Electrochemical ozone generation

I've been playing with HV ozone for a little while now.. The results from this thread have prompted me to reinvestigate the basic tubular dielectrically separated electrodes..
The only convenient setup I've had to play with though was an 'as it was' 5" b/w TV flyback circuit from one of those Memorex karaoke machines.. (I simply use the HV+, and various wires cut from the CRT's yoke)..
This is a PUNY POS flyback with recifier built right into it.. I don't know details on its output.. (I fried an old multimeter on it though, so that should answer the question asked earlier about whether that is safe.)
This unit by itself will snap a spark at ~4mm, and that can be pulled to atleast 8mm before the streamer dies.. In my experience, the tube design doesn't work, although I only had crappy plastic tubes of appropriate size (yea its pretty pathetic to be here, and not own a test tube ATM.. Anyways, I never got corona that way.. Depending on the config, it either sparked, or seemed like way too much separation and did nothing.. I tried many wire types/sizes..
Two methods I tried produced a decent amount of various oxidizing gases.. Two sheetmetal plates separated by glass seemed to do nothing.. Then I tried allowing the sheets to overhang the edge of the glass such that only air separated a small area of the 2 sheets, and voila, I got a blue glow in the crevice crawling from one plate, across the glass edge, and to the other plate.. It gets really intense and smelly when hit by humid breath.. Surface area/Power must be an issue, because the gap size (as in the surface area separated by only air) was highly tunable.. (Btw, this is one nasty capacitor, so always discharge!) The downfall is intermittent sparking when I try to maximize the corona, but with careful assembly that can be nearly eliminated..
Another method I tried was positive pin corona.. This one is IMPRESSIVE but touchy.. I used an aluminum plate, and many unbraided 'fine' wires fanned out where they were stripped (about 20 braided wires stripped), and positioned perpendicular to the negative plate.. (I found SS is more corona prone than Cu btw).. The contraption was built into a plastic P Butter jar so the lid's threading could be used to adjust spacing.. Many streamers, and tons of hissing, but again maximization is a nightmare since each of many strands needed be perfectly gapped, and decented fanned apart from its sister strands.. In anycase, the best I ever did was ~30 good streamers without others sparking, but even a couple of streamers pump the O3 nicely.. I want to see how a fine brass brush works on the pin side since it may be ideal for calibration..
Negative pins is a whole different shebang.. Rather than streamers, the wire tips only emit corona dots.. Sparking is way less likely, but not as much O3, and when a spark does occur its red/hot, and burns the wire strand.. (Unfortunately metal balls up at the tip which is poor for corona, otherwise I'd use that aspect to evenly space the pins via burning..
Other downside to the sparking is that the EMP loves to crash my router etc..
I've collected quite a bit of literature on corona.. I'll try to collect it all into one place.. If I post a link to anything that may put the site into a copyright delemma then I appologize.. I'm not entirely versed on site policy..
Anyways, as I dig them up I'll post them all in the same directory on my webserver (/scimasdness).. For now:
http://triggernum5.servebeer.com/scimadness/coronadischarge.... <-Very comprehensive, begins at basics, and even discusses driver circuits..
http://triggernum5.servebeer.com/scimadness/PositivePoint2Pl... A bit o' data..

I was wondering if I could get a critique on this schematic I adopted for use as a power supply in an ozone generator.

Original, Fly-back based design:


Crappy Schematic:


Attempt to create board traces:


The estimated 960V DC is being fed by a 120V, 1-6A AC --6:1 step up transformer--> ~720V AC --Full wave 1-Phase bridge recitifier rated @ 1200V, 35A--> ~960V DC.

The idea of this scheme is to create a power supply in which both the frequency and the ampreage can be controlled. In this case, the supposed ideal is roughly 30kV, 10mA, 18-22kHZ. This is based both on the yet-to-be constructed ozonators design and also several scientific papers on the production of ozone.

Please feel free to point out any and all flaws, and if the knowledgeable would be so kind as to explain a solution for those flaws, I would be most grateful.

My sincere thanks,
Natures Natrium

Alright, thanks again for the rapid reply. I did a web search for an inverter NST, didn't get anything. Most of the inverter schematics I could find were specifically for producing 60hZ 110v AC from a 12v DC source. I found references to inverters which produce 20khz AC internally, but could find no schematic which does the same. I found high current, high voltage transformers for welders, but the frequency there is usually around 1khz, plus they are expensive.

