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| CO2 sensor! https://aquatictechtank.com/viewtopic.php?f=11&t=9 |
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| Author: | mistergreen [ Wed Dec 12, 2012 10:34 pm ] |
| Post subject: | CO2 sensor! |
| Author: | mistergreen [ Wed Dec 12, 2012 10:35 pm ] |
| Post subject: | Re: CO2 sensor! |
I'll stuff it in a breather bag to test things out. I'll think about the design of the enclosure later. Here's a link on how to interface it with the arduino via UART via IC http://cdn.shopify.com/s/files/1/0019/5 ... 1264294173 I'll have to make a bunch of Close enough par sensors first before I get to this. |
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| Author: | mistergreen [ Wed Dec 12, 2012 10:35 pm ] |
| Post subject: | Re: CO2 sensor! |
The sensor arrived. Cost: $75 shipped Will have to get some breather bags. |
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| Author: | mistergreen [ Wed Dec 12, 2012 10:36 pm ] |
| Post subject: | Re: CO2 sensor! |
Things look good for a bit! 1701ppm outside water I didn't see any noticeable leak so I went ahead with the experiment It took a few minutes but the ppm started dropping. It dropped 1 ppm every 2-3 seconds. This is totally responsive in an aquarium where we're looking at 9ppm - 50ppm max. The ppm is a lot more stable in the container compared to air. There was a 2-3 ppm deviation sometimes. I wanted to see where it would wind up but the readings stopped and notice there was a little water. The experiment ended at 1648ppm. I'm drying things out now. Hopefully there's no permanent damage. I'll need more silicone and thicker band next time. |
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| Author: | mistergreen [ Wed Dec 12, 2012 10:38 pm ] |
| Post subject: | Re: CO2 sensor! |
Converting ppmv to ppmw ppmw = (ppmv)(MW) / [(0.08205) (¦K)] / density of Water where: ppmv = air pollutant concentration, in parts per million by volume mg/m3 = milligrams of pollutant per cubic meter of air - (ppmv)(MW) / [(0.08205) (¦K)] ¦K = atmospheric temperature in degrees Kelvin = 273.15 + ¦C 0.08205 = universal gas law constant in (atm+liter)/(gmol+¦K) MW = molecular weight of the air pollutant (dimensionless) - mol weight of CO2 (44.01g/mol) 1000 kg/m^3 (density of water) density of Water = 1000 (kg/m3) - use 1000 as default since you'll need to measure the density to get accurate numbers. The density does vary due to temperature but very minor. 400ppmv of CO2 = .720ppmw |
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| Author: | mistergreen [ Wed Dec 12, 2012 10:39 pm ] |
| Post subject: | Re: CO2 sensor! |
Well, things look good. I found a little box with clasps at Michael's. I built a little container within it out of acrylic sheets and silicon glue. The lip has silicon on it so it'll make a good seal with the membrane. The top is the lid with a home made gasket make out of silicone. Everything assembled with silicone for extra measure. It is leak free. So then it got dunked into my high tech tank. It rose at about 1ppmw per minute. Final reading was 44.01 ppmw in my tank. It took 30 minutes to get there from 6 ppmw. All in all a successful experiment. I have ideas on making it even more responsive. Adding more holes in the lid might help and I made a thin sheet of silicone I will replace the breather bag. So now the next step if to hook this up to a relay to control the solenoid. |
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| Author: | mistergreen [ Wed Dec 12, 2012 10:41 pm ] |
| Post subject: | Re: CO2 sensor! |
| Author: | mistergreen [ Wed Dec 12, 2012 10:42 pm ] |
| Post subject: | Re: CO2 sensor! |
I made my own silicone membrane between 2 pieces of wax paper. It's 1 mm in thickness about 3x as thick as the breather bag. It's also twice as reactive allowing about 2ppm per minute. I also finished building the relay connections and will hook it up later today. I'll run for a month and observe fish reaction and BBa. ** oh, I just figured there's a mathematical limit to this sensor. You can only read 0 - 44.01 ppmw (this is what we want) and 0 -10,000 ppmv. It's good for growing plants. I probably had higher CO2 levels in my tank. I thought it looked suspicious that it stopped at 44.01ppm every time. I knew there's a reason why my fishes were so skittish. |
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| Author: | mistergreen [ Wed Dec 12, 2012 10:42 pm ] |
| Post subject: | Re: CO2 sensor! |
I tried making it thinner but it was impossible remove in one piece. Well at least it's better than the breather bag. I also have a big sheet of vytek. I'll try that later. Making the silicone membrane was easy. A glob of silicone between wax paper and a rolling pin or in my case a wine bottle. Let cure for a few days and peel slowly of one piece and then let it cure completely. I just did some equipment check and was trying to figure out why the relay wouldn't trigger the solenoid. It turned out the water still had 44+ppm of co2 in it. This is 6 hours after lights out. I'm going to stay with ranges of 35- 40 ppm. My fishes just aren't happy with the amount I've been pumping in and BBa isn't completely eliminated. I've put the sensor farthest from the outtake so some area will be more than 40 ppm I'm sure. Can you imagine the amount of co2 we're pumping into these tanks? Over 33x the amount in air. I'll check the co2 sensor manufacturer if they make something higher than 10,000 ppmv. **** they do make a 30,000ppm and a 300,0000 ppm model but they're $250. The 30,000 module should work. The maximum value is 132 ppmw. |
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| Author: | mistergreen [ Wed Dec 12, 2012 10:43 pm ] |
| Post subject: | Re: CO2 sensor! |
Ok, I bit the bullet and bought .010" silicone from I could have gone thinner but I'm afraid it might be too fragile. We'll see. |
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