xLED not working?

I picked up one of the HF xLED’s at the implant party in Seattle but I can’t get it to light up at all, even on my ACR122u. Am I using it incorrectly somehow? I would assume w/ something like ACR122u that it should be fairly easy to get it to light up. I haven’t had a chance to try it with a 125khz door reader just in case the LF was packaged inside the HF box, but I should have a chance to find that out in the next couple of days) – any other suggestions to try?


Is the ACR122 plugged into a computer? I noticed it won’t turn on the field until it starts talking to a driver. (i.e. you can’t just plug it into power)

Once it is on, and the xLED is in the right orientation (near and perpendicular to one of the long edges), it should light it up bright.

As you mentioned, the other test would be with a LF reader.

Yes, it was plugged in a reading my xNT, still couldn’t get the xled to light up. I’ll check it with a 125khz probably tomorrow and update.

If you’re ever wondering whether you have the LF or HF xLED, you can tell them apart by looking at the coil.

The LF one has a lot more windings than the HF one. On the LF, the coil covers most of the ferrite rod. The HF one, the coil only covers a very small amount of the rod.

LF on top, HF below:

Mine definitely looks like the HF one, I just can’t get it to light up at all. I used an imaginary grid across the front of the of the ACR122u and tried 6 orientations on each of the imaginary squares, just to be extra sure … it didn’t light up on any of them … but I can get it to read my xNT implant no problem.

In this picture, I’ve got the xLED in what I believe should be a position that would make it light up, and in fact, the readers light is turning green from the proximity of my phone while I took the picture, so the ACR122u is definitely on and emitting/receiving. Seems like maybe my xLED is defective, but are there any other tests I can try?

The 1/3 of the ACR122 closest to the cord is all the electonics. So the position would be better if it was closer to the other end, but same orientation… But regardless, it definitely seems to have an issue.

This a little video I made that should show you exactly the best position/orientation.
It’s auto-embedding the video. skip to 3m45s

Thanks for the video … still getting nothing out of my xLED :frowning:

Hmm… we tested all these but it might be possible a few duds got through… since these are definitely not commonly manufactured they all had to be manually soldered… very slow tedious process with a lot of failures.

Before we replace it, try this position;

If it still does not work, then @mdanger can sort you out with a replacement.

@amal, @mdanger

Here it is aligned as requested. Again, the ACR122u is registering a read from my phones proximity while taking a picture (as a tangent… this is surprising as it’s a good 4-5 inches away and my phone normally has fairly bad nfc ranges).

Any other orientations or diagnostics you would like me to try?

Meh, it’s dead. Sorry about that! @mdanger will replace it for you. Please PM her with your shipping address.


Hi Cinja,

I’ll get a replacement out today for you. Sorry for the inconvenience!

My best,


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