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Air Ionizer/Purifier

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LAN_403

CT2

Mon Dec 10 2007, 03:50AM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

A while ago (on the old forum I think) someone made an air purifier/ionizer thing. Basically their design was a 555 driving an iggy coil with some diodes on the output, this was all put in a cardboard box with a fan and aluminum foil. Well I decided I was going to build one aswell.

I went out and got the wood and made a box seperated in two halfs; one for electronics and one for the air/ionizer. Added some hinges so it could easily be opened for cleaning, and cut holes for the fan and switches. I added a main power switch and a micro switch that acts as a safety switch for when the door is opened. Then I built the ionizing part out of some wire, it is kind of like a pointy copper christmas tree, I think this should do a good job of ion spraying. I was also contemplating adding barriers for the air to blow around, that way all the charged dust and stuff in the air will have more of a chance to settle (the inside of the box will be coated in tin foil). For the electronics I decided to go with a flyback over the iggy coil because it has a built in rectifier. Now this thing has to be pretty fail safe because it will be left running unattended, so I opted for Steve Conner's flyback driver

only with a half bridge instead of the H bridge..

I built the circuit to test and it seemed to work decent, the FET's got kinda hot and it didn't make very impressive arcs, then as I was adjusting the frequency knob the FET's died. Ok so that didn't work, next I built a new half bridge only this time I used a GDT to switch them. A pair of UCC 22/21 is used to boost the TL494's output. When I hooked it all up though it didn't work... of course not. For some reason it appears the UCC's are "latching" (?) up. When I turn power off to them they emit a brief burst of square waves, and when I turn the power back on they work for a split second. I have 2uF in series with the primary and diodes on the outputs of the IC's (1N4148 though, no schottky). I couldn't figure it out, it's probably something dumb though.

Well this is beginning to get annoying, so I just grabbed some IGBT's I had, lashed up a half bridge (no GDT this time), and finally it works. I'm feeding it 30V AC voltage doubled, so no load 95V, with the circuit running it drops to about 56 I think (small transformer). The IGBT's are on a pretty big heat sink but they still get warmer then I would like, I added 2uF cap in series with primary and this reduced heating and increased output, so that was a plus, but still too warm. Also I noticed that the flyback acrs between pins and to the core if I'm not careful, so I think it's puttin out a good amount of volts, maybe too much. I threw it all in the box to get an idea of space, and to see if it would actually work. I let it run for a minute or two and the tin foil had collected some dust already. So I think it works a little, and the fresh ion air smells good.

Now at this point I'm kind of stuck again. D3 in Steves schematic gets pretty hot, I'm using 2 parallel 1n4007's, is there a certain diode I should use? D2 also gets pretty hot, would it be worth while switching it to a schottky? Or would I be better off trying to solve that GDT/UCC problem? If anyone sees anywhere for improvement please let me know, I'm half guessing most of this

Hazmatt_(The Underdog)

Mon Dec 10 2007, 04:49AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

It's really no where nearly this complicated. You don't even really need a fan you know. All you need to do this is a single mosfet flyback driver using 35-60W and two metal meshes seperated by an inch or so. I did this while playing with my flyback driver and created a farily substancial flow rate of Ozone that could easily be felt on my face, and this from just two stainless meshes 1" square seperated by approximately an inch.

Just get rid of the pin farm and you'll be getting in the right direction in no time. After that its the choice of how many L/s of Ozone you want to generate, and power supply topology.

Electroholic

Mon Dec 10 2007, 07:17AM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

its also easier to just use a small 15 to 20 stage CW multiplier, adn hook it up to main.

...

Mon Dec 10 2007, 09:03AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

If you are curious as to how the 'real' ones look...the commercial Honeywell ones have small wires (about 1 every 2 inches), that are in front of some metal plates, about 3" deep. Like imagine a bunch of 3" wide rulers stacked parallel to each other spaced about .25" apart with a wire running above them on every 8th ruler. They were fed with a large NST looking transformer, but the new ones have a high frequency inverter and 5 stage CW multiplier. The ones we have use 2 cartridges about 12" by 24" that is in series with the main HVAC blower, and are good for some insane amount of air flow.

The idea behind the long plates is you can use a lower voltage (=less ozone, a plus for 99.9+% of people...), and you can pump tons of air through them and still catch the 99.9% of the dust coming through.

In any case, I would recommend putting more sheets of foil in you ioniser, space them like 1" or so apart. The should increase the effectiveness of the air purifier greatly

Steve Conner

Mon Dec 10 2007, 12:02PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

You need ultrafast diodes (UF4007, UF5408, etc) for my circuit.

Dr. Dark Current

Mon Dec 10 2007, 03:31PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

For the flyback driver part.. if you want a reliable and efficient circuit, go for the "zvs"/"mazilli" driver.

Mates

Mon Dec 10 2007, 04:14PM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

I would never close long term running fly-back inside a wooden box.There is quite high risk of fire...

Marko

Mon Dec 10 2007, 06:38PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I must admit I never understood the hype about these ionizers and air purifiers.

If you just want tons of ozone to purify air, then you should create large amounts of corona (not arcing in any case); I think it is mostly done by using plastic insulator between two conductive meshes, powered by high voltage AC and blown by fan.

Problem is that well constructed device like that is going to build toxic amounts of ozone very quickly - not something you want to have turned on for 24 hours in your living room!

You could do the same with mercury lamps.

Then there are those 'ionizers' which seem to use much less power, usually a small mains-powered CW multiplier fed to array of pointed needles, and blown by fan.

These produce hardly any corona at all.

I'm unsure about how negative ions are generated there.
Wouldn't they, acting as charge carriers, instantly recombine in contact with ground and humans?

How are they beneficial to health, and is it really worth leaving such a thing on 24 hours a day?

Marko

...

Mon Dec 10 2007, 11:31PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

The purpose is that they precipitate out particles in the air.

You charge up the dust with a negative HV source, and then they are attracted to the grounded metal plates.

Most commercial ones are specifically designed to give off little ozone (see my previous post), although they do give off a small amount. There are also some designed specifically to give off ozone, which can be used for sanitation (a replacement for brominee in hot tubs is common) or to mask other odors.

CT2

Tue Dec 11 2007, 06:43AM

Registered Member #180 Joined: Thu Feb 16 2006, 02:12AM
Location: Ontario, Canada
Posts: 187

Thanks for all the replys, but I guues I should have been a little more descriptive. This unit is meant to be used like an air filter, it uses negative charged ions to charge all the particles suspended in the air, then they are attracted to the foil and settle out. It isn't meant for making you feel better or anything like that, but that wouldn't be a bad side effect. It isn't meant to produce large amounts of ozone, infact the least amount possible would probably be best. Although I'm not sure how much it will produce, I do wan't some. I'm trying to figure out exactly what you meant about the 'real' ones. Is it like this, or am I completely off (I googled to try and find it but I could only get pictures of the units not the insides)?

I think the TL494 + hlafbridge will be better then the ZVS, mainly because I haven't gotten the ZVS driver to work very well, and the TL494 seems to do a good job, and hopefully better after a few fixes. I'll switch to the UF diodes, I thought that might be the problem, but how come I can use a 1n4148 diode for D1 but not D3? Once I get everything tested and worked out I'll make sure it is nice and tidy and that nothing can catch fire, plus it won't be on for too long unnatended. Maybe I'll add a little timer that turns it off after half an hour or something, just a little 555 that disables the circuit.

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