Electric blanket driving me nutz!!

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shawn73

Member
Location
Napoleon, Ohio
How's that for a catchy subject. Here's a question to help my wife from killing me in my sleep!! (Just Kiddin') I bought this nice electric matress pad, (Brand-Spring Air) dual controls, low voltage operation, and everything. Should have been great, huh?? No. It has a pulsating static sound in our baby monitor when power is off to the blanket, and when it is on it's a constant static in the monitor and even messes up the TV! It has a 120VAC in and 14VDC out power supply. I wired up a small box with an in line filter hoping to take care of the problem, but it didn't work. Any ideas?? Why does this happen?? Thank you.
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
Re: Electric blanket driving me nutz!!

It happens because

(1) The Baby Monitor uses a radio frequency signal that is transmitted between the baby?s room and yours, and

(2) The electronic device that controls the temperature electric blanket, like every other thing that carries current, creates around itself an electromagnetic field, but unlike most other things that carry current, this one is very much non-linear, and finally,

(3) The two signals interfere with each other.

Please note that even when the blanket is turned off, the electronic controller is not turned off (unless you unplug the blanket). It will still create a field, though not as severe as when the blanket is turned on.

My suggestion is to separate the two as much as you can. For example, can you place the Baby Monitor in a far corner of your bedroom, then turn its volume up high enough that you would still be able to hear it? Try that, and see if the interference problem goes away, or is at least reduced.
 

roger

Moderator
Staff member
Location
Fl
Occupation
Electrician
Re: Electric blanket driving me nutz!!

Ryan, I knew somebody was going to ask that, so I didn't. ;) :eek:

Roger
 

physis

Senior Member
Re: Electric blanket driving me nutz!!

If the 14 VDC is produced by a switching supply the reynolds wrap and concrete is probably the only solution. Seriously shielding would help.

If it's a linear supply or a triac output, you could try connecting a .05uf capacitor rated at a couple hundred volts across the output. If the noise exists there that should shunt it.
 
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