Death of a GS

QUOTE=Giles;4783724]Ha ha ... hey, a healthy debate and a (slight) difference of opinion (especially between two job riders who both coach) in my book is a good thing.



It's probably all bollox though ..... :D[/QUOTE]

:beerjug: As Beth pointed out to me once 'Debate fosters understanding...' a good thing, and I'm in truth always interested in different viewpoints. Weigh the rationale, try it out and see if you're persuaded.

Like you say, why wouldn't you ride in the gutter if it's beneficial ? Everything by reason - Nothing by rote. Oh, and phooey is definitely a bit looser these days but nothing has fallen off yet ;)
 
fred_jb said:
As I said in a previous post, I believe the LEDs are only pulsed when in tail light mode, and this is done in order to reduce their brightness from the maximum output that is only used in brake light mode. In the case of the GS it appears that you get the equivalent of an approximately 3V supply voltage (at least that is what I have measured) due to the ratio of on time to off time used. I would expect the maximum output of the LEDs would be used when the brake light is required, and this is pretty much confirmed by the fact that when the brakes are activated the measured supply voltages increases to the full 12V.

There are definitely places in the video where the rear light increases greatly in brightness, and looks just too bright for a tail light, but it difficult to say that it is definitely braking as the aliasing with the video capture frequency may produce apparent differences in brightness as well as the on/off pulsing effect.

(I expect you are just trying to keep your explanation simple, but there is no mechanical shutter, just a periodic readout and reset of the sensor, generally 25 or 50 times a second.)
Click to expand...

That's why I put 'shutter' in quotes - thought it would be easier for the non electronics people to understand - I will check the brake light multiplexing as I assumed that it would also be multiplexed as it is the same LEDs but just at a much higher M/S ratio than the tale light?????
 
Look on the bright side, 'Andy' can now go and buy a superior KTM or Ducati and not be troubled by the GS fork stanchion recall:D
 
JohnnyBoxer said:
Look on the bright side, 'Andy' can now go and buy a superior KTM or Ducati and not be troubled by the GS fork stanchion recall:D
Click to expand...

Good point .. !

Steve ... ???? Go and get yourself a 1290S with yer insurance payout .... :D
 
JohnnyBoxer said:
Look on the bright side, 'Andy' can now go and buy a superior KTM or Ducati and not be troubled by the GS fork stanchion recall:D
Click to expand...

Giles said:
Good point .. !

Steve ... ???? Go and get yourself a 1290S with yer insurance payout .... :D
Click to expand...
We will have to await tomorrow afternoon to find out !! :D
 
Engineer said:
That's why I put 'shutter' in quotes - thought it would be easier for the non electronics people to understand - I will check the brake light multiplexing as I assumed that it would also be multiplexed as it is the same LEDs but just at a much higher M/S ratio than the tale light?????
Click to expand...

Yes - although I have an electronics background the latest vehicle electronics are new to me, so I'm not sure either about the brake light. However, anything less than 100% duty cycle/on time is going to mean that you need more powerful LEDs for a given brake light output, and if vehicle manufacturers can avoid over speccing components they generally will. For that reason I assumed that once the brakes go on the lights will be powered in a way which means they are giving maximum output continuously.

From a bit of Googling it seems that the most common frequency for the PWM (pulse width modulation) supplies on vehicle LED rear lights is 200 Hz, which is probably not fast enough as some people can still see this as flicker with their peripheral vision, as this is more sensitive to motion (in the form of intensity variations) than central vision. I've also seen figures of around 30% as being a typical duty cycle for the tail lights, so allowing around three times the brightness if run in brake light mode, presumably at or near 100% duty cycle.
 
fred_jb said:
Yes - although I have an electronics background the latest vehicle electronics are new to me, so I'm not sure either about the brake light. However, anything less than 100% duty cycle/on time is going to mean that you need more powerful LEDs for a given brake light output, and if vehicle manufacturers can avoid over speccing components they generally will. For that reason I assumed that once the brakes go on the lights will be powered in a way which means they are giving maximum output continuously.

From a bit of Googling it seems that the most common frequency for the PWM (pulse width modulation) supplies on vehicle LED rear lights is 200 Hz, which is probably not fast enough as some people can still see this as flicker with their peripheral vision, as this is more sensitive to motion (in the form of intensity variations) than central vision. I've also seen figures of around 30% as being a typical duty cycle for the tail lights, so allowing around three times the brightness if run in brake light mode, presumably at or near 100% duty cycle.
Click to expand...

There are all sorts of tricks one can play with LEDs - apparent brightness is a weird thing and there is not a direct relationship between PWM Mark/Space and apparent brightness - the LEDs on our newer products are all PWM RGBs so we can have full control BUT it is remarkable how the eye perceives brightness and 100% Mark/Space does not appear that much brighter than say 50% - However I digress :)
 
Giles said:
Good point .. !

Steve ... ???? Go and get yourself a 1290S with yer insurance payout .... :D
Click to expand...

Too late pick up a Rallye Sport tomorrow.

And i can assure you I have never had a broom stuck up my Ass, or anything else fir that matter
 
Engineer said:
There are all sorts of tricks one can play with LEDs - apparent brightness is a weird thing and there is not a direct relationship between PWM Mark/Space and apparent brightness - the LEDs on our newer products are all PWM RGBs so we can have full control BUT it is remarkable how the eye perceives brightness and 100% Mark/Space does not appear that much brighter than say 50% - However I digress :)
Click to expand...
Yes - I'm sure you are right that LED power does not correspond linearly to perceived brightness - maybe it's logarithmic or similar, like loudness of sounds is with the Decibel scale. :)

If we assume 25 Hz video v 200 Hz PWM then the video should be reasonably representative, even with aliasing and the rolling shutter effect due to line by line readouts, however I don't think there are enough consecutive frames of apparently high brightness to conclude that the brakes were actually activated.

I guess this is vaguely relevant to the thread in trying to work out if we are just seeing the on period of the tail light, or the brake light, though probably only of academic interest at this point, so I don't think I will bore people with further speculations on this, however interesting it is to me!
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
You must log in or register to reply here.

Similar threads

Adventure Boy
Thinking of swapping the XR for a GS !!
11 12 13
Replies
246
Views
9,702
Adventure Boy
Adventure Boy
just had delivert of a 2004 bmw 1150 gs adventure only 1 key
Replies
19
Views
1,256
TommoUK
EU death of the Sportster
2
Replies
36
Views
6,444
adm1
vee5
Rear caliper rebuild
Replies
10
Views
2,465
Slipperyeel
Slipperyeel
Tricky
There Is a Light That Never Goes Out...
2
Replies
25
Views
3,468
Roberto
Roberto


Back
Top Bottom