Exploring wireless LEDs with schematic and waveforms
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- Опубликовано: 21 июл 2024
- These wireless LEDs seem to be aimed at modellers to allow them to add lights to models without any complex wiring. They work well, but are not bright. Fine for low level indoor lighting though, and the power use is less than one watt.
I've seen other videos about them, but they don't go into much technical detail, so here's the video that does.
It's intriguing that the system is based around a standard chip designed for inductive charging. It looks as though it could have other transformer drive applications too.
Here's a link to the aliexpress listing I bought the coil from. It wasn't shown as being shipped with LEDs, but did come with some in my order. The current price is £5.78 plus shipping.
www.aliexpress.com/item/40012...
The MOSFET package on the PCB remained cool throughout my experiments, even when I put over 100 LEDs inside the loop and the current doubled. It was typically about 15C above ambient room temperature.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
www.bigclive.com/coffee.htm
This also keeps the channel independent of RUclips's advertising algorithms allowing it to be a bit more dangerous and naughty.
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Let's appreciate how Clive turned all 100 LEDs right side up before starting the video. :D
It hurt when he scooted them and they tumbled around
Nope, he missed one. 5:37 Look to right of the bottom of the lot (5 o'clock position?). There's one on it's side.
Let's appreciate how the commenter took the time to count the LEDs 😂
@@gary_rumain_you_peons who is this comment _really_ for? Other than yourself
@@owlredshift Now that I came back to visit, I appreciate the accuracy.
@Gary Rumain
the first thing that came into mind, seeing the coil and how the LEDs behave, was a riddle for an escape room or something, where you have maybe a pattern of LEDs shown, some will not light up, some in different colors etc. and you have like a magnifying glass with the coil in it.
My exact thoughts!
Why did you have to tell everybody? ;)
I was just typing the exact same idea and then thought I'd better check other replies....... I would also add an earlier stage of the game that "activates" the "magic" magnifying glass.
@@mfx1 yep, the classic first step of blood sacrifice and selling your soul, gets people in the right mood for beeing trapped in a room.... ;-)
I was thinking some kind of interactive exhibit/sensory experience where a wand could be waved over strategically placed LEDs would be cool. Fun patterns could be made with different colours or flashing LEDs.
Another fun thing you can do is use different cap values on different LEDs, so they resonate at different frequencies, so you can have a few seperately controllable channels.
That's a really neat suggestion!
Would this be sort of like having them twinkle when quickly changing frequencies if they are all in the same coil?
The coil is very low Q though so frequency discrimination is poor. The idea is good if you were to change the led circuit so it can be higher Q a d better match the LED impedance.
@@jamarforsythe7262 might be possible to use frequency modulation and a low Q coil on the transmitter side, and high Q coils of slightly different inductances for various receivers.
That's a good idea. You're good at thinking out of the box.
I played with this stuff a couple of years ago. Having the cap for a tuned circuit makes a significant difference to performance at lower signal levels. If the signal is weak, the resonance will build up over multiple cycles until it reaches the Vf of the LED. It will work without, but much better with.
A fun variation is an RGB LED with coils at 90 degrees to each other - colour varies with the orientation of the unit in the coil
That's cool! Did you make a video of it?
That RGB version sounds good. Definitely a good call for a short video.
@@Peter_A1466 Never got round to it - didn't think of the modelmaking application - could probably have made a few quid before the Chinese took over!
@@bigclivedotcom You measured 223khz - the inductor/capacitor resonance of the 330pf & 220mh coil is: 1/(2*pi^sqrt(220^-3 X 330^-12)) = 186Khz. Looks like resonant power transmission, kinda like radio!
Saying you're not sure if this is a tuned circuit is like saying you're not sure what the frequency dial of a radio tuner is good for. This is basic electromagnetic transmission.
The 2.2mH inductor and 330pF capacitor have a resonant frequency of 187kHz which is very close to the 222KHz you saw this oscillating at, so the capacitor is clearly there to make the efficiency better by resonating the coil.
