Two years ago I switched on a Negative Air Ion Generator I'd just built, and it's been running ever since. Click on the photos above to examine it, and kindly excuse its rather odd appearance. It was completely experimental, and never did get the much better-looking enclosure I'd planned for it. Yesterday I pulled it apart for cleaning and photographing, since I've decided to document it as a construction project.
The Generator proper is the stack of capacitors and diodes on the top platform. It sits above a small computer fan that blows the ions away and spreads them more quickly than air currents around the device. Most of the circuitry below it is for the fan; the ion generator circuitry itself is very simple, and the fan can be done away with in the next version since I've come up with a better idea.
Although a PCB (Printed Circuit Board) could be designed, the construction in the photos is actually simpler, more reliable, and more interesting. As can be seen in the right-hand photos, the capacitors are glued together in two back-to-back rows, and the diodes are connected in a rising spiral around them that mirrors the topology of the circuit.
The circuit topology used is known historically as a Cockroft-Walton Generator (CW Generator) after those who first devised it. As explained on the NMS website, "The Cockcroft-Walton generator was developed at the University of Cambridge in the early 1930s to accomplish the first artificial splitting of the atom. These generators became an essential part of particle accelerators and other devices in research laboratories throughout the world." Two photos of laboratory EHT (Extra High Tension) generators are shown below the schematics.
The circuit schematic of the NAIG is shown at top right. Below it is the traditional diagram drawn with the diodes angled between the capacitors, since this assists in understanding its operation.
The circuit has two independent sections as marked. The top section is the ion generator. The bottom section is a block schematic of the fan power supply and speed control which is not needed if the physical construction described below is used.
The theory of operation of the CW Generator is given at the bottom of the page: click here to jump down to it.
Constructing the NAIG
CW Generator theory of operation
The half-wave version is most commonly seen, but the full-wave version is usually used in EHT (Extra High Tension) laboratory generators.