Also, it somewhat shames me to admit I could not find anything regarding a workable chopper circuit. Everything I found regarding that subject was in reference to signal processing.

So, I did some brainstorming and came up with a couple of ideas, and shot most of them down myself after some thought.

The only one which I think might work is placing the step-up transformer between two of the IBGTs aligned directionally, and have both IBGTs triggered by the same signal from pin 3 of the 555. When the signal stops and the gates close, the coil is isolated from the circuit, and a capcitor (with in-line resistors) with leads connected to both ends of the transformer absorb any kickback and feed it back into the system.

Perhaps I should have mentioned that the transformer I have in mind is not an autotransformer, but is rather an air-core with high K-coupling.

Speaking of high voltage transformers, I was able to locate a few online, although all of them are metal core and therefor probably not suitable for the higher frequency applications. Since the DC voltage has dropped to 300v, I will need 100:1 step-up in order to achieve 30kv.

Admittedly I am just picking at straws at this point. I saw an interesting diagram that used 4 transistors to route the energy back and forth across the primary, but they didnt go into any detail on how the timing circuit for controlling those was set up.

For that matter, it did occur to me at one point that I might go 110v AC mains -> 160v DC -> 110v AC 20khz and feed that into my 10kV 30mA NST. Might even go so far as take the 10kV and try to step it up via a 3:1 air core to get my 30kV-20khz-10mA. I have no idea how the insides of the NST are setup, and therfor how it would react to high frequency current, however.

Meh, like I said just brainstorming and throwing out ideas. Back to the drawing board, for the moment.

thanks again,
-NN

Quote:

Since the DC voltage has dropped to 300v, I will need 100:1 step-up in order to achieve 30kv.

So? That's 5000 turns from a 50 turn primary, or only 1000 from a 10 turn primary (you'll need a high frequency to keep currents reasonable from such a supply voltage though). Consider yourself lucky, that's quite modest for thirty fucking thousand volts.

Not quite. You may get a nice hot chunk of steel though. The laminated iron core in your transformer will pick up most of that energy by hysteresis and eddy current losses. Here's a strip of similar transformer iron exposed to similar magnetism:



Tim

[Edited on 4-26-2008 by 12AX7]

That's the one.

Goldwasser, shoulda known!

Tim

Plenty. Don't use a 555

Crack open a dead computer supply nearby and extract the TL494 (90% use a 494, the remainder use KA7500 -- same thing, SG3524, etc. All fundamentally the same, look up datasheet for pinout), wire it up and go. This chip is designed for push-pull / bridge operation. Push-pull BJTs or MOSFETs are the easiest, and a typical application is probably in the datasheet itself. Since you want AC rather than PWM, wire the control side so PWM is near maximum (48% or so). If you want frequency control, you can use a pot for that, or you might add a feedback loop consisting of a voltage or current or phase sensor and an error amp to control the frequency input. Alternately, a CD4060 PLL chip can be used for the same purpose, somewhat simpler.

I think the 4060 generates a plain square wave, so you may get shoot-through using it, which is the same problem as the 555's single square wave output. I'd use a differential pair to generate inverse lines, then a pair of transistors to switch that into a regular logic-ey sort of voltage for whatever is driven.

Tim

Hmm, since I got plenty of dead PC PS's kickin about, I'll have to look into this. (I had intended to use one as the 12V supply for timing circuit anyhow.)

However, in the meantime, I found a good site which discusses some of the basics of 555 timers, with plenty of examples and built-in calculators. This turned out to be a good thing because it pointed out a fatal mistake I had made some time ago, wherein I set up an excel spreadsheet with the calculations for controlling the timer, and forgot to note that I had set it to display kilohertz, not hertz. Consequently with my 120pF SMC and 10kohm pots, the lowest attainable frequency would have been 363khZ.

Anyways, found the attachment at http://home.cogeco.ca/~rpaisley4/LM555.html#5

Good page, and using the built in calculators gave me a better idea of mathematical relationships involved. Better to keep R1 fairly small and use a pot at R2 to adjust the frequency, thus resulting in a near 50% duty time regardless of output frequency.

Oh yes, the attachment. I am thinking that this circuit (I do actually have 2 identical 555s here), with the output from the 3s trigging my IBGTs A and B, respectively. I suppose also that Timer B would need to be permanently on, until timer A turns off.

