Relay contact ratings.

[Sylvia Else]

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.

 

[keithr]

On 13/12/2011 9:33 AM, dagmargoodboat@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.

 

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.

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!

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. : )

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?

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?

 

[Jasen Betts]

On 2011-12-13, Sylvia Else <sylvia@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,

--
⚂⚃ 100% natural

--- Posted via news://freenews.netfront.net/ - Complaints to news@netfront.net ---

 

[kreed]

On Dec 13, 7:14 pm, F Murtz <hagg...@hotmail.com> wrote:

kreed wrote:
On Dec 13, 5:12 pm, F Murtz<hagg...@hotmail.com>  wrote:
kreed wrote:
On Dec 11, 9:16 am, linnix<m...@linnix.info-for.us>    wrote:
On Dec 10, 2:39 pm, kreed<kenreed1...@gmail.com>    wrote:

On Dec 10, 9:00 pm, Sylvia Else<syl...@not.here.invalid>    wrote:

On 10/12/2011 9:33 PM, kreed wrote:

On Dec 10, 8:28 pm, Sylvia Else<syl...@not.here.invalid>      wrote:
On 10/12/2011 10:14 AM, David Eather wrote:

On 9/12/2011 10:56 AM, Sylvia Else wrote:
On 9/12/2011 4:23 AM, linnix wrote:
On Dec 8, 9:01 am, Fred Bloggs<bloggs.fredbloggs.f...@gmail.com
wrote:
On Dec 8, 1:50 am, Sylvia Else<syl...@not.here.invalid>      wrote:

The defrost timer in my fridge is failing, and given the cost of a
'genuine' replacement part, I was pondering the option of making
electronic timer driving an electromechanical relay.

It probably won't happen, but when I was looking at relay specs, I
found
that their ratings are usually specified as a highish reactive power,
and a much lower real power.

http://australia.rs-online.com/web/p/electromechanical-relays/1279550/

is typical, specifying in this case 300 W / 2500 VA.

I find this difficult to fathom. Imagine a purely inductive 2500VA
load.
So no real power being switched, but it would arc like crazy. What
am I
missing here?

Sylvia.

There are aftermarket universals better than the OEM
parthttp://compare.ebay.com/like/290638915750?var=lv<yp=AllFixedPriceIt...

There are plenty of relays you can salvage out of garage opener (12V),
microwave (12V) or furnace (24V). Add a micro or 555 for less than $5
and you are done. I am doing one for my furnace timer.

Not sure about getting a 555 to run at 1 cycle per six hours.

A PIC would no doubt do the job easily, but then I'd have to invest in
hardware to program it.

Sylvia.

Sylvia,

Try a PICAXE 08M2 - it costs $2.50 in one off's and programs in BASIC.
Software and examples are free fromwww.picaxe.co.uk
It is not uncommon for people totally new to the PICAXE have had them
running programs within 30 minutes of getting their first chip.

The only stuff you need to program one is a serial port (RS232 or TTL
level) and a resistor.

Interesting. Thanks.

I'm tempted to combine the timer with the thermostat, a replacement for
which I've been cursin..., er, I mean testing, today. (Sod's law
subsection 3.1 - a fridge must always enter defrost mode while a person
is attempting to adjust the upper and lower settings of a thermostat.)

Of course, I could just buy a new fridge.

Sylvia.

Depends on how old, and how good the current one is other than this
current problem.  New ones might be even worse

It would have to be at least ten, and it's been running all that time.

The big question, of course, is how much longer the compressor will
last, since it's probably not going to possible to source a replacement,
even if it would otherwise be economically worthwhile.

BTW, the wires are attached to the (mains-voltage) lamp socket by way of
spring clips. Seems a bit iffy to me.

Sylvia.

I remember a few years back there was one of these educational
programs on how things work, in particular household appliances.  They
actually went to a dump site where were were dozens of junked fridges,
and connected each one to power.  Almost all still cooled, but had
been dumped due to rust, broken shelves, seals etc or other similar
damage.  They said that the compressors were extremely reliable.

