Relay contact ratings.

[Les Cargill]

dagmargoodboat@yahoo.com wrote:

On Dec 13, 6:23 am, keithr<ke...@nowhere.com.au> wrote:
snip

I prefer competition, the same process that makes everything we do and
buy get constantly better, and cheaper. E.g., computers.

Except for Apple...

And, that's
voluntary. The gov't universally does the opposite--they've got the
wrong incentives and no controls. But, whatever we do, reality
matters, not spin. That's why I chimed in.

--
Cheers,
James Arthur

--
Les Cargill

 

[kreed]

On Dec 14, 6:48 am, dagmargoodb...@yahoo.com wrote:

On Dec 13, 6:23 am, keithr <ke...@nowhere.com.au> wrote:



On 13/12/2011 9:33 AM, dagmargoodb...@yahoo.com wrote:

On Dec 8, 7:36 pm, Trevor Wilson<tre...@SPAMBLOCKrageaudio.com.au
wrote:

The US lacks a cohesive socialised medical system. As a
consequence, some 50-odd million Americans have extremely poor access to
good medical services. Additionally, some 60% of personal bankruptcies
in the US are due to medical bills.

OT

FWIW, those are oft-cited misconceptions.  Media drones repeat them
without understanding their basis.

The number is ~32 million, and these are people who do not have
medical insurance.  That is not the same as "extremely poor access" to
care.  Numerically, some 10-12 million of that figure are illegal
aliens, and most of the remainder are young people who voluntarily
choose not to buy it.  Access is generally good to excellent.

60-odd % is the proportion of people who go bankrupt who, among their
other bills, also owe money to their doctors.  The number whose
medical costs *caused* their bankruptcy is a small fraction.

Last, everyone can get care.  There are countless medical programs for
the poor.

I personally have an acquaintance getting the full royal treatment,
for cancer, for nothing.  She's better than most at working the
system, but it's there for people who need it, and seek it.

I have to say that during the time that I lived in the US, the medical
care that I received was excellent and my co-payments were less than I
pay back in Australia *BUT* I had an employer paying for my medical and
pharmacy insurance. I was never quite comfortable though that, should I
have needed expensive treatment, my HMO would have the final word on
that treatment.

At to the poor, my wife used to volunteer at the emergency room at the
local hospital she had quite a few horror stories. I did my bit to fund
the programs for the poor, 5 1/2 years of maximum social security
payments that I am not going to see a penny of.

I have a friend there who is retired (not by choice) who has to spend a
fair proportion of his income on medical insurance, and, even then, when
his wife had a bad car accident, he still had some really big bills to pay.

Our biggest healthcare consumer is the gov't, and the more they buy,
the higher they drive the cost--it's always easier to spend when
you're spending someone else's money.  Everything they do costs more.

I prefer competition, the same process that makes everything we do and
buy get constantly better, and cheaper.  E.g., computers.  And, that's
voluntary.  The gov't universally does the opposite--they've got the
wrong incentives and no controls.  But, whatever we do, reality
matters, not spin.  That's why I chimed in.

Competition has always been very successful in giving all of us more -
for less.
Coupled with the freedom to voluntarily buy or not buy what we want
great things have been achieved


The opposite has never worked in the public interest.

--
Cheers,
James Arthur

 

[David Eather]

On 13/12/2011 8:41 PM, mrstarbom@gmail.com wrote:

On Tuesday, 13 December 2011 17:58:22 UTC+10, David Eather wrote:
On 13/12/2011 1:22 PM, mrst...@gmail.com wrote:

snip

In developing countries the "really poor" are on their way to middle
class and a consumer society. A trivial example - Pakistan and India
both export rice even though there are starving people in their own
countries. The owners of the resource sell it overseas because they can
get more profit for it. The more the starving can pay for that rice the
higher the price will be in the developed world (simple supply and
demand).

Why would they be starving if they're buying rice? I think it is quite complicated. Some developing countries only export when they have a surplus and import when there is a risk of shortage.
I'd like to see some evidence showing rice is exported when there is a famine. Are you saying they export to decrease the deficit and rely on aid in a famine? If so it would be evidence of a problem in government not of a shortage of resources. There are supposed to be export taxes or incentives depending on the rice volume available in the domestic market. Japan is obliged to import (trade agreement) but doesn't sell domestically - stores it and uses it for aid.

You're either an idiot or simply trying to be obtuse.

"The more the starving can pay for that rice the
higher the price will be in the developed world (simple supply and
demand)."

is pretty simple.

But we should definitely grow our own rice, encourage our rice growers, export to the world and not become reliant on agricultural imports.

