Swamp coolers collect and breed all kinds of bacteria and mold in the water. As the cooler operates, these organisms can travel into your home and cause a variety of health problems. Chemicals can be added to the water to kill bacteria, mold and algae, but can be difficult to maintain.
It's be a proven fact that Bacteria, Molds and Algae can be killed by introducing copper and zinc ions into the water. Silver works very well to, but may be difficult for the home owner to construct a proper electrode.
All that is needed is to connect a suitable electrode of these metals to a DC power supply. The following shows how I made a simple ion generator.
For the emitting electrode I used a brass pipe found in a hardware store. Most brass material is composed of 60 % copper and 40% zinc.
For the DC power supply, only a milliamp (1/1000 th of an amp) is required. I used a 2 watt 62K resistor in series with an 1N4005 diode and connected it to a line cord for plugging into the 120 AC outlet that powers the swamp cooler pump. Heat shrink tubing covers the assembly. The diode forms a half wave rectifier and the resistor limits the short circuit current to about a milliamp. Ions are generated on the positive half of the line frequency and travel off the electrode as bursts of ions at 60 hertz.
The resistor value determines how many ions are generated. It operates like the principle of electroplating, but in reverse. We are "unplating" the zinc and copper from the brass pipe.
It's be a proven fact that Bacteria, Molds and Algae can be killed by introducing copper and zinc ions into the water. Silver works very well to, but may be difficult for the home owner to construct a proper electrode.
All that is needed is to connect a suitable electrode of these metals to a DC power supply. The following shows how I made a simple ion generator.
For the emitting electrode I used a brass pipe found in a hardware store. Most brass material is composed of 60 % copper and 40% zinc.
For the DC power supply, only a milliamp (1/1000 th of an amp) is required. I used a 2 watt 62K resistor in series with an 1N4005 diode and connected it to a line cord for plugging into the 120 AC outlet that powers the swamp cooler pump. Heat shrink tubing covers the assembly. The diode forms a half wave rectifier and the resistor limits the short circuit current to about a milliamp. Ions are generated on the positive half of the line frequency and travel off the electrode as bursts of ions at 60 hertz.
The resistor value determines how many ions are generated. It operates like the principle of electroplating, but in reverse. We are "unplating" the zinc and copper from the brass pipe.
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Is the fishy smell gone?
While I don't doubt it, I would like to see relevant links that back this claim up.
Also, I consider this to be a very dangerous project. Let's say that you have grounded the entire swamp cooler and it's working well. Then one day the ground becomes broken, or high resistance. Suddenly your swamp cooler is at 120V potential. Not only that, but your water pipes are likely to be energized. Yes, they will provide an inefficient return path to ground, but at points along the water supply you may touch a faucet and feel a shock. The low current may seem to prevent fatalities or injuries, but those components are not rated for AC safety use - they could fail shorted (lightning, large motors starting, AC line spikes, etc).
Even if everything works perfectly, let's think about the path you're forcing your current through:
Start at the AC transformer outside the home. Go to the breaker box, through house wiring to outlet and then to your circuit. At this point everything is low resistance and appropiate. Now the current goes to the electrode and into the water. The water has impurities in it, so it conducts a small amount of electricity - but to where exactly? You haven't defined in this instructable exactly how the current goes to ground. You specify that the swamp cooler must be grounded, but how does the water touch that ground? Will it work exactly the same way in every model of swamp cooler in use today?
Assume it goes through the plumbing. Now you've electrified all of the plumbing in your house. Then it flows to ground through either the dirt outside your home and then to a ground rod at the utility transformer or one outside your home, or through a ground clamp on the plumbing pipe leading to the breaker box. This is a poor return path, and at times it will rise to a 120VAC potential. Further, if you experience a huge line spike (regardless of whether your circuit fails or not) while you are touching a faucet or perhaps showering the incident may in fact be fatal. Further, this constant ground current may cause problems with grounding rods and plumbing scaling, to the detriment of the house's grounding system.
If we assume it goes through the swamp cooler's grounding system (maybe the pool of water touches the grounded metal) then you've electrified the swamp cooler. The ground then goes back to the electrical box then to the utility transformer. The current has a very poor path not only through the water (which is intended) but then has to go through the scale, muck, and slime that covers the metal in the cooler. The grounding screw in the cooler may be covered in oxides and provide a poor return path. The entire ground circuit from that outlet back to the breaker box is now electrified. Under the most ideal circumstances the resistance is low enough that the swamp cooler is only a few volts above "real" ground. House wiring is far from ideal. Not only is the swamp cooler likely to be at a dangerous potential, but any electrical item grounded in the same circuit is going to share that potential, and will also be several volts, dozens, of volts, over a hundred volts, and under bad conditions thousands of volts above ground potential.
