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Cool Convoy

JohnnyDangerous

Estoril
Joined
12 Jun 2013
Messages
3,620
 
kas750 said:
I do like those rapid flash brakelights.

Not sure they are rapid flash brake lights or just the way LED's actually flicker in real life, but is accentuated when filmed. Someone will be along shortly (probably GT4 as he knows loads of stuff like that) to confirm or otherwise. I think they flash too rapidly for the human eye to notice but when videod, you can see it.
 
Can't imagen what all those caravan people were thinking! Must have been quite funny watching them being over and undertaken lol
 
kas750 said:
Pretty sure they are available on some cars. :?:

They are and bikes, the idea is they catch your eye more, the bike ones have like 15 diff paterns of flash.
 
Never saw so many caravans in one hit!

- Maxie :lol:
 
RobIpswichUK said:
kas750 said:
I do like those rapid flash brakelights.

Not sure they are rapid flash brake lights or just the way LED's actually flicker in real life, but is accentuated when filmed. Someone will be along shortly (probably GT4 as he knows loads of stuff like that) to confirm or otherwise. I think they flash too rapidly for the human eye to notice but when videod, you can see it.

You won't see any of that with your naked eye.

Multiplexed LED driver circuits I'll have you know!

This saves power, allows many more "bulbs" to be run ALMOST simultaneously (simultaneously as far as the human eye is concerned), and most importantly, allows dimming functions (which LEDs aren't strictly capable of in the normal sense, as they are current devices, not voltage devices).

The less intense (dimmer) driving lights (as opposed to intense braking output) are achieved from the same LEDs by a partial duty cycle, or pulse width modulation.

Basically, the brightness depends on the average power through the LED, and you can acheive this by tuning them on and off quickly, but by varying how long they are actually on and off.

So:

BRAKE = (say) 80% ON, 20% OFF @ 100 Hz basis (so on for total of 8/10 sec off 2/10 sec).
TAIL = (say) 20% ON, 80% OFF @ 100 Hz basis (so on for total 2/10 sec off 8/10 sec).

By persistence of vision, the "frame rate" must exceed about 10 times a second.

However, due to the UP and DOWN edges of the signal train, ideally this should be doubled. This also complies with the Nyquist requirement of sampling. Some tailights run on a 500 Hz basis (0.02s ON, 0.18s OFF).

TV is 25 Hz (full frame - interlaced or field rate is 50Hz) and analogue films are 24 Hz (frames per second). Newer films may be at 48 fps.

However, for "true" persistence of vision under all contrast and motion speeds, a frame rate of closer to 120 Hz is required (or 240i!). (at 10% duty cycle this would actually require a 1,200 Hz basis gate).

The reason the camera "sees" the flicker is the aliasing between the camera capture frame rate and the source frame rate.

Like when you see a video of a TV picture - you can see it sweep or flicker as the image changes.

30 fps capture - 25 fps TV = 5 Hz flicker.

Modern LED Brake Lights flash in a video, hidden away from the human eye!

Note the "circular" or "snake" motion of the lamp bulbs as they are lit in order:

 
JohnnyDangerous said:
kas750 said:
Pretty sure they are available on some cars. :?:

They are and bikes, the idea is they catch your eye more, the bike ones have like 15 diff paterns of flash.

See above.

The intentional heavy breaking flash (EBL) is not the same phenomenon (they are designed to be seen by the naked eye!)
 
Is it just me or did anyone else wonder why only a couple indicated to join the main carriageway? I always do and assumed others did too?
 
Nice vid but jeez it must be a miracle not one of them crashed !
 
DavidL said:
Is it just me or did anyone else wonder why only a couple indicated to join the main carriageway? I always do and assumed others did too?

It is not required to indicate when joining a motorway or dual carriageway, when you exit or change lanes yes but where else would they be going ???
 
Maxie said:
Never saw so many caravans in one hit!

- Maxie :lol:

No it's the same guy taking the piss by going off at the next junction and doubling back. :D
 

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