Let's take a look at an UltraViolet nail curing device and I've only just discovered a feature if you put your hand and it automatically turns on when it senses you're breaking a beam I did not not know it did that. This thing has a multiple times it's got a half in full power. If I press the half power, it goes down to half power. If I press again, it goes up to full power.

It's got five seconds, 30 second or 60 second and presumably when you stick your fingers in. It starts that sequence and the box says let your beauty eternal glory which is quite helpful Professional Nail lamp Um, it says helpful things like sunshine, non-harmful non-black and UV LED 48 watt power. Now the 48 watt power I Have to contest that a little bit because the box also says it runs from a five volt power supply. Recommended two amps which would be 10 watts, but if we actually test that if I bring the unit in, its quiescent current is 25 milliamps.

I'll Zoom down the display here for this 25 milliamps and if I stuff my hand in through the light beam, it goes to 1.36 amps and that's at full power. So if I get the Kink calculator in and I go 1.36 amps times 5 volts, it's about 6.8 Watts total and that is assuming 100 efficiency, which it probably isn't It's probably losing a bit when the driving of the LEDs I'm intrigued to find out. uh, there's the infrared beam I presume it's infrared there. It's quite good.

That's an interesting bit, Secretary, it claims LEDs are too Wavelength 365 nanometer and 405 nanometer. Hard to tell because the ones with the uh, they've got a bit of phosphor over them just to make it look really bright. So everybody says, oh yes, that's doing the job. It's really bright because real ultraviolet wouldn't be that bright.

Um, and LEDs I'm thinking there may be lots of little circuit boards in here and looking down the top and think the back circuit board of the bulk the LEDs in it may actually have the buttons as well. with the LEDs being recessed down quite low below those, it's quite hard to see them. Actually, when you press them, you can just barely see the LED just glimmering in the distance behind that. A little light guide would have been nice.

Anyway, let's test this with ultraviolet cured resin. So here is some ultraviolet cured resin. I'll put a Big Blob in there so we can test how effective it is in curing it because that could be a real good use of this. So I'm going to select, put it over I'm going to select 30 seconds I think is that full part that is full power.

Okay, so we'll give it 30 seconds. Now it's interesting to note that there's a current belief that some of these units that ultraviolet units may be causing skin cancer and supermodels hands because they're always getting their fingers done them. I'm not so much convinced that it's the ultraviolet because to me, that's uh, isn't it not even going to compete with daylight, particularly if they go out in the sunlight, but covering their fingers in photosensitive resins and then dipping them in buckets of solvent to dissolve those resins off. To me, that is a real issue.

I Think that's possibly going to be found to be the the practicality? That's pretty hard. It's got this sticky surface it usually has ER you said dabbing his fingers in supermodel resin, but it has done a good job of solidifying that resin. Good, That's what we want I shall put that in the bin. No, because I don't particularly want resin everywhere I already have got resin everywhere.

Let's open it. so I'll unplug this and unplug my little Harpy and the power supply stuff over there. The USB lead it comes with has a Jack in it. It's useful to note that comes in useful for our things.

Let's unscrew it. Kind of intrigue to see its infrared sensing circuitry. Now is it modulated I wonder the cost wasn't dramatic was that I can't remember the cost? I'll put it I'll put a link to it or I'll put a link to the Search keywords and uh, so that if I can't be linked to a specific Ebay listing because they will instantly go to the price. That's what they do.

As soon as there's a burst of orders, the price just goes up with every order. Oh so the the way. here's a circuit board. Oh, it's a little satellite circuit board sitting above and they've got sort of aluminum heat sinks that's interesting.

The way they've put these in, they've clamped them and placed a vertical screw just clamping against the side of that. That's unusual, but kind of fits about the molding. Lily Pin Maker Controller: As you might expect, how is it doing the infrared sensing? We'll discover that because I'm going to like take it to bits obviously. Uh, these uh centers, the infrared LED and receiver are basically just covered in silicone at the side and then these are all just chained together and we've got The Two Reds going down here.

and then they just chain out either side and uh, this thing is the green wires going out and down onto this panel, then looking off. that? Okay, right. I'm gonna take the circuit board off and we shall explore the circuitry one moment, please. The reverse engineering is complete and it's quite an interesting little circuit.