I could go on, but the upshot is that this project should be torn down and re-developed. At minimum the project should be isolated, and a neutral electrode (not ground) should be placed near the hot electrode in the pool so the current follows a "correct" path. Isolation could be easily and cheaply accomplished with two back-to-back transformers if you don't have access to a real isolation transformer. A fuse and perhaps an MOV or two would add more security in case the transformer windings short, or the components fail. You should use a diode and resistor that will fail open under most common power problems (although the MOV and transformers will signifcantly protect the rest of the circuit, and clean up the AC a bit). I'd also consider using a constant current supply, rather than just a resistor.
Personally, I'd consider using a wall wart to provide the DC power - it'll have the isolation required, convert AC to DC for you, etc. You only need a few volts to get the electrode to dissolve in water. Since you're drawing less than a milliamp, a 9volt battery would last a month (625mAH/0.9mA/24H = 28 days).
Please don't encourage others to do what you've done. A disclaimer isn't appropiate here - this is design cannot be safely done even by an expert without huge changes. A disclamer is only appropiate where the design and execution are sound, but the workmanship requires special care or expertise. You may also want to touch on the buildup of hydrogen and oxygen gas. Keep it covered in the winter but forget to turn off the power and properly drain or evaporate the pool? oops...
2. I did provide a solution - the second to last paragraph suggested a wall wart or even a battery. The power source should be completely isolated from the 120 VAC line.
3. I hope that I didn't waste 20-30 minutes for this - my expectation is that my comment will help people understand that this design is fundamentally UNSAFE, and I hope that others will choose to implement something safer, such as I suggested. If this stops even one other person from dropping a non-isolated AC line into a swamp cooler then my time will not have been wasted.
4. I'm sorry if my phrasing suggests an antagonistic tone, that is certainly not my intention. But I must emphasize how unsafe this design is.
Lastly, I provided a design analysis. My comment is essentially the information I would have provided if this design was dropped in front of me at work and I was expected to critique it as an electrical engineer. Notice that I am not attacking the person. Notice also that I am providing substantial commentary - I didn't waltz in here and say, "Wow, this design is terribly unsafe, it could kill someone," and leave it at that. I carefully described why this design was unsafe, showed a few ways that it could prove dangerous to the occupants of the house, and then provided a suggestion that would lead to a better solution.
I'm sorry my comment was not helpful for you, but I do hope others have benefited or learned from it.
-Adam
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/gfi.html
Also, have you noticed any damage to plants due to the water coming out of your cooler with copper and zinc ions in it. I don't know if I need to dispose of the released water in a special way or not. I have heard that steel wool will grab excess copper ions, so could try it in a bucket under the overflow pipe if necessary.
My main problem is calculating the proper resistor to use for 1mA of current. Thanks for posting this project. It is very interesting. I hope it can help my sometimes fishy evaporative cooler.
As far as hurting the plants, copper is actually a required nutrient. I made a bubble lift hydroponic setup for a bell pepper plant. I used bare copper wire in the tubing to allow me to make a stiff bend and hoping the copper would stop algae growth. The plant did fine and the algae just continued to grow. With such low current, the copper ion production is also low. Copper ions quickly form low solubility compounds such as copper hydroxides in the soil, unless your soil is acidic.
I have a 1/2" X 6" brass pipe sitting on large a plastic coffee can lid one one side of the pump and several inches of 10 AWG stranded copper wire on the other side to act as a cathode. I hope ions will get pulled into the pump and circulated. I couldn't think of a good place to ground the cooler pan, since it's still in good shape. The paint doesn't appear to conduct well.
Everything appears to be working as intended. All components appear to be cool. Is the quarter watt resistor strong enough tolerate the load? Do you think ~1.43 mA is too much current? The pan holds close to ten gallons, but I don't have a purge pump or bleed off system. My soil is basic, so I'm glad to hear about the low solubility copper compounds. Thanks for all of the help.
http://www.freepatentsonline.com/y2004/0026264.html
http://en.wikipedia.org/wiki/Cathodic_protection
http://www.thinkzincanode.com/bustims.cfm
http://www.instructables.com/id/EWKMPVTF7FERIE2I8J/