eggs (in "test tubes", cool) in case I kill a bunch before I figure it all out.
3. I found glass at HD and grabbed 3 sheets of 12" X 10" and a glass cutter. I broke one sheet (whoops) but cutting the other two went well, so I will be building the tank hopefully tomorrow. It should be 10" wide by 5" deep by 6" tall
I have one of those Peltier coolers on my computer CPU, I'm thinking maybe during the summer ill take it out and put it on my 84 gallon aquarium. HAHA! Just kidding, but this is some seriously cool DIY stuff!!
My last semester in college I took a class called "Lifelong developments in Engineering" that discussed career development for engineers. We spent a bit of time discussing the relative merits of entrepreneur vs. working for a company. On our midterm we had a question that said something to the effect of "Do you want to be an entrepreneur? Why or why not?" and my response was that I got into EE to play with the really cool toys (test equipment, large scale systems, rockets, missiles, lasers, etc) and those either weren't affordable or feasible for small startups ("Guided Missiles 'R Us"?).
I got full credit for the question and a note that said "Hmm, never thought of it like that." Now I help design deep sea remote operated vehicles for a living. Wheee! (No, really. It's pretty darn fun when I stop to think about it)
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