OK, i am going dumper diving.

...
As for that electronic aftermarket timer from Ebay that is 120v - if
you get one and open it up, you might find that it has either a
switchmode power supply or a series capacitor type supply.  You can
modify these fairly easily to run from 240v, or make up a small power
supply that you can mount in the back of the fridge.  For something
like this a linear power supply might be best, as linear ones are very
reliable.

Actually, a good source of relays are garage openers.  I have a spare
board with 3 240V/5A w 24V/5A coil.  I guess it needs open/close/on.

I have worked on a couple of newer Australian made ones here and now
they have no relays at all in them.  Other brands
might have, or older models that are being replaced.

A lot of the modern ones use butane as a refrigerant so may be they do
not want open contacts in the very remote case of leaks

I meant garage door openers

Did not see that but it may also be the case with the newer fridges.

could be too

 

[Sylvia Else]

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

On 2011-12-13, Sylvia Else<sylvia@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.

 

[Sylvia Else]

On 13/12/2011 4:21 PM, kreed wrote:

On Dec 13, 10:44 am, Sylvia Else<syl...@not.here.invalid> wrote:
On 13/12/2011 7:26 AM, Michael A. Terrell wrote:





Sylvia Else wrote:

On 12/12/2011 5:58 PM, Michael A. Terrell wrote:
?
? Sylvia Else wrote:
??
?? On 12/12/2011 12:57 PM, John Fields wrote:
??? On Mon, 12 Dec 2011 12:30:26 +1100, Sylvia Else
??? ?syl...@not.here.invalid? wrote:
???
???? On 11/12/2011 5:00 PM, Michael A. Terrell wrote:
?????
????? Sylvia Else wrote:
??????
?????? On 11/12/2011 3:46 AM, Michael A. Terrell wrote:
???????
??????? Sylvia Else wrote:
?????????
????????? There are aftermarket universals better than the OEM part
?????????http://compare.ebay.com/like/290638915750?var=lv?ltyp=AllFixedPriceIt...
????????
???????? Though not 240V versions as far as I can see. Pity.
???????
???????
??????? Can't you find a cheap 240 to 120 VAC transformer?
???????
??????
?????? I could. Using it wouldn't be so straight forward. The timer has a
?????? single pin for input, which is both the source of power for the clock,
?????? and for running either the compressor and heater.
?????
?????
????? There is no neutral connection to the timer?
?????
?????
???? OK, I suppose that would work, though the thing would still be switching
???? voltage which is double its design rating.
????
???? Sylvia.
???
??? Huh???
???
??
?? Since I'm in Australia, both the defrost heater and the compressor are
?? rated at 240V. Anything that switches them on and off has to switch 240V.
?
?
? It would have to switch half the current it would on 120 VAC, and the
? relays are the same for either line volktage.
?
?

You've taken one apart?

I've taken apart a lot of things and I've never seen a power relay
with 120 volt rated contacts. Do whatever you want, I'm done with this
thread.

Well, I obviously can't say what you've see, but here's relay with 120V
rated contacts.

http://australia.rs-online.com/web/p/electromechanical-relays/4936458/

Sylvia.


I have checked a few from my junk box, any that are intended to switch
mains power and not signal
circuits have a 240v rating. Many were out of junked
US made equipment and made in Japan, Mexico or Taiwan.

As they are for the world market, I would think that most would be
rated 240v.

One Japan made one that is UL rated has an inductive rating of 5a
240VAC and 0.5a at 120VDC for inductive loads.

5A 120V and 32v for resistive loads.


The contact clearance is about 1mm.

Still, are you going to put your hand on your heart, and say that some
unknown relay in an appliance designed for 110VAC will be safe to use at
240VAC?

That aside, this subthread related to electronic defrost timers. They
may not be using electromechanical relays at all, but semiconductor
devices.

Sylvia.

 

[kreed]

On Dec 13, 10:52 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.

This is an interesting question. Whether the compressor starts
immediately as the heater
turns off, or waits a few minutes for the evaporator to "cool" , would
make no difference IMHO.


