Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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On Wed, 13 Feb 2008 23:46:43 GMT, Winston
wrote:

Dan wrote:
I know this is off topic, but I know some of you know the answer.

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.

(...)

http://www.amveco.com/pdf/AC1020_11-01.pdf
http://rocky.digikey.com/WebLib/Amve...15,AC-1020.jpg

This is Digikey TE-1020-ND, a current transformer. Its small and will fit within a 1" cube.
Disconnect the defrost heater and thread its wire through the hole in the middle of this
part, then reconnect it. Solder a 100 ohm 1/8W resistor across the output of the
transformer. Every amp flowing into your defrost heater will now be indicated by a
voltage of about 0.1V AC at the output of the transformer, across the resistor.

Connect one of these loggers (US$25.00)to the output of your current transformer and log
the data to your PC.

http://www.dataq.com/products/startkit/di194rs.htm

That's what I would do.

--Winston



Wouldnt it be better to use a thermistor and have it actually tell if
there is a temperature change, rather than just power on the heating
coils? If you have an open in the coils..you will have power, but no
heat.

Gunner



"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner
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I know this is off topic, but I know some of you know the answer.

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.

It is the defrost coil on my freezer. I have had more than one defrost
controller fail. One failed at Christmas and one at Thanksgiving. I
would like to monitor the temperature of the coil using my PC over
time so I can see that the temperature has increased and then
decreased over some time, probably 24 hrs.

When the defrost controller fails, the freezer freezes up over a 2
week period. If I can find a way to verify that the heating element is
heating or not, I can tell if I'm headed for trouble.
This is a 5-year-old Maytag. Expensive, so throwing it out isn't an
option. I just want to see a freeze-up coming. I have a spare
controller. I just need to know when the existing one failed.

I would like to monitor this with a PC input device that can handle an
input of some kind. Like an RTD or even a 120VAC pulse. The controller
switches the element to ground so I'm not sure how to pickup the 120
pulse.
I know you smart guys can come up with something I can use to see that
this dam thing is heating and defrosting the freezer coil.
Thanks Guys,


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On Feb 13, 2:21 pm, Dan@ (Dan ) wrote:
I know this is off topic, but I know some of you know the answer.

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.

It is the defrost coil on my freezer. I have had more than one defrost
controller fail. One failed at Christmas and one at Thanksgiving. I
would like to monitor the temperature of the coil using my PC over
time so I can see that the temperature has increased and then
decreased over some time, probably 24 hrs.

When the defrost controller fails, the freezer freezes up over a 2
week period. If I can find a way to verify that the heating element is
heating or not, I can tell if I'm headed for trouble.
This is a 5-year-old Maytag. Expensive, so throwing it out isn't an
option. I just want to see a freeze-up coming. I have a spare
controller. I just need to know when the existing one failed.

I would like to monitor this with a PC input device that can handle an
input of some kind. Like an RTD or even a 120VAC pulse. The controller
switches the element to ground so I'm not sure how to pickup the 120
pulse.
I know you smart guys can come up with something I can use to see that
this dam thing is heating and defrosting the freezer coil.
Thanks Guys,


Are you capable of writing the software necessary to monitor an
external device? what sort of PC? An old one running DOS is a piece of
cake if you use the game port, or even a serial port and one of the
RTS/CTS pins. You might even get away using one of the input pins on a
parallel printer port.

If you want it to be monitored using a Windows based computer, then it
gets a wee bit more complicated. Perhaps what would be easier and
cheaper would be a freeze monitoring device with an alarm bell.

Paul
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Dan wrote:
I know this is off topic, but I know some of you know the answer.

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.

It is the defrost coil on my freezer. I have had more than one defrost
controller fail. One failed at Christmas and one at Thanksgiving. I
would like to monitor the temperature of the coil using my PC over
time so I can see that the temperature has increased and then
decreased over some time, probably 24 hrs.

When the defrost controller fails, the freezer freezes up over a 2
week period. If I can find a way to verify that the heating element is
heating or not, I can tell if I'm headed for trouble.
This is a 5-year-old Maytag. Expensive, so throwing it out isn't an
option. I just want to see a freeze-up coming. I have a spare
controller. I just need to know when the existing one failed.

