Bit rot in micro controllers?...

[Don Y]

On 12/12/2021 3:56 AM, Tom Gardner wrote:

On 12/12/21 00:26, Sylvia Else wrote:

It doesn\'t seem likely that the system is writing its flash every time it is
turned on, or off. Indeed, it doesn\'t sound like it has a reason to write its
flash at all, with flash being used merely because it was cheaper than
getting a custom ROM.

Such things are done in some instruments, to save the
current control settings between sessions.

I don\'t believe that device can \"program itself\" at the byte level.
I suspect it is just an EPROM alternative, as Sylvia suggested.

 

[server]

On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com>
wrote:

Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be turned
off. Unfortunately, instead of analog it\'s all buttons that are operated
via port pins of a micro controller. Pressing several of those
willy-nilly made the on/off button work, at least long enough to turn it
off. When the circuit board is cold the botton always works but not when
warm after running the stove overnight.

I don\'t want a kitchen stove that is uP controlled. That\'s a horrible
environment for cheap electronics. If you want to buy a non-digital
kitchen range, expect to pay a large multiple over the GE-type
electronic junk. Wolf, Viking, Bosch do good brass.

Our house came with a double oven. For some reason, one section has
electronic controls and one has the classic pneumatic-mechanical
thermostat. Guess which one still works.



--

I yam what I yam - Popeye

 

[Joerg]

On 12/12/21 3:06 AM, Sylvia Else wrote:

On 12-Dec-21 9:36 pm, Jasen Betts wrote:
On 2021-12-12, Sylvia Else <sylvia@email.invalid> wrote:
On 12-Dec-21 11:14 am, Jeff Liebermann wrote:
On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com
wrote:

The micro controller is a Winbond W78E52BF-24 running on a 12MHz
crystal. It is based on what they call electrically erasable MTP-ROM
with which I assume they mean EEPROM. Date code is 2001 and that is
also
when we had that pellet stove installed.

Can these things develop loss of flash memory (bit rot) this soon,
after
only two decades? Any remedy short or reprogramming or is it toast?

MTP-ROM is suppose to be good for up to 1 million write cycles:
https://anysilicon.com/semipedia/multi-time-programmable-mtp-memory-ip/

However, after only 1,000 erase/write cycles, the erase/write voltages
begins to change.  See Fig 15:
https://onlinelibrary.wiley.com/doi/full/10.4218/etrij.15.0114.1428
     \"After 1,000 erasing/writing cycles at a program
     voltage of ±6 V with a write time of 5 ms, the
     VT of a programmed cell is lowered from 2.92 V
     to 2.9 V and the VT of an erased cell is raised
     from -1.3 V to -0.5 V.\"
If the MTP-ROM device initially worked properly, and then slowly
started failing to recognize button pushes, that might be the problem.
Assuming you run the pellet burner for half the year and turn it
on/off once per day, that would be:
    180 days * 1 cycle/day * 20 years = 3,600 erase/write cycles
which might be sufficient to see the problem.

Note:  I don\'t have any experience with the Winbond W78E52BF-24.
Therefore, I don\'t know if it has this problem.


It doesn\'t seem likely that the system is writing its flash every time
it is turned on, or off. Indeed, it doesn\'t sound like it has a reason
to write its flash at all, with flash being used merely because it was
cheaper than getting a custom ROM.

Sylvia

It could be storing thermostat settings in eeprom,  but that seems
unrelated to the fault reported.


Even where the device stores some information, I would expect it to do
so only when the information changes.

It definitely doesn\'t commit any button presses to EEPROM as it forgets
every single one of them after a power outage.

if it doesn\'t like the heat the fault is probably some heat sensitive
part,
an electrolytic capacitor for example.


I\'m inclined to agree that that\'s more likely.

That sure is my hope though then I\'d expect the LED bar graph to become
iffy and it doesn\'t.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 12/12/21 9:18 AM, Don Y wrote:

On 12/12/2021 3:56 AM, Tom Gardner wrote:
On 12/12/21 00:26, Sylvia Else wrote:

It doesn\'t seem likely that the system is writing its flash every
time it is turned on, or off. Indeed, it doesn\'t sound like it has a
reason to write its flash at all, with flash being used merely
because it was cheaper than getting a custom ROM.

Such things are done in some instruments, to save the
current control settings between sessions.

I don\'t believe that device can \"program itself\" at the byte level.
I suspect it is just an EPROM alternative, as Sylvia suggested.

