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