Some newer models of ceiling fans, especially those made by Casablanca fan company, have an onboard computer that can connect to a central home network and sense what room the fan is located in.
This allows the fan to follow the owner’s temperature and humidity preferences. This computer interface is known as X-10, and is used in many home automation systems. Other fans have sensors that can detect the air temperature and adjust the fan speed accordingly. In this case, a fan has a thermistor that measures the air temperature in the room.
The thermistor works like a resistor with a variable resistance that is dependent on the temperature. It has a low resistance at high temperatures and a high resistance at low temperatures.
When the thermistor is hooked up to the fan’s power supply, it will affect the voltage across the power supply. The fan’s controller will then use this voltage to adjust the fan speed. In most cases, these fans also have a manual override that can be used to control the fan speed in case the sensors cannot make the correct speed adjustment.
In the early days of ceiling fans, the pull chains (also called pullcords or pullwires) were made of twisted yarn or embroidery floss and were very loosely woven to prevent them from catching on things as people walked by. They also were very long to prevent them from being pulled out or tangled. This also made them very hard to replace. Modern pull chains are light, small-gauge wire, often with a plastic or metal coating.
Most are not meant to be replaced, but are simply snapped out and replaced with a new one. If a pull chain gets broken, it is usually possible to repair it. Loosely woven pull chains can be re-knotted. If the chain is frayed or knotted, it usually can be unwoven and re-knotted.
Modern fans usually have a re-circulating fan mode. This means that the fan pulls most of the air through the room from the front to the back (or through the ceiling), and then pushes the air back into the room through the back (or through the ceiling). In this mode, the blades are angled so that they push air forward, and the motor is reversed so that it is pushing air instead of pulling air. In this mode, the fan can be run at a slower speed than normal, since the blades are working harder.
The fan can also be run in a non-reversing mode. In this mode, the fan pulls the air through the room from the front to the back, but then the air is simply blown back into the room from the back (or from above). One of the most important design considerations of a ceiling fan is the location of the fan’s center of gravity.
The center of gravity is important because the fan rotates around itself, and if the center of gravity is too high or too low, the fan can be unstable. The traditional center of gravity is about 1/3 of the distance from the base to the top of the motor housing. As long as the blades are balanced, this is a good location for the center of gravity.
However, some manufacturers have chosen to move the center of gravity forward or backward in an attempt to make the fan quieter, or to make the fan more efficient. The main disadvantages of this approach are that, in general, the fan will not be as quiet, and that the fan will not be as aesthetically appealing. Ceiling fan blades are usually made of wood or a composite material, such as pressed wood or a plastic such as ABS.
The blades are often shaped like an airfoil and are designed to move air efficiently. Some fans come with a reverse switch for the blades. In this mode, the blades are not angled so that they push air forward, but instead they are angled so that they pull air backward. Some ceiling fans are designed to operate in both forward and reverse modes, but most are designed to operate in only one mode or the other. The fan’s speed is controlled by a switch that is usually mounted on the fan’s motor housing, the switch housing, the canopy, or on the wall.
This is usually a pull-chain or a push-button switch. Some fans also have a speed control in the form of a knob on the motor housing. Some newer models may have a remote control that can be used to control the fan’s functions. In the early days of ceiling fans, the switch was usually a pull-chain or a pull-wire. Pull chains became known by the public as pull-cords. In the 1920s, the most common switch was a lever-operated pull-wire (push-pull switch).
This was replaced in the 1930s by a rocker-type switch, which is still used on many fans. The first push-button fan switch was made by Emerson in 1934. The switch was called the “Emerson Quick-Flip” and was a spring-return switch. The fan would run in either the forward or reverse direction for as long as the button was held down. Once the button was released, the fan would return to a neutral position.
This was different from the rocker type switch, which would hold the fan in whatever position it had been left in. Other manufacturers quickly adopted this type of switch, and it remains the most popular type of fan switch today.