How to Make a Negative Ion air ionizer

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 VOLTAGES present 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.
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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.

t.rohner3 years ago
Nice instructable. I made one of these some 30 years ago. My mum wasn't that happy about it, because the high voltage charges fine dust particles and they are attracted by more or less grounded surfaces like walls and even windows ;-) If you direct the ion flow trough a grounded tube, you have a electrostatic air cleaner. (you can have a thin wire insulated in the center of the tube and connect the high voltage there. As it's done in laser printers.) You can also make a ion propulsion propeller...
2010-08-19 17.12.53.jpg
itsMeaMario made it!25 days ago

Thanks a lot for this nice inscrutable. I made a hack to an old one air ionizer which gave life. This way I was able to keep the old case and precious steel metal HV grid.

I used the half-wave method. It works like a charm. Only flaw is safety which will be worked on later on.

Now some pic's. There you see the 2 row caps with diodes on the back of the device. Next one is steel neutral plate which is pushed in from side so it is possible to clean those plates. front view w/o covers. Those sharp triangles is the HV tip. Next picture is neutral plates pushed in the device. Last one are old guts.

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petercd (author)  itsMeaMario24 days ago
Nicely done.
It seems to have been the trend to pot the HV components in resin back in the day.
I think they relied on the resin for insulation and thats usually where something burnt out. :(
white settler6 months ago
Hey Peter CD, still on this? I want to make an electrostatic precipitator for a wood burning stove, will one end of your ioniser stick in the air intake of the stove, with a positive charge sent by co-ax to the collector about 15 feet away? Can the charges pos and neg be collected from the same unit?
petercd (author)  white settler6 months ago
nope, neg only, you'd need to build another unit with all the diudes reversed to make a positive charge.
mmo66 months ago
question... how about? :

• help lift mood
• alleviate depression including winter depression(SAD)
petercd (author)  mmo66 months ago
mmmm, dont think so, however I live in Cape Town and have never seen snow here, hailed hard once or twice in the last 50 yrs, basically my point being that I dont get SAD in the first place so Im unable to tell you what would lift it.

I did notice that on the odd occasion Ive left it on all nite, that come morning left hand sinus is blocked.
So it lends some weight to a theory that the nostrils polarize the air positively or negatively depending on the bodys need.
bengtang9 months ago
Hi, if after unplugging it, you short the HV output (via the safety resistors) to the AC neutral wire input (or neutral grid), does that discharge all the capacitors (so you don't get a shock from touching the output or the caps)? What is the difference between doing this and shorting the live and neutral of the 220V AC input after unplugging? I am thinking of incorporating a discharge circuit into a switch for the thing so when i switch it off it disconnects the mains power and also discharges the capacitors, but i am not sure which points to short to accomplish this.
petercd (author)  bengtang9 months ago
"short the HV output (via the safety resistors) to the AC neutral wire input (or neutral grid), does that discharge all the capacitors (so you don't get a shock from touching the output or the caps)"


What is the difference between doing this and shorting the live and neutral of the 220V AC input after unplugging?

This doesnt short out the caps because the rectifier bridge blocks the rest of the circuit and if you short out after the rectifier you will only discharge one cap the others being blocked by the diodes

There is a strong discharge when shorting the circuit so its best to use a resistor to do it gently to avoid damaging other components

bengtang petercd9 months ago
Thanks, so to discharge all the caps i have to both short the HV output to the neutral terminal, and also short the live input terminal to the neutral terminal?

Anyway my plan of having a 2 way switch which shorts the HV output to the neutral end of the cockcroft-walton multiplier when the device is switched off won't work because it would cause arcing inside the switch while the device was on (unless i fill the switch with oil, then it leaks out and is messy). So i am just going to have the switch short out the live and neutral input ends of the multiplier through a resistor when it is switched off.

On another note, here are some ideas for other electrodes / ion emitters: A round wire brush of the kind used in drills for brushing rust off metal - the wires are thick and not very sharp, but there are a lot of them, and the places where they touch each other inside the brush also act like needle points.

A wire pipe cleaner / rifle barrel cleaner type brush, these have thinner wires so might work better. An ioniser using one of these had the highest ion output count among competing models analysed by the Elrana ioniser company, see this page, it has images of ioniser PCBs:

I have also seen razor blades recommended in one scientific paper - the super sharp edge is a brilliant at generating corona at low voltages, and the performance does not degrade as much with wear, compared to needle electrodes.

And the edge of thin gold or aluminium foil is also good, especially if it is cut at an angle, or you tear it using the serrated foil cutter on the kitchen foil box. This produces a serrated and thin edge. Get the thinnest (which is usually also cheapest) foil you can find.

Also, if you want to maximise corona production (which may also make a lot of ozone though), put a grounded or opposite charged electrode made of fine wire mesh near the emitter tips. The finer the mesh the stronger the effect, due to something about how electric fields behave when going to conductors shaped like a plane with slots.
petercd (author)  bengtang9 months ago
Eventually I upgraded both to the carbon fiber tips as in step 4, burnt the end of cf pieces with a lighter and then frayed out all the strands and shrink wrapped them to the ends of the HV pins.

