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  • #31
    Well I looked around today and didn't see anything I liked. I'll keep looking. In the meantime I checked the resistance of a roll of wire I have. 7 ohms. I have a transformer that will power that to about 40 watts. I have some blanket materials that would be perfect- so I could do it- I'll hold off for now. I do plan to get myself checked out soon- I know, everybody says that right- it's on my do list. In the meantime if I can keep the house temperature down and still sleep warm enough, I can save more of my pension for other needs. A little bit of 'point of use warmth' for my feet and I'll be good. We'll see what I might find tomorrow.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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    • #32
      The wife was using an electric heating pad on her leg that overheated and burned her badly. She was asleep and the burn occurred so slowly she didn't notice it till she woke up. Cooked the meat all the way to the bone. Very long recovery time. She now only uses a hot water bottle.

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      • #33
        I took an electric blanket apart and salvaged the wire. Ohmed it out and cut it to a length that would make 10 watts of heat with 12vdc. Made electric grips for my motorcycle. Back in the day when I was young enough to ride in freezing temps. The wire I used was very difficult to solder, had to use crimp connectors or special flux.

        You could repurpose electric blanket wire to make a 1' x 2' pad with 10-20 watts at most any DC voltage you have handy.

        Mike

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        • #34
          Well I bought one. Sunbeam throw. Three speed and probably digital too- has a timer.
          I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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          • #35
            This will work for you. https://www.amazon.com/Heating-Snugg.../dp/B0014LJKUA

            Heat in a microwave, and It will retain heat all night. Whatever try use for a filling in it, melts when heated, and solidifies as it cools.

            They make microwave heatable pads in lots of shapes, filled with rice, flax seed, clay…. Wife has tried them all, none of them retain heat like the link above.
            Last edited by Hawkeye; 10-05-2021, 01:42 AM.
            When I get Time... I'll...

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            • #36
              Originally posted by darryl View Post
              Well I bought one. Sunbeam throw. Three speed and probably digital too- has a timer.
              I bought a 12" x 15" 50W max Sunbeam awhile back at Princess Auto (surplus section) and I really like it. I think I will splurge and pic up a full sized electric blanket this fall before winter sets in.
              Location: Saskatoon, Saskatchewan, Canada

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              • #37
                Well, the first thing I liked was climbing into bed and it was already warm. Funny thing- usually I can move my legs around and find the cooler spots- for when my feet are hot- but now when I move around it's only warmer spots. That just proves that my body is absorbing the heat, which is good- I'm not complaining. I woke up early this AM with the sheets and blankets all over the place. I got up and put it all back together, then went back to bed. Woke up later and it was the same again. I don't usually destroy the bed to that extent. I am a restless sleeper so I expect some of that- this was beyond what is normal though. Still not complaining.
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                • #38
                  Oh, for Pete's sake!

                  We all, well most of us, know that. But after some, SHORT period of time, a DC circuit will settle down to a point where it is not possible to measure any difference. Sure, some pulse of EM energy is traveling out to the far corners of the universe from the last time (or the first time) that I switched my pocket flashlight on, but I defy you to show me an instrument that can detect it.

                  As for a DC circuit that will be turned off at some future time, that would be getting into some real hairy areas of physics. Way beyond my pay grade or lowly BS degree thereof.

                  In the real world, we classify circuits as AC and DC and we treat them accordingly.



                  Originally posted by J Tiers View Post

                  Well if there WERE anything to be called "DC", that would be true. But there is not!

                  True DC would always have been flowing, and will never stop. Everything else is a varying current, and so not really DC.

                  You can turn a switch and begin drawing current from a battery. You say "that's DC". But, there was a time when it was not flowing, a time during which it flowed, and now, the battery is exhausted, so it is no longer flowing.

                  When the switch was turned on, there was a change in electromagnetic field. That change propagated outward. You could hear it on an AM radio, for instance, at a distance and a slight delay in time, proving that propagation. The change as it stopped flowing when the battery was exhausted also propagated outward, although it may not have been detected on a radio, as it would be outside of the frequency range the radio could detect.

                  What you made was a single pulse of what could be a square wave, albeit a low frequency one. That clearly could, and would, propagate.

                  Does that really change anything? In general, probably not. But if you are talking about "definitions", it is a significant matter.
                  Paul A.
                  SE Texas

                  And if you look REAL close at an analog signal,
                  You will find that it has discrete steps.

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                  • #39
                    Well, the DC circuit's magnetic field also is everywhere.... after a delay while it travels there.

                    There was comment about the lack of a field with DC.... 'tain't so.

                    Originally posted by J Tiers View Post
                    ...............

                    Does that really change anything? In general, probably not. But if you are talking about "definitions", it is a significant matter.
                    2730

                    Keep eye on ball.
                    Hashim Khan

                    Everything not impossible is compulsory

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                    • #40
                      Originally posted by J Tiers View Post
                      Well, the DC circuit's magnetic field also is everywhere.... after a delay while it travels there.