I would like to monitor this with a PC input device that can handle an
input of some kind. Like an RTD or even a 120VAC pulse. The controller
switches the element to ground so I'm not sure how to pickup the 120
pulse.
I know you smart guys can come up with something I can use to see that
this dam thing is heating and defrosting the freezer coil.
Thanks Guys,



An initial thought would be a DVM with thermocouple input and RS232
output. These are available relatively cheaply these days. You might
find one with monitoring software or you may have to knock up a simple
app to pick up the data.
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Dan writes:

I know you smart guys can come up with something I can use to see that
this dam thing is heating and defrosting the freezer coil.


Radio Shack sells cheap DVMs with PC interface. You can just monitor the
voltage across the defrost coil to detect whether it is on or off.

There are more clever ways to roll your own PC-interface line voltage
detector, but the Radio Shack product is just ready to go.

I've used this method to log water heater duty cycles and disprove the myth
that idling water heaters waste (any significant amount of) power.


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Dan wrote:
I know this is off topic, but I know some of you know the answer.

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.

(...)

http://www.amveco.com/pdf/AC1020_11-01.pdf
http://rocky.digikey.com/WebLib/Amve...15,AC-1020.jpg

This is Digikey TE-1020-ND, a current transformer. Its small and will fit within a 1" cube.
Disconnect the defrost heater and thread its wire through the hole in the middle of this
part, then reconnect it. Solder a 100 ohm 1/8W resistor across the output of the
transformer. Every amp flowing into your defrost heater will now be indicated by a
voltage of about 0.1V AC at the output of the transformer, across the resistor.

Connect one of these loggers (US$25.00)to the output of your current transformer and log
the data to your PC.

http://www.dataq.com/products/startkit/di194rs.htm

That's what I would do.

--Winston
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"Winston" wrote in message
newsjLsj.4753$rh.1058@trnddc02...
Dan wrote:
I know this is off topic, but I know some of you know the answer. I need
to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.

(...)

http://www.amveco.com/pdf/AC1020_11-01.pdf
http://rocky.digikey.com/WebLib/Amve...15,AC-1020.jpg

This is Digikey TE-1020-ND, a current transformer. Its small and will fit
within a 1" cube.
Disconnect the defrost heater and thread its wire through the hole in the
middle of this part, then reconnect it. Solder a 100 ohm 1/8W resistor
across the output of the transformer. Every amp flowing into your defrost
heater will now be indicated by a voltage of about 0.1V AC at the output
of the transformer, across the resistor.

Connect one of these loggers (US$25.00)to the output of your current
transformer and log the data to your PC.

http://www.dataq.com/products/startkit/di194rs.htm

That's what I would do.

That's what I would do also. Or you could find a toriod choke coil and do
the same. It could even light a LED for direct visual indication.

Tom


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Dan wrote:

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off.

When the defrost controller fails, the freezer freezes up


How about a low tech approach. You're not checking temp, but need to
know if the controller is cycling power.
Buy a cheap HH/MM/SS timer. Set it to NN hours. Put a relay coil across
the heating element terminals. Wire the relay contacts across the timer
reset contacts to reset the timer. If the timer is not reset, the alarm
goes off. The dog then barks, alerting you to the need to change
controllers.


Kevin Gallimore

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"Gunner Asch" wrote in message
news
On Wed, 13 Feb 2008 23:46:43 GMT, Winston
wrote:

Dan wrote:
I know this is off topic, but I know some of you know the answer.

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.

(...)

http://www.amveco.com/pdf/AC1020_11-01.pdf
http://rocky.digikey.com/WebLib/Amve...15,AC-1020.jpg

This is Digikey TE-1020-ND, a current transformer. Its small and will fit
within a 1" cube.
Disconnect the defrost heater and thread its wire through the hole in the
middle of this
part, then reconnect it. Solder a 100 ohm 1/8W resistor across the output
of the
transformer. Every amp flowing into your defrost heater will now be
indicated by a
voltage of about 0.1V AC at the output of the transformer, across the
resistor.

Connect one of these loggers (US$25.00)to the output of your current
transformer and log
the data to your PC.

http://www.dataq.com/products/startkit/di194rs.htm

That's what I would do.

--Winston



Wouldnt it be better to use a thermistor and have it actually tell if
there is a temperature change, rather than just power on the heating
coils? If you have an open in the coils..you will have power, but no
heat.


You will have both, voltage and current. That equals power (heat).

Using the current transformer means you don't need to disturb any factory
wiring and gives excellent isolation.

Sometimes the defrost heater is really buried inside the unit and would be a
pain to get to place the thermister (or any temp probe). Since he already
replaced the timer, it's a good bet the heater is bad or intermittent.