"187kHz which is very close to the 222KHz" "Very"? :P
The LEDs have 2.2mH inductors and 330pF capacitors. Their resonant frequency is 187KHz.
Try swapping the capacitor to 240pF (220pF would do and more common) to get a better match to 220KHz the coil puts out.
Wow, I've never seen those little lights before. Being assembled directly onto the SMD inductors is super cool! Might be a neat way to do light up clothing.
It won't work well for clothing. The two coils (transmitter and receiver) have to be "on axis" for power to be transferred. You'd have to ensure that the coils stay aligned, which will be really hard to do with clothing, unless you're talking about something rigid ("cosplay armor"?), at which point you might as well use wires.
@@superdau I was imagining more like, have a few of these sewn into a small section of a coat or jacket, sealed in resin to make it waterproof and washable. Have a little pocket on the inside where you could place the coil and battery when you want to have lights. My thought was more that it's an easy way to have the power source completely removable so washing and waterproofing would be easier. :)
@@superdau Maybe, but if you're adding dozens to the armor-- for a cosplay S.F. character, as an example -- this installation could be simpler than wires. Also, if it flexes somewhat, the intensity would change as you move. Of course, as Clive demonstrated, these things aren't all that visible, except in a dim room -- like, say, an S.F. masquerade.
@@superdau With a small tesla coil running several feet away they might light fairly well. I have not tried it with these but I know you can do it with just the lead length of standard LEDs and a zener diode with a small tesla coil and light LEDs wirelessly from 4-5 feet away.
@@BlondieSL shouldn't that read "OMG, HE'S LITERALLY FABULOUS!"
That magnifying effect would be PERFECT for some kind of interactive queue element or activity at a Disney or Universal park. Like gem searching for kids.
Yes would be cool if done some sort of way like that or something somewhere
The Leds with the LC Circuit form a Tuned Circuit and draw energy from the Electromagnetic Field of the Transmitter, like a Grid dip meter does.
0:24 - you can see the white LED that is pretty far away from the coil lights up. Seems that this one picks up stray energy and seems to have some "problem" because it starts flickering and such. Interesting stuff.
I know this is an older video that came back into my playlist, but it is interesting to see that the seller on AE was so impressed by your video that they have incorporated it onto their marketing on the sales page.
One way to think of how this works is to consider the big coil to be the primary winding of a transformer and the little coils to be secondary windings.
And an even better way is to see them as a tuned receiver, because this is not a transformer.
@@graealex Air coil transformer?
@@leef_me8112 Transformers usually aren't resonant, and don't require any tuning. The best comparison would be a Tesla coil, although the C part of the LC isn't that obvious with them.
The circuit being resonant is what allows it to transmit over several cm and significant amounts of power.
Anyway, the transformer comparison is as appropriate as saying your VHF/DAB radio at home is the secondary side of a big transformer, with the primary side being the big radio transmitter.
@@graealex A resonant LLC power supply has a tuned transformer to take advantage of the efficiencies of zero voltage switching. Lm of the transformer is part of the tank circuit.
@@rickjljr11 Obviously you can always add capacity, and it remains intrinsically a transformer. Or add semiconductors and make the behavior completely non-linear anyway.
In the context of energy transmission, it's still closer to a tuned receiver. If the receiver isn't matched to the transmitter frequency, no energy is received.
There is one example of wireless energy transmission that actually is nothing more than a simple transformer, and that's with electric toothbrushes. Especially since they operate directly at 50/60 Hz instead of in the kH-range.
It is definitely a resonant circuit. 5 uH and 100 nF resonates at 225 KHz. Ignoring the capacitance of the LED chip, 2.2 mH and 330 pF resonances at 187 KHz. The parallel capacitance of the LED would probably drop the resonant frequency. The coil driver seems to be right on spec. The little LEDs seem like they’re a little off peak resonance, but that might be intentional to tweak the voltage across the LEDs. Right on resonance might be too much voltage. The Q factor of the ferrite core inductor and chip capacitor combination is probably fairly high given the type of components, thus the voltage right on resonance will be fairly high. The air gap makes the mutual inductance quite low and the little LEDs function almost independently more like radio receivers in the far field of a radio transmitter rather than primary and secondary windings of a transformer.