                      There was comment about the lack of a field with DC.... 'tain't so.

                      You're probably referring to my original remark. What I said was "with DC electromagnetic effects will not be negligible, they'll be nonexistent". It never occurred to me that I should have said "an electromagnetic field", because -well- who would be confused? (Yes, I know you're not confused.)

                      Anyway: yes, a DC current will set up a magnetic field. That's how DC electromagnets work. But, as you know perfectly well, it takes a changing current to establish an electromagnetic field. And not your rather silly remark about when the DC is first turned on, but Paul A. has covered that nicely - yes, there might be a keyclick pulse.

                      As has been mentioned, the energy in an electromagnetic field is described by the formula E = hv (sorry, can't find the characters for h-bar and nu)*. Since the frequency of the DC current is -yes- zero, the energy in the alleged photons would also be zero. Zero energy photons do not exist.

                      Anyhow, this has been entertaining and I trust all of us know that we're just bantering now. Please, no demands for a duel at dawn. I'm too old for that.

                      -js


                      *https://en.wikipedia.org/wiki/Nu_(letter) and https://en.wikipedia.org/wiki/Planck_constant
                      There are no stupid questions. But there are lots of stupid answers. This is the internet.

                      Location: SF Bay Area

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                      • #41
                        It's pretty negligible, for sure.

                        But not really "silly". There is energy in a magnetic field. If it is constant (DC), it is a fixed energy being "stored". If it is changing, the energy is being added to or removed.

                        The "keyclick" is detectable at a distance. And after a travel time delay. So it is being transmitted, the field is expanding, and the energy is becoming spread out, as well as lost to things like your AM receiver antenna, etc.

                        The energy will continue to be spread out (transmitted) until it is absorbed by the universe, and no longer exists aside from a very tiny amount of heat. So it is not entirely correct to say that there is no propagating EM field. Nor that there is no energy. The field is created, and it expands, but it's energy is not added to, once the current reaches it's final value and no longer is changing. That is actually asymptotic, so it never reaches a final state, but within a reasonable time further change is very theoretical (and below the minimum quantum of energy).

                        The field inside the loop is constant, so long as the loop area is not changed. That outside is expanding, and so energy density is decreasing with time

                        Any variation of current is also transmitted as a propagating EM field.

                        Again, this really has no practical significance, but from the standpoint of theory and definitions, it is true.

                        No need for knives at daybreak, whether they be magnetized or not.😉
                        Last edited by J Tiers; 10-05-2021, 10:50 PM.
                        2730

                        Keep eye on ball.
                        Hashim Khan

                        Everything not impossible is compulsory

                        Comment


                        • #42
                          Originally posted by darryl View Post
                          Well I bought one. Sunbeam throw. Three speed and probably digital too- has a timer.
                          You will find that electric heat is sort of like sex, a bit awkward at first, but you will find yourself reaching for it on a cold night.

                          Sarge41

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                          • #43
                            A duel at dawn- almost seems like what I'm experiencing . So far every day I wake up with the bed destroyed- one blanket off one side, another off the other side, the heating blanket off one way or the other. The top sheet could be anywhere- this morning it was bundled up on one side of the bed. I must be machining in my sleep. Somebody told me yesterday that maybe my feet are getting too hot now and in my sleep I'm thrashing around subconsciously trying to cool them off.

                            I'll try a new strategy- since the thing is made for a three hour on time, I'll start it an hour and a half before I go to bed. Then it will only be on for another hour and a half. I'll have to leave it at one heat setting since I think that the timed period is from the last setting change.

                            I'm still not complaining- I am liking it. Maybe what I can do is pin the top sheet edges to the top blanket using some super magnets- hmm.

                            One thing I found was the controller gets fairly warm- I could use it as a hand warmer-
                            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                            • #44
                              It sounds as if you do not tolerate the heating very well. I don't either.

                              Your strategy of pre-heating the bed sounds right. And it has a long history.... bed-warming pans were used long ago to warm up the bed before getting in. You get the benefit of a warm place in bed without the all-night extra heat. The heat will dissipate, but by then your toes are warm enough and you can get to sleep without thrashing.

                              Those blankets must have an on-off switch. Just get in, and if all is warm, simply turn it off.

                              Or, delete the electric blanket, and warm your feet on a heating pad before hitting the sack. Warm feet let you sleep, cold feet do not..
                              2730

                              Keep eye on ball.
                              Hashim Khan

                              Everything not impossible is compulsory

                              Comment


                              • #45
                                I use a "Hot Pocket" by Sierra Madre Research, US company. Made for camping is battery powered initally meant for warming sleeping bags. Two settings, one about body temperarure runs longer, one setting a bit higher on timer. A bit pricey. Portable I can use it anywhere as in my car.

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