Does LED make for a good strobe?

"Ian Field"

** Huh ?

Start by making the discharge cap about 100 times smaller - ie about 1uF.

... Phil

Reply to
Phil Allison
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**Indeed. Flash tubes in typical cameras are rated for around 1 ~ 2 Watts of average power. This assumes a cycle time in the order of several seconds. Discharging (say) 100uF or more @ 300 Volts at a rate of (say) 50 ~ 100 times per second will destroy almost any flash tube rapidly.

Funny this thread appeared this week. A couple of weeks back an old girlfriend asked me about the strobe light I built when I was in school. She wanted it for her daughter's art display. I dug it out and gingerly switched it on. The damned thing actually still worked! The tube flashed erratically, as it certaintly showed significant signs of many hours of use (at parties and nightclubs). It is a 5 Watt tube, which I managed to overdrive (at times) to around 10 Watts. Very forgiving things. Still, they do have limits and it is wise to remain within those limits for reliable operation. We decided to use an LED.

A high power RGB LED makes a lot more sense. Cheap and dead easy to use.

--
Trevor Wilson www.rageaudio.com.au
Reply to
Trevor Wilson

That's interesting, I didn't know these existed. Cheap too.

Reply to
Jordan

Some LD modules don't like to be turned on & off quickly - perhaps due to the integrated driver circuitry.

Also some LD modules are already strobing the LD, I think this is done as a cheap way of controlling LD power dissipation. I've got a couple where if you rapidly sweep the beam across a surface you can see the light o/p going on & off.

Reply to
Rodwell

Yes, silly me.

Reply to
Jordan

Fujitsu used to use a bank of flash tubes as the fuser for their mainframe laser printers. Powering the tubes was a ferking big bank of capacitors. Lovely things to work on you grounded them with a foot long grounding stick, left them like that for 15 minutes, took it off for another 10 then waited another 10 minutes with the ground on again and left it on while you worked on the system.

Reply to
keithr

Bare laser diodes aren't all that hard to find, one of the chips in a DVD laser is visible. If you can get hold of scrap point of sale equipment - most of the bar code readers use visible lasers.

Reply to
Ian Field

lamps. These are very effective at "stopping dead" the

Any chance with LEDs?

This project uses a white LED as a strobe, published in August & September 2008.

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SC did some testing of the 1W white Luxeon and a Cree XR-C . The 10% to 90% full brightness measurement was 290nS, 90% to 10% was 360nS. To get enough light though, they made the minimum strobe flash period 32uS.

BTW Some people confuse the slow phosphor used in CRO tubes with white LEDs. The phosphor used in most white LEDs does not phosphoresce but emits light by scintillation, an effect that has virtually no light persistence, so the speed is mostly determined by the underlying blue LED.

Xenon are much brighter and faster and would be better in bright ambient light.

Reply to
yaputya

lamps. These are very effective at "stopping dead" the

image. Any chance with LEDs?

2008.

the speed

**You may be correct. Specs on Luxeon emitters seem to bear out the rise and fall times will be fast enough for most purposes.

light.

**Certainly, but a 5 Watt LED would deliver plenty of light for anything but for use in direct sunlight. IOW: In a car engine bay, a white LED will easily be adequate.
--
Trevor Wilson www.rageaudio.com.au
Reply to
Trevor Wilson

lamps. These are very effective at "stopping dead"

image. Any chance with LEDs?

2008.

the speed

fall times will be fast enough for most purposes.

Here is the info from SC

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light.

for use in direct sunlight. IOW: In a car engine bay,

You still have to stretch the LED pulse out to get much light whereas the Xenon flash is brighter at shorter pulse widths. You can see the result in digital camera flash comparisons:

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Reply to
yaputya

"Phil Allison"

** Seems this info is wrong - like many others I had read comments about white LED persistence in more than one place.

In fact, the very lack of persistane is an issue with LED lighting that operates from 50/60 Hz sources - either rectified or not - because it can produce annoying strobing effects.

BTW:

On a few occasions I have replaced the 6.3 volt bezel lamp on the front of a valve amplifier with a red LED and resistor.

Worked fine and no obvious flicker.

... Phil

Reply to
Phil Allison

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