The voltage is always clamped by the LED, so you never get more than one half-cycle of resonant rise. The high DC resistance of teh fine wire in teh coil also limits max LED current.
@@mikeselectricstuff Excellent comment. Thank you. It is still interesting they aren’t matching resonance of the driver coil and the LED assembly. I was presuming the Q would be fairly high, but you’re right, that is pretty fine wire, probably with appreciable resistance. Maybe they have the resonance offset so there is less variation in intensity versus position with respect to the driver coil. I am assuming the LED junction in parallel with the 330 pF has appreciable capacitance and that would lower the resonance of the LED assembly to less than 187 KHz.
Timing of this video for me was great. Just been playing around with some inductors and a new lcr meter! Thanks again for another great video!
I'm so glad I found a video of Sean Connery teaching me electronics!
That coil is a bonded coil. There is a coating on the outside of the wire (bond coat) so when it's being wound, there is a heat gun close to it so the wire bonds together and holds it's shape.
I have made these and use these for years testing switch mode power supplies in car radios and instrument clusters. I put clear heat shrink tubing over top. Excellent work Big Clive
The capacitor and tuned circuit may be there to achieve "zero-voltage switching" of the MOSFET. When the MOSFET turns off, the current flowing "downwards" through the inductor will first charge up the capacitor. When the voltage across the capacitor rises high enough, the inductor current will be driven back to zero, and then start flowing in the other direction, discharging the capacitor again so that the voltage across the MOSFET is back to nearly zero when it turns on again. This is the half-cycle of a sine wave you see in the scope traces. But I wouldn't have thought ZVS would be necessary at such low power levels... edit: it probably helps to protect the MOSFET from high back EMF without just dumping the energy through a diode.
I think that also. At 11:29 note how they tuned the circuit so it switches when the voltage on the capacitor is zero (looks like < 1 Volt). all the energy of the resonant circuit is in the inductor and starts getting added to
Unloaded is there about 3 Amps peak to peak between the inductor and the cap?
Just built a low buck version with 3mm red led, 330pf ceramic, and 1mH axial inductor. Works a treat. Thanks Clive!
The enameled wire is usually coated in a secondary "hot glue" resin that can be melted by putting some i^2*R power into the copper once the bobbin has been wound. I have also heard of ethanol or IPA-activated glue-layres. It has no electrical function; just mechanical.
I've made the equivalent of these using some NE-2 neon indicator lights. Just get a big enough inductor. Guaranteed proof of concept is the primary winding from an old 9V wall-wart on top of one of those Qi charger pads. Just connect the NE-2 bulb across the coil and you're in business.
Surely, if you drop one - just turn off the lights, energize your coil and scan the carpet!
Where is my Tesla-coil...?
I've had my eye on these for a while but haven't purchased yet. Thanks for the breakdown, now I don't have to do it!
It's one of those things that's neat, but I cant think of a practical application. The current being so low, the potential applications are even more limited.
Could be cool for something wearable or a simple indicator light based on proximity.
Now, if you could push a good 20W through this, there's tons of other applications.
Hello! If you are looking for a ready-to-use solution, we've released a more powerful wireless light set which you can see on our channel :)
That looks like it will be fun for LW and MW wireless listeners next door.
You make my science day more enlighten & wirefree.. Nicely done ..... brilliantly explained.
Love your videos. Always informative. Maybe one day you can look into those old keychains that were ringing when you whistled so you can find your keys, or maybe GSM controlled power sockets.
It was such nice how you explained it, although i didn't understand much but i found it better then most of the electonics Taught in my university.
Way more than I needed to know about these lights but very much appreciated.
For the interested ones: atomic14, a scottish youtuber, was playing around with those, as well. He made an attempt to self build the LEDs in one of his videos.
