Angelina Jolie eating habaneros and firing pottery nekkid in Death Valley.
So the other day, my mild-mannered, well-behaved oven went all emo and heated itself up to the surface temperature of Venus, nearly incinerating a tray of french fries in the process. Now, handy as it may be sometimes to have a crematorium right in the comfort of your own home (I mean, have you ever tried to dispose of a body after 6pm on a Sunday?), there's nothing like a normal, everyday stove for warming up a stromboli or cranking out batch after batch of totally sweet Shrinky Dinks.
The state of the oven might have troubled some people, what with the risk of horrible fiery death and all, and sent them thumbing frantically through the yellow pages in search of a qualified professional oven doctor. But not me, stubborn fool I am. No, I saw it as the perfect excuse to completely dismantle a large kitchen appliance.
My trusty accomplice and I attacked the thing with a flurry of screwdrivers and swearing, and soon uncovered a series of odd little boxes and colorful wires that somehow magically made the stove go. The thermostat itself turned up in the unlikeliest of places: directly connected to the temperature dial. This actually makes a ton of sense, if you're the type to look for your video card inside your monitor.
Thinking of the stove as an electronic device will get you nowhere. It's a mechanical monster, an analog artifact sent from the bleak 80s to confuse and bewilder and astound. The fact that the thermostat managed to do anything without chips and circuit boards was downright mystifying at first. But here's the thing: there's not much to it. You can look at it and see how it's connected. You can touch it and see how it moves. There are no inscrutable black chips or firmware, just springs and hinges and switches.
Here's how it works:
The oven has a nine-inch rod (heh heh) attached to an inside wall. One end of the sensor rod has a long bare wire that leads to the thermostat. Presumably, when the oven gets hot, the rod and wire transfer heat to the thermostat.
The temperature dial is actually a screw; it moves up and down a little when you turn it. So when you turn the temperature up, the dial screw moves down, and pushes on a switch inside the thermostat. The switch is a little platform with springs that hold it in the "off" position until the dial screw pushes down enough to overcome the springs and turn the oven on.
But here's the neat part: the platform bends as the sensor wire heats it up, and unbends as it cools down (bimetallic magic of some sort). The dial screw stays in the same position, holding down one end of the platform. But the other end of the platform has the springs pulling on it, and as it heats up, the metal starts to bend. Eventually, it curls enough that it's back in the "off" position, and the oven stops heating.
As the oven cools back down, the platform also cools and starts to stiffen back into its original shape. The dial screw is still pushing on it, so pretty soon it pulls away from the "off" position, and the oven turns back on. The cycle keeps going until you turn the oven off, thereby releasing the platform.
When you turn the oven temperature up, the dial screw pushes the platform down more, and it has to bend farther to reach the "off" position. It takes time to move that extra distance, so the oven is heating longer, and gets hotter.
At least that's my best guess. In any case, I am so impressed. I hope whoever invented that thing got tons of cookies and other pleasures for it.
Short version: It's magic.
Of course, after taking the damned thing apart, torturing out its secrets, and testing its switches against the handy circuit diagram that came with the oven, there appeared to be absolutely nothing at all wrong with it. So back into the console it went, and sure enough, the oven was working normally again. Very disconcerting. The thermostat cannot be trusted. It may go inferno again at any time! It shall have to be replaced, or there can never be cake again.
The state of the oven might have troubled some people, what with the risk of horrible fiery death and all, and sent them thumbing frantically through the yellow pages in search of a qualified professional oven doctor. But not me, stubborn fool I am. No, I saw it as the perfect excuse to completely dismantle a large kitchen appliance.
My trusty accomplice and I attacked the thing with a flurry of screwdrivers and swearing, and soon uncovered a series of odd little boxes and colorful wires that somehow magically made the stove go. The thermostat itself turned up in the unlikeliest of places: directly connected to the temperature dial. This actually makes a ton of sense, if you're the type to look for your video card inside your monitor.
Thinking of the stove as an electronic device will get you nowhere. It's a mechanical monster, an analog artifact sent from the bleak 80s to confuse and bewilder and astound. The fact that the thermostat managed to do anything without chips and circuit boards was downright mystifying at first. But here's the thing: there's not much to it. You can look at it and see how it's connected. You can touch it and see how it moves. There are no inscrutable black chips or firmware, just springs and hinges and switches.
Here's how it works:
The oven has a nine-inch rod (heh heh) attached to an inside wall. One end of the sensor rod has a long bare wire that leads to the thermostat. Presumably, when the oven gets hot, the rod and wire transfer heat to the thermostat.
The temperature dial is actually a screw; it moves up and down a little when you turn it. So when you turn the temperature up, the dial screw moves down, and pushes on a switch inside the thermostat. The switch is a little platform with springs that hold it in the "off" position until the dial screw pushes down enough to overcome the springs and turn the oven on.
But here's the neat part: the platform bends as the sensor wire heats it up, and unbends as it cools down (bimetallic magic of some sort). The dial screw stays in the same position, holding down one end of the platform. But the other end of the platform has the springs pulling on it, and as it heats up, the metal starts to bend. Eventually, it curls enough that it's back in the "off" position, and the oven stops heating.
As the oven cools back down, the platform also cools and starts to stiffen back into its original shape. The dial screw is still pushing on it, so pretty soon it pulls away from the "off" position, and the oven turns back on. The cycle keeps going until you turn the oven off, thereby releasing the platform.
When you turn the oven temperature up, the dial screw pushes the platform down more, and it has to bend farther to reach the "off" position. It takes time to move that extra distance, so the oven is heating longer, and gets hotter.
At least that's my best guess. In any case, I am so impressed. I hope whoever invented that thing got tons of cookies and other pleasures for it.
Short version: It's magic.
Of course, after taking the damned thing apart, torturing out its secrets, and testing its switches against the handy circuit diagram that came with the oven, there appeared to be absolutely nothing at all wrong with it. So back into the console it went, and sure enough, the oven was working normally again. Very disconcerting. The thermostat cannot be trusted. It may go inferno again at any time! It shall have to be replaced, or there can never be cake again.