Relay contact ratings.

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=AllFixedPriceItemTypes&var=sbar

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?


--
You can't have a sense of humor, if you have no sense.
 
On 11/12/2011 10:09 AM, John Fields wrote:
On Sun, 11 Dec 2011 07:30:25 +1000, David Eather<eather@tpg.com.au
wrote:

On 10/12/2011 10:32 AM, John Fields wrote:
On Sat, 10 Dec 2011 09:14:27 +1000, David Eather<eather@tpg.com.au
wrote:

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

---
Not true; consider Moore's law.


Consider that Moore's Law is not a law.

---
OK, Moore's conjecture then, if that pleases you.

The point is that we _have_ addressed the fundamental truth that
endless growth is impossible in a finite world by stalling the
inevitable using miniaturization.
You mean we have found a way to avoid having to do anything unpleasant
to ourselves by foisting the problem on a latter generation. And you
think this is a "solution"?

--
We have failed to address the fundamental truth that endless growth is
impossible in a finite world.
 
On Mon, 12 Dec 2011 07:50:45 +1000, David Eather <eather@tpg.com.au>
wrote:

On 11/12/2011 10:09 AM, John Fields wrote:
On Sun, 11 Dec 2011 07:30:25 +1000, David Eather<eather@tpg.com.au
wrote:

On 10/12/2011 10:32 AM, John Fields wrote:
On Sat, 10 Dec 2011 09:14:27 +1000, David Eather<eather@tpg.com.au
wrote:

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

---
Not true; consider Moore's law.


Consider that Moore's Law is not a law.

---
OK, Moore's conjecture then, if that pleases you.

The point is that we _have_ addressed the fundamental truth that
endless growth is impossible in a finite world by stalling the
inevitable using miniaturization.


You mean we have found a way to avoid having to do anything unpleasant
to ourselves by foisting the problem on a latter generation. And you
think this is a "solution"?
---
Certainly you must have misunderstood.

In the context of Moore's Law:

http://en.wikipedia.org/wiki/File:Transistor_Count_and_Moore%27s_Law_-_2011.svg

we _have_ addressed the fundamental truth that endless growth is
impossible in a finite world by diminishing the size of transistors in
order to pack more and more of them into smaller areas as time goes
by.

This allows us to build more powerful machines which, rather than
foisting out problems on future generations, will help us solve some
of ours, and theirs as well.

Your suggestion that we should make life more unpleasant for ourselves
by not taking Moore's Law into account and building computers out of,
say, 2N2222's is puzzling

--
JF
 
On Sat, 10 Dec 2011 17:19:52 -0800 (PST), linnix
<me@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.

--
JF
 
A motherhood statement which avoids dealing with any unpleasant details. Could you state the problem clearly please. What is your solution?
 
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? Then go with the number from commerical
defrost timer.

http://www.grainger.com/Grainger/PARAGON-Time-InitiatedTime-Terminated-Defrost-5X454?Pid=search

4 minutes to 110 minutes in 2 minutes step.
4 to 12 cycles per day.

I would go with 2 pots + 2 A2D. adjust and time it with a micro.
 
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=AllFixedPriceItemTypes&var=sbar

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.
 
On Sun, 11 Dec 2011 16:20:48 -0800 (PST), linnix
<me@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-Terminated-Defrost-5X454?Pid=search
---
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?

--
JF
 
On Mon, 12 Dec 2011 12:30:26 +1100, Sylvia Else
<sylvia@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=AllFixedPriceItemTypes&var=sbar

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???

--
JF
 
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]);
}

....
 
On 12/12/2011 12:57 PM, John Fields wrote:
On Mon, 12 Dec 2011 12:30:26 +1100, Sylvia Else
sylvia@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=AllFixedPriceItemTypes&var=sbar

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.

Sylvia.
 
Sylvia Else wrote:
On 12/12/2011 12:57 PM, John Fields wrote:
On Mon, 12 Dec 2011 12:30:26 +1100, Sylvia Else
sylvia@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=AllFixedPriceItemTypes&var=sbar

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 can't have a sense of humor, if you have no sense.
 
Sylvia Else 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=AllFixedPriceItemTypes&var=sbar

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.

Really? You think the relay can only handle 120 VAC, just because
that's what poweres the timer circuit?


--
You can't have a sense of humor, if you have no sense.
 
On 12/12/2011 5:59 PM, Michael A. Terrell wrote:
Sylvia Else 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=AllFixedPriceItemTypes&var=sbar

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.


Really? You think the relay can only handle 120 VAC, just because
that's what poweres the timer circuit?
Unless you've actually pulled one apart, and determined the exact
specification of the relay, or semiconductor device, involved, it's only
safe to assume that it's specified to perform the particular task
intended for it. It may well be a part that's specified to handle higher
voltages, but it would be rash to assume that.

Sylvia.
 