Should probably upgrade the original doc.
bengtang10 months ago
Another option for the discharge electrode is to use a piece of recycled old bicycle brake cable. Trim it or sharpen it so the wire ends are sharper, then fray the end by untwisting the strands. Multi strand copper wire where the strands are very thin, like hair-like, may also work.
lucek3 years ago
WARNING! Devices like this have produced O3 aka Ozone. This has shown to aggravate breathing conditions like asthma. DO NOT repeat DO NOT use ionic cleaners if you or someone in the residence has breathing conditions. Further there is some risk of developing breathing conditions including but not limited to lung cancer.
bengtang lucek10 months ago
To reduce ozone production use less stages for lower output voltage, commercial air ionisers use 11 stages (= 22 caps half wave or 33 caps full wave), partly for this reason (and also to cut cost).
Thoth lucek3 years ago
A way too avoid or minimize the the dangers associated with breathing ozone, is simply to run the device while no one is in the room and turn it off before the room is to be occupied, it has a short half-life.
Wesley666 Thoth2 years ago
Isn't Ozone's half life like 3 days?
half life 3 you say? ;)
Don't they keep extending the date of release for that? I heard it was supposed to come out like 3 years ago and its still not here yet...
Yea the joke that people have been expecting it for like 7 years but valve will neither deny or confirm whether it is being worked on :/
If they make it, they should release it quietly in the dead of night with no warning, no advertising. I have always wanted to see what would happen if someone did that. I think it would cause quite a stir.
lucek Wesley6662 years ago
DNF came out so HL3 can't be far off. Or our fiery death.
lucek Thoth3 years ago
or just not to use them at all.
Skyriam lucek3 years ago
Don't get in a car, you may die. Don't go out while raining, you can get struck by lightning... twice. Come on man, the benefits are greater than the risks, besides ozone is very easy to detect, its smell is very strong and if you don't smell it then its far too small to cause any harm. Chill.
lucek Skyriam3 years ago
There is a question of risk vs. benefit. The risk is real. The benefit is minor. you receive less dust in the air but the same results can be had with a simple filter. if you argue that the ionic air purifiers work better (witch isn't proven) I'll point that only people with severe respiratory problems need that purity of air and they are the most susceptible to Ozone. BTW the safety levels are set at 0.05 ppm by the FDA far less then is noticeable. OSHA sets the safety level at twice that over 8 hours but still to small to smell.
Skyriam lucek3 years ago
There's more ozone/negative ions in the sea, forest and mountain environments than this little thing produces. So if you live near any of this places do you get sick from ozone? NO.
lucek Skyriam3 years ago
Materialistic fallacy doesn't work sorry. Again I listed safety levels. We have no tests of this device so we can't judge it's safety or ones built on it's design. Until it is tested we should assume it can be dangerous and the same should go for every one built on the design. When it comes to O3 "good up high - bad nearby".
lucek lucek2 years ago
Typo:Naturalistic fallacy.
Wesley666 lucek2 years ago
I like how you correct yourself more then a year later.
lucek Wesley6662 years ago
I didn't look at the post for a year. When I saw my error fixing it was important to me.
Wesley666 lucek2 years ago
No worries, that's what I meant, it's nice to see someone worried about spelling. I have done that too, finding an old post and realizing something was wrong and correcting it.
but ozone smells so good! like lightning!
正安1 year ago
Can I use a variac transformer which can output 0~260VAC(5A) and then connect a Cockroft Walton Voltage Multipliers which use camera capacitor 104/1KV and 1N4007 as diode.
I made it series connection about 10 stages,theoretically it can output 10X(input voltage),but I didn't get that much. Here is my situation:
Is there anything wrong?Why can't i get that 10 times voltage?
bengtang 正安10 months ago
You will never get the full calculated output voltage because of losses due to leaks and ripple voltages (AC wave forms superimposed on the DC output which decrease average Vout). The more the stages the more these losses, so adding more stages increases the voltage less and less. To reduce the losses use the full wave version and/or bigger capacity caps in the lower stages. Also the type of cap has a big effect.
See for more info:

Blaze Labs research Experiment 15 - Cockcroft Walton Multiplier
and Voltage Multipliers and the Cockcroft-Walton generator. Jason Merritt and Sam Asare
Which shows you that the type of capacitor also matters, and that one side of the cap array is more important than the other side.
petercd (author)  正安1 year ago
not too sure, maybe you'll have to check each stage to see if there are popped caps or something.
Otherwise it might have something to do with the variac.
bengtang10 months ago
RE: @fullnfi (for some reason the reply button won't let me reply to your post)

The theoretical output voltage of both the half and full wave versions is given by

Vout = 2 x Vin(as AC RMS) x 1.414 x (# of stages)

In practice it is lower because of losses via discharge, and ripple voltages. Each stage in the ½ wave version consists of 2 caps and 2 resistors, in the full wave version it is 3 caps and 4 resistors, so for 30 caps you have 15 stages half wave (more stages), or 10 stages full wave (less stages). The advantage of full wave is that it is more efficient, produces higher output current, and less ripple voltage (an AC waveform superimposed on the DC output which decreases average output voltage) for the same number of stages, so for a 10 stage multiplier, full wave will give more voltage and current output than half wave, but it needs more components than half wave.

Another way to reduce ripple voltage is to use higher capacity caps in the lower stages. For more info see: Blaze Labs research Experiment 15 - Cockcroft Walton Multiplier
and Voltage Multipliers and the Cockcroft-Walton generator. Jason Merritt and Sam Asare
Which shows you that the type of capacitor also matters, and that one side of the cap array is more important than the other side.
bengtang bengtang10 months ago
Oops not resistors, diodes
nox14681 year ago
one question, could you theoretically make one that runs on DC instead of AC?
petercd (author)  nox14681 year ago
sure, but seeing as the ac voltage is principle for the device, you would need an inverter and run the device off the output of the inverter.
nox14681 year ago
nice work,but i was wondering if this ionizer could be used in this project
and if not, were i could find an ionizer that would work for it.
petercd (author)  nox14681 year ago
I also don't advise touching these devices to build up static in your fingers.
I blew every one of the diodes whilst messing with an ion propeller and it accidentally touched earth, it would probably be safer to touch a taser, at least that wont kill you.

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