Electronic Interference

[Bolster]

This forum is OFF TOPIC, right? Well this is as off topic as it gets.

Have been changing out to LEDs where I can. Got around to putting an LED bulb into the garage door opener at my house.

Suddenly the wife (who has the only car that gets to live in the garage) was unable to open the garage door from outside. Messing with it, it appeared the radio signal’s range had shortened to about 1/3 of what it was previously. If I stood with my nose to the garage door and pressed the remote, it would sometimes open. Any further back, no.

Searched Duck Duck Go for “garage door range suddenly shortened” and got a hit. Answer: Don’t use an LED in a garage door opener, it interferes with the radio signal reception. I swapped the front bulb to a regular incan, and got my remote range back. Oddly, the BACK bulb of the opener can have an LED, but not the front bulb.

This has nothing to do with knives, other than I am making sheaths for knives in said garage. But I hope this will help someone, somewhere, who is searching for the same answer...!

[Bolster]

While we are completely off topic and in the weeds about interference, here's another random oddity I've discovered. If I place my external hard drive at 2 o'clock in relation to my computer, my bluetooth keyboard will stop working.

The idea of tin foil hats doesn't seem so funny anymore.

OK, what's your electronic interference story?

[RustyIron]

OK, what's your electronic interference story?

It's a little late, but electrical noise is a phenomenon that I love to beat my head against. I could write for hours.

About your specific problem, just call it a win and pour yourself a beer for being your wife's hero. We don't know the light circuit of your opener. We don't know the radio circuit of your opener. We don't know the isolation provided by the power supplies in your opener. In other words, we don't know anything about the electronics involved, but we know the solution. Everyone lives happily ever after.

Factors that affect electrical noise are PROXIMITY to other electrical circuits. High current can make a lot of noise. Higher frequencies can make crazy noise. If you have conductors running parallel, they're more susceptible to noise. A lot of time and money has been spent to harden electronics from electrical noise.

One electrical interference story I have is somewhat easy to understand, but it gave other people fits, and took me a while to figure out. It's not hard to understand. I ended up faced with a intermittent problem that had been going on for a long time. The machine was a giant motor that was controlled by a hundred different devices and a handful of computers. Every few days, there would be an error indicating that a mechanical brake had failed. It wasn't something repeatable where I could set it up and then observe. But rest assured, it would fail once or twice a week. The computer was telling the brake to turn on, that's for sure. Was it the brake's power circuit that was acting wacky? Was it the switching circuit? How about the feedback circuit telling the computer that the brake was on/off? Maybe the computer wasn't really telling the brake to turn on. Maybe the computer wasn't paying attention to the signal from the brake telling it that it was on. What to do? What to do?

I finally figured out that the brake was working as intended, but the high current running through motor wiring was inducing noise in the brake feedback circuit. The computer was seeing the noise, and thought there was a problem. I could have a crew come out and route high voltage and low voltage wiring further apart (which is good practice regardless), but I chose to build little suppressor circuits to dampen the noise. In the future, though, installations were built with this problem in mind.

Here's another example that's simple when explained, but could be a challenge to figure out. Automated doors open, people walk through the doorway, doors close, computers go berserk, and that's the end of the story. Alas, people behind closed doors tend to become unhappy very quickly. The problem is simple if you can actually see the symptoms in real time.
Here's how it works: The contactor is a big switch that turns on by a big electromagnetic inductive coil The contractor gets turned on by a computer and an amplifier. The contactor turns the motor on and the door closes. Once the door is closed, the computer turns the contactor off. But here's another little effect that wasn't anticipated: When switched off, the magnetic field of the contactor collapses, inducing back voltage into the circuit. The back voltage is pretty large, the computer see's the noise, goes nuts, and turns itself off... and the people on the other side of the door are sad.

Like I said, I could write for hours, but it's late. Hopefully this has cured your insomnia.

[The Deacon]

I've heard of this happening before, but wonder if it's something specific to certain makes and models of garage door openers. Reason being that I've been using an LED bulb in my 10+ year old Liftmaster Professional 1/2HP, which has just a single front mounted bulb, and in the two overhead light fixtures in my garage for a couple years now without experiencing any problems.

As for interference, no "electrical" stories per se, but when I was into CB radio and hooked up a 50 watt linear amplifier to my base station to boost output my next door neighbor thought she was going nuts because she'd hear my voice coming out of her telephone which was sitting in its cradle at the time.

[Bolster]

Wow, these are fascinating examples. I had no idea I'd stumbled onto such a pervasive phenomenon with effects far more serious than garage doors and keyboards!!

The plot thickens:

https://conversation.which.co.uk/techno ... -dab-test/
https://blog.1000bulbs.com/home/are-my-bulbs-rf-quiet

The Cliff's Notes version, as regards garage door openers:

"check your lighting’s product specifications for FCC Part 18 before you buy"

[bearfacedkiller]

[Naperville]

I stole that tinfoil hat image! That's a keeper. I have a ton of memes, I guess you could say I collect them. Every year or so I put them in a folder and start anew. It's strange to look at them in a few years and see what was trending. Some memes are hilarious and every time that you see them you get a laugh, and laughing is important for sanity.

In the early 80's when I lived in Chicago, somebody on the block had a HAM radio and it would cut into our TVs. We bought filters for the rabbit ears and that took care of it.