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Chopperp

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Joined: 03/01/2018
Location: Australia
Posts: 1106

Posted: 02:02pm 14 Jun 2018

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Sent a couple of 28 pinners to Silicon Heaven this afternoon while playing around. The first one I think just has one U/S pin (that I know of) vital to the task at hand, the other makes the 5V - 3.3V regulator get very hot. I'm usually fairly neat & tidy with my breadboard layouts but this one wasn't. Just waiting for trouble to happen & it eventually did.

So thought it time to take stock of my working environment & have a bit of a clean up. Found a few things I had been looking for buried under other things which was good. Amazing how stuff can accumulate around you if you are not watching.

More to be done, then redo the breadboard layout. One spare chip left. More chips coming from RS tomorrow I hope.

ChopperP

crez

Senior Member

Joined: 24/10/2012
Location: Australia
Posts: 152

Posted: 10:32pm 14 Jun 2018

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I killed a couple of microcontrollers before finding that I had an earthed oscilloscope and an unearthed power supply. Individual input pins died after being zapped by the potential difference. I spent a while looking for a software bug before I found the problem.

bigmik

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Joined: 20/06/2011
Location: Australia
Posts: 2971

Posted: 11:31pm 14 Jun 2018

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Lads,

To date the only one I have killed was a 170 that I plugged upside down into my ZIF socket for programming it still programs and erases fine but no IO seems to work.. I haven�t tossed it away as it sits in my collection of blanks to remind me to be careful of chip orientation..

It all stems from me mounting the ZIF socket with the lever DOWN to allow access to the ICSP header (I use a MuP as my base for programming them)..

I have also recently bought a ZIF socket for the SSOP types that I plug into the DIP ZIF socket..

I have always been careful (read SCARED) with grounded Scopes and non-Gnd based test subjects..

I remember a frequency counter of my brothers that let out a lot of smoke by just that..

Mick

Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<<

Chopperp

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Joined: 03/01/2018
Location: Australia
Posts: 1106

Posted: 12:23am 15 Jun 2018

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Chips just arrived. Got to be more careful this time. Good point Mick on grounded Scope leads.

I had one end of a wire jumper with 5V on the other end that must have momentarily touch the wrong part of the breadboard which damaged one pin. The other I plugged a 3.3V lead into part of the breadboard before thinking too much.

ChopperP

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3308

Posted: 08:12am 15 Jun 2018

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Amazingly I have yet to kill a PIC32. On one instance I swapped the ground and 3.3V supplies yet, when I corrected the fault, it worked perfectly.

Tough little sod!

Geoff Graham - http://geoffg.net

Chopperp

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Joined: 03/01/2018
Location: Australia
Posts: 1106

Posted: 08:23am 15 Jun 2018

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@Geoff,

Speaking of tough chips. I had the one in your GPS Logger running at over 7.5V for good while. Wondering why the USB O/P wasn't working. I'd stuffed up the power supply somehow. Modified a 12V-5V car adaptor to 3.3V & used that mounted inside the case.

ChopperP

austfox
Newbie

Joined: 05/03/2016
Location: Australia
Posts: 18

Posted: 04:21pm 16 Jun 2018

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crez said I killed a couple of microcontrollers before finding that I had an earthed oscilloscope and an unearthed power supply.

Forgive my ignorance, but I thought an unearthed power supply was good when probing with an oscilloscope? I thought the danger was when both the oscilloscope and the power supply shared the same earth?

mikeb

Senior Member

Joined: 10/04/2016
Location: Australia
Posts: 177

Posted: 12:43am 17 Jun 2018

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An earth loop between the secondary of your power supply and the ground lead of your oscilloscope probe is the problem. If your power supply has a transformer then there should be no reason to earth the output of your power supply. Eliminate it with a 1:1 isolation transformer supplying the mains input of your oscilloscope.
DO NOT CUT OFF THE EARTH PIN OF THE POWER PLUG. I've seen this done. Muppets !!!!
Another method is to use an isolated differential probe. Note however that these can be relatively expensive.
Many switchmode power supplies have EMI components connecting the power input to the mains supply earth. This can be equally problematic.

Regards, Mike B.

There are 10 kinds of people in the world.
Those that understand binary and those that don't.

PeterB
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Joined: 05/02/2015
Location: Australia
Posts: 655

Posted: 03:08am 17 Jun 2018

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I agree with Geoff. They are almost indestructible however, regulated plug packs can float their output up to 120V wrt ground and that can be a bit destructive.
About 25 years ago a mate told me about a 16F84 getting a bit hot because it was plugged in back to front but was not damaged. That convinced me that they are good things.
Peter

Chopperp

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Joined: 03/01/2018
Location: Australia
Posts: 1106

Posted: 03:16am 17 Jun 2018

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Ah the good old 16F84. Looked at an old bit of code the other day I did many years ago. Over 1000 lines in Assembler. Much fun

ChopperP

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