I've seen a number of cars with flashing brake lights. How long have they been around!
clark20,
Feb 3, 10:41am
The brake lights flash when the ABS is triggered as an extra warning on newer cars
esprit,
Feb 3, 10:53am
As has been said, some newer cars will flash their brake lights under extremely heavy braking. However, on TV, some newer cars equipped with LED rear lights will appear to flash because of the frequency difference between the capture rate on the camera and the LED emittance frequency causes a beat frequency, which is seen as flashing or strobing.
pollymay,
Feb 3, 11:01am
Or maladjusted stop light switch bouncing on bumps
kokako14,
Feb 3, 11:28am
Jezz, arnt cars complicated now. some newer cars equipped with LED rear lights will appear to flash because of the frequency difference between the capture rate on the camera and the LED emittance frequency causes a beat frequency Henry Ford would be spinning in his grave, or should that be flashing
NZTools,
Feb 3, 6:58pm
Tis no different to wheels appearing to be turning backwards on tv.
biddy6,
Feb 3, 7:32pm
Any one remember those sequential rear indicators on the big yank tank cars of the 60/s maybe early 70/s. I cant recall what models had them now.
That's what I am seeing. In the CCTV camera they are flashing, and with the naked eye they are not flashing. What frequency is the LED emittance frequency! I imagine the CCTV is 25 frames per second.
studio1,
Feb 3, 10:36pm
The best way to drive LEDs at high brightness is to pulse them. Short, sharp pulses of energy make them glow really bright but do not allow them to get too hot - which a consistent current would (and cause them to burn out). A pulse rate of anywhere over 200 times a second is invisible to the human eye, so it's probably somewhere in this vicinity or higher. You'd be correct in assuming the CCTV scan rate is 25 Hz.
Not to be confused with OP's impression of flashing brake lights which do so at a slow rate - maybe 2 or 3 times a second as a more visible 'warning' to people following. I remember seeing a project a couple of years ago in an electronics magazine for a unit you could build yourself. It wasn't triggered by the brake light switch, but by a sensor on the accelerator. The theory being is that if you need to stop in a hurry, your foot comes off the accelerator faster than it goes on the brake. The circuit senses the 'sudden' removal of pressure from the accelerator and flashes the brake lights sooner than what you would get if it was just being triggered by the brake light switch.
aredwood,
Feb 3, 11:43pm
Could be interesting on a manual car. The brake lights would flash on each gear change when accelerating.
zak1998,
Feb 4, 12:00am
Yank cars flash
studio1,
Feb 4, 12:23am
The circuit is able to discriminate between taking your foot off the gas when gear changing and suddenly doing it when needing to stop in a hurry. If you think about it, when you're changing gear, the speed at which you take pressure off the gas is much less than if you have to urgently brake.
I don't know of anyone that built one of those units, so I don't know how good they were. Another circuit I have seen is one that causes your brake lights to flash twice a second for around 3 seconds every time you touch the brake pedal.
offrd1,
Feb 4, 12:37am
I have flashing brake lights on the bike.just touch the brake and they flash 3 or 4 tmes,i think they came as a kit when the first owner up graded to LEDs [ quite expensive i'm told ] good on a bike as they really get noticed
thejazzpianoma,
Feb 4, 3:41am
No doubt others do it too but with VW's like the Mk5 Golf, Audi, Skoda etc you can turn this feature on or off when you hook it up to the VW diagnostic software. There's a lot you can adjust on modern cars like that, brightness of your fog lights, whether you want the car to beep when you lock it, driving lights on/of, transmission shift patterns. etc etc.
modie61,
Feb 4, 3:55am
Is it legal to have flashing brake lights ! Dont get me wrong i think its a great idea. As long as when 1 side blows it doesnt get confused as an indicator,not that anyone uses indicators round here anyway. Lol.
Not under normal conditions, they should not flash. The ABS is an emergency thing.
offrd1,
Feb 4, 4:54am
Yes legal,and the cops like them,have had quite a few comments when pulled up all good,they reckon all bikes should have them .lol.mine has nothing to do with ABS as my bike doesn't have it
trade4us2,
Feb 4, 6:14am
I am the OP, and the flashing I was seeing in the TV was at least 10 times per second, on a few modern cars, just doing normal braking. However the slower flashing lights are a good idea.
clark20,
Feb 4, 7:24am
Then it is "pulse width modulation" used to regulate the LED tail lamps. The lights are on and off very fast (not seen by the normal eye) however the camera can catch them on or off, so it looks flashing on the TV
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