Activity LED dimly lit

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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stryker
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Activity LED dimly lit

Post by stryker » Sat Jan 14, 2012 2:59 pm

Hi

I notice frequently when I first power up my Eleven the orange D13 activity light is dimly lit. Uploading the blink example correctly toggles bright-on to completely off, and from then on the LED behaves like I expect it should.

Is this normal/expected for the Eleven? I've had it for only a few weeks but have only noticed this recently...I can't be sure it's always done it however.

Otherwise, completely LOVE the Eleven and have been having a ball with it. Will be buying it a sibling before too long I'm sure.

Thanks,
Geoff

tomgreen
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Re: Activity LED dimly lit

Post by tomgreen » Tue Jan 31, 2012 7:18 pm

I was getting a dim D13 on the Eleven on which I (I think) killed the regulator, by trying to power a Sparkfun cellular shield (large load) through it off a nominally 12vdc supply that was actually chucking out 16.5vdc.

The other thing is that perhaps the line is floating (neither high nor low) before the first time you deliberately set the state of D13. I'd be surprised if the Eleven circuit didn't have a pull-down to prevent this though.

I assume no dim LED if you do a digitalWrite(13, LOW); as the first statement in setup()?

My current, non-damaged-power-regulator Eleven does not have a dim LED - it's either on or off.

Tom

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stryker
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Re: Activity LED dimly lit

Post by stryker » Tue Jan 31, 2012 9:02 pm

Hi Tom

You are right, when using it with sketches that use the 13 LED I don't see it, and there doesn't seem to be any other symptoms I've found. So far this Arduino hasn't been used on any heavy duties like you describe - a oneWire thermometer, a Bees shield with Bluetooth and a Wifly, and a 16x2 LCD shield have been attached to it at different stages without the slightest hiccup.

Very soon this one is going to be permanently mounted in an enclosure so it won't be visible at all and I've avoided using 13 on this project just in case. Since posting this it's worked flawlessly aside from every now and again seeing the dim LED so it's been more of a curiosity than an issue.

And since there's not been a deluge of replies here explaining they all do it I'm presuming it's a one-off. Perhaps that pull-down you mention is on the edge of tolerance on this example.

Thanks for your reply, Geoff

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Re: Activity LED dimly lit

Post by jonoxer » Sun Feb 19, 2012 6:54 am

tomgreen wrote:I was getting a dim D13 on the Eleven on which I (I think) killed the regulator, by trying to power a Sparkfun cellular shield (large load) through it off a nominally 12vdc supply that was actually chucking out 16.5vdc
Odd, that shouldn't kill the reg. It has built-in thermal overload protection so the worst that should happen is that if it gets really hot (which means "burn your fingers if you touch it" hot) it'll just turn itself off until it cools down again. Unless the reg is subjected to an excessively high voltage on its input (perhaps 35V or above) it shouldn't be possible to kill it just by pulling a large amount of current through and overheating it.

I'm not discounting what's happened to you, and it sounds like you do have a dead reg, but I'm a bit surprised that it failed.
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Re: Activity LED dimly lit

Post by jonoxer » Sun Feb 19, 2012 6:58 am

stryker wrote:I notice frequently when I first power up my Eleven the orange D13 activity light is dimly lit. Uploading the blink example correctly toggles bright-on to completely off, and from then on the LED behaves like I expect it should.
That's nothing to worry about. It's possible that you've loaded a sketch that sets the internal pull-up resistor on D13 inside the MCU, which has the effect of illuminating it dimly. The ATmega internal pull-ups about 20k (from memory). What may be happening is that the pull-up was left active in the MCU from the previously executing sketch so it provides a light bias to the pin, then when your sketch begins it strongly asserts either high or low on D13 and forcibly biases it one way or the other.
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stryker
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Re: Activity LED dimly lit

Post by stryker » Sun Feb 19, 2012 7:11 am

Hi

You'd think it might be something odd like that, but I use this one for lots of sketches and the common thread is if the activity LED isn't actively driven in the sketch, it's half lit. On a positive, it means I can ID mine from a lineup :D

Geoff

ilium007
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Re: Activity LED dimly lit

Post by ilium007 » Fri Jun 22, 2012 12:35 am

I have the same issue. Even in void setup{} if I drive the LED LOW it still remains lit. Its a bit annoying because it means I can;t use PIN 13 for anything I suspect because it always seems to be HIGH.

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stryker
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Re: Activity LED dimly lit

Post by stryker » Fri Jun 22, 2012 12:51 pm

ilium007 wrote:I have the same issue. Even in void setup{} if I drive the LED LOW it still remains lit. Its a bit annoying because it means I can;t use PIN 13 for anything I suspect because it always seems to be HIGH.
Since originally reporting this I now have 4 Elevens and each one does the same. I've bought them over the intervening months since that first post, and from 3 different sources so they're not the same batch. However if you drive them specifically HIGH or LOW they do function as they are supposed to. It's only when you don't drive the D13 LED directly that it remains dimly lit.
I've had no other issues (obviously, or I'd not have kept buying them :D ). Yours might be a different case if you can't set it to output and then digitalWrite(13, LOW) to get it to stay off.
It's something about the Eleven specifically but they're fine otherwise.
Cheers ! Geoff

ilium007
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Re: Activity LED dimly lit

Post by ilium007 » Fri Jun 22, 2012 1:25 pm

Mine is an EtherTen. Even when I pull pin 13 low there is a tiny glow from the on board LED.

Agent
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Re: Activity LED dimly lit

Post by Agent » Tue Jul 01, 2014 1:17 pm

First post, (found the forum by googling this Q) and just wanted to say, I have the same issue. My description is as follows:

Upload to the Eleven, and get a solid D13 board light. Program runs fine AFAIK.

Hit reset button, D13 board light goes out. Program runs fine AFAIK. D13 light creeps up dimly.

D13 board light goes full brightness when I physically tap on the ICSP pins. Repeat action, light goes out or dim. Not sure of cause.

[Edit: At no point have I applied a voltage above 5VDC 500mA USB from computer to the board.

Have exposed D13 to a blink program without a resistor in place by mistake when I first got the kit. Don't think that matters. Frequently wrong.]

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