I can't think of a lot of worse failure modes

[xela]

I know Microsoft has been selling into the embedded market for a few years now, so I have to wonder if deep down inside our new wall oven runs Windows.....

I picked up some ready-to-bake bread at the grocery store earlier, and just about exactly an hour ago stuck it in the oven. This being the second time we have used the brand new oven.*

About 20 minutes later, I sat down to eat dinner. Just as I was finishing, Chris walked by the oven and stopped and stared at it. I apologized for leaving the light on, and he said, "No - it's still on. I hear the fan."

"I know I hit the off button."

To make a long story short, all the off button appears to do currently is change the display to its normal, oven-off, state: showing only the clock. Without changing anything else: the fan keeps on going, and, more important, the oven keeps on heating.

After about 20 minutes, we rebooted it by turning off the breaker. When we restored power, the display came up with "please set the clock" - and the fan came back on, and the oven started heating again.

(If you're interested, it's a Whirlpool KEBS208SSS02. The kicker? When Chris was shopping, it came down to this and a GE. He went with this one because of some discussion online of a problem with the GE. What problem, you might ask? Turning the oven off didn't actually turn it off....)

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* It's a double oven. so technically, this was the second time we've used the upper oven. The lower oven still has packing materials in it.

Comments

[sammason.livejournal.com]

If it's so new, it's under warranty. So you could get it replaced for free. That would be irritating because it sounds like something that needs installation, but at least you'd end up with an oven. I hope bread wasn't an essential part of the meal you wanted to eat.

[yakshaver.livejournal.com]

Oh, definitely under warranty. They're coming Tuesday to repair it. (July 4 is a big holiday here, and falling on a weekend means that a lot of companies (and even more people) take Friday and/or Monday off.)

One of the things a good engineer thinks — and thinks hard — about is How can this fail? And how should it fail? It sure looks like the engineers responsible for this oven (and the GE one we didn't buy) dropped that on the floor. Engineers like to swap stories of engineering failures, whether their own or someone else's; this post was mostly about sharing such a story.

[zkzkz.livejournal.com]

Leaving the packing materials in the other oven sounds sketchy? Are you sure it doesn't get hot enough to melt them or start a fire when you operate the upper oven?

[yakshaver.livejournal.com]

> Are you sure....

Yes.

[zkzkz.livejournal.com]

I woudln't be surprised if the two ovens were actually the same inside or had the same firmware with the same bugs. It's like buying an ethernet card and discovering it uses the same driver as all the other ethernet cards from other vendors...

[yakshaver.livejournal.com]

Yeah, that's what we're thinking. Not that we're likely to find out....

[jered]

This actually sounds like a hardware problem to me, like a stuck relay. No oven manufacturer is going to go for Windows for Devices because the hardware would be too expensive, unless you have an oven you can surf the web from too. Appliance manufacturers are incredibly cheap, and if they can shave a dime off a part they will because that adds up with tens of thousands of devices.

I recently repaired my renters' refrigerator. The problem was the defrost timer -- all freezer/fridge systems have a heating wire that runs through the coils, which turns on to melt off the ice periodically. (This is a contributing factor to freezer burn, but it's necessary to prevent the freezer from turning into a huge block of ice.) The defrost timer wasn't, so the duct between the freezer and fridge iced up and the fridge didn't cool anymore.

How would you design a defrost timer? I would have a small timer IC connected to a relay. Hah!

The cheapest fridges still use a mechanical defrost timer. I took it apart, and it's really quite clever. There's a very small motor connected to a small worm gear connected to a series of step-down gears, the last of which rotates once every 10 hours. That is connected to -- this is hard to describe -- a thick round gear where the outside is a ramp; that is, if you were touching the outside of the gear as it turned your finger would move out until it reached the end of the ramp and dropped back.

Inside that section are also three relay-like contacts that are the external timer interface. The center one gets power, the left-most goes to the compressor and the right-most goes to the defrost wire. These are springy and pressed against the ramped wheel. Normally the two left ones are in contact, running the compressor. As the wheel rotates they move out towards the third contact... then the first contact falls of the wheel (it's slightly shorter) and the outer two make contact, running the defrost wire until the second contact falls and the process starts again.

[yakshaver.livejournal.com]

I didn't actually think it was running Windows. It's just that this kind of failure always makes me think of Microsoft....

By the way, your "thick round gear where the outside is a ramp" is, unless we're totally failing to communicate, a cam.

[sammason.livejournal.com]

I rather like the idea of an oven with internet access. It probably exists already and I bet there's a market for it. People could download recipes, or instructions for bringing the work of outside caterers from delivery box to their own table. People could instruct their home oven 'I'm setting off from work now, so switch on and preheat' or 'switch on to cook the dish I left inside, with you set to "chiller" mode to keep my food fresh.'

[jered]

Yes, I believe it would be correct to call it a cam. I usually associate that with the kind illustrated in the diagram (one bump on a circle) but I think this qualifies as well.

[nuclearpolymer.livejournal.com]

What a pain.

The nice thing about a gas oven is that if you turn it off with the physical dial, it's really off. Though I suppose you might get some mechanical problem that results in a leak, which would be bad.

Don't all electrical appliances theoretically have a failure mode where the off switch stops working or where they get stuck in the on position? That's why I unplug my electric kettle when I'm not using it. And hot air poppers actually have no switch, so you just plug them in when you want to turn them on.

[gnibbles.livejournal.com]

About that gas oven with a dial thing. Ours not only failed to turn off when you turned the dial, it managed to disconnect from the dial, which subsequently flopped off the oven dashboard.

Twiddle dials with care.