What are "active" resources?

Simple concept - think usable. Some stuff is usable only once.

Hmmm, I think you made it up. : ) But non-recyclable has been known to become recyclable. Are you sure you don't mean 'nonrenewable'?

Other
stuff is easily recyclable to be used many times.

What makes you so sure there is no way to stop that growth?

No one has yet. I said there might be a solution but that it is probably
unacceptable.

After all, the world is finite. It is very likely that lifespans will
begin to decrease due to lifestyle and 'modern' toxins,

Rubbish. Life span may go down a few years from obesity etc but life
expectancy has (in Oz for example) increased by more than 10 years since
1975. It is going to take a whole lot of fat to reverse that - and ill
health also consumes more resources.

You may see a marked change over the next couple of generations due to a sedentary lifestyle etc. The people who are reaching those ages had a very different life. 'Modern' toxins - I know smoking has been around a while but there is evidence that it alters DNA. What my grandfather and his grandfather did will have some effect on me. What cumulative effect will multiple vaccines, IVF, late child bearing and drugs have on populations long term?

and at any time thousands could be wiped out very rapidly by some new
plague.

20 million have been wiped out by aids - did you notice the population
is still growing - its a drop in the bucket.

I realize a thousand isn't significant unless you happen to be one of that thousand. However, in former times they did not constantly fly all over the world and the world was not so densely populated. Yet the plague of 1500-1520 decreased England's population by 60%. It took until 1750 to reach the population of the Middle Ages. I don't think you can exclude the possibility of a pandemic which would make aids look like nothin.

A pandemic cannot be called a solution. I'm just trying to point out that the future is unpredictable. So keep your hair on!

I refer you to Jacob Bernoulli's comment on the law of averages.

Apparently, the Chinese are working on another 'solution'. Having tried building without reinforcing, they are now stretching the steel used in reinforcing.
BTW - how many children do you have?

MYOB

Oh, I see - nearly as many as Bach. : )

Family should be off limits - especially in a group about electronics.
So what if I had a lot of kids - I was not born with the information and
reasoning I now have. You are a prick for wanting to persecute someone
for learning something.

FYI, in my mid to late thirties I learnt that my genetics should never
be passed on. I am disabled by them.

They're more likely to suffer as a result of doing something stupid than
because the world is finite.

Currently true. May not always be true.

You believe your children will grow wiser or the world will become infinite?

This is both stupid and illogical.

Your comment was

"They're more likely to suffer as a result of doing something stupid
than because the world is finite."

My response to that was simple and clear

"Currently true. May not always be true."

When economic pressure builds because of limited supply and increasing
economic competition they may indeed suffer more because the world is
finite than for doing something stupid.

Your description sounds quite a bit like rural Australia, for some people..

Unfortunately, that is a difficult problem.



Excuse me, but I need to make a couple of changes to the following:


We need not address the obvious, that infinite growth
is impossible in a world which will end. There are many more important and immediate matters.

Are you bored yet?

No, but the low level of your logic and reasoning makes this thread
unworthy of anyone's time. SO I am finished with answering you.


--
We have failed to address the fundamental truth that endless growth is
impossible in a finite world.

 

[David Eather]

On 14/12/2011 8:33 AM, mrstarbom@gmail.com wrote:

http://www.google.com.au/publicdata/explore?ds=d5bncppjof8f9_&met_y=sp_pop_grow&idim=countryAK&dl=en&hl=en&q=pakistan+population+growth

You have singularly missed the point. A *world* *wide* *growing*
*population* combined with increasing economic power in previously
undeveloped countries will increase demand for resources beyond what can
possibly be supplied the only possible result is a lower standard of
living for the previously developed world.

This is simple supply and demand.


--
We have failed to address the fundamental truth that endless growth is
impossible in a finite world.

 

[Phil Hobbs]

On 12/13/2011 6:58 PM, David Eather wrote:

On 14/12/2011 8:33 AM, mrstarbom@gmail.com wrote:
http://www.google.com.au/publicdata/explore?ds=d5bncppjof8f9_&met_y=sp_pop_grow&idim=countryAK&dl=en&hl=en&q=pakistan+population+growth


You have singularly missed the point. A *world* *wide* *growing*
*population* combined with increasing economic power in previously
undeveloped countries will increase demand for resources beyond what can
possibly be supplied the only possible result is a lower standard of
living for the previously developed world.

This is simple supply and demand.

