Either will be dangerously hot. You were measuring the outside casting
though and the heat is generated in the coils which I expect got quite a
bit hotter at least for a short time.
So, anyone care to guestimate what temp one wants to keep a spinning
etek under? Like Chris says, the spinning part is really important.
I wasn't even going very fast when mine let go. Maybe 20 mph - tops.
I checked the temp within 3 minutes of the event on the outside of
the case and it was 160 F. (I checked, it was indeed Fahrenheit.)
I'm looking at some thermal switches by Airpax:
http://www.airpax.net/site/sensing/bimetal/index.html
http://www.airpax.net/site/utilities/eliterature/pdfs/Airpax_SCSF_6700_0607.pdf
http://www.airpax.net/site/utilities/eliterature/pdfs/Airpax_SCSF_6600_0607.pdf
http://www.airpax.net/site/utilities/eliterature/pdfs/Airpax_SCSF_6500_0607.pdf
Here's what's percolating in my mind:
Plan A)
Have three switches set to trigger at 3 different temps. Two
normally open and one normally closed.
Switch A closes at X degrees. This turns a fan on.
Switch B closes at X+ degrees. This turns a light on to warn of
impending shutdown.
Finally, switch C opens at X++ degrees. This is in series with the
main contactor and shuts the power to the motor off but still allows
the dc/dc converter to power the cooling fan.
Plan B)
Uses a Dallas Semiconductor DS18B20 (or similar) sending signals to
your micro. The micro controls the fan and main contactor.
Maxim has pretty wide selection of thermal switches, temp doodads and
other hot/cold related things. I haven't had a chance to go over
their site much yet:
http://www.maxim-ic.com/products/sensors/
Mike
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