According to wikipedia here:
http://en.wikipedia.org/wiki/Flyback_converter

The estimated voltage feedback against the switch for a 960V 5:162 (1:32) turns transformer with a duty cycle of .5 (50% on, 50% off, which I am working towards) is about 990V, or roughly 3.1% higher than the input voltages. However, it also says that doesnt include voltage gain from leakage induction, and doesnt provide a way to calculate that. Couldnt find one either. Equation or link, maybe please? :-)

Also, I imagine with a two transistor push-pull setup, there is a lot less feed back since the circuit spends most of its time in the on-state. I was also wondering if the two 5 turns are each counted as a separate primary as each respective transistor turns on, thus a 10-turn center tapped primary and a 100 turn secondary is actually a 1:20 transformer, not a 1:10.

Part of the reason I am eager to go with a higher voltage feed to the primary is to reduce the number of turns needed on the secondary. I took apart that old flyback I had, and salvaged the core out of it. Got pics of that I may post some time, but the point is that if I have to go with more than ~150 to ~200 turns I am going to have to start layering the turns. Im not even quite sure how thats supposed to work. Somehow wrapping from the bottom up the first layer, then insulation, then continuing the wrap in the same direction (say, clockwise from an above perspective) but having each consecutive wrap proceed back down the core doesnt seem right intuitively.

Hmm, found some tl494s on the interwebs, they are cheap, but most places have a minimum order. Will have to try to find them locally first. Havent had much luck scrounging components off of old boards, I'd rather just get them new. This does look quite promising, although I haven't yet found a representative schematic for controlling an inverter.

Well, Im done for the day. Thanks again for the assistance.

-NN

Miniature plasma generators, working in atmospheric air using mini-power supplies (high kV/lowmA) will generate Ozone. There are shitloads of papers on its use to purge contaminated air streams of organics (such as might come from a small homebuilt-hood)

Ozone electrolytic generator

I came up with a picture (attached). It shows chlor-alkali-like setup, where hydrogen is produced at the cat and oxygen and ozone at the ano site.

I suggest the following construction:

A vat, with glued, welded or otherwise jointed groove for membrane
A membrane, 10mm thick, made out of commercial quality clay plate
A cathodic pack, common steel plate, thickness of 1-2mm
An anodic pack, 316 stainless steel, thickness of 1-2mm

Cathodes can be placed intimate with the clay plate, but they can be installed in their own gas traps as well. A 0.5-1% NaOH solution should be boiled and used as the electrolyte to get higher electrolytic conductivity.

Cell needs a power of 2-6 volts, higher the amperage, higher the yield. A common microvave transformer can be cut apart carefully and the secondary re-winded for this purpose: using a 30-50mm2 copper cable at 6 turns with primary winding that has equal turns ratio to the mains power voltage input will generate 6-volt power source of about 1000 watts at 160 amps. The power needs to be rectified from AC to DC, a single diode rectifier is enough, but it will give only 50% of the nominal power, so if a bridge rectifier is available, or one is willing to make a bridge from 4 diodes, one should really consider using this method to get 100% of the nominal power to the cell. Rectified DC current is very well suited for electrolysis.

Ozone and O2 should be produced from the anode. All parts must be 316, since ozone will eat through everything but it and teflon within moments. The cathode can be any junk metal as long as it has high electric conductivity. The conductance of 316 steel is 3% of that of copper(which has about 6A per mm2), so when calculating the power of the cell, make sure the electrodes have enough cross sectional area or they will bottle-neck the power of the cell. The gas content of this electrolyte cell should consist as high as 25-30% of ozone off the total amount of oxygenes produced at the anode.

This is because ozone can be used for several reactions, like making AN from ammonia solution, making SO3 from SO2, creating high-quality lead dioxide electrodes for perchlorate cells, making benzaldehyde from styrene, etc. Ozone will oxidize most elements into their maximum oxidative state within contact and react detonatively with several organic materials, especially in liquid form.



[Edited on 10-7-2013 by testimento]

Quote: Originally posted by Pyrotrons

The third neck of the flask would be the exit for O3 which then goes into a graham condenser cooled with Acetone/Dry Ice.

Quote: Originally posted by Pyrotrons

watson.fawkes, care to add anything else?

Quote: Originally posted by Pulverulescent

Quote: Does anyone have experience on these cheap chinese ozone generators costing less than $20 a piece with ceramic platelets, noted to be producing up to 7 grams of ozone per hour? Nope! Nor want to ─ their claims of grams per hour should be taken with excess halide . . . They'll readily produce NO2 in moist air, too! But you know, you get what you pay for!