Nonsense. People redefine what they expect from their standard of
living as we go along. The amount of energy required per unit of
inflation-adjusted GDP has gone down a lot since the 1970s.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

 

I get the feeling you choose to be simple when it suits you and abusive when it doesn't. Calling a person a prick does not actually strengthen your case. Nor does suggesting I'm obtuse or an idiot. It just reflects badly on you and the wonderful land of Oz.

Supply and demand isn't simple, not when governments and organizations legislate against it.

Rubbish. Life span may go down a few years from obesity etc but life
expectancy has (in Oz for example) increased by more than 10 years since
1975.

FYI Life expectancy does not predict how long people alive today will live.
http://www.aihw.gov.au/how-is-life-expectancy-calculated/

There is no need to get snakey. Why mention your children if you didn't want to discuss them? Many foolish notions are predicated on a supposed concern for future generations.

No, but the low level of your logic and reasoning makes this thread
unworthy of anyone's time. SO I am finished with answering you.

Ah, so you're going to take your bat and ball and go home? Pity, but by all means go and do something worthwhile. : )

 

[Ralph Barone]

At 10 cents a post, we could have taken up a collection and bought a new
OEM timer for the OP

 

David Eather
Post reply
09:54 (1 hour ago)
On 13/12/2011 8:41 PM, mrst...@gmail.com wrote:

On Tuesday, 13 December 2011 17:58:22 UTC+10, David Eather wrote:
On 13/12/2011 1:22 PM, mrs...@gmail.com wrote:

I refer you to Jacob Bernoulli's comment on the law of averages.

However, God is not subject to Jacob Bernoulli's comment on the law of averages.

For fundamental truth I refer you to John 14:6 and 1 John 4:16

 

[kreed]

On Dec 14, 9:52 am, Les Cargill <lcargil...@comcast.com> wrote:

dagmargoodb...@yahoo.com wrote:
On Dec 13, 6:23 am, keithr<ke...@nowhere.com.au>  wrote:
snip

I prefer competition, the same process that makes everything we do and
buy get constantly better, and cheaper.  E.g., computers.

Except for Apple...

There are alternatives, you can voluntarily use Windows, Android,
Linux etc, even a pen and paper,
or you have the free choice to simply use nothing

And, that's
voluntary.  The gov't universally does the opposite--they've got the
wrong incentives and no controls.  But, whatever we do, reality
matters, not spin.  That's why I chimed in.

--
Cheers,
James Arthur

--
Les Cargill

 

[linnix]

On Dec 13, 6:11 pm, Ralph Barone <address...@invalid.invalid> wrote:

At 10 cents a post, we could have taken up a collection and bought a new
OEM timer for the OP

That's not the point. We are designing a better solution. It might
not even be a timer.

 

[Ralph Barone]

linnix <me@linnix.info-for.us> wrote:

On Dec 13, 6:11 pm, Ralph Barone <address...@invalid.invalid> wrote:
At 10 cents a post, we could have taken up a collection and bought a new
OEM timer for the OP

That's not the point. We are designing a better solution. It might
not even be a timer.

While I love the design process and we're all having lots of fun here; for
a one-off solution, it's pretty hard to beat buying an OEM spare part and
just stuffing it back in.

 

[krw@att.bizzzzzzzzzzzz]

On Tue, 13 Dec 2011 17:52:48 -0600, Les Cargill <lcargill99@comcast.com>
wrote:

dagmargoodboat@yahoo.com wrote:
On Dec 13, 6:23 am, keithr<ke...@nowhere.com.au> wrote:
snip

I prefer competition, the same process that makes everything we do and
buy get constantly better, and cheaper. E.g., computers.

Except for Apple...

Eveb Apple gets better, and cheaper. Your point?

 

[linnix]

On Dec 13, 6:30 pm, Sylvia Else <syl...@not.here.invalid> wrote:

On 14/12/2011 3:09 AM, linnix wrote:









On Dec 13, 2:43 am, Sylvia Else<syl...@not.here.invalid>  wrote:
On 13/12/2011 4:01 PM, kreed wrote:

On Dec 13, 10:40 am, Sylvia Else<syl...@not.here.invalid>    wrote:
On 13/12/2011 9:23 AM, NT wrote:

On Dec 12, 5:20 am, linnix<m...@linnix.info-for.us>      wrote:
On Dec 11, 5:48 pm, John Fields<jfie...@austininstruments.com>      wrote:

On Sun, 11 Dec 2011 16:20:48 -0800 (PST), linnix

m...@linnix.info-for.us>      wrote:
On Dec 11, 3:09 pm, John Fields<jfie...@austininstruments.com>      wrote:
On Sat, 10 Dec 2011 17:19:52 -0800 (PST), linnix

m...@linnix.info-for.us>      wrote:
On Dec 10, 5:06 pm, John Fields<jfie...@austininstruments.com>      wrote:
You've said the defrost only happens every six hours, but for how long
is the heater energized?

knowing that will allow us to determine the duty cycle of the timer
and cause it to mimic the motor timer.

