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My computer does "Morse Code" when I run my VTTC!

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LAN_403

Cool Dude Clem

Sun Mar 29 2015, 05:35PM

Registered Member #53981 Joined: Tue Dec 16 2014, 02:23AM
Location:
Posts: 7

This is something that really spooked me, but it's true, I was just tinkering with a VTTC project, and as soon as I started it running, my computer made random beeping noises, as if someone was doing Morse code on it! Obviously it's messing my computer up, but HOW in the world is it making it do THAT? I would just expect maybe a single beep from the little built in piezo buzzer and the computer to lock up, but these beeps are coming out of the speakers, what's even more weird is that the beeps continued for a couple of seconds even after I turned my coil off. it seems to happen even more often when I'm not getting much output from my coil.

PLEASE Reply with a solution of HOW I can stop this happening, I don't want to fry my computer with interference from my TC experiments, it cost a bomb to build.

hen918

Sun Mar 29 2015, 06:57PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

I wonder if there is a harmonic in the audible frequency being picked up by the unshielded wire from the computer to the speakers, and being amplified and output?
Does the noise persist after the speakers are unplugged from the computer?

Cool Dude Clem

Sun Mar 29 2015, 07:12PM

Registered Member #53981 Joined: Tue Dec 16 2014, 02:23AM
Location:
Posts: 7

Strange thing is like I said before, the beeps continued for a couple of seconds after I tuned the coil off, it's definitely the computer itself producing the 500hz beeps (that's about what frequency it sounds like), and yes when I turn the computer off and try my coil again the beeps do not happen.

Dr. Slack

Sun Mar 29 2015, 07:51PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Large amounts of EMI from a coil are quite capable of causing soft errors in a nearby PC. Once you have such errors, *anything* can happen, beeps sound like the least of it.

What you have there is an ideal experimental rig for studying the effectiveness of EMI containment for the TC, and EMI hardness for the PC. Normally, neither of those are particularly bad, so I would suspect you are doing something to exacerbate the interference, some sort of unintentional radiator.

Happy learning!

...

Sun Mar 29 2015, 08:53PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

What operating system are you running?

Many linux kernels will attempt to beep out debugging information through Morse code (IIRC the one which ships with Debian tries to use the numlock light, but it is not much of a stretch to assume that some are configured to use the system beeper). Many BIOSs will also beep out status codes under fault conditions, although I have only seen computers which do this at boot.

One other, unlikely, possibility is that it is actually your phone causing some EMI. It is quite common that GSM based cell phones will cause a Morse code like sequence of beeps in poorly shielded audio amplifiers (although these beeps are not actually morse code) when they are communicating with a tower, especially right before receiving a call. So I propose that it is possible that you have your cell phone sitting close to your computer, and that when you turn on your coil you cause enough interference to 'wake up' your phone and start it searching for new towers, which then causes noise on your computer speakers.
I encountered a situation similar to this back when I was in high school, on my commute to school I drove past a house which was clearly being used for some type of HAM/CB/etc use (gigantic antenna tower with a number of HF antennas and possibly some higher frequency stuff), and one week I noticed that right as I drove past the house my car radio would start to beep unexpectedly. I recognized the beeping patters as the GSM phone interference, and turned my phone off the next day and the beeping stopped.

Cool Dude Clem

Sun Mar 29 2015, 09:24PM

Registered Member #53981 Joined: Tue Dec 16 2014, 02:23AM
Location:
Posts: 7

I don't even have a cell phone, I've never wanted or needed one, and I'm on Windows 7, I tried Linux Mint 17 a few weeks ago and all I got from it was crashes and errors no matter what I tried, so I went back to Windows 7.

Antonio

Mon Mar 30 2015, 12:40AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

This is probably interference through the keyboard. Some keyboards beep if a key is pressed for too long time or if several keys are pressed simultaneously. The interference is simulating this. Better do not operate the VTTC close to the computer.

Sigurthr

Mon Mar 30 2015, 05:04AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

As for solutions; three words: proper RF grounding.

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