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Sensors, Actuators, and Robotics » Operating a Xenon Flash Tube

June 07, 2012
by karam
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Hi; I'm thinking of buying this Xenon flash tube:

Just wondering if anyone has experience working with flash tubes. I understand that the circuitry required to create a flash with one of these involves large capacitors and very high voltages, but I have not been able to find a good resource for building a circuit. Thanks in advance!

June 08, 2012
by mongo
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I have messed around with them from time to time. This bulb is a high powered strobe and extra care will need to be exercised. It operates at 800VDC. At 1KW flash, quite a difference from the 40 watt 250V U shaped tubes in strobe lights or the tiny 10 watt flash tube in a camera.

Triggering is simple through an optoisolated scr. The 800v supply is a charged capacitor directly across the flash tube. it is charged through a ballast resistor so you typically have a charge time of about 5 seconds. A second capacitor is connected through the scr and a trigger transformer, which generates a sharp pulse of between 5000 and 15000 volts. The high voltage output goes to the fine trigger wire, while the other side is common to usually, the negative side of the tube circuit.

Theory goes like this:

Voltage Multiplier or other high voltage source charges the main capacitor and the trigger capacitor through ballast resistors. The resistors are just to limit the current and prevents overloading the high voltage supply.

A signal to the scr from any source is sufficient to trigger the ionization transformer. These are usually a pretty small transformer but remember, the primary voltage is still around 800V.

As the trigger fires, it causes the xenon gas in the tube to become ionized. At that point, it becomes conductive and discharges the capacitor through the tube, resulting in the flash.

I equate it to captured lightning.

June 08, 2012
by mongo
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I have to draw a couple of schematics for the site over the weekend. I'll add this to the list.

June 09, 2012
by mongo
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OK, here is a representation of an externally triggered flash tube circuit. Note: Not all components are correctly labeled, as I just dug up suitable components from a library of parts that may not be of correct values. (Some are correct) flashtube

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