--
JF

It should be long enough to melt the ice and let the water drain off.
It can easily be programmable in a micro, at least during
development.  Perhaps a 5 to 10 minutes range.

---
Thanks, but I'd prefer some real numbers from Sylvia so that I can
work up a hardware solution for her.

You don't like my numbers?

---
I don't care for conjecture, which is all you're offering.
---

Then go with the number from commerical
defrost timer.
4 minutes to 110 minutes in 2 minutes step.
4 to 12 cycles per day.

http://www.grainger.com/Grainger/PARAGON-Time-InitiatedTime-Terminate...

---
That's USD 184.75, and she's in Oz, so it'd more likely be about USD
250 before she got the part in hand.

Plus, she's got an old fridge and if went belly-up shortly after
spending the money for the defroster she'd probably wind up with a new
fridge and a homeless new defroster.
---

I would go with 2 pots + 2 A2D. adjust and time it with a micro.

---
Yeah, sure you would...

Why not post a schematic and some code showing how you'd propose to
implement your wily scheme, and I'll do the same proposing a strictly
hardware solution?

Game on?

OK, changed my mind, let do digital.

Let start with perhaps 4 buttons. Two to change cycles per day and two
to change durations.  Three bits driving 138 (one of eight) to
indicate cycles (eight cycles should be plenty).  Another three bits
to indicate durations such as 5,7,10,15,20,25,30 minutes.  I doubt we
really want to defrost beyond 30 minutes anyway.  So far, we can do it
with 10 port pins and 16 LEDs.

Just a quick first draft:

char cycle[8] = {1,2,3,4,5,6,7};
char duration[8] = {5,7,10,15,20,25,30};
int c_idx;
int d_idx;

while(1)
{
    if(port(c_up))
     c_idx++;
    if(port(c_dn))
     c_idx--;
    if(port(d_up))
     d_idx++;
    if(port(d_dn))
     d_idx--;

     defrost_on();
     delay(d_idx);
     defrost_off();

     delay_hrs(24/cycle[c_idx]);

}

...

Its a better idea to stop defrost cycle when the exchanger temp rises
above freezing. Otherwie you're wasting energy, and at some point the
machine will likely ice up.

NT

The 'standard' self-defrost implementation has an additional thermostat
on the cooling element, which trips open when the element reaches some
predetermined temperature (11C on mine), and closes again at some lower
temperature (0C on mine).

11C seems rather high, but I suppose it's intended to ensure that the
entire element has defrosted, not just the part near the thermostat. It
also means the thermostat need not be that accurate.

Switching the cooling back on immediately after the thermostat trips off
seems attractive, to avoid defrosting the stuff in the freezer, but I
have some misgivings about the impact on the compressor of starting when
the element is that warm.

It's not clear to me why the machine would ice up if the defrost cycle
is left running too long.

Sylvia.

You could design a defrost system like was on the New Inventors last
year.
IIRC a resistive strip was placed in the freezer, a known voltage
passed through it periodically
and the resistance of it measured (heat causes resistance to rise, and
the more frost/ice formed on the strip
the longer it took to heat up and resistance to rise) and turn on the
defrost system only when
sufficient ice was detected.

I suppose it depends what one is trying to achieve. Clearly, it's
wasteful of energy to heat up, and then cool, an element that doesn't
have much ice on it.

On the other hand, keeping it that way means that the defrost cycle
doesn't have to take long, which is helpful is one's primary goal is to
keep the freezer compartment below a certain temperature.

Sylvia.

Sound like we should wire the whole fridge with sensors.  But that's
fine, thermistors are cheap.  PIC32 can handle up to 16 analog
channels.

Bad idea. All that would happen would be that you'd discover that the
distribution of emperatures in the fridge are not what you'd like them
to be,

At least all around the heat exchanger and pipes.

but that since all you have is on/off switches for the
compressor, fan, and defrost heater, there's little you can do about it.

We can control how much to defrost, by measuring temperature changes
based on compressor and fan timings and loads. There are plenty of
parameters we can measures and to adjust in heatings.

But if you're also adding some mechanically operated vents, and some
additional fans, then now you're talking.

I would add additional hot water pipes. It's more cost efficient than
electric heat.

