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What is the response time for the LED?

I'm planning on purchasing a few of these as a solution for a project needing a strobing effect. I was hoping to know the responsiveness for how fast the LED turns on and turns off. Could someone tell me the time of which it takes the LED to go from 0 Lum to 500 Lum and then back to 0 Lum? I ask as some LEDs seem to slowly light up/out. I guess another way to put it is how instantaneous can the light goto max and then switch off? Are there problems with this being a perpetual action?

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So is it now possible to set these lights up with a custom strobe function?


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Due to the typical field of application of visible LEDs, their datasheets generally do not specify switching characteristics (like it happens with regular diodes or IR LEDs). However, from the electrical point of view, you could assume that they are fast enough for the application you describe (for high power LEDs, typical turn-on and turn-off times are in the order of tens of nanoseconds, but achieving this level of performance requires careful driving techniques).

With that in mind and, IF your application uses monochromatic LEDs (includes IR), then you could assume an optical switching performance similar to the electrical switching (light emission is proportional to the LED current). This means that, with relative ease, you could achieve an optical switching frequency in the order of 10 kHz, or even more depending on driving techniques (for your reference, optical modulation on common IR remote controls tipically operate above 30 kHz).

However.... if your application requires white LEDs, then I'm afraid that the response time of the phosphor coating is much slower than that of the LED itself. Whether it is fast enough for your application will depend on the maximum operating frequency you need. Unfortunately I have no data on phosphor performance.

If you need a really fast white-light strobe frequency, maybe you should consider using mixed color LEDs (RGB) instead of phosphor-converted white LEDs.

Regarding continuous operation, if the maximum electrical operating limits are respected (peak current, pulse width, duty cycle and heatsinking), then it should be possible to attain the full lifetime specified by the manufacturer (typically about 50000 hs, depending on the LED, but phosphor based LEDs age faster, though).

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Bad formatting in comments, moving comment to a second answer.


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I've written some fairly high-precision strobing code on the hexbright; the limit you first hit isn't electrical switching, it's actually jitter due to arduino's interrupts (which can be disabled, but will prevent communication over the serial port among other things).

The hexbright library supports strobing, but it doesn't disable interrupts or interrupt the execution of the rest of the library:

The library will strobe within a 25microsecond window of when it should strobe or not at all (sometimes causing irregular flicker due to missed strobes). The convenience functions may be useful:

// set_strobe_fpm(59500);

// get_strobe_fpm(); // returns 59523

// get_strobe_error(); // returns 703

// you are strobing at 59523 fpm, +- 703 fpm.

This code could use calibration/tuning; I've not verified it with a frequency counter (and if you *do* test it with a frequency counter, make sure to account for the linear offset of the actual crystal oscillator frequency).

The code as written will also short circuit (one irregular strobe) every ~70 minutes of operation, as we don't handle the integer rollover.

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