A tall glass of iced tea or lemonade seems to symbolize summer, and it seems we are all adding ice to our drinks. I remember those old fashioned metal ice cube trays with a lever that was lifted to release the cubes. Those were followed by plastic trays that we twisted to get to the ice. Now I have noticed that it is nearly impossible to find a new refrigerator without an automatic ice maker built into it. If you’ve ever listened to your freezer making ice and wondered exactly how the system works, howstuffworks.com has the answer for you. We’ll share the gist of for you:

An ice maker works like those plastic trays, but the process of pouring water and extracting cubes is fully automated. A home ice maker is an ice-cube assembly line.

Most ice makers use an electric motor, an electrically operated water valve and an electrical heating unit. To provide power to all these elements, you have to hook the icemaker up to the electrical circuit powering your refrigerator. You also have to hook the icemaker up to the plumbing line in your house, to provide fresh water for the ice cubes. The power line and the water-intake tube both run through a hole in the back of the freezer.

When everything is hooked up, the ice maker begins its cycle. The cycle is usually controlled by a simple electrical circuit and a series of switches.

• At the beginning of the cycle, a timed switch in the circuit briefly sends current to a solenoid water valve. In most designs, the water valve is actually positioned behind the refrigerator, but it is connected to the central circuit via electrical wires. When the circuit sends current down these wires, the charge moves a solenoid (a type of electromagnet), which opens the valve.
• The valve is only open for about seven seconds; it lets in just enough water to fill the ice mold. The ice mold is a plastic well, with several connected cavities. Typically, these cavities have a curved, half-circle shape. Each of the cavity walls has a small notch in it so each ice cube will be attached to the cube next to it.
• Once the mold is filled, the machine waits for the water in the mold to freeze. The cooling unit in the refrigerator does the actual work of freezing the water, not the ice maker itself. The ice maker has a built-in thermostat, which monitors the temperature level of the water in the molds. When the temperature dips to a particular level — say, 9 degrees Fahrenheit (-13 degrees Celsius) — the thermostat closes a switch in the electrical circuit.
• Closing this switch lets electrical current flow through a heating coil underneath the ice maker. As the coil heats up, it warms the bottom of the ice mold, loosening the ice cubes from the mold surface.
• The electrical circuit then activates the ice maker’s motor. The motor spins a gear, which rotates another gear attached to a long plastic shaft. The shaft has a series of ejector blades extending out from it. As the blades revolve, they scoop the ice cubes up and out of the mold, pushing them to the front of the ice maker. Since the cubes are connected to one another, they move as a single unit.
• At the front of the ice maker, there are plastic notches in the housing that match up with the ejector blades. The blades pass through these notches, and the cubes are pushed out to a collection bin underneath the ice maker.
• The revolving shaft has a notched plastic cam at its base. Just before the cubes are pushed out of the ice maker, the cam catches hold of the shut-off arm, lifting it up. After the cubes are ejected, the arm falls down again. When the arm reaches its lowest resting position, it throws a switch in the circuit, which activates the water valve to begin another cycle. If the arm can’t reach its lowest position, because there are stacked-up ice cubes in the way, the cycle is interrupted. This keeps the ice maker from filling your entire freezer with ice; it will only make more cubes when there is room in the collection bin.

It’s quite a system, and one we should appreciate on a 100 degree day.