 

[Les Cargill]

krw@att.bizzzzzzzzzzzz wrote:

On Tue, 13 Dec 2011 17:52:48 -0600, Les Cargill<lcargill99@comcast.com
wrote:

dagmargoodboat@yahoo.com wrote:
On Dec 13, 6:23 am, keithr<ke...@nowhere.com.au> wrote:
snip

I prefer competition, the same process that makes everything we do and
buy get constantly better, and cheaper. E.g., computers.

Except for Apple...

Eveb Apple gets better, and cheaper. Your point?

Apple has chosen not to compete on price, and have had
staggering profits. Much corporate medical care
in the US also does not compete on price, if at all.

As a larger issue, when people drill
down into the details, competition as we generally
think of it rarely matters much - differences in
cost of orders of magnitude will matter while differences
of even as much as 2x will not.

But the more something is a commodity, especially
a commodity that has high volume, the more small
differences in price matter.

Medical care is a craft good, and the farthest thing
there is from a commodity. Will that change? Probably.

Specific to medical care 1) we do not have competitive
provision of medical care in the US, and 2) universal
care ala Yurp has actuarial effects very much
in favor of it.

--
Les Cargill

 

[linnix]

On Dec 13, 6:58 pm, Ralph Barone <address...@invalid.invalid> wrote:

linnix <m...@linnix.info-for.us> wrote:
On Dec 13, 6:11 pm, Ralph Barone <address...@invalid.invalid> wrote:
At 10 cents a post, we could have taken up a collection and bought a new
OEM timer for the OP

That's not the point.  We are designing a better solution.  It might
not even be a timer.

While I love the design process and we're all having lots of fun here; for
a one-off solution, it's pretty hard to beat buying an OEM spare part and
just stuffing it back in.

While going through this thread and searching on the net. I believe
that we can make the old fridges much more efficient. We are not
talking about stuffing back inefficient OEM parts. Timer is an
inefficient open-loop control. Using temperature sensing closed loop,
we can reduce the cooling-heating cycles and energies.

 

[NT]

On Dec 13, 12:40 am, Sylvia Else <syl...@not.here.invalid> wrote:

On 13/12/2011 9:23 AM, NT wrote:



On Dec 12, 5:20 am, linnix<m...@linnix.info-for.us>  wrote:
On Dec 11, 5:48 pm, John Fields<jfie...@austininstruments.com>  wrote:

On Sun, 11 Dec 2011 16:20:48 -0800 (PST), linnix

m...@linnix.info-for.us>  wrote:
On Dec 11, 3:09 pm, John Fields<jfie...@austininstruments.com>  wrote:
On Sat, 10 Dec 2011 17:19:52 -0800 (PST), linnix

m...@linnix.info-for.us>  wrote:
On Dec 10, 5:06 pm, John Fields<jfie...@austininstruments.com>  wrote:
You've said the defrost only happens every six hours, but for how long
is the heater energized?

knowing that will allow us to determine the duty cycle of the timer
and cause it to mimic the motor timer.

--
JF

It should be long enough to melt the ice and let the water drain off.
It can easily be programmable in a micro, at least during
development.  Perhaps a 5 to 10 minutes range.

---
Thanks, but I'd prefer some real numbers from Sylvia so that I can
work up a hardware solution for her.

You don't like my numbers?

---
I don't care for conjecture, which is all you're offering.
---

Then go with the number from commerical
defrost timer.
4 minutes to 110 minutes in 2 minutes step.
4 to 12 cycles per day.

http://www.grainger.com/Grainger/PARAGON-Time-InitiatedTime-Terminate....

---
That's USD 184.75, and she's in Oz, so it'd more likely be about USD
250 before she got the part in hand.

Plus, she's got an old fridge and if went belly-up shortly after
spending the money for the defroster she'd probably wind up with a new
fridge and a homeless new defroster.
---

I would go with 2 pots + 2 A2D. adjust and time it with a micro.

---
Yeah, sure you would...

Why not post a schematic and some code showing how you'd propose to
implement your wily scheme, and I'll do the same proposing a strictly
hardware solution?

Game on?

OK, changed my mind, let do digital.

Let start with perhaps 4 buttons. Two to change cycles per day and two
to change durations.  Three bits driving 138 (one of eight) to
indicate cycles (eight cycles should be plenty).  Another three bits
to indicate durations such as 5,7,10,15,20,25,30 minutes.  I doubt we
really want to defrost beyond 30 minutes anyway.  So far, we can do it
with 10 port pins and 16 LEDs.