Yup, looks like it.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 12/12/21 4:15 AM, John Walliker wrote:

On Sunday, 12 December 2021 at 09:38:30 UTC, Michael Schwingen wrote:

Can these things develop loss of flash memory (bit rot) this soon, after
only two decades? Any remedy short or reprogramming or is it toast?
Quite probably yes - I remember a series of TFT monitors some years ago
where that happened to the on-board controller. Raising/lowering VCC may
help a bit (if it is not read-protected, you might try to read the memory at
different VCC levels and see if you can get correct data, and then
re-program).

Oh, that doesn\'t sound good. In that case I\'d rather redesign it to
fully analog. Seems like less work and then it\'ll never fail again.

My HP vector network analyzer developed \"bit rot\" when it was around 25 years
old. One bit in one of the many uv-erasable eproms changed state. I found
it by varying the supply voltage and looking for the first bit to change. I
programmed a new eprom with the edited data and it has been working fine
ever since.

My Wavetek 23 funtion generator lost EPROM content as well but not after
20 years.

I still have some HP gear, HP3577A and HP4191A. Time to let those go I
guess, now that I retired.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 12/12/21 1:46 AM, Martin Brown wrote:

On 11/12/2021 19:51, Joerg wrote:
Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be
turned off. Unfortunately, instead of analog it\'s all buttons that are
operated via port pins of a micro controller. Pressing several of
those willy-nilly made the on/off button work, at least long enough to
turn it off. When the circuit board is cold the botton always works
but not when warm after running the stove overnight.

The micro controller is a Winbond W78E52BF-24 running on a 12MHz
crystal. It is based on what they call electrically erasable MTP-ROM
with which I assume they mean EEPROM. Date code is 2001 and that is
also when we had that pellet stove installed.

Can these things develop loss of flash memory (bit rot) this soon,
after only two decades? Any remedy short or reprogramming or is it toast?

My instinct would be there is a failing electrolytic capacitor somewhere
that is allowing the CPU to see glitches that blind it to the on/off
button. ...

I hope so as that\'s wasy to fix

Have to wait for warmer days to look though because the missus doesn\'t
like it cold downstairs.

... Some polling algorithms are a bit stupid so another button stuck
down might also have the same effect. You might have hoped that there
would be a failsafe emergency stop button on something that makes fire!

I never trust CPUs for safety interlocks! There is good reason.

Luckily this stove has hardware safety interlocks for vacuum and proof
of fire which the CPU cannot override.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 12/12/21 3:05 AM, Tom Gardner wrote:

On 11/12/21 19:51, Joerg wrote:
Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be
turned off. Unfortunately, instead of analog it\'s all buttons that are
operated via port pins of a micro controller. Pressing several of
those willy-nilly made the on/off button work, at least long enough to
turn it off. When the circuit board is cold the botton always works
but not when warm after running the stove overnight.

The micro controller is a Winbond W78E52BF-24 running on a 12MHz
crystal. It is based on what they call electrically erasable MTP-ROM
with which I assume they mean EEPROM. Date code is 2001 and that is
also when we had that pellet stove installed.

Can these things develop loss of flash memory (bit rot) this soon,
after only two decades? Any remedy short or reprogramming or is it toast?

I\'d look for other solutions before considering bit rot.

Obviously the connectors and switches need to be examined
and possibly IPA or DeOxit applied.

Electrolytic capacitors are the next failure point. Sometimes
they are obviously \"distressed\", sometimes subtly faulty.

Check the PSU rails for voltage and transients, of course.

I had an SMPS where something would:
  - take a minute to start
  - turn off then on, immediately start
  - turn off for an hour then on, 50s to start
  - turn off for 12 hours then on, 60s to start
Debugging that was one /good/ use case for a DSO.

Turned out to be a dicky electrolytic fed by a high
value resistor; it was almost as if the capacitor
was so \"dry\" had to reform the barrier before it
would work.

This has a linear power supply but yes, when the weather gets warmer
I\'ll take it apart and check.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 12/12/21 8:54 AM, Martin Brown wrote:

On 12/12/2021 16:02, Hul Tytus wrote:
In the 60\'s & 70\'s 20 years was mentioned as a life span for diffused
silicon. Somebody\'s diffusion rate.

Diffusion rate is *very* temperature dependent. I can\'t see a small
microcontroller at a modest clock rate running particularly hot.

