Here in the UK they sometimes use low output ozone generators in public toilets to reduce odours instead of just masking them with aroma dispensers. The idea is that the active oxygen generated by corona discharge oxidises the odours and makes the air smell clean.
This device is quite neat in that it allows you to set low, medium or high ozone generation and also has a light sensor to detect the lighting in the toilets so it can operate either continuously, when it's bright (lights on, toilets open) or when it's dark (lights off, toilets closed.)
The unit is designed for easy maintenance and cleaning with a single tamper-proof quarter-turn screw holding the lid closed. When unlocked it hinges out and unhooks with the shielded mains power supply (12V DC unregulated) staying on the wall-plate and the circuitry and ozone module coming off with the lid.
The ozone generator module consists of a small computer style fan in a removable plastic frame with three contacts on the sides. A common connection for the fan and corona plate, a 12V feed for the fan and a high voltage AC feed for the corona plate. The corona plate consists of a rectangular piece of thin ceramic with a foil pattern on both sides that overlaps in the central area so that when a high voltage, high frequency supply is applied to it a visible purple corona discharge is formed where the current is capacitively coupling from one side of the ceramic to the other. This occurs in lines at the edges of the foil plates.
The ceramic corona panel is replaceable, and held in place by springy steel connections.
The circuitry consists of an LM358N op-amp for the light sensor and an NE556N dual 555 style timer chip. One section of the timer is used to cycle the ozone generation on and off to vary its output, while the other seems to be driving the power transistor on the ozone plates high voltage transformer.
I'm not sure how old this particular unit is. It doesn't look old, but it does have a damaged contact on the ozone module which may suggest why I got it quite cheap on ebay. No problem to fix though. The circuitry almost seems a bit old fashioned, but is probably quite reliable.

12 thoughts on “A look at the insides of a public toilet ozone generator.”
  1. Avataaar/Circle Created with python_avatars Shannon Harris says:

    Happy to see you using a Fluke.

  2. Avataaar/Circle Created with python_avatars Peter Hutchinson says:

    I hate the word Corona

  3. Avataaar/Circle Created with python_avatars jlucasound says:

    Clive!! What are you doing on the "other" side of your work bench? It makes me dizzy. It is so wild to see how you have evolved since 2014. Only 5 years and you have mastered editing, (Not that this is bad), sound, video, your relaxed state (pretty much the same). Now, it is right there, and your creativity has bolstered your productions. (Yes you always had it, but now it is second nature to you.) You no longer think about the outcome, you just are being yourself and sharing your knowledge and abilities with the World. Too Sappy? 🙂 I want to send you "Ben and Jerry's" ice cream. It would have to be packed in dry ice and I would be have to be able to send it to the Island. It is made in Vermont. The best. If you haven't had it and can get it on the Isle, try it. If you cannot, let me know and I will send you some.

  4. Avataaar/Circle Created with python_avatars Scratch Dog 22 says:

    I've seen much larger units blowing into 30 yard trash compactors via 6" duct. They do work.

  5. Avataaar/Circle Created with python_avatars Gord Slater says:

    this showed up on my YT sidebar of related videos in truncated form – "A look at the insides of a public toilet"

  6. Avataaar/Circle Created with python_avatars Matt Carding-Woods says:

    Watching this in 2018 and it pleases me that the video quality makes it look like an Open University film from the 90s.

  7. Avataaar/Circle Created with python_avatars orion khan says:

    I'd have really liked to have seen the coronal glow… the PSU was worth it tho !!!

  8. Avataaar/Circle Created with python_avatars Lloyd Evans says:

    Not sure I really like the idea of these. When you want to make ozone cleanly in a chemistry lab, you run pure oxygen through the generator, so that you get a mixture of oxygen and ozone out of the other end. Only a few percent of the oxygen gets converted to ozone, so you have to recirculate the gas if you want a higher concentration. Or you can condense the ozone from the mixture afterwards, since it has a higher boiling point than oxygen.

    Running ordinary air through an ozone generator will of course make some ozone, but also makes nitrogen dioxide. Any corona discharge or spark generator will do the same thing. In fact, some of the nitrogen dioxide in petrol engine exhausts comes directly from air interacting with the spark plugs. Anyway, if the air has a reasonable humidity, the nitrogen dioxide can react with water vapour to make nitric acid, which is even worse.

  9. Avataaar/Circle Created with python_avatars Ron Thompson says:

    I never seen these in the u.s.,I wish we had them ,is there a replaceable filter for that unit,I guess that a u.k. thing,.

  10. Avataaar/Circle Created with python_avatars Jovan Janevski says:

    The solution to global warming is found in a public toilet.

  11. Avataaar/Circle Created with python_avatars Raymond J says:

    what is ozone exsatly and whats a corona discharge please thanks i love your channel i never learned so much stuff about electronis be cool take care

  12. Avataaar/Circle Created with python_avatars Mike Whitcombe says:

    Have you still got this thing? Can you show us the "purple discharge"? How effective is this thing anyway?

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