Introduction: How to Make a Negative Ion Air Ionizer

About: general bloke type of tinkering
Two models will be shown, one full-wave rectified and the other a half-wave rectified negative ion ionizer. Featuring an optional fan on the full-wave model.

Benefits of negative ions supposedly include
• freshen and purify the air
• help lift mood
• alleviate depression including winter depression(SAD)
• eliminate most tiny particles suspended in the air (indoors)

  • HIGH VOLTAGESpresent in both devices is high enough to induce a bad case of temporary Tourettes. ie twitching/profanity.
  • Be aware of the hazards when working with loose CARBON FIBRE filaments if using this option for high voltage grid instead of pins.

Step 1: Components and Design

Tools required:
  • soldering iron and solder.
  • screwdrivers, flat and star
  • cordless drill.
  • hot melt glue gun.
Optional tool:
  • wire wrapper.
The full wave rectified version has better performance but is a bit noisier if using the optional fan. The fan is a 60mm x 60mm CPU 12 brushless fan which I'm driving at
5v to reduce current consumption and noise.

The half wave version uses fewer components and less current, the smaller size is also trickier to build.

In both versions the negative band on the diode must point towards the ac voltage input.
If you follow the green arrows on the component diagrams, you will first encounter the negative side on the diode first, indicated by the white band.

Step 2: Full-Wave Ionizer Materials and Component Layout

Materials required for full-wave version:
  • 2 x 10meg ohm resistors. (limit output current for safety)
  • 40 x diode 1N4007.
  • 30 x capacitor 100nF 275V class x2 suppression.
  • 1 length 350mm ega tube trunking.
  • 2 ega tube end caps for trunking.
  • 4 x self tappers for end caps.
  • low amperage hookup wire, ATX power supply type wire is fine.
  • 1metre 3 core 220v ac lead.
  • standard pins (or carbonfibre) for high voltage grid.
Optional components
  • 60mm x 60mm 12V dc fan, old cpu fan works well.
  • finger guard for above fan.
  • old cellphone charger +/- 5V dc to power fan.
  • small switch for fan, necessary for silent operation.

Step 3: Half-Wave Ionizer Materials and Component Layout

Materials required for Half-wave version:
  • 50mm PVC pipe approx 330mm long.
  • 2x 50mm pvc end stops.
  • 2x 50mm tube joiners, necessary for fitting the end stops.
  • 2 small self tappers, for fitting the removable end stops.
  • 1metre twin core 220v power, 5 amp is fine.
  • 2 x 10meg ohm resistors. (limit output current for safety)
  • 30 x diode 1N4007.
  • 30 x capacitor 100nF 275V class x2 suppression.
  • standard pins (or carbon fibre) for high voltage grid.

Step 4: Carbon Fibre Vs Pins for High Voltage Grid.

The two components of an air ionizer are high voltage and sharp points on the high voltage grid.

I prefer carbon fibre (CF) due to the thousands of very small points from which the negative ions escape, versus just one compared to a pin.

However my method of obtaining said CF might seem a bit dodgy to some folk. What I did was use a broken CF tube from one of my RC planes(crashed :( ) and broke 3 small 2mm  x 20mm long splinters. I briefly set the tips alight and then blew the flame out, then I flicked the tips clean of loose ash/ fibres.
Try not to breathe these loose fibres or the result might be a persistent cough.
Once clean the pieces were wrapped with thin copper wire, to act as a pigtail for soldering electrical connections to, and then shrink wrapped.
I keep the working tips about 3mm long to prevent them flaring out and shorting out on something.

Initially I sharpened standard dressmakers pins which worked well in the full wave version, however I might still consider an upgrade to CF tips for the full wave ionizer,

Step 5: Speed Wiring Tip

After completing the full wave ionizer, I discovered things go a lot faster if you're able to acquire a wire wrapper, seen in the pic below.
I use the one leg of the cap as the post to wrap the other 3 leads on.

It is also possible to make do without the wrapper and just use the same technique, but its just more fiddly and takes longer even though the end product will look neater.

Step 6: Full Wave Ionizer

The full wave rectified ionizer seems to work a bit better than its half wave brother, the optional fan also boosts performance, although some folk seem to think it gets in the way of the ion flow, possibly absorbing quite a few to the detriment of better performance.

The performance increases greatly with the finger guard grounded, which is why the fan is reversed with the finger guard facing inwards.

Step 7: Full Wave Component Assembly

First all the capacitors were glued end to end, 3 rows, then the diodes were laid on top and soldered. Observe the correct diode polarity with the white neg band pointing towards the ac input side.

The ground lead must be on the middle row of caps, and either outside row for live or neutral.
Once the components are soldered I put blobs of glue on the sharp soldered points to reduce corona discharge which improves HV (high voltage)performance.

The completed HV voltage multiplier array is then glued to the side wall of the ega tube, which also assists in component separation to prevent the high voltages from skipping across components.

Step 8: The Optional Fan and Its Power Supply

I used a nokia 5V charger although any cellphone charger rated at 5V will work, 4.5V doesn't seem to however.
A 60 x 60mm fan fits inside the ega tube stopend, which makes it easier to mount the switch, which is spliced into the dc output wire, nearby.
The fan will not work with its power reversed, so connect it up and see which way it blows. Then mount it such that it sucks the air out of the ionizer, with the finger guard on the inside, which is grounded to the green earth lead of the ac input.

Its best to remove any metal in the ion path including the metal foil sticker on the fan blades, it could absorb negative ions greatly lowering performance.

Step 9: The HV Pin Grid

Once the cap/diode array is glued in place, then the HV pins can be placed and mounted. I used pieces of the ega tube trunking hot glued and drilled for a small cable tie. Then the fan/grid assembly is spaced (1cm) from the pin tips, and the trunking is sawed off to size.
I also drilled the end caps to make them removable, 4 self tappers is all they need.

Step 10: The Half Wave Ionizer

Start off by gluing all the capacitors, 2 rows of 15 each. This format provides voltage separation between all the HV components, better performance, safer too.

Next I insulated all the connections with blobs of glue. I heard a lot of hissing when testing the unit upside down on a formica countertop, so I decided to do all the bare wires with the hot melt glue.
Its quite safe seeing as nothing gets hot enough to cause the glue to go transparent let alone melt.

Step 11: The End Cap, HV Grid and Neutral Grid

A bare copper wire was formed and glued in the pvc endcap, this will be connected to the neutral wire so care should be taken to keep where fingers cant reach.
Once again small pieces of pvc are used for mounting the HV CF tips.

Step 12: Final Assembly

The reason I dont bother with any fuses in the live leg of the AC input, is that you can get badly shocked from the HV side of things and the fuse is not even going to blow, let alone protect you.

I noticed that the cap array has a tendency to rotate inside the pvc tube so I glued some locating sections inside to stop it from doing so.

The important thing to remember is to discharge the unit if you want to work on it again, short the neutral grid to the HV side via the 10Meg resistors to avoid stressing any components.

DON'T FORGET to short out the 220v ac input once you have pulled it out of the wall socket, the caps still carry enough of a charge to wake you up rather rudely.

My future TO DO list might include:
  • upgrading the HV pins in the full wave version to CF tips
  • change the neutral wired grid in the half wave version to proper earth/ground grid, which just means I'll need a 3 core cable for the input instead of the present twin-flex.

The last image is a view of the upgraded CF tip array after a lot of use so its rather dusty in there.