However, this one live in a pellet stove. Though it doesn\'t get sizzling
hot, you can still touch it.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 12/12/21 9:19 AM, Don Y wrote:

On 12/12/2021 9:12 AM, Wond wrote:
On Sat, 11 Dec 2021 11:51:11 -0800, Joerg wrote:

Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be turned
off. Unfortunately, instead of analog it\'s all buttons that are operated
via port pins of a micro controller. Pressing several of those
willy-nilly made the on/off button work, at least long enough to turn it
off. When the circuit board is cold the botton always works but not when
warm after running the stove overnight.

The micro controller is a Winbond W78E52BF-24 running on a 12MHz
crystal. It is based on what they call electrically erasable MTP-ROM
with which I assume they mean EEPROM. Date code is 2001 and that is also
when we had that pellet stove installed.

Can these things develop loss of flash memory (bit rot) this soon, after
only two decades? Any remedy short or reprogramming or is it toast?

   OTOH adding wood to the stove is a pleasant chore, even in the middle
of the night.

Would you make the same claim wrt \"pellets\"?  :

A friend tried that for kicks, throwing small chunks of oak and pine
into the burn pot. The results was that he had to replace the bearings
of the exhaust blower which was a nasty job.

In hindsight I should have installed a wod stove downstairs, just like
we did upstairs. Less complicated, no misson-critical electronics and,
therefore, more reliable.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 12/12/21 9:17 AM, Don Y wrote:

On 12/11/2021 12:51 PM, Joerg wrote:
Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be
turned off. Unfortunately, instead of analog it\'s all buttons that are
operated via port pins of a micro controller. Pressing several of
those willy-nilly made the on/off button work, at least long enough to
turn it off. When the circuit board is cold the botton always works
but not when warm after running the stove overnight.

The micro controller is a Winbond W78E52BF-24 running on a 12MHz
crystal. It is based on what they call electrically erasable MTP-ROM
with which I assume they mean EEPROM. Date code is 2001 and that is
also when we had that pellet stove installed.

Can these things develop loss of flash memory (bit rot) this soon,
after only two decades? Any remedy short or reprogramming or is it toast?

More likely something analog -- power supply sag/spikes, bad caps, a
floating configuration pin, etc.

Can you verify that the processor is actually *running* when it
\"misbehaves\"?
(i.e., activity on ANY pins?)

It is definitely running because it continues to issue pulses for the
auger motor, feeding the pellets into the burn pot.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

On 12/12/21 2:50 PM, jlarkin@highlandsniptechnology.com wrote:

On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com
wrote:

Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be turned
off. Unfortunately, instead of analog it\'s all buttons that are operated
via port pins of a micro controller. Pressing several of those
willy-nilly made the on/off button work, at least long enough to turn it
off. When the circuit board is cold the botton always works but not when
warm after running the stove overnight.

I don\'t want a kitchen stove that is uP controlled. That\'s a horrible
environment for cheap electronics. If you want to buy a non-digital
kitchen range, expect to pay a large multiple over the GE-type
electronic junk. Wolf, Viking, Bosch do good brass.

Our house came with a double oven. For some reason, one section has
electronic controls and one has the classic pneumatic-mechanical
thermostat. Guess which one still works.

A friend had replaced their double-oven electronics three times. When
board #3 also croaked he got rid of the whole thing and obtained a
steampunk oven. Which, of course, still works fine.

My cooking is real steampunk. It\'ll happen again in 30mins despite the
rain. I\'ll steal some almond wood coals from our wood stove in the
living room and dump them into the Weber kettle. It still has the
snuffed out coals from yesterdays bread and chicken and sauce cooking
and the glowing coals will reignite yesterday\'s coals within minutes.
Then a tasty tritip will be cooked, along with some more bread plus
cowboy beans in a cast iron skillet.

The old Weber is like my old Citroen was. Zero electronics, not even a
lone diode. So it\'ll survive me some day.

Last week I repaired our 25 year old fridge/freezer. Aside from
environmental reasons the main motivator was that I absolutely
positively do not want a high-falutin digitally controlled new unit,
which will inevitably fail and then possibly become irrepairable because
they don\'t make the board anymore. The old Kenmore was easy, I replaced
the mechanical defrost timer and the also mechanical thermostat .. done.
In the wake of that I also gave it LED lighting so technically it now
contains electronics but those aren\'t mission-critical.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[server]

On Sun, 12 Dec 2021 15:24:23 -0800, Joerg <news@analogconsultants.com>
wrote:

On 12/12/21 2:50 PM, jlarkin@highlandsniptechnology.com wrote:
On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com
wrote:

Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be turned
off. Unfortunately, instead of analog it\'s all buttons that are operated
via port pins of a micro controller. Pressing several of those
willy-nilly made the on/off button work, at least long enough to turn it
off. When the circuit board is cold the botton always works but not when
warm after running the stove overnight.