Tom


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One thing to remember on this go bad all the time stuff -

My stove was under insurance covered. But I paid a walk in fee.

On the third controller for the kitchen range - I was there every second.
Trouble shooting skills were lacking - they were 'black box' exchange guys.
The controller was replaced and it worked - then I moved a wire within.
It went out just like before. This burnt looking wire was ok - the
far end was to a pcb trace and it was not soldered! It had been working
on press fit and a hope.

I showed it to the tech and he wondered how that could be fixed.
I went to the shop and got a few tools - taught him how to solder.

I hope he got an iron at Radio shack, but those guys - service calls
keep them paid. Mine hasn't failed yet.

Might be something like that on the far end of the harness - wire vibrates off
a screw...

Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


Tom M wrote:
"Gunner Asch" wrote in message
news
On Wed, 13 Feb 2008 23:46:43 GMT, Winston
wrote:

Dan wrote:
I know this is off topic, but I know some of you know the answer.

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.
(...)

http://www.amveco.com/pdf/AC1020_11-01.pdf
http://rocky.digikey.com/WebLib/Amve...15,AC-1020.jpg

This is Digikey TE-1020-ND, a current transformer. Its small and will fit
within a 1" cube.
Disconnect the defrost heater and thread its wire through the hole in the
middle of this
part, then reconnect it. Solder a 100 ohm 1/8W resistor across the output
of the
transformer. Every amp flowing into your defrost heater will now be
indicated by a
voltage of about 0.1V AC at the output of the transformer, across the
resistor.

Connect one of these loggers (US$25.00)to the output of your current
transformer and log
the data to your PC.

http://www.dataq.com/products/startkit/di194rs.htm

That's what I would do.

--Winston


Wouldnt it be better to use a thermistor and have it actually tell if
there is a temperature change, rather than just power on the heating
coils? If you have an open in the coils..you will have power, but no
heat.


You will have both, voltage and current. That equals power (heat).

Using the current transformer means you don't need to disturb any factory
wiring and gives excellent isolation.

Sometimes the defrost heater is really buried inside the unit and would be a
pain to get to place the thermister (or any temp probe). Since he already
replaced the timer, it's a good bet the heater is bad or intermittent.

Tom




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This is exactly what I was looking for. Thank you guys.

As far as why the defrost controllers are failing, I feel it is a
manufacturing problem. I took the cover off the latest failed
controller and found a burnt capacitor. 22uf 50V. I bought 3 of them
for $.75. I'll solder it in and have a spare.

I did a search on the web for
Maytag MSD2556AEW defrost controller failure and found a ton of
information. These things are failing at a high rate. And they fit
several model refrigerators. The next one that goes, I'm going to
extend the wires so the controller and plug sit on the top shelf and
changing it will take about 30 seconds, instead of the 1 hour it takes
me now.
Thanks again for all your suggestions.
Dan

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Dan -

What do you mean burned up on the capacitor ?

It is an electrolytic or is it a plastic drop looking ?

If a drop looking - that is the issue bad manufacturer of Tantalum caps.
This was long time a problem - PC motherboards and so many others.

You can replace it with a wet slug or tubular type or pick a new company.
Be careful how you solder drops in - or any for that matter - there are
+ and - ends on them and in reverse they will burn.

That might be the issue - they might have a design goof and mark one lead
as + when (and only maybe) it is -.

You would have to measure the voltage across it - the higher + is on the
red dot side or the + side. If it is in reverse - we found the bug.

TWN issued lots of these in their plants. Might be starting again.
Often the burned is the center of the tip is burnt. It might all glow!
Martin

Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
http://lufkinced.com/


Dan wrote:
This is exactly what I was looking for. Thank you guys.

As far as why the defrost controllers are failing, I feel it is a
manufacturing problem. I took the cover off the latest failed
controller and found a burnt capacitor. 22uf 50V. I bought 3 of them
for $.75. I'll solder it in and have a spare.

I did a search on the web for
Maytag MSD2556AEW defrost controller failure and found a ton of
information. These things are failing at a high rate. And they fit
several model refrigerators. The next one that goes, I'm going to
extend the wires so the controller and plug sit on the top shelf and
changing it will take about 30 seconds, instead of the 1 hour it takes
me now.
Thanks again for all your suggestions.
Dan

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It is an electrolitic cap. When I looked at it the end had popped out
and some of the goo came out.
I made wure to mark which way it came out so I put it back in
correctly.
The second controller lasted for about 15mos. Hopefully, if I get the
now spare board fixed, I'll never need it.
Dan


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On Feb 13, 5:21*pm, Dan@ (Dan ) wrote:
I know this is off topic, but I know some of you know the answer.

