China UVC 2023 I Find it hard to believe that the pandemic happened in 2020, but here we are starting 2023 and I thought I'd Take a look at some of the lamps being sold as Germicidal lamps on AliExpress and we'll start off with these ones which were clearly never going to be UVC but that's what they were being passed off as let me plug this in to have no quanzo plugging this man because I know it's not going to harm me with dangerous UVC energy because it's UVA Let me turn the light off and you'll see what I mean See that deep purple I'll just take the exposure off and it'll swamp out that fantastic color I mean nice color but not UVC Watch your eyes the light is about to come back. The light is back. Uh. Power consumption two Watts I Worked out that the current through the LEDs and there's two parallel circuits about 48 LEDs 24 in each circuit.

The current through the LEDs is about 15 milliamps, which is okay. That's not going to be too bad. However, this is one of those lamps that has a capacitive dropper because I've tested onto the connections and uh does pose a slight rest. don't touch the front of the lamp.

Incidentally, just for those wondering, this is a dodgy Chinese Factory Test box with lots of exciting means: 240 volt outlets on things like test probe connections. It's exciting I Just thought I'd mention that in case you've not seen it before, let's see if we can pop this open and take a look inside. It is it glued in it may be glued in? Maybe I should Flex it first to try and break some of that glue. Uh, well.

I'm just going to go and actually I'll get the vice of knowledge. That's the best thing to do. We shall squeeze it in the vice of knowledge to impart its inner secrets. Looking through the back of I can see there is a capacitive dropper inside it from the back on the back of the circuit board, which is not uncommon.

I don't hear crunchy noises I I prefer to hear crunchy noise and I'm squeezing like this and probably just basically splitting all the LEDs off. This one may be about to sacrifice itself for the greater knowledge. I shall try squishing this down underneath. Let's see if I can stab myself in the process.

Oh, that is tight. That is a very tight fit. Oh, it's making crunchy noises. I Think this is ordinary circuit board material about it.

You know that is not one to come out. it's kind of glued in. here. is the capacitive dropper right? Say what one of them.

I'm just going to reverse engineer this actually I won't bother pausing to reverse engineer I can see what's in here. Um, we have a 479 of heart capacity the bridge rect for actually you know what? I shall pause and I shall draw this down one moment. please. No surprises whatsoever.

Let's zoom in. One nice thing about this. the resistor that is used as a safety discharge resistor across the Uh The Dropper capacitor here. This little resistor underneath the red capacitor here is a quite a big resistor.

Physically, it's quite big. They've not skimped in the resistor sizes as they sometimes do, so it's probably better rated for having a fairly high voltage cross it. The purpose of that resistor is just to make sure this capacitor discharges so you don't get a little pop off the pins when you touch them. Uh, so it's got the capacitor which limits the current on each half cycle by allowing a portion through.

It's got the redirect fire. It's got the smoothing capacitor which is 2.2 microfarad 400 volts which is amply enough for this. It's nice that they used 400 volt because it means if the LED's golden circuit, the capacitor won't vent, it won't gradually build up pressure and pop. Uh, it's got one Meg ohm discharge resistor across it and also that acts as a slight load to prevent uh, the lamp ghost glowing.

then. rather nice. It's got a 100 ohm resistor in series. it does say 330.

Oh, it says about 330. it could be 330 ohm. Or it could be 330 as the value of the color code which would be 33 ohm. In this instance, it's 100 ohm.

and then it's got two strings of 24 LEDs to make up the 48 LEDs in this. and they're just wired and parallel with the current shared between them. That also is the advantage that in the event of a One LED green open circuit, the other half light as what they stay lit, but it's not necessarily that great. I think I'm just going to check here.

Are they just wired? They are just wired and tanned and parallel. If one goes out, just the other one will take extra duty, but that'll be seeing the fuel current about 30 milliamps quite. High Okie dokie. Uh, let's bring in the UVC tube now.

just zoom back out again and I'm going to actually power up this UVC tube and then let you see it lit. but I'm not going to expose myself to it too much because this is the real deal. This is UVC that will will hurt MD watching it. So let's stuff these wires into my dangerous electrical connector here.

not actually recommended for use out with China and I shall uh pause momentarily while this warms up making being careful not to stick my finger in the end of this because that's beer. live electrical connections in the end of it as these things tend to do right. Tell you what. I'm just going to turn this on, then pause and walk away one moment.

Please prepare to behold the curse of UV seed tubes. If I turn the light off, it's this absolutely Exquisite turquoisey blue. It's very pretty to look at, but don't look at it. Uh, one moment please.

the light is coming back. Watch your eyes. Yeah, let's not leave that running too long. You see that Exquisite color We can see a little bead of mercury is that America is mercury droplets in there? Uh, the Exquisite color is because a Mercury discharge has visible spectrums as well as the ultraviolet ones.

and the ones we're seeing here is of a blue and green. Spectrum It gives this lovely turquoisey color. but unfortunately, if you look at one of these tubes with your Naked Eyes I.E no glasses, no eye protection I have eye protection. then the more dangerous wavelength that it emits 254 nanometer will cause eye irritation.