The reason being that even if the heat is allowed time to dissipate
from the evaporator before re-starting
the compressor this heat is only going to dissipate into the freezer/
refrigeration compartment and if nothing else, warm the compartment
and food slightly more. The compressor still has to work to remove
this heat, as it is still in the cabinet, just in a different place.


It will just take longer for this dissipated heat to "come back:" to
the evaporator and be removed via the normal refrigeration process. If
turned on straight away, this heat is removed first, then the unwanted
heat from the rest of the refrigeration cabinet, including the food
within. Theoretically the instant changeover is better for the food
from preventing this temperature rise , by admittedly a very very
tiny amount that is certain to be irrelevant in this application.


If you were defrosting by a heater something like a heatsink or
radiator that was being refrigerated to cool it, but was operating in
open air and not in a closed cabinet, it would be slightly more
beneficial from a power saving viewpoint to let the defrost heater's
heat dissipate first before re-starting the compressor.



PS: this discussion motivated me to defrost the small fridge in the
office. Thanks for that

What a mess.

 

[kreed]

On Dec 13, 10:59 pm, Sylvia Else <syl...@not.here.invalid> wrote:

On 13/12/2011 4:21 PM, kreed wrote:









On Dec 13, 10:44 am, Sylvia Else<syl...@not.here.invalid>  wrote:
On 13/12/2011 7:26 AM, Michael A. Terrell wrote:

Sylvia Else wrote:

On 12/12/2011 5:58 PM, Michael A. Terrell wrote:
?
? Sylvia Else wrote:
??
?? On 12/12/2011 12:57 PM, John Fields wrote:
??? On Mon, 12 Dec 2011 12:30:26 +1100, Sylvia Else
??? ?syl...@not.here.invalid?   wrote:
???
???? On 11/12/2011 5:00 PM, Michael A. Terrell wrote:
?????
????? Sylvia Else wrote:
??????
?????? On 11/12/2011 3:46 AM, Michael A. Terrell wrote:
???????
??????? Sylvia Else wrote:
?????????
????????? There are aftermarket universals better than the OEM part
?????????http://compare.ebay.com/like/290638915750?var=lv?ltyp=AllFixedPriceIt...
????????
???????? Though not 240V versions as far as I can see. Pity.
???????
???????
???????        Can't you find a cheap 240 to 120 VAC transformer?
???????
??????
?????? I could. Using it wouldn't be so straight forward. The timer has a
?????? single pin for input, which is both the source of power for the clock,
?????? and for running either the compressor and heater.
?????
?????
?????       There is no neutral connection to the timer?
?????
?????
???? OK, I suppose that would work, though the thing would still be switching
???? voltage which is double its design rating.
????
???? Sylvia.
???
??? Huh???
???
??
?? Since I'm in Australia, both the defrost heater and the compressor are
?? rated at 240V. Anything that switches them on and off has to switch 240V.
?
?
?     It would have to switch half the current it would on 120 VAC, and the
? relays are the same for either line volktage.
?
?

You've taken one apart?

     I've taken apart a lot of things and I've never seen a power relay
with 120 volt rated contacts. Do whatever you want, I'm done with this
thread.

Well, I obviously can't say what you've see, but here's relay with 120V
rated contacts.

http://australia.rs-online.com/web/p/electromechanical-relays/4936458/

Sylvia.

I have checked a few from my junk box, any that are intended to switch
mains power and not signal
circuits have a 240v rating.  Many were out of junked
US made equipment and made in Japan, Mexico or Taiwan.

As they are for the world market, I would think that most would be
rated 240v.

One Japan made one that is UL rated has an inductive rating of 5a
240VAC and 0.5a at 120VDC for inductive loads.

5A 120V and 32v for resistive loads.

The contact clearance is about 1mm.

Still, are you going to put your hand on your heart, and say that some
unknown relay in an appliance designed for 110VAC will be safe to use at
240VAC?

