Strobe Light - Scientific Explanation of Flashtubes

Scientific Explanation of Flashtubes

Strobe lights usually use flashtubes with energy supplied from a capacitor, an energy storage device much like a battery, but capable of charging and releasing energy much faster. Recently, some strobe lights have been found to use rectified mains electricity and no capacitors at all. In a capacitor based strobe light, the capacitor is charged up to around 300V. Once the capacitor has been charged, a small amount of power is diverted into a trigger transformer, a small transformer with a high turns ratio, which generates a weak, but high voltage spike required to ionize the xenon gas in a flash tube. An arc is created inside the tube, which acts as a bridge for the much bigger pulse to flow down later. Arcs present almost a direct short circuit, allowing the capacitors to quickly release their energy into the arc. This rapidly heats the xenon gas, creating an extremely bright plasma discharge, which is seen as a flash.

A strobe without a capacitor storage device simply discharges mains voltages across the tube once it's fired. This method means no charging times are required, and flash rates can be much faster, but drastically reduce the lifetime of the flash tube if powered for excess amounts of time. These strobes require a form of current limiting, as mentioned before, an arc acts as a short circuit. If this current limiting was eliminated, the flash tube would attempt to draw high currents from the electricity source, potentially tripping electrical breakers or causing voltage drops in the power supply line.

A strobe flash typically lasts around 200 microseconds, however can be faster or slower depending on the use of the strobe. Some strobes even offer continuous mode, where the arc is sustained, providing an extremely high intensity light, but usually only for small amounts of time to prevent overheating of the flash tube and thus breakage.