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
sylvia@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=AllFixedPriceItemTypes&var=sbar

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?

Sylvia.
 
On 12/12/2011 4:20 PM, linnix 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]);
}

...
Are c_idx and d_idx in non-volatile RAM? I'd prefer my fridge to
continue working, without intervention, after a power outage.

There appears to be a defrost-cycle period between each opportunity to
change the settings by one. Could take a while.

Sylvia.
 
On Dec 12, 5:53 am, Sylvia Else <syl...@not.here.invalid> wrote:
On 12/12/2011 4:20 PM, linnix 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]);
}

...

Are c_idx and d_idx in non-volatile RAM? I'd prefer my fridge to
continue working, without intervention, after a power outage.
Depends on the micro. Some can save to EEPROM. That's why i though
about pots in the first place. Pots are non-volatile. We need an A2D
to read from thermistor anyway, so perhaps using 3 channels A2D. One
port for the defrost heater and one more for the compressor. One more
set of decoder/LEDs for temp. settling. So, to do all the fridge
control:

PIC32MX256DA206 (using 11 digital ports and 3 analog ports)
100K Pots (x3)
74XXX138 (x3)
LED (x24)
Thermistor
240V/5A AC relay (x2)
etc.
 
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
??? ?sylvia@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=AllFixedPriceItemTypes?var=sbar
????????
???????? 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.


--
You can't have a sense of humor, if you have no sense.
 
On 13/12/2011 2:41 AM, linnix wrote:
On Dec 12, 5:53 am, Sylvia Else<syl...@not.here.invalid> wrote:
On 12/12/2011 4:20 PM, linnix 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]);
}

...

Are c_idx and d_idx in non-volatile RAM? I'd prefer my fridge to
continue working, without intervention, after a power outage.

Depends on the micro. Some can save to EEPROM. That's why i though
about pots in the first place. Pots are non-volatile. We need an A2D
to read from thermistor anyway, so perhaps using 3 channels A2D. One
port for the defrost heater and one more for the compressor. One more
set of decoder/LEDs for temp. settling. So, to do all the fridge
control:

PIC32MX256DA206 (using 11 digital ports and 3 analog ports)
100K Pots (x3)
74XXX138 (x3)
LED (x24)
Thermistor
240V/5A AC relay (x2)
etc.
Seriously, PICAXE 08M2 - 3 x 10 bit digital ports, configures and reads
as 8 or ten bits with with a single "readadc" or "readadc10" command
(IIRC) and 256 bytes eeprom reads and writes with simple single line
instructions. PICAXE is the simplest and fastest solution to any one off
that needs a little smarts and not too much speed bar none. If you need
lots of LEDs one of the bigger PICAXE chips will do.

I have programmed (and still do) PIC's in assembler (very badly - I
still do that very badly too), Microchip C, Swordfish Basic, and
PICBASIC Pro. For speed, cost effectiveness and ease of producing a
one-off PICAXE easily cleans the floor with all of them.

(I don't really like the guy who invented the PICAXE or his business
model but it is a good product)

--
We have failed to address the fundamental truth that endless growth is
impossible in a finite world.
 
On 12/12/2011 8:59 AM, John Fields wrote:
On Mon, 12 Dec 2011 07:50:45 +1000, David Eather<eather@tpg.com.au
wrote:

On 11/12/2011 10:09 AM, John Fields wrote:
On Sun, 11 Dec 2011 07:30:25 +1000, David Eather<eather@tpg.com.au
wrote:

On 10/12/2011 10:32 AM, John Fields wrote:
On Sat, 10 Dec 2011 09:14:27 +1000, David Eather<eather@tpg.com.au
wrote:

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

---
Not true; consider Moore's law.


Consider that Moore's Law is not a law.

---
OK, Moore's conjecture then, if that pleases you.

The point is that we _have_ addressed the fundamental truth that
endless growth is impossible in a finite world by stalling the
inevitable using miniaturization.


You mean we have found a way to avoid having to do anything unpleasant
to ourselves by foisting the problem on a latter generation. And you
think this is a "solution"?

---
Certainly you must have misunderstood.

In the context of Moore's Law:

http://en.wikipedia.org/wiki/File:Transistor_Count_and_Moore%27s_Law_-_2011.svg

we _have_ addressed the fundamental truth that endless growth is
impossible in a finite world by diminishing the size of transistors in
order to pack more and more of them into smaller areas as time goes
by.

This allows us to build more powerful machines which, rather than
foisting out problems on future generations, will help us solve some
of ours, and theirs as well.

Your suggestion that we should make life more unpleasant for ourselves
by not taking Moore's Law into account and building computers out of,
say, 2N2222's is puzzling
"Moore's Law" fails when you get to one atom sized conductors (in
practical terms we can expect it to fail before then)

"Moor's law" is about one, specific and small situation. By appealing to
"Moore's Law" as a general solution you are burying your head in the sand.

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

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