Photon D7 LED installed backwards?

Troubleshooting
1

I am getting stared with my Photon and I cannot get the D7 LED to turn on using the Tinker app. When I connect a meter to D7 I can toggle the voltage from 3.3V to 0V, and I have the same voltage showing up on the LED pad nearest to D7. The other side of the LED is connected to ground. Looking at the data sheet for the LED (Everlight 19-217/BHC-ZL1M2RY/3T) it looks like there is a notch on one of the pads indicating cathode, which should be connected to ground. In the attached picture, it looks like the notch is where the anode should be. Would someone with a working D7 LED compare theirs to this picture? Thanks.

2

@cpl, I can’t vouch for the “notch” but the orientation of the LED “pad” is correct. The LED may be a dud. I assume you set the tinker pin to “HIGH” to turn it on.

3

I don’t have a magnifying glass handy, so I can’t get a good picture of my working LED. From here it looks like there’s a notch on both sides (?)

4

Yes, I set High to turn it on and Low to turn it off. My meter shows that it is responding when I do this. I can also control the DAC from the app and measure the voltage on that pin, so the app appears to be controlling the board.

This is a tiny part so I’m trying to verify if it is reversed before I try to remove it and rotate it (or try to get a replacement board)

5

If your multimeter has a “Diode” test feature, use it and determine the Anode and Cathode position.

Ping @will

6

Hey @cpl,

Let us know what you find. I can’t quite tell from the picture if the LED was installed backwards, but each board undergoes AOI (automated optical inspection) that checks for things like incorrect orientation, etc. So, it’s more likely that the LED is a dud or was damaged than it was placed backwards.

If you’re having issues with it, definitely send us an email at hello@particle.io and we can help to process a replacement. Just reference this thread in your support ticket and we’ll make sure you get taken care of :slight_smile:

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7

I connected a Fluke meter with a diode function as Kenneth suggested and it shows a forward voltage of ~1.55V with the red lead on the diode pad farthest from D7 and the black lead (common) on the diode pad closest to D7. When this is reversed, the meter shows “OL” (no current). This is what I expect to see if the diode is installed backwards.

8

It seems like the diode is one of the rare manufacturing defect. :smiley:

like Will mentioned, drop them an email and get it replaced :wink:

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9

:+1: to what @kennethlimcp said!

10

@cpl, you could alternatively think of it as a REALLY low power LED for a really low power application :stuck_out_tongue_winking_eye:

11

Thanks for the input everyone. I have put in a support request for a replacement. I wasn’t sure at first if I wanted to do that since the board appears to be working otherwise, but having a blinky light sure is handy when developing code on these small boards.

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