Question about LED headlamps and other external lamps

[ekrampitzjr]

LEDs in use on buildings running off mains power often fail by "strobing", meaning flashing on and off quickly.

Can LED headlamps, taillamps, etc., on cars fail in this same way? Normally they simply seem to fail by going out. If they can "strobe", that would seem to be a hazard. If they cannot strobe, why not? Are they designed not to, or are the controlling electronics simply different from those used with LEDs in buildings?

Thanks.

 

[ctechbob]

Usually, the power supplies in 12v lighting is much more simple than the switching supplies of the lights you see pulsing. The AC lights that you see pulsing are usually switching power supplies that have failed in some way, causing their controllers to pulse. DC lighting will usually just burn out the LED or pop some passive device which will kill the light.

 

[BlueOvalFitter]

Why is it that when you put an LED bulb in your vehicles light socket, it won't light up until you 180* it?

 

[ctechbob]

Probably because it is a Light Emitting Diode. By design, diodes only pass current (light) one direction, although I do believe there are some designs that are capable of working either way, but that depends on other circuitry and not the design of the actual emitter.

 

[tnt_motorsports]

@BlueOvalFitter
I’ve always thought of diodes like an electrical check valve. Current can only flow in 1 direction.

Just my $0.02

 

[repairman54]

Automotive LED can fail and blink off / on. Had it many times on license plate bulbs with the cheaper online bulbs. Also with interior LED bulbs.
DC electronics are polarity dependent, which LED bulbs are electronic devices.

 

[ekrampitzjr]

Probably because it is a Light Emitting Diode. By design, diodes only pass current (light) one direction, although I do believe there are some designs that are capable of working either way, but that depends on other circuitry and not the design of the actual emitter.

Back in the days of Radio Shack, a commonly available LED lit different colors depending on current flow. It had three leads with one of them a common anode. The bulb was clear, but glowed red if current ran through one cathode and green if through the other cathode. Versions are still available. Also, an RGB tri-color LED for screen use is available today.

 

[BlueOvalFitter]

@BlueOvalFitter
I’ve always thought of diodes like an electrical check valve. Current can only flow in 1 direction.

Just my $0.02

Hey, in my old field of work I used to install BOO KOO check valves, 1/8" up to 48".

 

[circuitsmith]

are the controlling electronics simply different from those used with LEDs in buildings?

This.
It's the driver circuitry that controls the voltage and current to the diode that fails and strobes, not the LED itself.
It's todays common switchmode drivers that fail in this mode.
Many low power DC applications simply use a series resistor.
Earlier AC applications used a capacitor's impedance to limit current plus rectifiers to convert to DC; no regulation.

 

[Vern_in_IL]

Possibly, but automotive electronics are much more robust because of NHTSA.

 

[HouseTiger]

To expand a tad on the OP - at what point do load balancing resistors come into play ? Is there a year when everything became LED compatible ??

I know on most older cars (made before common use of LED lights) had a dedicated flasher module and if you put LED bulbs in as replacement for turn signals, they'd behave in a very erratic manner, assuming they worked at all.

I've not seen this on many newer cars, especially those that have part of the exterior illumination using LEDs. I've been told the main computer control module now regulates turn signals. Does anyone know if the electrical circuits used more recently come with load balanced circuits from the factory for replacing incandescent lamps with LEDs ??

 

[Jetronic]

Back in the days of Radio Shack, a commonly available LED lit different colors depending on current flow. It had three leads with one of them a common anode. The bulb was clear, but glowed red if current ran through one cathode and green if through the other cathode. Versions are still available. Also, an RGB tri-color LED for screen use is available today.

most likely it had 2 leds in it

 

[paulo57509]

Back in the days of Radio Shack, a commonly available LED lit different colors depending on current flow. It had three leads with one of them a common anode. The bulb was clear, but glowed red if current ran through one cathode and green if through the other cathode. Versions are still available. Also, an RGB tri-color LED for screen use is available today.

They're still available from places like Mouser.

 

[brianl703]

Possibly, but automotive electronics are much more robust because of NHTSA.

The cheap Chinese LED crap doesn't comply with NHTSA or any other regulations.

 

[Skippy722]

To expand a tad on the OP - at what point do load balancing resistors come into play ? Is there a year when everything became LED compatible ??

