Light dimmer circuits

Description

This is a standard text-book circuit. A triac may be considered as two SCR's (Silicon Controlled Rectifiers)connected in opposite directions. A diac is a gate trigger device. Triacs, diacs & SCR's are different types ofThyristors.

A triac is a 3 terminal AC semiconductor switch which is triggered ON when a low energy signal is applied to itsGate. Switching is fast. The low energy of switching means that a wide range of low cost control circuits canbe used. Since the triac is bilateral (2 SCR's connected in opposite directions) the terms anode and cathode have no meaning. So the terms Main Terminal 1 and 2 (MT1, MT2) are used. It is standard to use MT1 as a reference point.

 

The circuit controls the average power to a load through the triac by phase control. The AC supply is applied to the load for only a controlled fraction of each cycle. The triac is held in an OFF condition for a portion of its cycle then is triggered ON at a time determined by the circuit.

Each time the triac is turned on, the load current changes very quickly - a few micro seconds - from zero to a value determined by the lamp resistance and the value of the mains voltage at that instant in time. This transition generates Radio Frequency Interference. It is greatest when the triac is triggered at 90 degree and least when it is triggered at close to zero or 180 degree of the mains AC waveform. L-C suppression network is thus used to suppress these electrical noise.

Light Dimmer Circuit Parts List

The parts list of the project is as shown below.

Lighting

Lighting or illumination is the deliberate application of light to achieve some aesthetic or practical effect. Lighting includes use of both artificial light sources such as lamps and natural illumination of interiors from daylight. Daylighting (through windows, skylights, etc.) is often used as the main source of light during daytime in buildings given its high quality and low cost. Artificial lighting represents a major component of energy consumption, accounting for a significant part of all energy consumed worldwide. Artificial lighting is most commonly provided today by electric lights, but gas lighting, candles, or oil lamps were used in the past, and still are used in certain situations. Proper lighting can enhance task performance or aesthetics, while there can be energy wastage and adverse health effects of poorly designed lighting. Indoor lighting is a form of fixture or furnishing, and a key part of interior design. Lighting can also be an intrinsic component of landscaping.

Lamps

Main article: Lamp (electrical component)

Commonly called 'light bulbs', lamps are the removable and replaceable part of a light fixture, which converts electrical energy into electromagnetic radiation. While lamps are often rated in terms of how much power they use in watts, the power does not necessarily correspond to the amount of light produced. For example, a 60 W incandescent light bulb produces about the same amount of light as a 13 W compact fluorescent lamp. Each of these technologies has a different efficacy in converting electrical energy to visible light. Visible light output is typically measured in lumens. This unit only quantifies the visible radiation, and excludes invisible infrared and ultraviolet light.

It is important to be able to differentiate types of lamps and lamp technologies. These include:

• Ballast: A ballast is an auxiliary piece of equipment designed to start and properly control the flow of power to discharge light sources such as fluorescent and high intensity discharge (HID) lamps. Some lamps require the ballast to have thermal protection.
• fluorescent light: A long straight tube coated with phosphor containing low pressure mercury vapor that produces white light.
• Halogen: High pressure incandescent lamps containing halogen gases such as iodine or bromine, allowing filaments to be operated at higher temperatures.
• Neon: A low pressure gas contained within a glass tube; the color emitted depends on the gas.
• Light emitting diodes: Light emitting diodes (LED) are solid state lamps without the filaments that would burn out on ordinary light bulbs. LEDs emit light produced from the movement of electrons in a semiconductor material.
• Compact fluorescent lamps: CFLs are designed to replace incandescent lamps in existing and new installations.