Just a quick first draft:

char cycle[8] = {1,2,3,4,5,6,7};
char duration[8] = {5,7,10,15,20,25,30};
int c_idx;
int d_idx;

while(1)
{
  if(port(c_up))
   c_idx++;
  if(port(c_dn))
   c_idx--;
  if(port(d_up))
   d_idx++;
  if(port(d_dn))
   d_idx--;

   defrost_on();
   delay(d_idx);
   defrost_off();

   delay_hrs(24/cycle[c_idx]);

}

...

Its a better idea to stop defrost cycle when the exchanger temp rises
above freezing. Otherwie you're wasting energy, and at some point the
machine will likely ice up.

NT

The 'standard' self-defrost implementation has an additional thermostat
on the cooling element, which trips open when the element reaches some
predetermined temperature (11C on mine), and closes again at some lower
temperature (0C on mine).

11C seems rather high, but I suppose it's intended to ensure that the
entire element has defrosted, not just the part near the thermostat. It
also means the thermostat need not be that accurate.

Switching the cooling back on immediately after the thermostat trips off
seems attractive, to avoid defrosting the stuff in the freezer, but I
have some misgivings about the impact on the compressor of starting when
the element is that warm.

It's not clear to me why the machine would ice up if the defrost cycle
is left running too long.

Sylvia.

They don't. If the defrost time isnt properly controlled, its bound to
end up being a compromise, too long most of the time but on occasion
too short. That's when the system ices.

The temp the evporator reaches dont matter to the compressor, the
latter has plenty of thermal capacity and some leeway.


NT

 

[NT]

On Dec 13, 10:43 am, Sylvia Else <syl...@not.here.invalid> wrote:

On 13/12/2011 4:01 PM, kreed wrote:



On Dec 13, 10:40 am, Sylvia Else<syl...@not.here.invalid>  wrote:
On 13/12/2011 9:23 AM, NT wrote:

On Dec 12, 5:20 am, linnix<m...@linnix.info-for.us>    wrote:
On Dec 11, 5:48 pm, John Fields<jfie...@austininstruments.com>    wrote:

On Sun, 11 Dec 2011 16:20:48 -0800 (PST), linnix

m...@linnix.info-for.us>    wrote:
On Dec 11, 3:09 pm, John Fields<jfie...@austininstruments.com>    wrote:
On Sat, 10 Dec 2011 17:19:52 -0800 (PST), linnix

m...@linnix.info-for.us>    wrote:
On Dec 10, 5:06 pm, John Fields<jfie...@austininstruments.com>    wrote:
You've said the defrost only happens every six hours, but for how long
is the heater energized?

knowing that will allow us to determine the duty cycle of the timer
and cause it to mimic the motor timer.

--
JF

It should be long enough to melt the ice and let the water drain off.
It can easily be programmable in a micro, at least during
development.  Perhaps a 5 to 10 minutes range.

---
Thanks, but I'd prefer some real numbers from Sylvia so that I can
work up a hardware solution for her.

You don't like my numbers?

---
I don't care for conjecture, which is all you're offering.
---

Then go with the number from commerical
defrost timer.
4 minutes to 110 minutes in 2 minutes step.
4 to 12 cycles per day.

http://www.grainger.com/Grainger/PARAGON-Time-InitiatedTime-Terminate...

---
That's USD 184.75, and she's in Oz, so it'd more likely be about USD
250 before she got the part in hand.

Plus, she's got an old fridge and if went belly-up shortly after
spending the money for the defroster she'd probably wind up with a new
fridge and a homeless new defroster.
---

I would go with 2 pots + 2 A2D. adjust and time it with a micro.

---
Yeah, sure you would...

Why not post a schematic and some code showing how you'd propose to
implement your wily scheme, and I'll do the same proposing a strictly
hardware solution?

Game on?

OK, changed my mind, let do digital.

Let start with perhaps 4 buttons. Two to change cycles per day and two
to change durations.  Three bits driving 138 (one of eight) to
indicate cycles (eight cycles should be plenty).  Another three bits
to indicate durations such as 5,7,10,15,20,25,30 minutes.  I doubt we
really want to defrost beyond 30 minutes anyway.  So far, we can do it
with 10 port pins and 16 LEDs.

Just a quick first draft:

char cycle[8] = {1,2,3,4,5,6,7};
char duration[8] = {5,7,10,15,20,25,30};
int c_idx;
int d_idx;

while(1)
{
   if(port(c_up))
    c_idx++;
   if(port(c_dn))
    c_idx--;
   if(port(d_up))
    d_idx++;
   if(port(d_dn))
    d_idx--;

    defrost_on();
    delay(d_idx);
    defrost_off();

    delay_hrs(24/cycle[c_idx]);

}

...

