Static Electricity Fries Garage Door Opener; Faraday Cage Protects?
April 26, 2008 4:22 PM   Subscribe

(Electronics) Is Static Electricity frying my garage door opener, and can a partial Faraday Cage protect it?

In the winter, it is very cold and very dry. Very. Lots of static electricity.

I keep the garage door remote control opener in my jacket chest pocket. It lives there through the winter. To operate the opener, I don't take it out of the jacket pocket; I just press the button through the cloth. The jacket is some kind of synthetic. It crackles with static discharge when I take it off.

(1) Is static electricity harming the remote control? I've gone through a couple. (Alternate culprits might be extreme heat/cold cycles, getting tossed around, low-quality electronics, etc.)

(2) If so, would a partial Faraday cage, e.g., aluminum foil wrapped around most of the opener, protect it? (wrapping it completely blocks the signal that opens the garage door)
posted by coffeefilter to Technology (3 answers total)
 
Physical abuse is much more likely to be the culprit here than static electricity. For one thing, if it's like every garage door opener I've seen, then the case is made of plastic and it's a poor conductor. (For another thing, it isn't grounded so there won't be much current flow.)

Wrapping it in aluminum foil is unlikely to do anything other than convince your friends that you also keep foil in your hat.
posted by Class Goat at 8:04 PM on April 26, 2008


Best answer: Remotes like this are usually pulse-modulated AM transmitters, and again, almost always have a single integrated circuit and a minimum of external passive components. Codes are programmed in via three state switches which tie a series of inputs to V+, Ground, or open circuit. V+ and Ground settings would be less susceptible to static damage, but the open circuit inputs would be more susceptible. (You might try resetting the remote code to all ON or all OFF states as opposed to the middle states.)

Static is high voltage, low current stuff. Because of the high voltages, it has the potential (pardon the engineering pun!) to do things that lower voltages do not, like pierce internal oxide layers essential to the operation of the IC.

Static charges as low as a few volts, when applied to a vulnerable active component, can cause latent and/or immediate damage to an IC.

Most of the parts in your remote aren't too susceptible to static (i.e., switches, resistors, caps, LED (if present)) but the IC would be. It has internal parts that suppress transients, but they have their limits and hundreds of repeated insults can introduce damage.

Since your observations are of static related to your jacket, I'd lean heavily in that direction. Going through more than one remote pretty much tells me that your environment is to blame, and this is the most obvious thing.

Will a foil wrap help? Maybe with the static. It might also impact the range of the device.

You can solder a small cap... 1 uF, 35V across the switch inputs to snub transients there. That and the code reset might help.

BTW, when I was first out of college in the 70's, I had an assignment running an assembly line of primarily women making video games for RCA. We asked the ladies not to wear nylon undies, to minimize static generation on the line. Also, at one test station, test equipment failures happened a lot more frequenty, and when I observed the operator discretely from a distance for an hour or so, I saw her remove and don her nylon jacket repeatedly because the temperature there was unstable, and in the process, she had to remove her static wrist strap and reapply it to get the jacket on/off. THat was the culprit. We improved her thermal environment, the jacket stayed off, and the failures went away.
posted by FauxScot at 6:18 AM on April 27, 2008


Response by poster: Thanks for the responses -- Interesting, that nylon jacket story. That was some good QC/reliability analysis. I checked my jacket tag, and it, too, is nylon. And for wintertime static electricity, the climate here is arctic cold and arctic dry.

I actually did start using the partial Faraday cage towards the end of the winter, and the opener still works. If it survives through all of next winter, I may consider it a success.
posted by coffeefilter at 10:40 PM on April 28, 2008


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