Microwave vs. Computer, and the Microwave is winning.

June 28, 2008 6:43 AM

The kitchen computer has a little trackpad/keyboard combo that sits atop of the microwave. When the microwave turns on, the trackpad stops working. Looking for suggestions on shielding, putting a filter in line with the cable, grounding, anything to help me cook and mouse at the same time.

This has been going on for a while but last night, after some extended nuking of some delicious lasagna, the computer warned me that a USB device was not functioning properly and was disabled, forcing a restart of the whole thing to get the keyboard working again.

So what to do? I know about basic electronics from fixing guitars and such, but not the RF/Magnetic interference voodoo. I'm fully prepared to crack this thing open, get into ferrite beads, soldering, grounding wires, etc. if it will help. Yes, the problem goes away if I move the keyboard a few inches away from the microwave, but the way my kitchen is set up this is really the best spot for things.

posted by sol to computers & internet (5 comments total)

Touchpads work on measuring changes in capacitance.

With your pad so close to a leaky 1000W 2.45 GHz microwave transmitter (aka a Microwave Oven) you are more than likely creating a resonant cavity and loading the pad up with enough charge to overwhelm the circuits. Shielding/filtering the USB cable won't accomplish anything. Grounding will only make it worse. Because you're in the region of the near-field shielding the keyboard for EMI won't probably make any difference at all.

On the other hand, moving the touchpad as far away as you can from that transmitter will help very much.
posted by three blind mice at 7:13 AM on June 28 [1 favorite]

OK, so I'm guessing that the touchpad surface or circuitry in the keyboard next to the microwave case is creating this cavity. Would changing the shape (angling the keyboard) help as well as moving it apart? Is this the kind of situation where subtle changes can have large effects, or is simple proximity the solution?
posted by sol at 7:46 AM on June 28

Not to really answer the question, but if that computer is wi-fi, expect other problems. I've learned to not even bother trying to access anything online while the microwave is on.

In my case, it would be too much trouble to wire the apartment with ethernet, and the modem/router/etc is necessarily across the room from where my desk is. Being somewhat open-concept, there's nothing to block the microwave interference.

To attempt to answer the question, look around at the other cables in your place. There's a good chance you'll find one with one of those oval'ish plastic filters on it. Swipe it temporarily and give it a try.
posted by hungrysquirrels at 9:01 AM on June 28

Is this the kind of situation where subtle changes can have large effects, or is simple proximity the solution?

Proximity.
posted by three blind mice at 9:29 AM on June 28

You could try a different microwave. Seriously, leakage is unit dependent, meaning that even the same model, different unit might have less leakage.

I suspect you will not be successful.

Generally, the operational scenario you have is likely to cause problems. Ferrite beads aren't likely to help, and if you don't have visualization hardware (i.e., a spectrum analyzer and the technical skills to use it and interpret what you are seeing) you're attacking the problem blind.

What you are asking is kind of like 'Hey, why can't I hear this whisper when the vacuum is running?' Physics is unlikely to cooperate with you and your admitted lack of knowledge in this area means pure guesswork.

My best suggestion.... put the trackpad on top of a thick wooden cutting board on top of the microwave. Experiment with vertically separating the two if you can't manage to come up with a better separation. Distance is your friend in this matter. Perhaps you can shield the bottom of the cutting board with a ferrous plate, grounded to the same ground as the microwave. Worth a try.

Spend a reasonable amount of time with your guesses, and if it doesn't work, give up.
posted by FauxScot at 11:22 AM on June 28