Its a better idea to stop defrost cycle when the exchanger temp rises
above freezing. Otherwie you're wasting energy, and at some point the
machine will likely ice up.

NT

The 'standard' self-defrost implementation has an additional thermostat
on the cooling element, which trips open when the element reaches some
predetermined temperature (11C on mine), and closes again at some lower
temperature (0C on mine).

11C seems rather high, but I suppose it's intended to ensure that the
entire element has defrosted, not just the part near the thermostat. It
also means the thermostat need not be that accurate.

Switching the cooling back on immediately after the thermostat trips off
seems attractive, to avoid defrosting the stuff in the freezer, but I
have some misgivings about the impact on the compressor of starting when
the element is that warm.

It's not clear to me why the machine would ice up if the defrost cycle
is left running too long.

Sylvia.

You could design a defrost system like was on the New Inventors last
year.
IIRC a resistive strip was placed in the freezer, a known voltage
passed through it periodically
and the resistance of it measured (heat causes resistance to rise, and
the more frost/ice formed on the strip
the longer it took to heat up and resistance to rise) and turn on the
defrost system only when
sufficient ice was detected.

I suppose it depends what one is trying to achieve. Clearly, it's
wasteful of energy to heat up, and then cool, an element that doesn't
have much ice on it.

not at all, ice doesnt conduct heat well, so removing a thin layer of
ice makes the cooling more energy efficient.

On the other hand, keeping it that way means that the defrost cycle
doesn't have to take long, which is helpful is one's primary goal is to
keep the freezer compartment below a certain temperature.

Sylvia.

 

[linnix]

On Dec 14, 7:35 am, NT <meow2...@care2.com> wrote:

On Dec 13, 12:40 am, Sylvia Else <syl...@not.here.invalid> wrote:









On 13/12/2011 9:23 AM, NT wrote:

On Dec 12, 5:20 am, linnix<m...@linnix.info-for.us>  wrote:
On Dec 11, 5:48 pm, John Fields<jfie...@austininstruments.com>  wrote:

On Sun, 11 Dec 2011 16:20:48 -0800 (PST), linnix

m...@linnix.info-for.us>  wrote:
On Dec 11, 3:09 pm, John Fields<jfie...@austininstruments.com>  wrote:
On Sat, 10 Dec 2011 17:19:52 -0800 (PST), linnix

m...@linnix.info-for.us>  wrote:
On Dec 10, 5:06 pm, John Fields<jfie...@austininstruments.com>  wrote:
You've said the defrost only happens every six hours, but for how long
is the heater energized?

knowing that will allow us to determine the duty cycle of the timer
and cause it to mimic the motor timer.

--
JF

It should be long enough to melt the ice and let the water drain off.
It can easily be programmable in a micro, at least during
development.  Perhaps a 5 to 10 minutes range.

---
Thanks, but I'd prefer some real numbers from Sylvia so that I can
work up a hardware solution for her.

You don't like my numbers?

---
I don't care for conjecture, which is all you're offering.
---

Then go with the number from commerical
defrost timer.
4 minutes to 110 minutes in 2 minutes step.
4 to 12 cycles per day.

http://www.grainger.com/Grainger/PARAGON-Time-InitiatedTime-Terminate...

---
That's USD 184.75, and she's in Oz, so it'd more likely be about USD
250 before she got the part in hand.

Plus, she's got an old fridge and if went belly-up shortly after
spending the money for the defroster she'd probably wind up with a new
fridge and a homeless new defroster.
---

I would go with 2 pots + 2 A2D. adjust and time it with a micro.

---
Yeah, sure you would...

Why not post a schematic and some code showing how you'd propose to
implement your wily scheme, and I'll do the same proposing a strictly
hardware solution?

Game on?

OK, changed my mind, let do digital.

Let start with perhaps 4 buttons. Two to change cycles per day and two
to change durations.  Three bits driving 138 (one of eight) to
indicate cycles (eight cycles should be plenty).  Another three bits
to indicate durations such as 5,7,10,15,20,25,30 minutes.  I doubt we
really want to defrost beyond 30 minutes anyway.  So far, we can do it
with 10 port pins and 16 LEDs.

Just a quick first draft:

char cycle[8] = {1,2,3,4,5,6,7};
char duration[8] = {5,7,10,15,20,25,30};
int c_idx;
int d_idx;

while(1)
{
  if(port(c_up))
   c_idx++;
  if(port(c_dn))
   c_idx--;
  if(port(d_up))
   d_idx++;
  if(port(d_dn))
   d_idx--;

   defrost_on();
   delay(d_idx);
   defrost_off();

   delay_hrs(24/cycle[c_idx]);

}

...

