Christmas is upon us, and the shops are going crazy. Soon the family will gather around the tree and exchange their gifts of love. Someone is bound to want to take a flash photo of the occasion. As you wait for the camera to click, you may wonder how it produces such a bright flash from such a small battery. You guessed it. There is a capacitor behind the tiny miracle.
The Basics behind Flash Bulb Design
Digi cameras, smartphone cameras, and single-lens reflex cameras mostly use a gas discharge tube full of xenon gas. The general idea is to pass an electrical current through it, causing the atoms of the gas to emit visible light photons.
The photo illustrates the principle applied to larger, standalone flashguns. In its natural state, xenon gas does not have sufficient free electrons to do the job. We help it along with a metal plate at the negative end of the bulb. If we apply sufficient power to this, it will pull more electrons from the xenon atoms causing a chain reaction of energy.
What Happens Next When You Take a Flash Photo
The free electrons emerging from the metal plate have just one thing in mind. They want to reach the positive electrode as soon as possible. They collide with other xenon atoms in the rush causing them to energize and generate light. We need to pump a few thousand volts through the system for this to happen.
Another Drum Roll for Another Capacitor
An electronic circuit takes power from the camera battery, processes it, and stores it in a capacitor when we turn on the flash.
Photo flash capacitors in compact and disposable cameras have capacitance for 180 to 330 volts. This increases in larger cameras.
When somebody is about to take a flash photo and says, ‘Stand by, the bulb is charging up,’ you can smile and say. ‘Actually, it’s the trigger capacitor topping up.’
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