Just be cautious, while correctly working Air Ionisers are safe, poorly working or designed ones can produce Ozone which is unsafe (particularly over prolonged periods or high exposures). This article has more information (in particular citation 10 used in Adverse health effects):
Personally I don't see the benefit over a HEPA filter on a standard electrical fan, or a commercial unit with a similar design. Yes, replacing filters is annoying/has a cost, but there's no health downsides to the design and it is effective at removing air particulate. Building one requires an off the shelf HEPA filter, an off the shelf fan, and a couple of rubber bands. It isn't "sexy" or technically sophisticated, but it works. Want it improve effectiveness? Increase the surface area/make it bigger/increase the airflow.
Let's also consider what both devices (when working correctly) do. An Ioniser gives particulate a charge causing it to be attracted to and stick on surfaces. A HEPA traps particulate within a filter membrane. Or to phase that differently an Ioniser causes the particulate to dust onto every surface within range, causing dirt buildup/stains, dust blooms when disturbs, and people may still contact the air contaminants (since they still exist, now on surface rather than in the air). HEPA allows you to simply remove the particulate from the environment, Ionisers just move it from one location (air) to another (surface).
In addition to the health concerns, ozone attacks unprotected polymers causing them to quickly break-down and release additional toxins into the air. I run an ESD ionizer at my well ventilated re-work / soldering station and have had plastic storage bins on the bench crumble at the touch from the ozone exposure.
This is especially ironic in this case, because the entire premise of the article was: "I have always had the issue of dust settling in every week on everything if I open the windows. Cleaning that up every week is a pain."
They then proceed to build a device that will, if anything, exacerbate this exact issue.
Ozone is actually a useful disinfectant, just make sure to ventilate the room well after treatment. Obviously not the outcome anyone building an ioniser is after.
I don’t find that at all. The dust that sticks to surfaces in my apartment can’t be moved even by forceful blowing on it. It has to be wiped away.
Also, I notice that when I brush stuck-on dust off a surface (e.g. my coffee table), it’s still ionized—so it just either gets pulled back to the sides of the table, or to the floor.
As the former owner of a biggish HVAC-integrated electrostatic precipitator, these things are not really worthwhile. An ESP needs frequent cleaning to work well, in comparison to a plain old MERV 13 or so filter, which will work for quite a while with no maintenance.
An ionizer doesn’t need maintenance, but that’s because it deposits all the gunk nearby. Eww.
Lap soldered mains connection (can break off easily). Not double insulated (think small children and fingers). Also the actual ioniser port is usually recessed to avoid accidental contact as it hurts if you touch it.
Also lots of hand soldered MLCC caps are high potentials. They like to crack and explode if you do that. They need to be machine soldered really.
Edit: also the design doesn’t use proper voltage rated resistors on the output. I haven’t checked the other parts but it’s probably marginal. You’ll get home one day and find your house burned down.
what about "manual" solder paste reflow ? I think I saw a few vids where people hinted at the fact that it's uneven heat and physical stress from handling that caused damage
Those needles connected to active make me uncomfortable, though there's a 10M resistor, I'd have an isolating transformer on the mains - not an engineer though.
Fuse would be good. Here in UK there’s one in the plug. The 10M resistor will current limit. Or probably flash over here.
Isolation transformer is not required if the enclosure is better. It also doesn’t help you if you stick yourself across it somewhere, only helping yourself with respect to ground. If you’re testing it or doing development with it I would use one. But I wouldn’t build it.
I used to hang around inside old valve radios when I was a kid. You learn respect for high voltages very quickly.
Hey you guys,
Author of the article here. Thanks for mentioning the issues. I never meant it to go this viral. Crashed my website in the morning.
You seem to mention that the output resistor was wrongly chosen. Can you elaborate? I thought I designed it properly.
This post was not ever meant to be used without using basic safety features in mind. (Like keep it away from children and all). I will explicitly mention that to be taken care of in the post.
Happy to take any more constructive criticisms to make the post better.
Yeah no worries. We’re all hyper critical. Need to outline the dangers because people who are unaware of the issues working with mains tend to be the first to drop dead. This is followed by the people who suffer from Dunning-Kruger effect. Us amateur radio operators like to kill ourselves on vintage power amplifiers doing that.
The output resistor need to handle potential to ground so say 7kv across output to ground. Resistor is rated for 200V working voltage. Usually you use a chain of many smaller resistors here.
I haven’t reviewed the design entirely but the main problem is the enclosure and mains connection and the component choice. The mains connection should be clamped in the enclosure and either spade connections or screw terminals or ferrules. The enclosure should be double insulated. As mentioned a fuse would be a good idea as well.
It's 20M, which if connected directly across 240V causes 12uA to flow --- that's in the range of the natural leakage current in most SMPS, and not harmful at all.
The article mentions BigClive, and his YouTube channel does have a lot of stuff about ionisers, but his site has an article about them too: http://www.bigclive.com/ioniser.htm
He talks about carbon-fiber stuff to get lots of ionization points, but steel wool works great.
You will be able to smell if you are producing ozone, which you don't want unless you like permanent lung damage. The smell is sharp. like around electric sparks. If you get that, the voltage is too high. Just leave off a few voltage stages.
All comments seem to recommend a good old filter over an ionizer. Would an ionizer in series with a filter (e.g. in air ducts ) be more effective than a filter itself?
For some uses. I have to recommend the commercial Honeywell units highly: they're excellent at pulling tobacco smoke and smell out of the air; and yes the area around them will catch all the other dust around too.
An estimated power use of 4 kWh per year -- only costs 4 Rupees in Mumbai? (around $0.05 USD) That's surprisingly cheap power. The US average is 10x higher. ($0.13/kWh)
https://en.wikipedia.org/wiki/Air_ioniser#Adverse_health_eff...
Personally I don't see the benefit over a HEPA filter on a standard electrical fan, or a commercial unit with a similar design. Yes, replacing filters is annoying/has a cost, but there's no health downsides to the design and it is effective at removing air particulate. Building one requires an off the shelf HEPA filter, an off the shelf fan, and a couple of rubber bands. It isn't "sexy" or technically sophisticated, but it works. Want it improve effectiveness? Increase the surface area/make it bigger/increase the airflow.
Let's also consider what both devices (when working correctly) do. An Ioniser gives particulate a charge causing it to be attracted to and stick on surfaces. A HEPA traps particulate within a filter membrane. Or to phase that differently an Ioniser causes the particulate to dust onto every surface within range, causing dirt buildup/stains, dust blooms when disturbs, and people may still contact the air contaminants (since they still exist, now on surface rather than in the air). HEPA allows you to simply remove the particulate from the environment, Ionisers just move it from one location (air) to another (surface).