I’d love to see a schematic if you find the time! I look forward to seeing what you come up with, especially with those SMD mosfets you refer to. Any thoughts on how high voltage your current design / future designs need to be driven with?
I’ll post circuits when i pinpointed on which cirquit i use. On the one i use right now it works outstanding at lower frequencies but when i go higher the losses skyrocket and tgen drop again. So i might have to try different inductances for the power coil
on 2MHz i get a almost perfect sine wave with good coupling. On a bare bicolour led with only an inductor soldered to it it works quite well at that frequency with high efficiency.
But not so much when i bring it higher. At 6MHz the sine starts to look less pretty
And on 13,6 the transistors get very warm (as i said esrlier probably due to an impedance mismatch between powercoil and resonant capacitor) to the tries with the smd mosfets i didn’t build anything there yet since i forgot how much pain it is to solder smd free wired. I’ll try again today with a different soldering iron and maybe some kapton tape to hold it down
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Hey folks, I’ve been following this topic for a few weeks, and I started wondering- does this kind of thing exist in a non-bracelet form? Because like, if I’m just wanting to do something that will make my blinkies light up, I’m willing to just be holding a thing which is the battery + all the other stuff (oscillator, antenna, mosfet (I have no idea what a mosfet is for despite trying to learn about it online and here)) in a single case, which could open up to replace the battery and maybe a switch to turn the 13.56 MHz signal on and off… it wouldn’t even need to be too small or whatever, just fit in my hand, like a pill bottle, or a lighter, or something.
What I’m trying to say here is, if there’s another way to get my blinkies to light up without the use of my cellphone, I’m willing to compromise on the convenience of it in some ways.
Is it technically easy to put something together that just outputs a 13.56 MHz sine wave at a certain power? A lot of this discussion goes above my head in this thread 
I can’t help you much with the lower level stuff, but if you’re just wanting to light up your implant in a decently small form factor on the go, something arduino based would be an easy option (and it’s what I use, for showing off my xSIID).
With an Arduino pro-mini and a breakout board (I really like PN532 based boards) + a battery, you could make a decently small solution without having to do much actual work from an engineering POV
Especially if you go for an Arduino board that can do HID emulation stuff, you could always use the same device to act as a wedge reader, password typer, etc. @Vicarious has a great post about the password device he put together in a super nice form factor. That + a small battery and a mode switch (for constant light vs. actual authentication) would make a bad-ass device for showing off blinkies, would have an actual use too if desired, and would cost less than $30.
This is definitely an overkill solution that doesn’t give insane range for lighting up implants (depending on the breakout board, I can usually manage an inch or so with my xSIID), but it’s an easier option, if you aren’t able figure anything else out.
If you do work to build a more low level solution, like those in this post, I’d love to see it though 
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I have something that fits your criteria, though I’m not sure I like it, I’ll post a video in a sec
Edit, nvm
I thought if I plugged the little nano reader I have into a usb it would work… it refused to run on just power apparently
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This should do what you are after… just no LF
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Yeah, I’m working on a little keychain blaster like you’re describing. We’re calling it the lite version. Leumas95 is still working on the full version. It’s just not high on the priority list right at this moment, but I have most of the BOM worked out. I just need to narrow down my SMT mosfet choices a bit to get the best performance.
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@darthdomo, that sounds really cool! I was actually kind of thinking about getting into Arduino recently, they seem like a cool thing to learn and get into for a variety of reasons (like this!). I appreciate the idea and will keep this in mind!
@Pilgrimsmaster , that also looks like a really good solution, basically what I’m looking for, but at $90 that seems a little steep, especially considering I’m mostly wanting it for just the blinkies, not so much the other stuff. Cool find though, and cool website. Thanks for sharing.
@Satur9, very cool! Please keep us updated… if there’s anything I could possibly do to help out with this, I’ll be happy to offer whatever I could do, if anything.