They've used some cost saving techniques which are interesting so the LED is all. 30 of them are on these aluminum core Pcbs and I can see one visible chip, a purple chip lighting inside that is making the uh, the phosphor glow. There is another small black chip in there I'm not sure what it is, it's not a diode in Reverse parallel around for that, it's a Oddity Um, the circuit board itself. Let's Zoom down in this and take a closer look.

They've used the ubiquitous Eat pin chip classic pin out of something. I Pick Microcontroller. It's an anonymous chip as usual, so the positive from the USB Supply comes in the 5 volts goes straight over to the ultraviolet. LEDs There's no current limiting resistor.

It's just switch straight via this mosfet to the zero volt rail. so it's relying on the Uh tracks and the cables supplying it to limit the current. Really? I would guess. Um, unless that little thing in the resistors is a in the LEDs is a some sort of resistor.

but I Doubt that. I'm not really sure there is a resistor here that is upside down. it's 150 ohm and it's feeding the infrared. LED So let's just let continually.

When the unit is powered up, there's no modulation going on here. the receiver is over connected over here and it is just a photodiode with a resistor pulling up to the slightly lower voltage rail of the processor and then going to forming a voltage divider with the infrared receiver and going to a PIN to the processor. there's a mosfet and e09t to switch the Ultraviolet LEDs and then the four LEDs and the four buttons all share pins. Uh, it's a very minimalist pin count.

There is a rudimentary power supply involving a 270 Ohm resistor, uh, 4.4 volt, I measured Zener diode, and the little decoupling capacitor. I'll show you that in the schematic. Other things worth mentioning: a common 1K resistor for all the LEDs and then a separate little 1K resistor for all the buttons. Let me bring the schematic in and we shall explore it.

I've abbreviated it for ease of a viewing. So here's a five volt rail. It's feeding that infrared LED versus via the 151 resistor. Uh, it's also got a current limiting 270 Ohm resistor going down to this Zener Diode, which I measured 4.4 volts.

It's got a capacitor across and it's actually right next to the microcontroller, so that acts as a decoupling capacitor for that. Um, the receiver has a potential divider going from that 4.4 volt rail: a 15K resistor going to the photodiode that receives the infrared signal I Think the fact that the are recessed so deeply into the plastic here means that Strelay isn't really an issue with these, and they're certainly not going to be affected by the ultraviolet. The Receiver: I Guess that's the emitter because it's clear and the receiver does have the black filter uh, resin on it, but they just look like standard on modulated three millimeter LEDs just stuffed into those housings. Then comes the clever bit: They've got one common one key resistor fitting four LEDs I've just drawn one set of these just to keep it simple.

and there's one common pin from the processor for the LED and its matching button If it wants to light the LED, it pulls the, it assigns that pin as an output and pulls it low and that makes the LED light up if it wants to read the inputs and during the timing because it can detect the button presses while the LEDs are lit. During the timing cycle, it must repeatedly switch from being output to an input with a slight air pull up to the positive reel and it detects the button being pressed because that then pulls that pin low and that is repeated four times. For those, there's the microcontroller. There is the 15K pilot and resistor in the mosfet.

The reason they've used that instead the more traditional 10K is probably because they already had a 15 key on here as a potential divider for the infrared receiver, and it makes sense to reduce the component count for the pick and place machine. Just have two 15K resistors and then it's just driving tons of LEDs in parallel with that Ao90 mosfet. It's very straightforward. There's really, it's a very minimalist circuit.

It's quite neat. The circuit board does allude to it possibly being revision three. I Wonder what the other revisions look like, but that's it. It's a straightforward cost saving design.

Um, and it works. That's all it needs to do. Um I Wonder how they worked out how much current? I Guess maybe they just said you know we'll see what the current is through the LEDs and that'll be it because the only thing that really is limiting that is the cable that feeds it from the USB Supply perhaps the USB Supply itself and then the tracks and the circuit board and the mosfet. The mosfets get quite a low resistant so I'd guess really they're just relying on the cable limiting that current.

That's it. The ultraviolet nil varnish curing light that can also double up as your ultraviolet resin curing light too.