In the 90s round about the time of nokia phone dominance, when it was all tiny, little phones uh, these things called flashing stickers were available and they were self-powering. It's an echo of like the anti-five gears. Some of them were sold as anti-radiation devices, and this one says feature this flashing sticker absorb electromagnetic radiation during the use of cellular phones. You know they just said: stick this in your phone, it's going to protect you from harm.

I shall explain why. That was completely wrong in a moment, however, to show you what these look like. First, i'm going to zoom down onto this one in the middle here and i'm going to dim the lights and i'm going to warn you in advance. It's going to flicker because i'm going to emulate what it looked like.

I've actually had had to hardwire up with a resistor and lead here, but it will show you what they look like the back of the phone. So i'm just going to make sure that's in focus. That's probably not in focus now and one moment please, i'm just going to put the lights out. There is going to be flickering, so your phone call is coming in and the thing would start doing this.

It basically go with the sort of like pulses of rf energy from your phone and it would flicker and strobe like this, and inside it's got three little leds, i'm going to bring the light back one amendment, i'm not sure, if you're even going to be able To see the color here, because it just swamps out, let me turn the voltage to these down a little bit see no, it's very hard to see the color it just swamps out as lights, but anyway trust me when i say: there's a yellow one, a red One and a blue one, but anyway, let's get this off the bench out. The way turn the power supply off and i shall show you some of the circuit boards in these uh flash flicker they're called here. Works on mobile phones with an internal aerial will not affect normal use of the mobile phone. No batteries required it's worth mentioning that uh i'll just contain this down a little bit.

It's worth mentioning that uh, the reason they say works with the phone with an internal area is because in the early days it was all external here it was on the phone. You did get plug plug-in if phony rails that also flashed using similar circuitry uh. Well, i shall show you before. I go any further, why these stickers were bad news.

So if this is you with your phone and you've, got it up to your ear, what actually happens when you make a call, is it tries to communicate with the remote tower? So in the past, in the old days they used to be big beacon, towers in the distance and they used to be considerable distance. So the phone would basically increase its power until it could communicate. And if you blocked that signal, if you stuck on a little sticker here, that was going to absorb some of that to make some lights flash or if you put on your magnetic shielding sticker, to protect your brain from the radiation, it would reduce the phone's ability To actually communicate the signal and up to a certain degree, it would increase its power up to the point to could finally make communications. So by putting these stickers on it, increased the power of your phone needed to actually communicate the most station.

Part of the reason they don't work these days is the change of frequencies, those ones in that 2g era used to be 300 megahertz to about 1.9 gigahertz. These days, the frequencies are much wider, but also, instead of like one big remote station, you have buildings with a little unit on the side and you have maybe a electrical pillar with a little thing on top and they're all just dotted all around you. So when you actually communicate with them, your phone communicates with the nearest one that's available. It's only going to be a very low level signal.

It's like your home house, wi-fi that's the point of 5g: that's how they get the speed and the uh, the sort of like the reduced signals, uh and the number of phones that can connect all the time. It's because they're, not relying on these old towers anymore. It's just lots of low power ones dotted about, but it's reassuring to know that people that were against 5g, where else against every other flavor in the past, let's bring in the showcase, so here's an ugly ugly sticker when you see up close, it's really ugly, but Anyway, it is what it is. These are fish, so one of the first versions had surface mount leds soldered on there's actually three in series and the voltage i measured across.

That is about 7 volts. That's quite a lot when you realize the antenna. This little package here looks like transistor is actually just two diodes, usually both going the same direction, so the positive will be feeding from that middle tap down to here and the other one will be going from the other direction. That's not helpful.

Is it this circuit board was notable also for being single sided, because this is a picture from the back there's the tool diode package, and this zigzag here is the antenna that was picking up that energy and there's the leds in the series. The next evolution of these - and i don't know if it is a good evolution, because this one keep in mind that the tracks are on the one side in this one. The next evolution was this equally ugly, one i'm not sure who's in charge of designing these stickers. But if you look very carefully, you will see that instead of using that two diode package, they've actually got two diodes tiny little diode chips on these pads here and then they've got the bare led chips on here, with little jump wires, going across more or less The same arrangement but they've just put the raw chips bonded in the surface, and with this one the antenna, i don't know why they did this.

They could have had it in the same side, but they actually used a double-sided board for no good reason, and i had them tennis snake in the back under the sticker. That's odd. They could have just saved the extra cost plated through holes. I don't know why they did that next evolution equally design, the three leds are still in series bonded on, but there's just a single diode and they're, using the three leds in series as the other died, which is actually kind of sensible when you think about it, And the design of this circuit board is even simpler.

Again, they've got the plated through holes onto an antenna at the back again. They didn't need to do that notice that this little track here, just in case you want a reverse engine at home - actually comes round here down here and over there uh, but it was ultimately the two little sneaky antennas and note that uh the sneaking antennas, if You look at them all. These two are fairly similar. Were they a very specific length, i'm guessing they were, but the one with the discrete leds soldered on, has a much longer thinner antenna, i'm not sure what the advantages of each were.

But anyway, let us get back to the notepad, and i shall show you what the circuit diagram is. It's very, very simple. That's it it's the diode in series with uh, the three leds and then an opposite diode uh. Just so that you know the push.

Pull effect effectively of the signal, the inductive coupling, perhaps i'm not really sure it gets covered across one direction, but it goes through the diodes in the other direction and that modified version with the missing diode just got rid of that one there. So it was effectively just the leds across there and the antennas were there specific lengths that rf geeks will know, but keep in mind that the frequency range of these was roughly 300 megahertz up to 1.9 gigahertz. So there may have been a sweet spot antenna, but it would have been just fairly random what you got, but that is it now. If you do go online and you look for flashing stickers for your phone, you will find them you'll find hold on.

Let me just grab a picture: one. I've lost them they're here, somewhere, you'll find this version, but this one is completely different. This is designed to go with your near field communication. I shall make a video about this.

Once i find the stickers they're, very small, i've lost them, but these stickers use a little inductive. Pickup and they've got two diodes to two capacitors. Two capacitors are common onto one of the connections. The two diodes are common to the other, and so this diode is charged positive.

This one's negative and the leds just slapped right across that, so that, as your near fuel communication communicates, it just makes the led pulse just while it's looking for a response and you're supposed to stick these they're not much smaller than this on your fingernail and then Put your nail varnish over and make yourself look pretty and have flashing nails. I would say that's pointless, but i was right into my flashing stickers in the 90s and my flashy antenna for my nokia nokia should i say that uh the little coil inside. Let me doodle that let me doodle that the little coil inside the knocker had this arrangement, but it was literally tapped across blob part of the coil and it was terrible uh. The rf policy will hate me for using that antenna because it, the antennas and mobile phones, were tuned very precisely.

They were a fixed wire length inside for the frequencies they transmitted on and sticking leds and diodes across them was not the done thing, but that's it. That's the flashing led stickers of yesteryear which are not commonly used. I couldn't make these flash at all, not even on a 2.4 gigahertz wi-fi router router um. I tried them on various things, tried them in the phone they're, just low power and different frequency.

They just don't work anymore, otherwise they would still sell them, but that's it. The interesting flashing stickers, self-powering flashing stickers, effectively from yesteryear.