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oh, and on that note, about what @Eriequiet posted, I’ve got the DT keyboard wedge device sitting on my desk, and I’ve tried holding this in the palm of my hand to see if I can get my xSIID on the other side of my hand to light up, to no avail. I realize that the 13.56 MHz EM waves have very short range, but getting absolutely nothing with even this device is a little disappointing because of how much power is going to be needed to go thru one of these devices just to be able to penetrate my flesh to the other side of my hand.
It’s not really easy to do. It’s still a frequency that can be managed but there are quite a few hurdals. To your question what a Mosfet is: it’s basicly a switch that starts to conduct when you put a voltage on one pin (the gate). The gate is basicly like a capacitor. You charge it to a voltage and it holds that voltage. When the gate has a voltage above 5v it will start to conduct between drain and source. From 5v on to 10v is the region where it conducts more and more the higher the voltage on the gate. Above 10v on the gate it’s fully on. The thing with switching mosfets at high frequencies is charging and discharging that gate 13560000 times per second for nfc. This uses an insane amount of current to do and you are basicly trying to put that current through a wire less than 1mm in diameter. To the range of your reading device: it’s basicly bound to the inverse square law. If you want go double the distance you need 4 times the energy to get the same field strength. What can also influence your range is coil diameter and coil geometry. A flat coil usually doesn’t reach as far as a cylindrical one.
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So i had very busy past weeks which crossed my plans to work more on it and try things out. I managed to do a few things though. I tried the second circuit with the smd mosfets and first i couldn’t get it to oscillate and then the tiny smd mosfets died. I also remembered why i don’t like free soldering smd parts. Oh well… yesterday i though why don’t i just order a pcb with it to just put the chips on board and don’t have the pain of free soldering. So i designed a pcb:
And ordered it on jlcpcb. It has the option of using smd mosfets on two different packages (sot23-3 and sot223) and using either two small caps or one large for the caps that see quite an amount of ripple. One thing that worries me though that it might not reach 14MHz is that it probably has quite a bit of capacity from the tracks alone. I’ll update you on that when the circuitboards arrived in about 2 weeks and i got around to populate one or two. Also i got the xled field tester keychains now so i could try the nfc one on the other circuit i was working on
So much to updates right now.
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Very nice, not sure if I’ve ever seen an xFD glow that bright.
Lemme d-rail 4 a sec.
so there is nothing to limit the current on a xled?
That means they re easy to blow out? (as if there qould be some regulation)
so you must trust the reader to not kill it?
Yep pretty much. That’s why the xsiid is a good option.
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For the LF xLED there’s basically no protection, but for the HF xLED the impedance (frequency dependant resistance) of the coil is very high. I doubt you could burn one of those out even intentionally.
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Please do try. If you have a function generator that can accommodate 13.56MHz I’d be interested to see your results. You might also want a VNA to find the actual resonant peak to deliver max power. It’s a bit off from 13.56, IIRC. I posted a video that explain how to set a cheapy one up for that kind of testing here
EDIT:
I calculated out that the impedance of the HF xLED coil should be more than 240Ω at 13.56MHz. The LED in the xLED is white so it’s probably something like 3.2V forward voltage and 40mA forward current. Since the negative portion of the AC waveform induced by a reader is cut off by the diode, that means the Pk-Pk voltage that would need to be induced into the xLED by an external device would need to be 20VAC to even meet the rated values, nevermind exceed them. I’ve only been able to induce 6VAC Pk-Pk in an LC tank circuit under ideal conditions, and the fact that it’s a periodic waveform means there’s time in between the pulses for the junction to cool. You might be able to burn it out, but I really don’t see how.
The reason why i bought the keychain is that i’m also worried to blow it. And i’m pretty sure i could do that. By the way… a friend of mine has a frequency generator that can output 500w of rf power at 13.56MHz without breaking a sweat. Anyways it’s not as bad to break the keychain than it is to break an implant so i went with the key chain. The xLed in my test got really quite bright at the sweet spot at the coil despite it was not being driven the right frequency and i only input like 3W of power into the circuit.
Feel free to give it a shot. If you can fry a field detector keychain and tell us how you did it then I’ll make sure Michelle sends you a replacement or two.