What causes the Red LED to glow?

The "Eleven" is our Uno-equivalent Arduino-compatible board, but with a number of improvements including prototyping area, a mini-USB connector, LEDs mounted near the edge, and the D13 LED isolated using a FET. [Product page]
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rachalmers
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What causes the Red LED to glow?

Post by rachalmers » Fri Aug 15, 2014 9:30 am

Sometimes the red LED glows, but if I move the board, it goes out?
What is it indicating?

or let me put it another way.
The Red LED on the edge of the board sometimes glimmers, or actually shines. I can bllink it on by tapping the board? Something loose? or what.

What does this LED indicate. What's it's purpose?

angusgr
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Re: What causes the Red LED to glow?

Post by angusgr » Mon Aug 18, 2014 7:03 am

Hi Robert,

This stumps people quite often and the answer is not obvious, we should add an FAQ for it!

The red LED is connected to digital pin 13, so it blinks when you run the Blink sketch or otherwise set pin 13 HIGH and LOW. An explanation of why it sometimes glows dimly can be found here: viewtopic.php?f=3&t=159&start=10

Regards,


Angus

rachalmers
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Re: What causes the Red LED to glow?

Post by rachalmers » Tue Sep 09, 2014 2:09 pm

Thanks, yes, that's exactly it. Strange, but now that you explain it, not unexpected. I had an idea it may have been induced capacitance changing something but as it wasn't affecting anything I haven't gotten back to it. So. No problems.
Thanks

skippyone
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Re: What causes the Red LED to glow?

Post by skippyone » Mon Oct 06, 2014 1:42 pm

Hello Freetronics

I have been using Arduino Eleven v1.0 for some time and its been great .I lashed out and got another one for another project and it was Eleven v2.2 R3 which works great except for the D13 LED When you not using it ,it comes on when ever it likes,my other Eleven doesnt do this it stays off ,I have noticed there has been changes to the PCB layout and Q2 has been rotated I have tested a few other boards the Twenty Ten OK,USBDroid D13 stays off ok ,EtherTen V1.1 D13 stays off,Arduino UNO Orig not R3 D13 stays off so its faulty by the looks.
I would have thought that when the Rev change is to make it better not worst now how can this be fixed do I return to place of purchase or are they all faulty.And why arent you putting all the circuit diagrams on the wed page for all devices it would make things a lot clearer,And the Information on the Web Page like the Article Eleven is outdated its the old Board v1.0 most would have the lastest version and changes in the revision change.

Thanks
R.shepherd

angusgr
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Re: What causes the Red LED to glow?

Post by angusgr » Tue Oct 07, 2014 6:05 am

Hi R.Shepherd,
skippyone wrote: I have been using Arduino Eleven v1.0 for some time and its been great .I lashed out and got another one for another project and it was Eleven v2.2 R3 which works great except for the D13 LED When you not using it ,it comes on when ever it likes,my other Eleven doesnt do this it stays off ,I have noticed there has been changes to the PCB layout and Q2 has been rotated I have tested a few other boards the Twenty Ten OK,USBDroid D13 stays off ok ,EtherTen V1.1 D13 stays off,Arduino UNO Orig not R3 D13 stays off so its faulty by the looks.
Sorry to hear this is causing you problems. The PCB changes might be the cause of the more-susceptible LED, but it may just be internal variations in the Q2 FET on the board - different FETs on the board may be more or less prone to switching on from ambient charge, but they're all functioning within specifications.

Even though the LED may come on when unused and disconnected, the choice to connect it via a FET (unlike the original Uno boards) does allow for some different options when using this pin as an input. Unfortunately we can't prevent the LED from occasionally glowing without removing the availability of those other features.

The post here explains somore more, and how to prevent the LED from glowing when running a sketch: viewtopic.php?f=3&t=159&start=10

If the steps given in the linked post don't work on your Eleven then there is a fault with the board, the glowing should only happen when the pin is set as an input and "floating".
skippyone wrote: how can this be fixed do I return to place of purchase or are they all faulty.
If you'd like to return it then please get in touch with us and we can arrange that. However a replacement is likely to be the same. As mentioned above, there's are steps you can take if the LED coming on is a problem.
skippyone wrote: And why arent you putting all the circuit diagrams on the wed page for all devices it would make things a lot clearer, And the Information on the Web Page like the Article Eleven is outdated its the old Board v1.0 most would have the lastest version and changes in the revision change.
Thanks for pointing these deficiencies out. The schematic was available via the "Design Files" link but I've added a direct link to the product page like we usually do. I've also updated the Getting Started guide to the current version with the newer product image.


Angus

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