The way you ran it across like a color revealing magnifying glass there at the intro was spectacular!
Crazy idea but gender reveal party?
I calculated the resonance frequency to be 228.77 KHz. Your demo shows it to be close enough.
The ones with the caps produce more voltage and hence light up sooner.
Also, inductors with this many turns, have al lot of capacitance all by themselves.
these are very fascinating to play with. Got some a couple of months ago.
I reviewed these things some time ago, and made a video to teach people how to build themselves their own LEDs... glad to see you also reviewed them. All sellers uses the small CD43 inductors, but i made some with smaller CD32 ones, and still works fine (a bit shorter range, i think remember). The original ones, the X-Base (Cross-Base) are quite expensive, the double base was about 200€, and then 10 or 15€ for a 10 unit pack... if you bulk buy them to aliexpress is quite cheaper.
Also, you can coat them with some epoxy to water proof them, and maybe run them underwater (in a fish tank perhaps...). Bigger bases gives wider range, the one you have is the small version, there's another with 20cm diameter coil.
Hey! Our company has actually just released a more affordable wireless light set at less than half the price last week, take a look at our channel if you are interested :)
@@Vosentech ehh, 25 LEDs and a coil for $100 isn't half price
Requesting video of the same concept but using omnidirectional holo diodes. Great content. From your vids I've learned a lot as though remembering what I already knew, not that did already, but is actually a reflection on you as being an excellent communicator and teacher. your content is appreciated!
Adafruit also sells a set with a larger, 20cm coil that runs on 24V and 10 wireless LEDs, which unfortunately is currently and most often out of stock.
They also have a 12 volt model with a middling sized coil. Also chronically out of stock.
I was going to link to the Adafruit ones until I realized they had no stock.
If you need it. You can try my products
ruclips.net/video/5-ajmfn24jM/видео.html
Thank you for the warnings when you bring the light back on! My photosensitivity appreciates it.
Food for thought - of course :)
Given that the best energy transfer occurs when the capacitor and coil reactances are equal, i.e. the circuit is in resonance, you can calculate the resonance frequency: f = 1/(2*pi*sqrt(L*C))
Manipulating the inductance or capacitance on the transmitter side without first changing the generator frequency will lead to energy losses and transistor overheating because of impedance mismatch, and doing the same on the receiver side will result in too little energy being delivered to the LED to light it. So, both sides have to be tuned to the same frequency.
Thank you so much for posting this clive. This is exactly the sort of thing that we have been waiting for. Low brightness is hardly ever a consideration, Quite the oposite1
I still instinctively close my eyes when you say “watch your eyes “.
🙏
You don't get any more light from inverse-parallel - with a single LED, the energy can built up over the non-conducting half-cycle and gets dumped into the LED on the next - with inverse-parallel LED, you just get half the power, so no net benefit
Are the leds effectively flashing rapidly? Or more or less fluctuating in intensity (fast)?
DO you get more light from parallel universe?
Only if connected in series
This depends because perception is as complicated thing. Humans are sensitive to peak brightness so with equal power a pulsed source can look brighter than two dimmer sources even if it's producing less light. We perceive a brighter light but if you were to measure it with sensors you'd get different results.
Luminous efficiency of LEDs is also not linear so a lower average current will be more efficient than pulses of higher current electrically.
This would be a little complicated to demonstrate because the currents are pulsed at a high enough frequency. You would need a photo detector with a fast enough response time and then average things properly keeping in mind the weird distortions out perceptions place on things.
I was not expecting visible pulsing. Was more wondering if the capacitor more or less smooth everything out or not, since this seems not the primary task of the capacitor in this circuit.
Thanks Clive, love this video
You can hook a small coil up to a function generator and sweep the frequency rang to find the optimum frequency to power a single LED. But by having the optimum frequency of the LEDs dissimilar to the coil, each LED will have very little impact on the driving coil. Operated at perfect resonance, a full circle would put a heavy load on the coil and alter the output of LEDs already inside the coil.
