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.
Step 1: Build the DC Power Supply
You will need a 1N4005 diode and a 62k ohm 2 watt resistor to make a pulsing DC power supply
Step 2: Mount Diode and Resistor
Mount the diode and resistor on a piece of perf board. The band (cathode) of the diode should be toward the left. The direction sets the polarity.
Step 3: Bend the Leads
Be sure to observe polarity of diode. The line cord is soldered at the resistor end and the electrode is attached at the diode end.
Step 4: Solder Joint in Middle
Don't forget to solder the joint between the resistor and the diode.
Step 5: Cut End Off Line Cord
Cut off the plug end of a line cord. Cut the green ground wire and the white neutral a little shorter that the black (120V hot). Strip only the black end and pre-tin the end with solder. Some line cords have a brown, blue and green/yell wire. The brown wire is the "hot" wire.
Step 6: Attach Assembly
Solder the black lead to the resistor end of the assembly.
Step 7: Attach Wire
Solder to the diode end a length of wire with a quick disconnect female connector.
Step 8: Cover With Shrink
Check your wiring and cover with two layers of heat shrink tubing. I used "sticky shrink" (the type with hot melt glue) on the final layer. The sticky shrink makes a damp proof assembly possible.
Step 9: Finished DC Power Supply
This is what it should look like. The generator is ready to have the electrode made.
Step 10: Attach Wire to Electrode
Attach a length of wire to the "electrode" with a pipe clamp to a 4 inch brass nipple with 1/2 inch inside diameter or larger. Use a heavy gauge wire because this will errode away in time too.
Step 11: Add Male Disconnect
Attach a male quick disconnect connector to the other end of the wire.
Step 12: Ready to Install
The completed ion generator with wiring ready to install in your swamp cooler
Step 13: Plugging In
Place the electrode in the water and plug it to the power outlet inside the swamp cooler. I modified the outlet so continuous 120 vac is supplied to the ion generator (bottom outlet), while power for the pump (top outlet) is only on when the fan is on. There is a small tab that joins both top and bottom "hot terminal" of the outlet made to break off with pliers. By keeping the ion generator on all the time keeps the water clean and also allows the electrode to act as a "impressed current anode" to save the cooler from corrosion.
Step 14: Working
The electrode can be placed near the intake of the water pump to allow water to flow though the pipe. Because the bottom of my cooler is epoxy, the electrode can be placed on the bottom without danger of shorting out. You may need to place the electrode on a piece of plastic or other insulating material.
In the photo, you can see "blobs" of something growing in the water, at the pump inlet. This is some type of a bioslime of mold or bacteria that I'm trying to get rid off.
In a few weeks or months I'll check to see if it is still present and see if this device works.
Because current will flow from the electrode (the copper and zinc ions) through the water and return back through the ground, be sure the swamp cooler is properly grounded.
Step 15: Current Is Flowing
Over time, small amounts of the brass will enter the water as ions of copper and zinc and will attack the mold and bacteria. Measured current of .89 milliamps with a meter connected in series with the device. Open circuit voltage is about 60 volts DC.
Step 16: Be Careful !
This Project at my website
Use care when handling the device when on. Remember the device is connected to the mains.
Current is limited, but a small shock may be felt if you touch the electrode, especially if it is wet.
This project should only be attemped with those with experience in electronic project building.