No, unless there was no choice but to keep the relay or device. In
that case, I would at least examine the contact
clearance and size and compare it to a known good relay that was
suitable, or simply use the device
to drive a relay that would do the job.

That aside, this subthread related to electronic defrost timers. They
may not be using electromechanical relays at all, but semiconductor
devices.

Sylvia.

I wouldn't EVER blindly trust a solid state device designed to switch
110v on a 240v supply, unless again you could
check the ratings of the SSR or SCR. Triac etc used, and ratings of
any associated components such as
suppressors, MOV's etc that might be involved.



You just reminded me of an actual situation where this happened.

I did come across this about 20 years ago, where a disco light control
unit in a juke box imported from the USA
ran from 120v, and ran 120v 15w bulbs that were unavailable in AUS,
and blew often. There was an internal stepdown
transformer fitted to provide the 120v needed for the entire
machine.

They wanted to change it to 240v 25w bulbs, and I will admit they did
look a hell of a lot better in the application than the 15's that were
not very satisfactory in brightness.

We were unable to determine the specs on the triacs fitted as they
only had a OEM part number on them,
but converted it to 240v use by replacing the Triacs with BT139's and
it worked well.

They were opto and physically isolated from the logic circuit, as
well as having a separate mains rated connector and wiring
at the opposite end of the board and outer casing so there was no
problem with the safety aspect of the modification.

 

[kreed]

On Dec 13, 9:23 pm, 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.

yes, its a wonderful feeling. I understand over there they have draft
legislation
on the table to grab private pension funds (401K ?) and put them into
gov bonds
that will disappear as the country has its inevitble financial
collapse.

Super is a scam in my book, unless you are close to the age of getting
a payout.

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.

 

[linnix]

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.

BTW, i also have a busted microwave and fridge to play with. If only
i have a robotic arm to move something from the fridge to the
microwave and nuke it in the morning.

 

[Michael A. Terrell]

linnix wrote:

If you were defrosting by a heater something like a heatsink or
radiator that was being refrigerated to cool it, but was operating in
open air and not in a closed cabinet, it would be slightly more
beneficial from a power saving viewpoint to let the defrost heater's
heat dissipate first before re-starting the compressor.

Given that our natural gas is 80% cheaper than electricity, and going
lower. I might replumb the fridge with (gas) hot water pipes, with
electromechanical water valves. Can i use plastic sprinkler valves
for warm water? I can install the valves at the outlet, so they won't
be too hot anyway.

Items made with the gray plastic for sprinklers isn't certified for
indoor use. It is low pressure & low temperature rated and easy to
break.
--
You can't have a sense of humor, if you have no sense.

 

[linnix]

If you were defrosting by a heater something like a heatsink or
radiator that was being refrigerated to cool it, but was operating  in
open air and not in a closed cabinet, it would be slightly more
beneficial from a power saving viewpoint to let the defrost heater's
heat dissipate first before re-starting the compressor.

Given that our natural gas is 80% cheaper than electricity, and going
lower. I might replumb the fridge with (gas) hot water pipes, with
electromechanical water valves. Can i use plastic sprinkler valves
for warm water? I can install the valves at the outlet, so they won't
be too hot anyway.

 

[linnix]

On Dec 13, 9:21 am, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

linnix wrote:

If you were defrosting by a heater something like a heatsink or
radiator that was being refrigerated to cool it, but was operating  in
open air and not in a closed cabinet, it would be slightly more
beneficial from a power saving viewpoint to let the defrost heater's
heat dissipate first before re-starting the compressor.

Given that our natural gas is 80% cheaper than electricity, and going
lower.  I might replumb the fridge with (gas) hot water pipes, with
electromechanical water valves.  Can i use plastic sprinkler valves
for warm water?  I can install the valves at the outlet, so they won't
be too hot anyway.

   Items made with the gray plastic for sprinklers isn't certified for
indoor use.  It is low pressure & low temperature rated

After passing through the fridge, the warm water should be cold
enough, if not too cold.

and easy to break.

I know, i just rebuilt six of them and five were internally broken.
But they are dirt cheap.
The high quality replacement part should outlast the cheap factory
part.