I like how you print up the circuit boards because it's a good teaching tool and it can be utilized in education
I want to use the design of this and superpower it with high voltage and elements to charge
I wanna see if I can excite atoms in certain materials and see if I get some results and also wireless charge batteries with reciver capps
The capacitor does form a tuned circuit that enhances coupling.
If you had a grid dip meter you could show the enhanced coupling.
Today we have $50 graphical antenna analyzers from china :)
The LEDs with capacitor light up first because the voltage of a parallel LC circuit will creep up under excitation until leakage offsets input energy, classic signal detector circuit where you pick LC for your center frequency and Q-factor (Xc/R) for bandwidth. The higher the Q, the more sensitive the circuit is at the expense of narrower bandwidth. The non-LC LEDs light up when inductive coupling into their inductor produces high enough voltage.
and if it's iron it goes _err, err, er err errr errrgh_
been waiting for you to have a look at these, knew you would sooner or later. i would end up losing them and having to go around in the dark with a coil to find the darned things.
Wow. If' you'd shown these to me ~30 years ago, I would probably still be talking about them. Seems like it could be a good teaching tool for RF and tuned circuits. Maybe couple your blue/violet LEDs with phosphor silicon or resin casts?
I don't understand anything this channel or these comments talk about but boy do I find them interesting.
love your videos ill try to keep my messages short lol well love the channel ive been watching you for over 5 years now and i allways leave a like on every video even if i dont watch them all the way lol well have a great day brother
Looks cool 😯
It would be interesting to see the oscilloscope traces across the coil for the various versions of LEDs.
It would be, but tricky to probe without the ground acting as a second receiving coil. If you took the hook off the oscilloscope probe, and used the little spring probe ground that goes right on the point, you might get it to work.
Agreed...
Loved this a lot. You are the best at what you do. So well done……
The small inductance and large cap on the sender produces a low impedance tuned circuit with low Q, in cost terms it saves money on wire too.
Aww damn I thought we were going to get a look at your oscilloscope 😂 always want to see more of your tools and Test equipment
I've done this without any circuitry, just feed it straight, works totally fine, I've also used it to transfer audio!
Now you have to build a lavalamp with these LEDs floating in silicon oil.
The resonant inductor for that capacitor is an order of magnitude smaller. 2.2nH
These are really interesting Clive but the only thing I can think of using them for is a model fairground in a Michael Bentine style without the flees. Cheers
I saw the same demo for plastic models like gundams instead of using traditional battery powered LED compartments. Pretty damn nice not replacing those batteries
Thanks you for warning me you were turning the lights back on. Lying in bed, that could have been uncomfortable. Gentleman status achieved.
Yeah, 2.2mH and 330 pF puts the resonant frequency at a bit over 180 kHz. The LED would then lower the Q far enough that it'll catch 220 kHz just fine. LC tank circuit resonant frequencies are easy enough to calculate by hand, and you can get online calculators to calculate them for you anyway.
I thought of a similar system when I was about 12 years old (1972) to light up an off shore light houses .To save having to use electric cables in the sea ! My teachers were totally dismissive of my suggestions ! Just think I could have been a genius ! 😁
Howdy Clive, must admit I'm fairly new, usually don't ultimately understand the 'schematic' part.. but this time 'gave it a go' and....... was somewhat confused on the colorized PCB... some things were making sense.. others werent.. until.. realized I had basically got the polarities switched vs marker color.. finally got it though, and thanks for the good work
Have you tried to make a much larger inductive loop and see if a larger area can be made active?
I wanted to make the video before blowing the module up, but will be doing further experiments.
Yes! Our company designed and released a wireless light set with a much larger active area in case you are interested :)
Try making shapes / letters.
What a cool sign to have the LEDs on a belt rolling over the magnetic lettering.
Encapsulated, they could be in the stream of a fountain with a large coil in the pool.
A larger loop would have different inductance, thus needing a different capacitor to get the desired resonance frequency.
mmmm, what about doing a "lava lamp" with those leds floating up and down?
