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Lomography Colorsplash Trigger Voltage


John Seaman
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This little three colour flashgun came to me with a job lot of other stuff. It's unbranded but I later saw one on the auction site. It's a Lomography Colorsplash. I have a habit of checking trigger voltages and found that this gun, powered by a single AA battery, has a scary trigger voltage of nearly 1000V, by far the highest I've seen. And that's using a moving coil meter, heaven knows what the open circuit voltage is. So it's heading for the bin, but just in case you are tempted to use one of these on a digital camera, don't!

 

Here it is, by the way the centre contact is negative on these.

 

LomoPN.jpg.5ac179dad670fcf59792c977be40e811.jpg

 

LomofPN.jpg.bbfebce09363f015c13a297e5c4f96ea.jpg

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Some older data on the problem of high trigger voltages on pre-2005 strobes

 

Photo Strobe Trigger Voltages

Oh no! Not a resurrection of the Botzilla list - Please!

 

A good idea, but a slapdash execution.

 

The issue is that hardly any of those Botzilla trigger voltage measurements were done properly or consistently.

 

Even a 10 megohm input DVM draws some current, and given the high internal resistance (> 2.2 megohms, typical) of 1970s or 1980s trigger circuits, this can lead to a 50% or more error between the measured voltage and the true open-circuit voltage. And it's the O/C voltage that can puncture the insulation of a semiconductor device and destroy it.

 

Typically, any older flash that measures over 100 volts on a DVM will have a true O/C trigger voltage of 330 to 350 volts; because that's the operating voltage of a Xenon tube, and those old trigger circuits were connected directly to the main capacitor via a 'safety' resistor.

 

The implication is that e.g. Nikon's stated 250 volt withstanding hotshoe, is not safe with almost any pre-1990 flash.

 

Basically, just round up any > 80v Botzilla readings to 350 volts, and you won't be far off.

 

As for the 1000v trigger of the 'Colorsplash'. I have no idea why it would need such a high voltage, or why its designer would even consider using such a voltage, given the rarity and cost of components with a 1Kv rating.

 

If anyone's interested I posted a thread on the subject of accurate trigger voltage measurement.

Edited by rodeo_joe|1
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When I first checked, the voltage was actually higher than 1K, with the meter needle going off the scale. I wondered if there was some flaw in my method, but I think not (apart from the lowering of the voltage caused by the operating current of the meter). I guess the battery had weakened somewhat before I photographed the test for photo.net.
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This little three colour flashgun came to me with a job lot of other stuff. It's unbranded but I later saw one on the auction site. It's a Lomography Colorsplash. I have a habit of checking trigger voltages and found that this gun, powered by a single AA battery, has a scary trigger voltage of nearly 1000V, by far the highest I've seen. And that's using a moving coil meter, heaven knows what the open circuit voltage is. So it's heading for the bin, but just in case you are tempted to use one of these on a digital camera, don't!

 

Here it is, by the way the centre contact is negative on these.

 

[ATTACH=full]1440359[/ATTACH]

 

[ATTACH=full]1440360[/ATTACH]

Wow that's a good way of checking the voltage ! I never tried it that way...

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When I first checked, the voltage was actually higher than 1K, with the meter needle going off the scale.

Just FWIW. Many of those 'old fashioned' moving-coil meters have an FS deflection current of only 50 uA, giving them a higher ohms-per-volt rating than a modern constant 10 Megohm input resistance DVM.

 

On the 1000 volt range, a 50uA 'mechanical' meter will have a resistance of 20 Megohms, and hence give a more accurate reading (than a DVM) of a high-resistance source.

 

I still can't figure out why anyone thought it necessary to have a constant 1KV or more floating around inside a tiny electronic flash gun. It might make a handy Taser in an emergency though. :eek:

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