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OscarT
09-10-2007, 03:47 PM
Dear All,

I have a propeller on a Proto board, that all of a sudden exhibits an amazing power dissipation. The chip got so hot that I actually burnt my finger when I wanted to feel its temperature.

I have tried to isolate the problem, and have disconnected all pins to external peripherals, but the dissipation stays. The chip takes >300mA, with only the external crystal connected.

Still, I am able to program the chip, and it runs like normal.

Could I have damaged one or more output stages in the chip in a way, that explains this behavior? Obviously I would like to prevent something similar from happening again, so I would like to understand what's going on. Any ideas?

Best regards
Oscar

QuattroRS4
09-10-2007, 05:59 PM
Is the 3.3v reg ok ... what is it reading?

The only time I had the prop get warm (not seriously hot) was running the multi cog routine - which was intended to demonstarte this .. is the draw still high·with a·simple prog ?

Can you run a prog. which uses the xtal multiplier e.g. VGA .. Just to check if the PLL is damaged..

300mA is not too encouraging though !

John Twomey

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'Necessity is the mother of invention'

Post Edited (QuattroRS4) : 9/10/2007 11:13:17 AM GMT

OscarT
09-10-2007, 06:09 PM
Well, I didn't check a reg (to be honest, I didn't know it even existed), but I did measure the 3.3V supply and it was ok (though the regulator gets quite hot as well, obviously)

Regards
Oscar

QuattroRS4
09-10-2007, 06:12 PM
Can you run a prog. which uses the xtal multiplier e.g. VGA routine.. Just to check if the PLL is damaged..

Regards,
John

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'Necessity is the mother of invention'

OscarT
09-10-2007, 06:24 PM
At this time I have no access to the HW, so that will take some time.
Would your theory be able to explain the dissipation though?
I'd say something would have to be damaged to get it this high?

QuattroRS4
09-10-2007, 06:59 PM
Yeah - there have been a few incidents where the PLL was the first point of failure - this is not a fault in design by any means - it is simply the first point of failure - Communication with the prop and programming is fine but the crystal multiplier does not work .. If section was to be beefed up - it would,most likely, only shift the point of failure .. this problem was reported - usually after reverse polarity connection or unprotected inductive loads ... I have to say that I have found the prop to be extremely robust and I have been bold with many of them !

Keep us updated - when you get a chance to check it out further..

Regards,
John

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'Necessity is the mother of invention'

OscarT
09-10-2007, 07:04 PM
I could run a test tonight. However, to isolate the problem, I have cut all traces from the prop to the outside. And it is on a proto board anyway, without VGA or other fancy things. I only had two MAX3232CPEs connected, plus a ADXL202 accelleration sensor.

Can you device a test that would give meaningful results to you?

Regards, Oscar

OscarT
09-10-2007, 07:06 PM
BTW, above I thought with reg you meant "register" (frequent abbreviation in my work environment), but I now see you meant regulator :). So yes, I did check the regulator and it is fine (but hot).

Franz Achatz
09-10-2007, 07:37 PM
@Oscar
do you use a Parallax Proto Board?

@John
I had the same problem with one of my Parallax protoboards.
The PLL is gone and i only had attached a VGA Monitor. I still can programm it
but the other I/Os are dead.
When i look at the schematic diagram, there are 3 x 10uf caps, but this caps are not at the board.
I can locate 3 x 100nf caps but no 10uf cap. The Regulators are running without 10uf caps :-(

best regards
Franz

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Please visit my online Propeller at:

http://achatz.xs4all.nl

Graham Stabler
09-10-2007, 07:46 PM
Franz,

Are the 1206(ish) sized ceramic caps not 10uF? They are located by the legs of the regulators, a single 1uF cap is located close to the prop itself.

Graham

OscarT
09-10-2007, 07:54 PM
Hi Franz,
Yes I use the proto board from Parallax.
Regards
Oscar

OscarT
09-10-2007, 07:55 PM
You are suggesting the power supply could overshoot?