This literally does look like magic although it isn't. The product images also look like they're conducting some kind of ritual. I love this tech!
I'm thinking to create a resonant circuit and putting it under plastic or aluminum clock hands. The coil must accommodate several led diodes in the middle. Hands must be minimum 5mm wide to accommodate coil + LED's + capacitor. All that put into classic quartz clock driver, driving coil under clock face and you got glowing clock hands
Awesome big Clive
White being the fusion centre of the spectrum the orange/yellow and green/yellow parts of the colour spectrum should be the brightest as its harnessing from 2 colour short circuits which produce the white - Walter Russell, cool stuff Clive. :)
The capacitor is there to calibrate the resonant frequency. The receiver and the transmitter both should have their resonance at about the same frequency.
Came for the oscilloscope traces. Stayed for the ambiance! ;) Another circuit made possible by the power of MosFETS!!
It may be very well a resonance circuit; 2.2 mH + 330 pF gives about 187 kHz, which is near the 220 kHz you measured. It would also explain why the LED with the capacitor removed was dimmer at first.
5 μH + 100 nF is 225 kHz. It all matches up. It will also mean that a larger coil, or one with more windings may perform worst.
5uH +100nF would have a very low Q-Factor. Looks like this is yet another source of Radio Frequency Interference. 225kHz was a frequency allocated to the UK for Radio 4 in Central Scotland, but there was too much interference from Poland. I believe that the Polish transmitter has already, or is about to close down.
@@blacksmock445 What would cause that particular combination to have a low Q? In this case that might be a feature since a low Q would mean it would mean a broader bandwidth, right? You wouldn't have to be too concerned about getting the frequency matched just so.
They'd be better feeding the output of the xkt001 into an audio amp or H bridge to effectively double the voltage swing of the output without increasing the supply voltage. I did something similar with an NS8002 audio amp and oscillator.
@@flapjack9495 Since the frequency seems to vary with the load (number of LEDs used) a High Q wouldn't be desirable. A radio tuned-loop antenna circuit would probably use an inductance of around 1.5mH with a capacitance of 365pF. Both of these components would have much higher reactances at resonance and a higher dynamic impedance and a higher Q. The combination of 5 uH and 100nF wouldn't make a very effective tuned-loop antenna for radio reception on 225kHz. They would be a lot easier to make if it did.
The receiver coils have the wrong capacitor value. It should be around 231pf instead of 330pf to match the forced frequency of the transmitter. The transmitter coil with its capacitor can also be tuned to improve consumption and efficiency. It actually only runs at a forced frequency determined from the driver, but not in matched natural LC resonance. Thanks a lot for your videos!
330pF is a standard value.
I'd be really interested to see if the addition of a capacitor back to the double LED units gives them even better range
Skylanders had some figures that would light up when placed on the portal. Through it was for NFC I guess it also produced enough power to light up quite a few of them.
Yes I do remember hearing about the Skylander is that Lit Up.
These remind me a bit of back in the 1970's when I discovered that if you held onto one end of a fluorescent tube and held it up in proximity to high voltage power lines, or held it next to the antenna of a CB radio which was transmitting, it would glow! :-)
I have an idea, make an analog clock with a inner ring of LEDs for seconds and outer ring for hours and a ring in the middle for minutes. You need three pointers (actually a cheap clock) with coils for this that rotate above the surface. When a pointer with a coil moves along it lights up a LED.
'Tis been done with Neopixels.
I recently designed something like this except hardwired, using only old-school logic chips.
It would probably be easier to do it with magnets and reed/hall effect switches.
@@paulsengupta971 It is not about ease, it is about the effect. I can imagion surrounded leds still glow a little when the pointer is off center to a led. So you will get a fade-in fade-out effect. This effect cannot be done with reed switches. I think this is easier to make than what you suggest. You can buy those leds with the coil attached. Soldering and wiring isn't required.
@@leef_me8112 The fun is, you don't need logic or programming for this.