 

[John Fields]

On Sun, 11 Dec 2011 21:20:03 -0800 (PST), linnix
<me@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

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]);
}

---
View with a fixed-pitch font.

This will give a 30 minute defrost cycle following a 6 hour freezing
period:


|<-------6 hr---------->| |<-------6 hr---------->|
NC _______________________ _______________________ __
COOL_| |_| |_|

->| |<-30 min ->| |<-30 min NO
_ _ _
HEAT |_______________________| |_______________________| |__

+V
|
.. 4060 Vcc +----+
.. +------+ | NAND |K | O---->C
.. +-976K--|Rs MR|-------|------+-A / DIODE COIL]- -|K1
.. | | | | | Y-+ | | O-> |<-O->NC
.. +-527K--|Rt | 10k +-B | +----+ |
.. | | | | | | | +-------->NO
.. +-1.0ľF-|Ct Q13|-100nF-+ +-A | C
.. +------+ | | Y-+--1k--B NPN
.. | +-B \ E
.. +-A | NAND |
.. NAND Y-+ GND
.. +-B |
.. | |
.. | B-+
.. +-Y NAND
.. | A-+
.. 4060 | |
.. +------+ | Vcc |
.. +-887k--|Rs MR|-------+ | |
.. | | | | |
.. +-442k--|Rt | 10k |
.. | | | | |
.. +-0.1ľF-|Ct Q13|-[100nF]--+---+
.. +------+

K1's contacts are completely isolated, so if theyr'e connected into
the rest of the fridge circuit the way the contacts on the motor
driven timer were, everything should work like it did when the motor
timer was in there.

No micro, no code, no programmer, no learning curve.

--
JF

 

[linnix]

On Dec 13, 9:21 am, "Michael A. Terrell" <mike.terr...@earthlink.net>
wrote:

linnix wrote:

If you were defrosting by a heater something like a heatsink or
radiator that was being refrigerated to cool it, but was operating  in
open air and not in a closed cabinet, it would be slightly more
beneficial from a power saving viewpoint to let the defrost heater's
heat dissipate first before re-starting the compressor.

Given that our natural gas is 80% cheaper than electricity, and going
lower.  I might replumb the fridge with (gas) hot water pipes, with
electromechanical water valves.  Can i use plastic sprinkler valves
for warm water?  I can install the valves at the outlet, so they won't
be too hot anyway.

   Items made with the gray plastic for sprinklers isn't certified for
indoor use.  It is low pressure & low temperature rated and easy to
break.

Added CAE, where some embedded designer are. We started with
defrosting the fridge, perhaps controlling the microwave, and piping
hot water through the fridge into the toilet. This way, we can
defrost the fridge everytime we flush the toilet. However, in case we
don't flush the toilet often enough, we need a PIC to monitor the
toilet as well.

We are going to need defrost cycle counters, duration timers, target
temperature, pipe temperature and toilet counters. So, first thing is
to build the counters. I've decided to build with 42 LEDs and 4 595
shift registers. See:

http://173.224.223.62/pic32

 

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.

--
Cheers,
James Arthur

 

[John Fields]

On Tue, 13 Dec 2011 12:52:04 -0600, John Fields
<jfields@austininstruments.com> wrote:

---
View with a fixed-pitch font.

This will give a 30 minute defrost cycle following a 6 hour freezing
period:

---
Oops...
Please ignore; I'm fixing the error.

--
JF

 

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

 

[John Fields]

On Tue, 13 Dec 2011 16:02:47 -0600, John Fields
<jfields@austininstruments.com> wrote:

On Tue, 13 Dec 2011 12:52:04 -0600, John Fields
jfields@austininstruments.com> wrote:


---
View with a fixed-pitch font.

This will give a 30 minute defrost cycle following a 6 hour freezing
period:

---
Oops...
Please ignore; I'm fixing the error.

---
Done.

news/t4nfe7d1lnj35s2a3thchv3diqc827gq3g@4ax.com

--
JF