• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

LED(s) as Strobe Light

Status
Not open for further replies.

adamey

Member
I need a circuit that can drive an LED at a higher than usual output for a very brief period of time so as to act like a strobe.

I also need a triggering circuit that will flash the LED on the trailing edge of a 5V digital signal (pulse train with a low duty cycle of about 10%).

Can Luxeon LED's be driven at very short pulse widths?
 

BrownOut

Banned
Use a multi-vibrator that generates a short pulse, and turn the LED voltage up past the normal spec. If you're lucky, it'll run for a few seconds before burning out.
 

justDIY

Active Member
Can Luxeon LED's be driven at very short pulse widths?
leds can be driven really fast, since they're nothing more than a semiconductor junction. the issue is, they're not any brighter flashing as they are solid on. driven at 1khz, the various luxeon parts are rated for only slightly higher currents than their constant state rating. lumileds and SSC both make leds rated for a very high pulse current but a very low constant current - specifically designed as mobile phone photo-flash sources.

there's no way you'll be able to outshine an arc discharge strobe with an led, even the tiny xenon tube in a disposable camera consumes more power than a large led array during its discharge.
 

marcbarker

New Member
I'm pretty cure a Luxeon LED can be driven at very narrow% duty cycle (i.e. pulsed > 10 A, maybe could get get 30 A through it?). If the average amps is kept below 100 mA then a heat sink won't be needed.
 

Karkas

Member
I've been thinking about the idea of using a triangle waveform to the LED and see if it gives the flashing effect. I talked about that in another threat. What do you think?
 

crutschow

Well-Known Member
Most Helpful Member
You just need a pulse train to get the flashing effect, not a triangular wave.
 

Karkas

Member
Do you know what exactly would i get with a trangular wave?
 

kpatz

New Member
At low enough frequencies, a triangle wave will cause the LED(s) to get gradually brighter and dimmer.

To get a strobe effect, you need pulses with a narrow pulse width (duty cycle).
 

Karkas

Member
thanks for the answer, if the frequency would be high(I make it high), wouldn't it make that effect but continuous? i mean the same effect than with the pulses.

In the other hand, I would get a strobe light with a simple astable multivibrator output, i'm i wrong?
 

Richard S

New Member
Kind of.

A proper stobe light has very fast pulses (very low duty cycle). A regular astable has a 50% duty cycle - an equal on and off time.

Richard
 

BrownOut

Banned
Mulitvibrators can be made to any produce any duty cycle. For a prope strobe light however, you need a circuit with a gas discharge device, ie a xenon tube.
 

Karkas

Member
Well yes, but i'm looking for a cheaper circuit that gives me the most similar effect, trying to design it.
 

justDIY

Active Member
There is no similar effect ... the output of the xenon tube is HUGE compared to anything an LED could generate. You need a lot of expensive leds to replicate that effect. You'll see this in police cars ... departments that have a lot of money but are low on brains buy LED light bars for their cars because they're sold on the long service life and the "wow" factor of something high tech. Older, established and cash strapped departments however still chose xenon strobe lights because they're inexpensive and very bright compared to the leds. The leds might have a higher apparent brightness because their pulse width is wider than that of the xenon tube. Apparent brightness only matters when you're looking directly at something... The short duration but immense power of a xenon strobe affects your peripheral vision, so you notice it even if looking in a different direction.
 

Karkas

Member
I'll try something, and posts results.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top