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Stroboscope - 2015

A xenon Flashtube is commonly used as a source of a short burst of wide-spectrum white light. They can be found in most digital cameras, and that is where I've salvaged mine from.
These Flashtubes require about 250V to operate, so a digital camera has to charge up a high voltage capacitor to produce a flash, and charging it from a low voltage battery takes a while. By using a mains voltage to charge the capacitor instead of using a battery, the charging time gets greatly reduced up to a point where it is possible to build a stroboscope.

As the following high quality picture of a schematic diagram shows, the 400V high voltage capacitor is charged directly from 230V mains voltage. After the bridge rectifier, there is about a 100R resistor in the path to limit the inrush current. The Flashtube is connected directly to the capacitor. However, the 320V that the capacitor gets charged to is not enough to produce a flash, so a high voltage transformer (taken from the same digital camera) must be present to produce a pulse of voltage that triggers the Flashtube. The transformer is controlled by an Attiny13 microcontroller that sets the timing. It has a microphone built-in, and I've hoped to be able to synchronize the stroboscope with surrounding music by thresholding the audio volume. Sadly, it does not work very well, and probably a better algorithm has to be used (but I have not dug deeper into it).

Stroboscope schematics

The circuit was fitted inside a plastic box to ensure at least some protection against the mains voltage. You can see the two 220R (~100R together) resistors that dissipate the inrush current into the high voltage capacitor. You can also see the small yellow high-voltage transformer that triggers the flash, a potentiometer that sets the timing (frequency), and the microcontroller that does the brainy stuff.

Stroboscope inside

One problem that I've overlooked is the power dissipation of the Flashtube itself. After some time (in particular with higher flashing frequencies), it gets pretty hot, and I have to lower the frequency or turn the stroboscope off. Some active cooling might be necessary to ensure a proper long-term operation.

Stroboscope front Stroboscope

I've also built a small battery powered version with a small high voltage generator. But it takes about 30 seconds to charge the capacitor inside, so it is hopelessly slow compared to digital cameras that use the same principle. However, it works.

Photoflash