I need to monitor the temperature of a heating element. I need to know
when it is on and when it is off. I don't need to know the
temperature, just that when it is getting hot and when it is not hot.

It is the defrost coil on my freezer. I have had more than one defrost
controller fail. One failed at Christmas and one at Thanksgiving. I
would like to monitor the temperature of the coil using my PC over
time so I can see that the temperature has increased and then
decreased over some time, probably 24 hrs.

When the defrost controller fails, the freezer freezes up over a 2
week period. If I can find a way to verify that the heating element is
heating or not, I can tell if I'm headed for trouble.
This is a 5-year-old Maytag. Expensive, so throwing it out isn't an
option. I just want to see a freeze-up coming. I have a spare
controller. I just need to know when the existing one failed.

I would like to monitor this with a PC input device that can handle an
input of some kind. Like an RTD or even a 120VAC pulse. The controller
switches the element to ground so I'm not sure how to pickup the 120
pulse.
I know you smart guys can come up with something I can use to see that
this dam thing is heating and defrosting the freezer coil.
Thanks Guys,


If you are going to build something, why not a general-purpose power
line current recorder? You should be able to recognize the defrost
cycle heater current and see it shut off after the thermostat trips.

Jim Wilkins
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Dan wrote:
Do you know why the previous cap failed? What steps have you taken to be sure the new cap doesn't fail? What other components failed or were weakened?



No I don't know why the cap failed. I'm hoping it was just a bad cap.


It *is* possible that this one component failed and you repaired the board by replacing
the cap. That is not a safe bet however. Fast forward 15 months. You will be very
unhappy if the currently installed board fails and your 'repaired' board is revealed to
have other issues which prevent it from working properly. You are now into a third board
that you need to purchase during another 'refrigerator emergency'.

Disclaimer: I own a Maytag fridge as well and am not looking forward to dealing with their
design issues:
http://www.applianceblog.com/mainfor...php/t-223.html


Anyhow, best of luck to you.

--Winston


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I read all that also. Doesn't bode well for hte Maytag repairman.
I hope the cap is an isolated incedent, but I guess I'll find out.
Maybe don't run your refrig on a generator, which I believe started
this whole mess.
Dan
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Dan wrote:

I read all that also. Doesn't bode well for hte Maytag repairman.
I hope the cap is an isolated incedent, but I guess I'll find out.
Maybe don't run your refrig on a generator, which I believe started
this whole mess.
Dan


I wouldn't blame the generator.
Maytag is the Chevrolet of appliances.
Not at all good RWT reliability but it has the best reputation that advertising dollars
can buy.

In 2004, I said 'Enough of this, I'm buying an *Amana*.'
http://en.wikipedia.org/wiki/Amana_Corporation

'.....D'oH!'

--Winston
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On Thu, 14 Feb 2008 17:10:52 GMT, Winston
wrote:

Dan wrote:

It is an electrolitic cap. When I looked at it the end had popped out
and some of the goo came out.

Do you know why the previous cap failed? What steps have you taken to be sure the new cap
doesn't fail? What other components failed or were weakened?
I made wure to mark which way it came out so I put it back in
correctly.
The second controller lasted for about 15mos. Hopefully, if I get the
now spare board fixed, I'll never need it.


1. Do you really want to be in the refrigerator repair business?
2. Do you have a way to test the repaired board?


--Winston

Being 5 years old it is quite possible the cap was made with the
"counterfeit" electroloyte that was in circulation at that time.
Many e0caps made in that era have died an early death.

--
Posted via a free Usenet account from http://www.teranews.com

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What's that Lassie? You say that Dan fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Thu, 14 Feb 2008 02:53:47 GMT:

As far as why the defrost controllers are failing, I feel it is a
manufacturing problem. I took the cover off the latest failed
controller and found a burnt capacitor. 22uf 50V. I bought 3 of them
for $.75. I'll solder it in and have a spare.



you can always use a higher voltage cap. in its place. Might last
longer if it is failing from over voltage spikes.

Dan
--

Dan
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"Richard J Kinch" wrote in message
. ..

You can just monitor the
voltage across the defrost coil to detect whether it is on or off.


That lashup won't detect any problem if the heater element happens to burn
out (it happens all the time) I think a thermocouple is the better idea, that
removes all doubt.

Vaughn


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