Running electric blanket on DC?

--Getcher self a couple of warm doggies; works wonders, heh.

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http://www.nmpproducts.com/intro.htm
---Decks a-wash in a sea of words---

On Fri, 03 Dec 2004 22:42:23 +0100, Rudolf Zeitschek wrote:

Don Kelly schrieb:
"Eric R Snow" <etpm@whidbey.com> wrote in message
I envision a full wave rectifier and a capacitor. And it looks like
there is enough room in the control for these extra parts. Is there
anything inside the blanket itself that precludes Dc operation?
Thanks,
Eric R Snow,

--------

It could be done but I wouldnt recommend it. The thermostat switch would
likely fail quickly and start a fire as it is much harder to interrupt DC.
What you would be doing is trading an insignificant (if present) hazard for
a much greater one. Much safer to leave it alone.

I agree and would like to mention a further problem:
If you just rectify (without filtering by a condenser) you get the same
heat, but you still have a lot of alternating current (and field).
If you filter to get pure DC, you need a very large condenser and ir
will give the peak voltage (165v for 117V AC) and the blanket will
overheat.....

I'd be worried about any modification to an electric blanket. How does the
thermostat actually sense the temperature of the blanket? Isn't the
resistance of the element itself the sensor? If so, then any messing with
it will upset its operation.

I agree with that other poster - leave the AC, because a DC magnetic field
will cause your blood to pool. ;-) Tell the wife you did some research and
found out that AC is actually beneficial! We're engineers, we ought to
know!

Good Luck!
Rich

On 3 Dec 2004 17:42:27 -0800, billb@eskimo.com (William J. Beaty)
wrote:

Eric R Snow <etpm@whidbey.com> wrote in message news:<rvgvq0hgrsmpr61bnb14sm25o4clg6adhb@4ax.com>. ..
Greetings All,
I know this is silly but here it goes:
My wife and I keep our bedroom un-heated so it gets cold in the
winter. An electric blanket warms the bed before we get in. My wife
would like to keep it on all night instead of using all the extra
covers but is concerned that the "electrical magnetic field" emanating
from the blanket will give us cancer or something.

Does the blanket generate a strong EM field? WHy not find out?

If you hook a coil to the input of an audio amp, then listen to
the amplified output using headphones, you can easily hear the 60Hz
magnetism detected by the coil. For instance, wave the coil around
an AC wall clock motor, or around an old-style (non-electronic)
fluorescent light ballast. BUZZZZZZ! Once you can detect strong
AC magnetic fields, wave your coil around the electric blanket and
see if it's stronger than, say, standing under a fluorescent ceiling
light.

Here's a great little $12 amp. All hobbyists should have one
of these (I have several. They have lots of uses.) :

Mini audio amplifier w/speaker, 9V
http://www.radioshack.com/product.as...%5Fid=277-1008


That, a couple of mini-jacks, and a telephone pickup coil, and
you're ready to scan the environment for those lethal 60Hz hums.


Telephone pickup coil
http://www.radioshack.com/basket.asp...%2D533%2C&iGo=


When I did this years ago at home, I discovered that the whole
house was full of 60Hz b-fields. It was wired with old-style
knob-and-tube wireing, where all of the conductors are several
feet apart, rather than being twisted together inside a steel pipe.



((((((((((((((((((((((( ( ( (o) ) ) )))))))))))))))))))))))
William J. Beaty Research Engineer
beaty@chem.washington.edu UW Chem Dept, Bagley Hall RM74
billb@eskimo.com Box 351700, Seattle, WA 98195-1700
ph206-543-6195 http//staff.washington.edu/wbeaty/
Greetings William,

Thanks for the link to the amp and the ideas to use it. I can already
think of other uses for it.
Eric R Snow

On Tue, 07 Dec 2004 20:20:29 GMT, Rich Grise <rich@example.net> wrote:

On Fri, 03 Dec 2004 22:42:23 +0100, Rudolf Zeitschek wrote:

Don Kelly schrieb:
"Eric R Snow" <etpm@whidbey.com> wrote in message
I envision a full wave rectifier and a capacitor. And it looks like
there is enough room in the control for these extra parts. Is there
anything inside the blanket itself that precludes Dc operation?
Thanks,
Eric R Snow,

--------

It could be done but I wouldnt recommend it. The thermostat switch would
likely fail quickly and start a fire as it is much harder to interrupt DC.
What you would be doing is trading an insignificant (if present) hazard for
a much greater one. Much safer to leave it alone.

I agree and would like to mention a further problem:
If you just rectify (without filtering by a condenser) you get the same
heat, but you still have a lot of alternating current (and field).
If you filter to get pure DC, you need a very large condenser and ir
will give the peak voltage (165v for 117V AC) and the blanket will
overheat.....

I'd be worried about any modification to an electric blanket. How does the
thermostat actually sense the temperature of the blanket? Isn't the
resistance of the element itself the sensor? If so, then any messing with
it will upset its operation.

I agree with that other poster - leave the AC, because a DC magnetic field
will cause your blood to pool. ;-) Tell the wife you did some research and
found out that AC is actually beneficial! We're engineers, we ought to
know!

Good Luck!
Rich

Perfect answer Rich! I'll just say that the engineers on line have

conducted a study and found that ac is actually good for you as it
keeps the blood evenly distributed.
Eric

[jakoalltrades]

Tim, you must not have much respect for women. Who's to say Eric's wife hasn't done an internet search like me and come across your remark?

Eric, women aren't stupid and (sixth sense and all) it is always better to be honest about these things.

Either do the research and lay it in front of her and then decide on it or make whatever change you can to the unit to make it as safe as you can.

I was just looking up the stats on the number of fires/accidents that have occured from 1992-2001 and there was only 1 death and fewer than 20 injuries in the 10 years combined. I think those are damn good odds!

All the best,
Rashmi


[quote="Tim Williams"]"Eric R Snow" <etpm@whidbey.com> wrote in message
news:rvgvq0hgrsmpr61bnb14sm25o4clg6adhb@4ax.com...

Then, I foolishly said that if
the blanket were run on DC we wouldn't need to worry. Now she wants me
to fix the blanket to run on DC.

Meh. Take it apart, look like you're doing something, then put it back
together as it was. As long as she knows you did something, but not exactly
what, she'll buy it.

Tim

[jakoalltrades]

Tim, you must not have much respect for women. Who's to say Eric's wife hasn't done an internet search like me and come across your remark?

Eric, women aren't stupid and (sixth sense and all) it is always better to be honest about these things.

Either do the research and lay it in front of her and then decide on it or make whatever change you can to the unit to make it as safe as you can.

I was just looking up the stats on the number of fires/accidents that have occured from 1992-2001 and there was only 1 death and fewer than 20 injuries in the 10 years combined. I think those are damn good odds!

All the best,
Rashmi


[quote="Tim Williams"]"Eric R Snow" <etpm@whidbey.com> wrote in message
news:rvgvq0hgrsmpr61bnb14sm25o4clg6adhb@4ax.com...

Then, I foolishly said that if
the blanket were run on DC we wouldn't need to worry. Now she wants me
to fix the blanket to run on DC.

Meh. Take it apart, look like you're doing something, then put it back
together as it was. As long as she knows you did something, but not exactly
what, she'll buy it.

Tim

[Cuban Bee]

Then you'll know if I'm quiet or sassy."