Hi @jtd one of the UV measurement Pdf which you have uploaded and was not accessible is now missing from that post. Can you please make it available.
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The black box is supposed to be an electronic ballast to drive the halogen lamps.
It’s function is to preheat the halogen lamp filaments, provide a sufficiently high voltage - 100Vac in this case - to trigger ionization and consequently UV emission, then drop the voltage across the lamp to it’s sustenance voltage - in this case 30Vac.
The old tube light choke and starter does precisely the above sequence of operations.
However the above black box is a ghastly piece of of circuitry. It uses some capacitors and diodes as a voltage multiplier. No preheating of the filament. It simply brute forces the ignition of the lamp and will drastically shorten the life span of the lamp.
I will now have to build a ballast before testing.
Nice info about UV lamps, ballasts etc.
https://pm.metastudio.org/s/zxfWRNBL7AgRS5y
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Maybe I will just fire up the lamps for a few secs to check ozone emission.
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If the chamber is created as part of a face mask, or a hood, it needs to manage an airflow of up to 2 litres per breath.
Actually, a healthy adult breathing actively needs to respirate 2.5 litres per breath, but many people are unaware of this capacity, and do not train themselves to breathe wholesomely.
While walking, I timed myself, and found that I took 10 breathing cycles in a minute. This was very relaxed, so let’s take it as a pragmatic datum. It works out to an air handling capacity of 20 litres per minute, bidirectional. The inward breath is absolutely critical to disinfect, the outward is both polite, and also will help to minimise the risk of infecting others (flattening the curve).
If the cleaning chamber is intended to be incorporated in a head cover, it must manage a cleaning rate of 20l/min at the minimum, and 25l/min to accommodate healthy breathers. With some leeway, perhaps a little more than 25 l/min. This should give a decent working number to use while designing the chamber and working out how to accommodate it in the hood, while ensuring that none of the UV light actually shines or reflects on the face, and especially not the eyes.
It’s probably best to fix the cleaning chamber at the back of the head, allowing the airflow round the head after disinfecting, so that it keeps the inside of the hood well ventilated and comfortable. It also allows the weight to be carried more comfortably.
Emitting the effluent air out the back might also be a good idea. This makes an f2f meeting much safer, at any distance. With a hood, spoken communication is very likely going to be less audible, and people will tend to crowd closer.
In fact, spoken communication needs an audio solution built into the hood. Probably, from the mouth and nostril area, a horn shape that leads to a flexible membrane, or two, one on either side, that will excite the open air. The horn may also then act as a venturi, to drive the effluent air to the back of the hood.
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“10 breathing cycles in a minute”
Or Six seconds of irradiation per breath of 2 li.
Or .333 Li /S
As per Predicted Inactivation of Viruses of Relevance to Biodefense by Solar Radiation - PMC Table 2 the required radiation dose at 254nM for Coronoviridae is 2.4 - 3.9J/M^2 or a 390uW/Cm^2/S
We can provide UVC dose of
0.021X10000=210J/M^2
Substantially more than required.
The volume of air in our gadget:
Air in a cylinder of dia 2 cm X 25cm - Light tube volume of dia 1.6cm X 25cm
.315L-.0785=.2365L
or 29% lower than required volume o.333L/S. We can increase the dia of the outer cylinder by 3 mm to get the required volume. However even if the air flow reduced the exposure time by half, we would still be exposing the air to 110J/M^2, 28 times more than required.
Methinks this is fesabile.
I am thinking of a belt strapped gadget hanging on one side.
But looking at the numbers and the ability of these lamps to deliver a far higher dosage several form factors are feasible.
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