It will give you basically arc flash what welders experience from the arcs and that manifests itself as you waking up middle of the night with really, really sore eyes. It feels like sand has been thrown into your eyes. Um, the welder's technique for relieving that discomfort. this may be People swear by this I don't know if it works.

it's I'm not giving medical advice here, but welders When they get it, they slice up a potato with a knife and then they scrape some of the liquid that came from the potato and they drip it into their eyes. Ah, that doesn't sound nice, but having said that, I've experienced mild ultraviolet eye damage and it does. It feels really itchy and horrible. The other wavelength that these can emit is 184 nanometer that emits ozone.

I Didn't think this was one of those tubes, but I'm getting a slight whiff of ozone from that brief operation. Um, it's all down to the glass Traditional fluorescent tubes are based on either. Well, usually soda glass I think these days and that blocks the harmful wavelengths. In fact, the 254 nanometer wavelength the the invisible wavelength it uh is converted to visible light and normal fluorescent tubes by the white phosphor inside.

And that's what basically I mean it's the bulk of the output isn't 24 54 nanometer and that's what makes all the light that stimulates in the phosphor. if the glass is even pure. still the quartz or uvial glass, it can also emit 184 nanometers which breaks apart oxygen molecules and they reform in various complex combinations. but notably ozone, which has three atoms of oxygen in one molecule short-lived Uh molecule that is a very strong oxidizing effect and that has a nice pervasive sterilizing effect in the area as well.

But the UVC energy and the simulator irritates your eyes and skin will kill bacteria. I'm just going to put a little plug off then to listen to true other things worthy of note. They used to think the UVC was very harmful in the sense that they believed it could cause skin cancer. Now they realize that the wavelength is so short it doesn't penetrate deep enough in your skin.

It over cause major irritation the surface, but it doesn't penetrate as deep as UVB and UVA which are much higher risk of doing that right. This is going to just be jammed in the end into let's open it up, it is just jammed in the end. I'm gonna have to cut wires I'm tight. Yes I am.

So we've got four wires here. two going to the end for the heater and d and general electrode and the other end I would expect the same thing right. I'm going to see if I can get the ballast out of this. This is going to require chopping wires.

What a shame. Oh, these two lamps from AliExpress cost uh, three pounds 86. So about two pounds each. Not bad for our ultraviolet effect lamp.

Uh, this one cost four pounds 74 inclusive of shipping. which is actually not too bad. Now theoretically I should be able to slide the ballast out. Here is it's wrapped in uh, in insulating plasticized paper.

Where's that a connect and I shall slip This it is. The research has been done saying that the Uva-ish wavelengths. this isn't true UVA this one. uh, this is what I'd call deep violet.

It's around about the 405 nanometer, 395 nanometer. It's a very deep violet color verging on infrared an UltraViolet should I say and people do kind of classify it as UV A. but it's not totally true that it's UVA I See a capacitor here I'm going to discharge that capacitor before I do it unexpectedly through my finger. he said booking it with a metal screwdriver.

It is dead, right? I Think we need to explore this circuit board. Um, right. I'm going to do that. I'm going to take some pictures of this and I'll reverse engineer it and I'll be back in a moment.

But uh, before I do that I was saying the UV They reckon that deep violet kind of a mild germicidal effect, but all this research I've seen on it is very vague and then at the end it says but it's me of a mild effect, but it's not considered very strong. They're basically covering their butts for that, right? Tell you what. I'm going to reverse engineer this one moment. Please.

Reverse engineering is complete. Let's explore. It's basically the circuitry of a compact fluorescent lamp or a typical electronic ballast. The main Supply comes in and there's a bridge rectifier based on four discrete diodes that then charges up this capacitor to create a fixed DC Supply from the main Supply that is used to power the circuit.

There is a oscillator, a self-oscillating oscillator based on these two transistors, and a feedback coil. The feedback coil has three windings on it. It's got the main winding at which the current flowing through the tube goes through this winding and it's got a little red and a blue winding and they are used to drive these transistors so that the way it's configured, only one can be on at a time, Which is just as well because they'd effectively short out. This means Supply Rectify Main Supply If they did turn on together, there is a inductor.

A fairly large chunky inductor at this end. It's got four pins, but two of them are just linked together. here. They're just strictly physical support, but it's basically got two connections.

it's an inductor and Sears the tube to limit the level of current flowing through it. Other things worth of note: Uh, this capacitor here is the in series with the tube under. effectively. as this oscillates, it charges and discharges.

act pasture I Think this will probably determine the amount of current that flush at the amount of power. The power rating of the circuit and this other capacitor here is between the two ends. The tube to act as a sort of almost like a electronic starter bypass a little bit of current that allows the heaters at the end of the tube to glow. Let me bring in the schematic, because it'll probably make a lot more sense if I do I'll zoom up just a tiny bit more just to get a bit of extra size.

