In article <548kcv$rob@niflheim.rutgers.edu> Phillip Debrito (debrito@niflheim.rutgers.edu) wrote: : I'm looking to build my own powder coating gun. For those not familiar : with electrostatic powder coating, let me provide some basic info... : So, do I create a series of metal loops in the gun with the (+) : lead and the pass the powder through these loops or what? How does it : work in those little air Ionizer/Purifiers? Hi Phil! I don't have direct experience with these, but I know some electrostatics. You want to generate a small area of plasma so that air passing through it becomes charged. The charged air molecules then attach themselves to the powder particles, charging them. The classic way to generate charged air is to place a sharp metal needle very close to a metal plate, then connect high voltage between the two parts and blow air between them. The voltage should be less than that needed to cause sparks. Which polarity of air comes out? If the negative supply lead goes to the needle, then the device will generate negative charged air. Another way to do the same is to suspend a very thin wire fairly close to a metal plate. (Copiers use tungsten wire, which isn't corroded as much by oxygen in the plasma.) A plasma forms around the wire, and the air passing through it will become charged. The charger assembly in your gun might take the form of a grid of needles near the inside surface of a metal plate, or maybe it's a sharp-edged cylinder held within a larger cylinder so that the sharp edge is close to the flat inner surface of the bigger one. Air blown through the slot between them will become charged. The key is to put a pointy (or sharp-edged) object near a flat object, so "st. elmo's fire" forms on the pointy object only. Two pointy objects give equal and opposite charge output, which is overall neutral. Two flat objects do the same, but only at much higher voltage. Hey, if you get it working, let me know how it turned out. Check out my electrostatics page at: "http://www.eskimo.com/~billb/emotor/statelec.html" -- ....................uuuu / oo \ uuuu........,............................. William Beaty voice:206-781-3320 bbs:206-789-0775 cserv:71241,3623 EE/Programmer/Science exhibit designer "http://www.eskimo.com/~billb/" Seattle, WA 98117 billb@eskimo.com SCIENCE HOBBYIST web page
Date: Sun, 20 Oct 1996 16:09:23 GMT
Original Subject: Re: Powder Coating Gun (High Voltage Ionizing)