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Faulty Netduino2 Boards


Best Answer Chris Walker, 14 May 2015 - 06:34 PM

Hi voytek,

Thanks for replying to my PM. We can diagnose the issue here in the forums thread (where others reading the thread can benefit) or via PM (which I totally understand, if your design is commercial and therefore of a sensitive IP nature).

If you don't reply back here, I'll assume that we take things from here via PM...

We're here to help,

Chris Go to the full post


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#1 voytek

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Posted 14 May 2015 - 06:36 AM

Hi,

 

We are kiosk manufacturer and are using your Netduino2 board as a general purpose controller in one of  products.

Its main purpose is to read some internal temperature sensors, control some PWM fans, read the fan speed, control a LED and a relay as well as some internal security switches.

We have designed our own custom shield to allow easy connection to our sensor and to condition the I/O signals such that they can work with the sensors.

 

We have built original batch of 25 units (about 2-3 months ago) without a single problem. They have been now deployed in the field and are working fine.

We have just started a build of further 150 units and have 14 faulty Netduino2 boards.

 

They all appeared to program OK (except perhaps one of them).

But once they are installed in the units they appear to be dead.

 

Once the boards are removed and inspected there seems to be a mixture of symptoms

Roughly half the boards only light up the white LED but not the blue LED, the other boards have both LEDs on.

Some boards emit buzzing sound (I assume it is the switching regulator experiencing excessive load)

All but one of the boards fail to connect to the PC in either boot loader mode or normal mode.

One board connects OK but the firmware download verify fails.

 

We would like your assistance in identifying the root cause of the problem, as you would have lot more experience with those boards.

Has anyone else reported similar problems ?

Is there a another method of resetting the CPU other than holding the button during power up sequence.

Any hints suggestions would be greatly appreciated.

 

Voytek



#2 Chris Walker

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Posted 14 May 2015 - 07:41 AM

Hi Voytek,

Sounds like a cool application. Thanks for adopting Netduino; let's make sure you're taken care of here...

All Netduinos are built with really nice parts and high quality standards, and we do a suite of tests to make sure all of the board features and LEDs are working on every single board before they get bagged and shipped.

That said...the boards do have limits.

A few questions:
1. What power source are you using for the boards? Is it an AC-DC adapter? Regulated? What voltage/current rating?
2. How much power are you drawing from the Netduino 2 board? Do you know what your peak current it?

A buzzing DC-DC switch would usually indicate that the 3.3V regulator has been damaged. This isn't common, but the most likely reason for that would be a big surge of power draw, etc.

P.S. Are you switching the relay with a transistor/FET? How are you providing power to the relay? At what voltage?

Chris

#3 Chris Walker

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Posted 14 May 2015 - 07:47 AM

P.S.

Is there a another method of resetting the CPU other than holding the button during power up sequence.


You can erase the current app using MFDeploy (without starting the board in bootloader mode).

In addition to being the firmware programming mode, the bootloader also the failsafe mode; if you can't get into that mode then the board is most likely physically damaged.

Chris

P.P.S. You have PM...

#4 energywave

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Posted 14 May 2015 - 09:59 AM

We're starting to use netduino 2 for our devices too (as a universal digital I/O remoter) and I'll report what happened to us, in the spirit of global knowledge.
In our laboratory, during our custom developed shields test, one netduino 2 became fried. The technician that was making the tests inserted an external connector that carry 12V and 3.3V... inverted. So that 12V came in 3.3V pin of netduino. I don't know what happened at the moment but after that I've checked the board and, obviously, it's unresponsive, only white led turn on (not the blue one) and no communication in USB port. My PC don't see anything anymore, so MFDeploy and netduino update see nothing too (obviously). The ARM chip is becoming very hot when powered but no buzzing sounds. Simply... fried! (our fault, of course)

But now I have a wonderful paperweight  :D



#5 Chris Walker

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Posted 14 May 2015 - 05:35 PM

In our laboratory, during our custom developed shields test, one netduino 2 became fried. The technician that was making the tests inserted an external connector that carry 12V and 3.3V... inverted.

Thanks for sharing this. Oh man, yeah, driving 8.7V+ of electrical pressure backwards through the 3.3V power system (which directly powers the MCU and other electronics) is going to result in a very unhappy/broken DC-DC switch and ARM chip.

We did put a reverse voltage diode on the VIN pin (so that external power supplied to VIN is protected against most accidental reverse voltage connections). I wish there was an easy way to protect the whole 3.3V subsystem as well.

We may need to make a tiny Netduino-blue mourning blanket to place over that little fallen soldier. I don't see many fried Netduinos--but when I do it makes me want to shed a tear or two...

energywave, are there any other sage bits of advice you can offer to all of us from the field?

Chris

#6 Chris Walker

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Posted 14 May 2015 - 06:34 PM   Best Answer

Hi voytek,

Thanks for replying to my PM. We can diagnose the issue here in the forums thread (where others reading the thread can benefit) or via PM (which I totally understand, if your design is commercial and therefore of a sensitive IP nature).

If you don't reply back here, I'll assume that we take things from here via PM...

We're here to help,

Chris




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