Okay, the first stumbling block. It uses Mje1301 transistors. The first: I looked up to find the pin out of those transistors rather than just work it out from the circuit. I Looked it up and found lots of pictures with a pin out.

but that pin out was wrong. It turns out the Mje1301 is available with two pin outs. This one is with the flat facing towards you Bass collector emitter Made much more sense after I'd done that. Okay, so here's the redirect font.

There's the capacitor. What's the value of that capacitor? that capacitor is? I'm going to guess 10 megafor it could be wrong. 3.3 microphones I was very wrong. 2.3 Microfarad 400 volts.

Okay, that's reasonable enough. So there's our DC Supply here one, and the positive goes to that capacitor and then through the heaters at each end of each tube via this. uh, coupling a capacitor here. So here's what happens when the circuit starts off and a lot happens at once, which is just a bit annoying.

but that's okay. Initially, when you power up, current flows through this resistor and this resistor and turns on this transistor here. Notable that there is a capacitor down here to isolate the base of that transistor from the zero volt rail, because otherwise the current would just take a short path to the zero volt. Rail and it might not turn on the transistor.

Reliably is also notable that's an electrolytic capacitor and that the negative isn't connected to zero volts. so the negative is actually connected. The positive side is connected to the negative side of the supply. I'm not quite sure why that is why they've done that.

The orange here indicates this little feedback. Transformer So what happens is that when this transistor turns on, the current will start flowing. because this capacitor is fully discharged effectively. the there'll be some current flow through that going through the inductor, through the tube, inductor, the little feedback circuit and down to the zero volt rail via this transistor because it's been turned on by that slight current through there.

As the current flows, the current flowing through this sense coil induces current in the base of this transistor circuit so that it actually starts to turn that transistor on. That from that little initial start trickle, it actually turns onto a solid drive to turn that transistor on. CE That capacitor is fully charged effectively. It is, uh, the current through this stops this transistor, turns off, the field starts collapsing, and uh, it turns this transistor on.

Via This coil which is the winding in the opposite direction and now the charger is put in that capacitor because this side was positive. This side is negative now, gets shunted so effectively discharges that capacitor. So the whole process of these transistors turning on and off is charging, discharging that capacitor via, then doctor to limit the sort of peak current and then through the tube that 3.3 nanofar capacitor just trickles that little bit past that. It will result in these giving heat and it just protects Electrodes also helps start the tube.

Anything else worth mentioning? There is one thing this resistor. here. It's not just providing a slight path of current for that start circuit. This is the most minimalist circuit.

This is a very what you might call cheap circuit. They normally use a Diac, an interesting sort of circuit to actually trigger the transistor decisively to start it. This is a very cheap and nasty type circuit, but ultimately maybe just super well cheap. that's why they do it, but it has a capacitor here that it also Bridges and that is presumably a filter.

I'm guessing to try and limit the Um high frequency noise on here. Above, you know the point. very high switching specs that could potentially cause disturbance in the transistors and make them trigger falsely and resulting in a bit of a bang. because that would if they did that basically through these 5.1 ohm resistors.

that would be a bridge from the post of negative I Don't know. it's uh, not quite sure what the proper snack pasture is I'm guessing it is for stability of the circuit. maybe even it's to control the frequency of oscillation in some way that I Thought that would have been done by this and doctor in this capacitor. here.

it's quite odd. If you have any ideas in that, let me know the other things about the note: There's a little diode between the emitter and the bass here. I Think that's just basically protection against the base. uh, well-being reverse polarity when the coil is the other coil is being driven.

Um, and that's it. It's an interesting little circuit. I Have to say I wouldn't like designing a circuit like this I Remember the early days of compact fluorescent lamps when they literally used to just explode, particularly when they got hot. And you think of it, a lot of them are based around this circuitry and a lot of them end up baking inside compact fluorescent lamps to the point that the circuit board is all brown and discolored because they've got so hot and yet they just keep working.

The capacitors are dried out, they just keep working forever. It's surprising how long some compact fluorescent lamps last, but when they do feel, they usually go with a bit of a bang and blow the tracks off the circuit board. But very interesting. So that is a look at the current state of ultraviolet, but with thick ultraviolet and the real UVC um interests here things revolving I'd Guess that now the pandemic is passed, they're going to be getting rid of a lot of excess stock.

But a good thing I Would say that One good thing that happened during the pandemic is it suddenly gave the incentive to the manufacturers of. well. UVC Real UVC LEDs Not these ones, but the little gold package ones. It actually established the market for those and it meant the company's making the fluorescent tubes.

They suddenly had a really big Market It must have been quite revitalizing to them in a way, but that's it. Quite interesting, worth opening up. Surprising how cheap this little light fitting was with the tube and with the electronic ballast inside. It was really, really cheap.

Um, but then I Guess that's just mass production for you. It's cheap and easy, but nice. Quite interesting to explore.