Ken Wright wrote:

I recently purchased a Sunbeam electric blanket. It
works ok except that its lowest setting is a bit too
high for my liking and I am looking for ways to reduce
its output.

I have read online that they use a heating wire with
a high positive temperature coefficient of resistance so
that it is not only a heater but also a temperature
sensor. I have monitored the current draw. When turned
on the current starts at 2 amps and gradually drops to
near an amp before the controller switches off.

Has anyone opened up one of these controllers? The product
description says it is solid state and noiseless and that if
there is an error condition the controller light will flash.
It sounds like it might have a microprocessor but I am
reluctant to open up the controller on a brand new item which
has a 5 year warranty if there is nothing inside which I can
tweak to lower the lowest setting.

My thinking now is that if it is microprocessor controlled it
would be difficult to modify. My first thought was to lower
the input voltage but I think the microprocessor would be able
to compensate.

Any ideas?

thanks
kw




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There must be a PTC (positive Temperature Coefficient) resistor in it.

Measure the value are room temperature and and place a small value
R in series with it to off set the calibration so that it'll operate
at a cooler level.
Or, reposition the PTC closer to a heating wire, it could of slip out
of the original position.


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