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Drivers may be constant current (CC) or constant voltage (CV). In CC drivers, the voltage changes while the current stays the same. CC drivers are used when the electrical load of the LED circuit is either unknown or fluctuates, for example, a lighting circuit where a variable number of LED lamp fixtures may be installed.
Dimming fluorescent ballasts and dimming LED drivers often use 0–10 V control signals to control dimming functions. In many cases, the dimming range of the power supply or ballast is limited. If the light output can only be dimmed from 100% down to 10%, there must be a switch or relay available to kill power to the system and turn the light ...
Digital Addressable Lighting Interface (DALI) is a trademark for network-based products that control lighting.The underlying technology was established by a consortium of lighting equipment manufacturers as a successor for 1-10 V/ 0–10 V lighting control systems, and as an open standard alternative to several proprietary protocols.
This unit is wired in series with the load. Diodes (D2, D3, D4 and D5) form a bridge, which generates pulsed DC. R1 and C1 form a circuit with a time constant. As the voltage increases from zero (at the start of every halfwave) C1 charges up. When C1 is able to make Zener diode D6 conduct and inject current into the SCR, the SCR fires. When the ...
A dimmable ballast is very similar to a rapid start ballast, except that the autotransformer is connected to a dimmer. A quadrac type light dimmer can be used with a dimming ballast, which maintains the heating current while allowing lamp current to be controlled. A resistor of about 10 kΩ is required to be connected in parallel with the ...
Eventually, though, when the coughing led to vomiting, doctors performed scans and detected a large, grapefruit-sized tumor in her middle chest cavity and right lung, which was completely blocking ...
The current in an LED or other diodes rises exponentially with the applied voltage (see Shockley diode equation), so a small change in voltage can cause a large change in current. Current through the LED must be regulated by an external circuit such as a constant current source to prevent damage. Since most common power supplies are (nearly ...
Trump was in the private cabin of his plane, flying to an April 2 campaign rally in Grand Rapids, Mich., when he picked up a document Wiles had placed atop a stack of papers.