I don\'t want a kitchen stove that is uP controlled. That\'s a horrible
environment for cheap electronics. If you want to buy a non-digital
kitchen range, expect to pay a large multiple over the GE-type
electronic junk. Wolf, Viking, Bosch do good brass.

Our house came with a double oven. For some reason, one section has
electronic controls and one has the classic pneumatic-mechanical
thermostat. Guess which one still works.


A friend had replaced their double-oven electronics three times. When
board #3 also croaked he got rid of the whole thing and obtained a
steampunk oven. Which, of course, still works fine.

My cooking is real steampunk. It\'ll happen again in 30mins despite the
rain. I\'ll steal some almond wood coals from our wood stove in the
living room and dump them into the Weber kettle. It still has the
snuffed out coals from yesterdays bread and chicken and sauce cooking
and the glowing coals will reignite yesterday\'s coals within minutes.
Then a tasty tritip will be cooked, along with some more bread plus
cowboy beans in a cast iron skillet.

The old Weber is like my old Citroen was. Zero electronics, not even a
lone diode. So it\'ll survive me some day.

Last week I repaired our 25 year old fridge/freezer. Aside from
environmental reasons the main motivator was that I absolutely
positively do not want a high-falutin digitally controlled new unit,
which will inevitably fail and then possibly become irrepairable because
they don\'t make the board anymore. The old Kenmore was easy, I replaced
the mechanical defrost timer and the also mechanical thermostat .. done.
In the wake of that I also gave it LED lighting so technically it now
contains electronics but those aren\'t mission-critical.

Piezo and electronic igniters are OK, as long as you can still use a
match. I have a bunch of the Zeitgeist matches in stock.





--

I yam what I yam - Popeye

 

[Tom Gardner]

On 12/12/21 23:24, Joerg wrote:

Last week I repaired our 25 year old fridge/freezer. Aside from environmental
reasons the main motivator was that I absolutely positively do not want a
high-falutin digitally controlled new unit, which will inevitably fail and then
possibly become irrepairable because they don\'t make the board anymore. The old
Kenmore was easy, I replaced the mechanical defrost timer and the also
mechanical thermostat .. done. In the wake of that I also gave it LED lighting
so technically it now contains electronics but those aren\'t mission-critical.

I replaced the thermostat on my 33yo fridge a couple of months ago.

The only thing I\'ve had to do to my 32yo dishwasher is put
Sugru around bits of the wire plate holders where the plastic
had cracked and the wire had begun to corrode.

Due to the rotating mechanical sequencer, I can understand
how that one is operating - unlike my parents\' one which has
LEDs indicating \"on\", \"active\" and \"end\". I\'ve never been
able to understand what the \"on\" LED signifies (and nobody
has been able to tell me!), nor how long before it finishes
the cycle.

 

[whit3rd]

On Sunday, December 12, 2021 at 8:02:25 AM UTC-8, Hul Tytus wrote:

In the 60\'s & 70\'s 20 years was mentioned as a life span for diffused
silicon. Somebody\'s diffusion rate.

In those days, diffusion from the surface was the doping mechanism; it
is usually ion implant nowadays (the profiles are very different). Also,
I\'d expect digital electronics (with a noise margin) might be at variance
with that result. 60\'s transistors often failed by low C-B breakdown voltage,
and didn\'t have much margin there to begin with.

Can these things develop loss of flash memory (bit rot) this soon, after
only two decades? Any remedy short or reprogramming or is it toast?

There\'s a \'remedy\' in the power-on self test (POST) for many systems, which
is a checksum. It wouldn\'t be a fix, just an \'uh-oh squad\' fingerpointing
exercise. Reprogramming or replacement is the best bet. My experience with older machines is,
EPROMs can often last a long time (1986 MacPlus still boots, 1983 auto computer still runs it).

 

[whit3rd]

On Sunday, December 12, 2021 at 2:50:47 PM UTC-8, jla...@highlandsniptechnology.com wrote:

I don\'t want a kitchen stove that is uP controlled. That\'s a horrible
environment for cheap electronics. If you want to buy a non-digital
kitchen range, expect to pay a large multiple over the GE-type
electronic junk. Wolf, Viking, Bosch do good brass.

