balast?
- Thread starter sisco100
- Start date
ru4r34l
Well-Known Member
Creditshttp://www.candlepowerforums.com/vb/showthread.php?32221-What-does-a-HID-ballast-do
Originally, the term "ballast" was used to describe large inductors used to limit AC current for fluorescent lighting and other gas-discharge lights (especially sodium vapor and mercury vapor streetlights). The application of the term "ballast" has now been broadaned to include a host of other devices which more closely resemble power supplies.
The modern electronic ballast used for HID lights (which are essentially metal halide gas-discharge lamps) is a DC to AC inverter with a current-limited or sometimes regulated output. There is also a circuit called a "striker" which is usually integrated into the ballast module. The striker generates a train of very high voltage (2-5kV) pulses which cause the gas inside the lamp to break down and ionize. Once the gas ionizes, it will conduct electrical current at a much lower voltage, and then the high frequency AC output of the inverter continues to keep it ionized and in operation. In this mode, the voltage present across the lamp's terminals may be anywhere between 70-300V, depending on the lamp and application.
A similar "ballast" is used for CCFL lighting found in LCD panel backlights (laptops, camcorders, digital cameras, and what have you) and some newer CCFL flashlights. These use a similar to gas-discharge lamps, but without the striker. Instead, the AC output of the inverter by iteslf is high enough to cause the fluorescent tube to ionize and begin conduction. A capacitor in series with the AC output limits the current.
The purpose of such DC-AC inverter-type ballasts is to take a low voltage DC source (such as your car's electrical system, a few 123's, or any other source for that matter) and convert it into the voltage required to start and operate the lamp.
Magnetic ballasts for gas-discharge lamps still need the use of a striker circuit to get the tube started, however the lamps they power are designed operate at a voltage lower than the supply voltage (120-240VAC). The impedance of the inductors limits the current to the lamp (at a given frequency) to a safe value.
Magnetic ballasts for standard hot-catholde fluorescent lamps are operated in a similar fashion, however they do not require the use of a striker. Older designs rely on the operation of a starter module, which is usually a miniature mercury vapor lamp which, when operating, conducts current through the filament electrodes of the primary lamp, allowing them to emit electrons at a lower voltage. Once the emission voltage is low enough, the primary lamp ionizes and the starter ceases to operate, now that the voltage across its terminals is below its operating voltage. Newer so-called "rapid-start" ballasts often use a solid-state device as part of a circuit that takes the place of the starter module.
regards,
Originally, the term "ballast" was used to describe large inductors used to limit AC current for fluorescent lighting and other gas-discharge lights (especially sodium vapor and mercury vapor streetlights). The application of the term "ballast" has now been broadaned to include a host of other devices which more closely resemble power supplies.
The modern electronic ballast used for HID lights (which are essentially metal halide gas-discharge lamps) is a DC to AC inverter with a current-limited or sometimes regulated output. There is also a circuit called a "striker" which is usually integrated into the ballast module. The striker generates a train of very high voltage (2-5kV) pulses which cause the gas inside the lamp to break down and ionize. Once the gas ionizes, it will conduct electrical current at a much lower voltage, and then the high frequency AC output of the inverter continues to keep it ionized and in operation. In this mode, the voltage present across the lamp's terminals may be anywhere between 70-300V, depending on the lamp and application.
A similar "ballast" is used for CCFL lighting found in LCD panel backlights (laptops, camcorders, digital cameras, and what have you) and some newer CCFL flashlights. These use a similar to gas-discharge lamps, but without the striker. Instead, the AC output of the inverter by iteslf is high enough to cause the fluorescent tube to ionize and begin conduction. A capacitor in series with the AC output limits the current.
The purpose of such DC-AC inverter-type ballasts is to take a low voltage DC source (such as your car's electrical system, a few 123's, or any other source for that matter) and convert it into the voltage required to start and operate the lamp.
Magnetic ballasts for gas-discharge lamps still need the use of a striker circuit to get the tube started, however the lamps they power are designed operate at a voltage lower than the supply voltage (120-240VAC). The impedance of the inductors limits the current to the lamp (at a given frequency) to a safe value.
Magnetic ballasts for standard hot-catholde fluorescent lamps are operated in a similar fashion, however they do not require the use of a striker. Older designs rely on the operation of a starter module, which is usually a miniature mercury vapor lamp which, when operating, conducts current through the filament electrodes of the primary lamp, allowing them to emit electrons at a lower voltage. Once the emission voltage is low enough, the primary lamp ionizes and the starter ceases to operate, now that the voltage across its terminals is below its operating voltage. Newer so-called "rapid-start" ballasts often use a solid-state device as part of a circuit that takes the place of the starter module.
regards,
Or, here is the short answer.
Grow lights that require a ballast usually run on a different voltage than normal household electricity, and some of them require a special "Kick in the ass" just to fire up (like "Pulse Start" Metal Halides for example). Yes, you really need them because they perform these two functions!
Every type and size of grow light bulb, worth having (that I know of) uses it's own dedicated ballast. In other words, a 250watt Metal Halide ballast is not compatible with a 250 watt High Pressure Sodium bulb, or even a 400 watt Metal Halide bulb. Some (most) CFL's don't require an "additional" ballast because they have one built-in internally - but they still use one.
Hugo Phurst
Well-Known Member
What those guys said.
Ballasts provide the required voltage and frequency to excite/ignite the gasses in the bulbs.
Ballasts provide the required voltage and frequency to excite/ignite the gasses in the bulbs.
that was very helpful. i read the first post and was like what.