The transmit circuit is a bit odd. The usual way to drive a resonant coil from a square wave is to connect the tuned circuit in series, because a series tuned circuit has a minimum impedance, so you get higher current.
Using a parallel tuned circuit is odd because it is a high impedance at resonance, plus the low resistance of the FETs will swamp the tuned circuit.
It would be worth hooking the TX tuned circuit in series to see if it gives greater output. You would probably have to retune the capacitor however.
And presumably the receiver coils are in parallel because the higher voltage is needed to light the led.
You have a tesla coil, the primary is a tuned circuit with the coil and capacitor bank, the secondary is not so obvious, but the top load is one plate of a capacitor, planet earth is the other plate.
If you change the tap point or the size of topload it won't work properly.
The primary and secondary are resonant circuits. the ones in the led system is a parallel tuned circuit, just look at any radio circuit diagram (plenty online)
ive been watching your videos for years now and ill cant wait to see you get to a million subz. i hope it happens soon brother. i love your vidoes and ive been taking things apart since i was a kid and im a twinand have 4 brothers and 1 sister lol so its been fun and where all around the same age. but anyways i even build my own grow lights out of old TV i take apart and put more LEDs on them and all sorts of stuff i do with leds and grow light lol well thanms for being you have a great day
I calculate 186KHZ for the resonant frequency of the LEDs and 225KHz for the driver coil plus capacitor, so it is not beyond the possibility that there is resonant coupling.
I think we will see them in little character model's with the coil in the base would be kinda nifty to have little wireless lights on them
besides a tuned Tesla coil, one of those inductive heaters tuned to them also may work too...
Love to see the oscilloscope traces!
"Seemed like a good idea at the time."
use this as axial distance measurement device, you know the exact power level to distance relationship, in the tracking pod, 3 axis pad gives you 3 coordinates, very accurately
One of those mini lamps was very effective and was lit up despite where the loop was....
The purpose of the capacitor would be to create an LC tuned "tank" circuit, tuned to the frequency put out by the coil driver.
The LC resonant frequency of the inductor and capacitor on the LEDs is about 187 KHz. That's reasonably close to what you measured with your scope, since the LED is going to load down the circuit, resulting in a low Q.
RF is a speciality here. They could improve this design by making the transmitter sweep frequency to find the peak in power draw by the devices placed near the coil.
I remember back in the early 2000's when places sold those tacky ass cell phone antenna LEDs that would activate when you got a call. Everyone in the trailer parks back then had them. This is the same thing basically
Me trying to replace the LEDs: "Look I made a molten blob!"
Somewhere in between that giant bulb you showed the other day and these microscopic thingies is my comfort level. :) Very neat though.
That's amazing! What will they come up with next?
Both the tuned circuits on the primary coils resonate at roughly 200kHz. So, I'd assume the capacitors are to make a tuned circuit.
Proximity warning light: For those who must park their car in tight quarters, one could bury the primary-coil under the plastic bumper cover of one's car and adhere an LED-secondary-coil module to the obstruction (wall, parking garage pillar, or etc.).
Clive said, "they will roll and you will not find them."
That is, until you bring out the neodymium magnet you got out of a hard disk drive and sweep the floor a few times. As long as they're ferrite they should stick.
Have you ever done an episode on LED throwies? Thanks.
You could also run a coil over the floor in the dark.
One different idea this gave me is what if this was used in some kind of escape room. You have a "magic" magnifying glass that simply has one of these transmitter coils in the rim, and you have to look for clues which will have these lights hidden inside of them and will glow when you examine them.
nice effect, grandfather clock pendulum could hide the coil, leds on the back of glass ,
altered weight might ruin time keeping part ... but that is adjustable ?
220uH and 2.3nF give a resonance of 223KHz so that cap at 2.2nF would make sense on the LED side. 100nF and 5.09uH works out to the 223KHz so each side is definitely a tuned circuit!
nice exprementation , you can use that wireless led to diagnose a power switching supply just put it over the transformer , an other idea if you decorate you clothes with many of them you will light up when you pass a walk through metal detector.