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Does anyone know how to construct a homemade air purifier. The ones that are popular right now are in $400 range. Some people are saying the ones on T.V. don't work that good. They are quite simple to build. The principles involved changing positive charged ions to negative. Would appreciate any info on this.
We say that an ion is negative when it takes on an electron. With air cleaners of this variety when an oxygen atom takes on an extra electron we call it a negative ion. Going a step further when there are three oxygen molecules together we have ozone. When enough ozone is emitted it will cancel out to an ideal condition. <p>Using a high voltage source like a transformer used for neon sign so it will emit HV energy or UV energy from a pin others construct a screens fashioned into a cylinder with a small fan.
At the heart of the electronics it is mainly a low current high voltage DC supply. One made from a diode ladder should get you started. Not sure of the optimal voltage but I would guess 8kV to 15kV to be a good range. Much higher and you need to space the electrodes widely to avoid arcing and corona effects (though plasmas are cool, I doubt they are efficient air cleaners). Current would be nA or uA at the most.<p>The real art is in the electrodes and how they are shaped and configured with respect to one another. One can easily create an electrostatic field but to coax air to flow through it passively is the secret to the ionic breeze. In a cleaner, the collection plate must have a large surface area and the emitter will probably be a point (since electrons can leave this shape more easily) but may take other forms that would distribute the ions into the airstream more efficiently (a metal comb perhaps)<p>Another brand is simialr but it adds a fan to move the air faster, a basic charcoal filter which gets out some dissolved gasses as well as preventing large particulates from clogging the plate quickly and a second stage ionizer where ions are injected into the room (mainly for a fresh feeling) but are not recollected. (my friend got one of these and I found we had to turn off the ion generator when I had a sinus infection, it gave me a headache. While healthy, it does not bother me)<p>Another difficulty is what happens when the collection plate gets dirty. Now a non conductive film of dirt builds up on its surface until it no nonger does its job efficiently. At that point every grounded surface in the room becomes a dirt collector. You still have clean air but your walls get filthy.<p>The solution is a circuit that monitors the current at the collection plate then lights an LED and shuts down the HV supply when it falls too low. Not sure exactly how that works, do they compare it to a fixed threshold or compare it to the current out of the emitting plate. This is a feature of the latest generation of cleaners as well as better electrode design.<p>Good luck finding a schematic which pulls all of thease features into one place as this would describe one of the commercial products out there. Examples of each stage should be obtainable and a careful look inside a cleaner in the store may give you a head start on the electrode design. Fortunately I don't think the electrodes need to be made of any particular material but stainless steel would be superior if you plan to wash the collector plate with water regularly, it also resists oxidation and corrosion
Look at the actual patent for some useful insights. I found this one by going to www.uspto.gov and doing a quick search on the term "Zenion" I got 17 hits and most are owned by sharper image<p>In fact if you have the patent number, you may find reasonable plans for a product right here. Though you may need to combine ideas from several patents and fill in the blanks where needed. While it is illegal to use this information to produce a marketable product you are entitled to make one for yourself under the fair use rule as long as it is for educational purposes.
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