What are the differences between neon lights and flurescent lights?

A neon light is the sort of light you see used in advertising signs. These signs are made of long, narrow glass tubes, and these tubes are often bent into all sorts of shapes. These tubes emit light in different colors.

A fluorescent light, on the other hand, is most often a long, straight tube that produces white light. Common places for fluorescent lights are in offices, stores and some home fixtures.

Inside the glass tube there insert gasese such as neon, argon or krypton at low pressure. At both ends of the tube there are metal electrodes. When you apply a high voltage to the electrodes, the neon gas ionizes, and electrons flow through the gas. These electrons excite the neon atoms and cause them to emit light that we can see. Neon emits red light when energized in this way. Other gases emit other colors.

A fluorescent light works in a similar fashion but it has an extra step. Inside a fluorescent light is low-pressure mercury vapor. When ionized, mercury vapor emits ultraviolet light. Human eyes are not sensitive to ultraviolet light. The inside of a fluorescent light is then coated with a phosphor. Phosphor is a substance that can accept energy in one form and emit the energy in the form of visible light. In a fluorescent lamp, the phosphor accepts the energy of ultraviolet photons and emits visible photons.

The light we see from a fluorescent tube is the light given off by the phosphor that coats the inside of the tube (the phosphor fluoresces when energized, hence the name). The light of a neon tube is the colored light that the neon atoms give off directly.

Neon sign transformer basics

Transformers come in many styles, sizes and shapes. Neon sign transformers are distinguished by being current limited and center grounded. Being center grounded means that the center of the transformers output winding is electrically connected to ground. This results in both output terminals being hot or live with respect to ground.

Current limited means that when the transformer's output is shorted, only a limited amount of current will flow thus preventing burn out or short circuiting. Current limiting is achieved by the use of a tightly coupled, magnetically saturable iron core. The iron core provides resistance to the fluctuating magnetic field which, in turn, impedes the current flow.