Here is a nice setup with who you can make negative or positive ions.
The coil is a car ignition coil, which most of you have at home.
The important thing is to use the 2 caps after the HV diode if you want negative ions. If you choose to get positive ions, you can use only the diode in the reversed direction.
Have fun and be carefull. HV can kill bugs and also humans....
Steve
The Ion Generator:
The design of the Negative-Ion Generator is fairly straightforward (see Fig. 1). The circuit is a high voltage generator. It contains a standard 555 timer that's used to generate square-wave pulses. The pulses are applied to the base of the TIP120 NPN Darlington transistor. The Darlington provides sufficient current to the base of the 2N3055 power transistor to turn it on. Each time that happens, current flows through the high voltage auto-transformer, T2. The high voltage lead of the transformer is connected to a 10 kilovolt high voltage diode. Notice the polarity of the diode. It is biased to place a negative charge on C3 and C4, leaving the discharge point negatively charged. The voltage at the discharge point negatively charges the air forced past it by the fan.
The author's prototype was built on sections of perfboard using point-to-point wiring. It is a suitable method that you can use in your won ion generator provided you follow some precautions: Make sure you place C3, C4, D1, and the discharge point (which we'll describe momentarily) on a piece of perf board all their own. The junctions between those components should be at least a centimeter (about 1/2-inch) apart. Both this little high voltage board and the autotransformer should also be kept at least 1 centimeter away from the perfboard containing the other components, the fan, and the power transformer.
In passing, if you chose not to buy D1 from the supplier (1992) mentioned in the Parts List, an exact replacement may be difficult to locate. However, even though it has a lower current rating, an ECG518 or NTE518 should work fine, although this substitution has not been tried.
The discharge point should be "pointy" to enhance the ionization of the air. You can use a sewing needle, for example. An alternate discharge point can be fashioned from a small piece of No. 22 stranded wire. Strip off about 1/2-inch from one end of the wire and separate the fine copper strands so that they are more of less evenly dispersed. When the wire is connected to the high negative voltage, the end of each strand will behave as a discharge point.
Any screen or covering on the fan-outlet hole should be non-metallic or plastic in nature. Using a metal screen would severely cut the efficiency of the generator because the negative ions that come into contact with the metal screen would be neutralized.
When testing the circuit, if you see any arcing or discharge from the high voltage transformer or high voltage capacitors, cut the power immediately. Let the project sit for awhile to let the capacitors discharge, and, without touching the project if possible, coat the faulty are with a little "No Arc" spray (available from Radio Shack or Tandy). Allow the material to dry before testing the unit again.
(Tony's comment: The ECG518 and NTE518 are still available, the added bonus is that the ECG/NTE518 supplies 25mA instead of 10mA by the IMD5210).
Parts List:
R1 = 15K, 1/4W, 5%
R2 = 1K, 1/4W, 5%
R3 = 2.2K, 1/4 W, 5%
R4 = 470, 1/4 W, 5%
C1 = 1000uF/25V, electrolytic
C2 = 0.047uF, polyester-film
C3,C4 = 0.002uF, 6000WVDC, ceramic disc
U1 = 555 timer, 8-pin IC (no CMOS)
Q1 = TIP120 or NTE261, NPN, Darlington transistor
Q2 = 2N3055, NPN, power transistor
D1 = 10,000 Volt, 10mA, SI rectifier diode (see text)
BR1 = 4A, 50-PIV bridge rectifier
Additional Parts and Materials:
T1 = 12 volt 1.2A, power transformer
T2 = 12 volt to 8 kilo volt autotransformer
FAN1 = 12 volt DC fan.
Enclosure, line cord, switch, TO-3 socket/heat sink, perfboard, wire, solder,
hardware, etc.