Franz Achatz
09-10-2007, 08:08 PM
Graham Stabler said...
Franz,

Are the 1206(ish) sized ceramic caps not 10uF? They are located by the legs of the regulators, a single 1uF cap is located close to the prop itself.

Graham
Graham,

they look like 100nf ceramic caps.
But ok, when these are the 10uf caps then the 100nf caps are missing :-(

Franz

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Please visit my online Propeller at:

http://achatz.xs4all.nl

Graham Stabler
09-10-2007, 08:58 PM
You must have oscilloscope eyes, I have lots of 10uF caps that look like those made by Murata. There is only one other cap shown on the diagram, a 1uF

QuattroRS4
09-10-2007, 09:28 PM
Oscar ... no.. I meant regulator ...

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'Necessity is the mother of invention'

OscarT
09-10-2007, 09:49 PM
Right. Like I said: it is ok, though it gets rather hot because of the high current

QuattroRS4
09-10-2007, 10:02 PM
Oscar,
You said you had no VGA connections or fancy things ! to check PLL - I noticed though that you mentioned MAX3232 - why not run a full duplex serial test program to hyperterminal or similar ...

Regards,
John

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'Necessity is the mother of invention'

OscarT
09-10-2007, 10:15 PM
Ok I will try that tomorrow night and report back. I'll have to reconnect the I/O of course.
I have done no extended tests up to now, because I was afraid to kill the prop completely by heating it up too much.

Thanks and I will keep you posted,
Oscar

Lawson
09-10-2007, 11:59 PM
heh, I guess u haven't seen the thread in this forum on the prop's initial temperature testing? Paul had one up to 190C ( http://forums.parallax.com/showthread.php?p=662112 about halfway down) and it was just fine.

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Lunch cures all problems! have you had lunch?

deSilva
09-11-2007, 01:05 AM
I checked one of the SpinStamps six weeks ago which - I think - are not very popular for various reasons, one being the price tag...
Nevertheless they are a marvelous piece of engineering in the line of the other "stamps".

I severly disabled it some weeks ago, by experimenting to boldly with video. It now sucks >200mA and the tiny 5 and 3v3 regulators on the hybrid board get hot (obviously!) in addition to the Prop itself.

Funnily programs still run, except the pins I used for video don't work any longer. I didn't check more but I can the next days...

Paul Baker
09-12-2007, 01:29 AM
Hi Oscar, have you tested each I/O pin to make sure it can output both a high and a low. If the output stage of a pin is indeed broken, it would show up.

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Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)

OscarT
09-12-2007, 02:56 AM
Hi Paul, I have just run a test that toggles all pins in at .5Hz. The PLL looks fine, but P16 and P17 don't toggle like the others do.

So it seems these are the culprit. What could have caused such damage?

Thanks for your support
Oscar

OscarT
09-13-2007, 12:38 AM
Still no clue. I have not used any 5V devices. P16/P17 had the X and Y outputs connected from an ADXL202 accelleration sensor.

Any further ideas?

Paul Baker
09-13-2007, 11:36 PM
So you were operating the ADXL202 sensor on 3.3V?

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Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)

OscarT
09-14-2007, 03:36 AM
Exactly. (Its operating range is 3V - 5.25V)

Best regards
Oscar

Paul Baker
09-14-2007, 05:05 AM
Ok, you've definitely fried the Propeller. I can't speculate exactly how you did it, but it's likely from a (possibly brief) overvoltage event. Send me your full name, address and phone number in a Private Message and I will forward it to Tech Support so we can get you a replacement board. To prevent this from occuring again, use current limiting resistors.

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Paul Baker (mailto:pbaker@parallax.com)
Propeller Applications Engineer
[/url][url=http://www.parallax.com] (http://www.parallax.com)
Parallax, Inc. (http://www.parallax.com)