Oh, no geared clockworks on stoves have ever impressed me as reliable.
I only once had a microwave\'s solid state clock/timer go bad (TTL with no
bypass capacitors; to fix, I hand-soldered some in and thought evil things
about 1980\'s Goldstar engineering).

 

[Phil Hobbs]

jlarkin@highlandsniptechnology.com wrote:

On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com
wrote:

Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be turned
off. Unfortunately, instead of analog it\'s all buttons that are operated
via port pins of a micro controller. Pressing several of those
willy-nilly made the on/off button work, at least long enough to turn it
off. When the circuit board is cold the botton always works but not when
warm after running the stove overnight.

I don\'t want a kitchen stove that is uP controlled. That\'s a horrible
environment for cheap electronics. If you want to buy a non-digital
kitchen range, expect to pay a large multiple over the GE-type
electronic junk. Wolf, Viking, Bosch do good brass.

Our house came with a double oven. For some reason, one section has
electronic controls and one has the classic pneumatic-mechanical
thermostat. Guess which one still works.

We have a separate gas cooktop, which has electronic ignition and works
perfectly after 11 years. (We re-did the kitchen 11 hears ago.)

Ditto for a wall-mounted double oven. The oven runs a separate fan to
keep the electronics cool, and has also worked fine that long.

Dishwashers are the real horror for electronics--we\'ve gone through
three of them in that time.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Rick C]

On Sunday, December 12, 2021 at 10:01:26 PM UTC-5, Phil Hobbs wrote:

jla...@highlandsniptechnology.com wrote:
On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <ne...@analogconsultants.com
wrote:

Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be turned
off. Unfortunately, instead of analog it\'s all buttons that are operated
via port pins of a micro controller. Pressing several of those
willy-nilly made the on/off button work, at least long enough to turn it
off. When the circuit board is cold the botton always works but not when
warm after running the stove overnight.

I don\'t want a kitchen stove that is uP controlled. That\'s a horrible
environment for cheap electronics. If you want to buy a non-digital
kitchen range, expect to pay a large multiple over the GE-type
electronic junk. Wolf, Viking, Bosch do good brass.

Our house came with a double oven. For some reason, one section has
electronic controls and one has the classic pneumatic-mechanical
thermostat. Guess which one still works.



We have a separate gas cooktop, which has electronic ignition and works
perfectly after 11 years. (We re-did the kitchen 11 hears ago.)

A home near here was blown up from a gas leak. This was a concrete building, floors, walls and roof turned into a bunch of rubble. All the other houses around it were also concrete, so people in them were not injured and those buildings were not seriously damaged. A stick built house could literally be blown apart by such a gas leak. It all depends on how much leaks before a source of ignition is found.

Ditto for a wall-mounted double oven. The oven runs a separate fan to
keep the electronics cool, and has also worked fine that long.

Dishwashers are the real horror for electronics--we\'ve gone through
three of them in that time.

I\'ve had the same dishwasher for over 30 years without a failure other than a frozen valve when the heat went out. I\'ve read about dishwashers that caught fire because of faulty crimp joints in the wiring. I think that was here actually.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Sylvia Else]

On 13-Dec-21 2:01 pm, Phil Hobbs wrote:

jlarkin@highlandsniptechnology.com wrote:
On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <news@analogconsultants.com
wrote:

Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be turned
off. Unfortunately, instead of analog it\'s all buttons that are operated
via port pins of a micro controller. Pressing several of those
willy-nilly made the on/off button work, at least long enough to turn it
off. When the circuit board is cold the botton always works but not when
warm after running the stove overnight.

I don\'t want a kitchen stove that is uP controlled. That\'s a horrible
environment for cheap electronics. If you want to buy a non-digital
kitchen range, expect to pay a large multiple over the GE-type
electronic junk. Wolf, Viking, Bosch do good brass.

Our house came with a double oven. For some reason, one section has
electronic controls and one has the classic pneumatic-mechanical
thermostat. Guess which one still works.



We have a separate gas cooktop, which has electronic ignition and works
perfectly after 11 years.  (We re-did the kitchen 11 hears ago.)

Ditto for a wall-mounted double oven.  The oven runs a separate fan to
keep the electronics cool, and has also worked fine that long.

Dishwashers are the real horror for electronics--we\'ve gone through
three of them in that time.