Its a better idea to stop defrost cycle when the exchanger temp rises
above freezing. Otherwie you're wasting energy, and at some point the
machine will likely ice up.

NT

The 'standard' self-defrost implementation has an additional thermostat
on the cooling element, which trips open when the element reaches some
predetermined temperature (11C on mine), and closes again at some lower
temperature (0C on mine).

11C seems rather high, but I suppose it's intended to ensure that the
entire element has defrosted, not just the part near the thermostat. It
also means the thermostat need not be that accurate.

Switching the cooling back on immediately after the thermostat trips off
seems attractive, to avoid defrosting the stuff in the freezer, but I
have some misgivings about the impact on the compressor of starting when
the element is that warm.

It's not clear to me why the machine would ice up if the defrost cycle
is left running too long.

Sylvia.

They don't. If the defrost time isnt properly controlled, its bound to
end up being a compromise, too long most of the time

And heat it up, just to cool it down later. I can't believe the
fridge industry is still using inefficient timer based open loop
control.

 

[NT]

On Dec 13, 12:52 pm, Sylvia Else <syl...@not.here.invalid> wrote:

On 13/12/2011 11:12 PM, Jasen Betts wrote:



On 2011-12-13, Sylvia Else<syl...@not.here.invalid>  wrote:

The 'standard' self-defrost implementation has an additional thermostat
on the cooling element, which trips open when the element reaches some
predetermined temperature (11C on mine), and closes again at some lower
temperature (0C on mine).

11C seems rather high, but I suppose it's intended to ensure that the
entire element has defrosted, not just the part near the thermostat. It
also means the thermostat need not be that accurate.

Switching the cooling back on immediately after the thermostat trips off
seems attractive, to avoid defrosting the stuff in the freezer, but I
have some misgivings about the impact on the compressor of starting when
the element is that warm.

the closer the inside temperature of the fridge is to the outside
temperatue the less work the compressor needs to do to circulate he
coolant.

a warm evaporator means the compressor's input is at a higner pressure
than normal and thus it needs to do less work to compress the gas
enough to condense in the condenser,

 From context, I assume you meant "more" in that last sentence.

The question is - does it matter? That is, will running the compressor
when the element is warm do anything more than consume some extra
electricity. I suppose it's no different from having the fridge turned
off for a while, and then turning it on, but it may have some long term
implications for the life of the compressor if it happens every six
hours. I'm speculating - I don't know.

Sylvia.

Its a nonissue. If you wanted to get every last drop of energy
efficiency, the compressor could be run backwards to defrost the
evaporator, thus making good use of the heat built up within it. Bu
that wuold mean more cost, so its not done.


NT

 

[linnix]

On Dec 14, 7:50 am, NT <meow2...@care2.com> wrote:

On Dec 13, 12:52 pm, Sylvia Else <syl...@not.here.invalid> wrote:









On 13/12/2011 11:12 PM, Jasen Betts wrote:

On 2011-12-13, Sylvia Else<syl...@not.here.invalid>  wrote:

The 'standard' self-defrost implementation has an additional thermostat
on the cooling element, which trips open when the element reaches some
predetermined temperature (11C on mine), and closes again at some lower
temperature (0C on mine).

11C seems rather high, but I suppose it's intended to ensure that the
entire element has defrosted, not just the part near the thermostat. It
also means the thermostat need not be that accurate.

Switching the cooling back on immediately after the thermostat trips off
seems attractive, to avoid defrosting the stuff in the freezer, but I
have some misgivings about the impact on the compressor of starting when
the element is that warm.

the closer the inside temperature of the fridge is to the outside
temperatue the less work the compressor needs to do to circulate he
coolant.

a warm evaporator means the compressor's input is at a higner pressure
than normal and thus it needs to do less work to compress the gas
enough to condense in the condenser,

 From context, I assume you meant "more" in that last sentence.

The question is - does it matter? That is, will running the compressor
when the element is warm do anything more than consume some extra
electricity. I suppose it's no different from having the fridge turned
off for a while, and then turning it on, but it may have some long term
implications for the life of the compressor if it happens every six
hours. I'm speculating - I don't know.

Sylvia.

Its a nonissue. If you wanted to get every last drop of energy
efficiency, the compressor could be run backwards to defrost the
evaporator, thus making good use of the heat built up within it. Bu
that wuold mean more cost, so its not done.

NT

It is done in some high end refrigeration system, with rerouting
pipes, rather than reversing the compressor. Some even try to capture
the heat build up by the compressor for defrosting.