A photoflash capacitor is an

electrolytic capacitor An electrolytic capacitor is a polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization. This oxide layer acts as the dielectric of the capacitor. A solid, liquid, or gel el ...

used in

flash Flash, flashes, or FLASH may refer to: Arts, entertainment, and media Fictional aliases * Flash (DC Comics character), several DC Comics superheroes with super speed: ** Flash (Barry Allen) ** Flash (Jay Garrick) ** Wally West, the first Kid ...

camera A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...

s, professional flashes, and also in solid-state

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The fir ...

power supplies. Their usual purpose is to briefly power a high-voltage

flash tube Flash, flashes, or FLASH may refer to: Arts, entertainment, and media Fictional aliases * Flash (DC Comics character), several DC Comics superheroes with super speed: ** Flash (Barry Allen) ** Flash (Jay Garrick) ** Wally West, the first Kid F ...

, used to illuminate a photographic subject or optically pump a laser rod. As flash tubes require very high current for a very short time to operate, photoflash capacitors are designed to supply high discharge current pulses without excessive internal heating.

Fundamentals

The principal properties of a capacitor are capacitance, working voltage,

equivalent series resistance Practical capacitors and inductors as used in electric circuits are not ideal components with only capacitance or inductance. However, they can be treated, to a very good degree of approximation, as being ideal capacitors and inductors in series ...

(ESR),

equivalent series inductance Equivalent series inductance (ESL) is an effective inductance that is used to describe the inductive part of the impedance of certain electrical components. Overview The theoretical treatment of devices such as capacitors and resistors tends to ...

(ESL), and working temperature Compared with electrolytic capacitors usually used for power supply filtering at power frequency, a photoflash capacitor is designed to have lower ESR, ESL, and capacitance

manufacturing tolerance Engineering tolerance is the permissible limit or limits of variation in: # a physical dimension; # a measured value or physical property of a material, manufactured object, system, or service; # other measured values (such as temperature, hum ...

, but does not need as high a working temperature.

Design

The light energy emitted by a flash is supplied by the capacitor, and is proportional to the product of the capacitance and the voltage squared; photoflash capacitors have capacitance in the range 80-160

microfarad The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base units ...

s (μF) and voltages from 180 to 330 volts for flash units built into small disposable and compact cameras, increasing for units delivering higher light energy. Forrest M. Mims, III, ''Forrest Mims' Circuit Scrapbook II'', Howard W. Sams & Co., Indianapolis IN, , page 149. Mims gives the rating of the Kodak Disc camera flash as 160 μF and 180 volts. A typical manufacturer's range includes capacitors operating at 330–380V, with capacitance from 80 to 1,500 μFHitachi Photo Flash Aluminum Electrolytic Capacitors
/ref> While normal electrolytic capacitors are often operated at not more than half their nominal voltage due to their high derating, photoflash capacitors are typically operated at their nominal working voltage (labelled as "WV" or "W.V." rather than just "V"). Photoflash capacitors are not subject to the high temperatures of cased electronic equipment in continuous operation, with nearby components and sometimes the capacitors themselves dissipating heat; they are often rated at a maximum

operating temperature An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the de ...

rate of typically 55 °C, compared to 85 °C–105 °C or more for capacitors for continuous use in electronic equipment. In most electronic applications an electrolytic capacitor can have a capacitance much larger than its nominal value without detracting from circuit performance; general-purpose electrolytics are often specified to have capacitance between 20% below and 80% above rated value, although tighter tolerances are available. The light energy of a flash is proportional to the capacitance and large variations are not acceptable, typical tolerance is -10+20%. Photoflash capacitors are designed to deliver a brief pulse of very high current, and are consequently sometimes used in

railgun A railgun or rail gun is a linear motor device, typically designed as a weapon, that uses Electromagnet, electromagnetic force to launch high velocity projectiles. The projectile normally does not contain explosives, instead relying on the proj ...

and

coilgun A coilgun, also known as a Gauss rifle, is a type of mass driver consisting of one or more coils used as electromagnets in the configuration of a linear motor that accelerate a ferromagnetic or conducting projectile to high velocity. In almost ...

designs.

References

{{DEFAULTSORT:Photoflash Capacitor Capacitors Flash photography