Cheers

Phil Hobbs

I had a gas oven that used electronics as a thermostat, with the gas
turned on and off, rather than up and down. If it failed to reignite
after about three tries, it just gave up, without so much as a warning beep.

So one could come back after an hour and not only discover that the
contents weren\'t cooked, one didn\'t even know how long it had been on for.

Also, why would one want a gas oven that requires electric power to
operate so that it cannot be used during a power outage?

Sylvia.

 

[Anthony William Sloman]

On Monday, December 13, 2021 at 2:01:26 PM UTC+11, Phil Hobbs wrote:

jla...@highlandsniptechnology.com wrote:
On Sat, 11 Dec 2021 11:51:11 -0800, Joerg <ne...@analogconsultants.com
wrote:

Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be turned
off. Unfortunately, instead of analog it\'s all buttons that are operated
via port pins of a micro controller. Pressing several of those
willy-nilly made the on/off button work, at least long enough to turn it
off. When the circuit board is cold the botton always works but not when
warm after running the stove overnight.

I don\'t want a kitchen stove that is uP controlled. That\'s a horrible
environment for cheap electronics. If you want to buy a non-digital
kitchen range, expect to pay a large multiple over the GE-type
electronic junk. Wolf, Viking, Bosch do good brass.

Our house came with a double oven. For some reason, one section has
electronic controls and one has the classic pneumatic-mechanical
thermostat. Guess which one still works.



We have a separate gas cooktop, which has electronic ignition and works
perfectly after 11 years. (We re-did the kitchen 11 hears ago.)

Ditto for a wall-mounted double oven. The oven runs a separate fan to
keep the electronics cool, and has also worked fine that long.

Dishwashers are the real horror for electronics--we\'ve gone through
three of them in that time.

Our dishwasher is fine as far as the electronics go - we bought it with the flat when we bought the flat, about fifteen years ago - and it is still working fine.

It\'s a Bosch SG14004/AU/07 and the plastic front panel that locates the the knobs and press buttons has lost enough plasticiser that it doesn\'t lock onto the metal door as originally intended. A certain amount of masking tape locks it place securely enough to keep everything engaged, so it\'s still working fine. I talked to Bosch (or at least their agent in Sydney about a replacement plastic moulding, but it is way too old for that to be an option..

--
Bill Sloman, Sydney

 

[Martin Brown]

On 12/12/2021 23:06, Joerg wrote:

On 12/12/21 1:46 AM, Martin Brown wrote:
On 11/12/2021 19:51, Joerg wrote:
Just repaired our fridge when, according to Murphy\'s law, the next
appliance became shaky. Our pellet stove has twice refused to be
turned off. Unfortunately, instead of analog it\'s all buttons that
are operated via port pins of a micro controller. Pressing several of
those willy-nilly made the on/off button work, at least long enough
to turn it off. When the circuit board is cold the botton always
works but not when warm after running the stove overnight.

The micro controller is a Winbond W78E52BF-24 running on a 12MHz
crystal. It is based on what they call electrically erasable MTP-ROM
with which I assume they mean EEPROM. Date code is 2001 and that is
also when we had that pellet stove installed.

Can these things develop loss of flash memory (bit rot) this soon,
after only two decades? Any remedy short or reprogramming or is it
toast?

My instinct would be there is a failing electrolytic capacitor
somewhere that is allowing the CPU to see glitches that blind it to
the on/off button. ...


I hope so as that\'s wasy to fix

Have to wait for warmer days to look though because the missus doesn\'t
like it cold downstairs.


  ... Some polling algorithms are a bit stupid so another button stuck
down might also have the same effect. You might have hoped that there
would be a failsafe emergency stop button on something that makes fire!

I never trust CPUs for safety interlocks! There is good reason.


Luckily this stove has hardware safety interlocks for vacuum and proof
of fire which the CPU cannot override.

Glad to hear it! I once worked at a place where the emergency stop
button was \"redesigned\" by a mechanical engineer and an unauthorised
electronics hack to fit the parts available at the time. It was to
shutdown a 2kW 9000K argon plasma torch if something went wrong.

The result was that whereas the big red stop button was originally
normally closed press to break (fails safe) it was swapped to normally
open press to close. Big problem was the thing had not been plugged in
to the wiring harness on the one that I was working on.

After that incident I paid a great deal of attention to safety
interlocks particularly if bits of me were in the beam line or near to
parts that would be at HT under normal operating conditions.

--
Regards,
Martin Brown