I know on most older cars (made before common use of LED lights) had a dedicated flasher module and if you put LED bulbs in as replacement for turn signals, they'd behave in a very erratic manner, assuming they worked at all.

I've not seen this on many newer cars, especially those that have part of the exterior illumination using LEDs. I've been told the main computer control module now regulates turn signals. Does anyone know if the electrical circuits used more recently come with load balanced circuits from the factory for replacing incandescent lamps with LEDs ??

Depends highly on the vehicle and even the years within a given generation of vehicle.

On most, if not all, newer cars with computer controlled circuits you can throw LED’s in place of incandescent bulbs and at worst they’ll hyperflash and/or give a bulb out warning. Some you can code for LED bulbs (like my Ram for example, just plug in AlphaOBD and tell it it has LED lights, no more problems), others require resistors and canbus adapter trickery to function properly without warnings. 2015 Ram’s for example are super finicky, but 2009-2014 and 2016+ 4th gens aren’t.

 

[meep]

The circuits driving LED’s at this point have become highly complex. Until the high intensity uses came about, when led’s were just simple on/off indicators, all one needed was a single current-limiting resistor wired in series with it. These were low brightness, low power emitters and you’d run them well under max output.

however, getting them to run at max output, just beneath the threshold where they melt down, requires a fairly complex, current-limiting power supply. Whereas incandescent light bulbs in a sense “self protect” by increasing resistance as they heat up, LEDs are the opposite; the hotter they become, the lower their resistance becomes, allowing more current to flow through them, creating more heat, until they invite self-destruction. For this reason, high brightness LEDs *should* have a current limiting power supply (or controller, or driver) behind them, which keeps them in that sweet spot between high output and overheating. A simple resistor just won’t do.

automotive electronics tend to be pretty robust - well sealed, protection against electrical spikes and noise, vibration standards, etc.. Vehicles are hard environments for electronics.

 

[George7941]

Slightly off topic here but I fitted Sylvania Zevo 9006 leds on my Sierra about five years ago and it is nice to to have not to check on whether you still have both headlamps working. The Zevos are legal in Canada and nobody has complained so far about the leds being too bright or blinding them.

We have one Freightliner at work that goes long distance and I fitted 9006 Zevos on it for the extreme reliability that comes with quality leds.

 

[dogememe]

Slightly off topic here but I fitted Sylvania Zevo 9006 leds on my Sierra about five years ago and it is nice to to have not to check on whether you still have both headlamps working. The Zevos are legal in Canada and nobody has complained so far about the leds being too bright or blinding them.

We have one Freightliner at work that goes long distance and I fitted 9006 Zevos on it for the extreme reliability that comes with quality leds.

Yeah, the Sylviania LEDs are nice. Not technically legal here in the US but I’ve had LED headlights in all my vehicles for years ranging from $25 eBay ones to the Sylvanias and never had any trouble. I always buy based on proper beam pattern and if needed for the application the ability to rotate it for proper alignment.

 

[HouseTiger]

Depends highly on the vehicle and even the years within a given generation of vehicle.

On most, if not all, newer cars with computer controlled circuits you can throw LED’s in place of incandescent bulbs and at worst they’ll hyperflash and/or give a bulb out warning. Some you can code for LED bulbs (like my Ram for example, just plug in AlphaOBD and tell it it has LED lights, no more problems), others require resistors and canbus adapter trickery to function properly without warnings. 2015 Ram’s for example are super finicky, but 2009-2014 and 2016+ 4th gens aren’t.

Thanks for the comeback. This is specifically on my wife's 2016 Chrysler Town & Country. The DRL (a/k/a high beam) element that is now an LED has a slight flicker when in Daytime Running Light mode. When running as high beam, it's solid. Also 'quirky' now is that when running in DRL, applying the turn signals will cancel out the LED on the side that's activated.

I'm thinking that maybe (?) because in DRL mode the LED runs at about half voltage that might be messing with things.

Guess I'll have to look into installing resistors or other adapters. Fun, fun, fun.

 

[Skippy722]

Thanks for the comeback. This is specifically on my wife's 2016 Chrysler Town & Country. The DRL (a/k/a high beam) element that is now an LED has a slight flicker when in Daytime Running Light mode. When running as high beam, it's solid. Also 'quirky' now is that when running in DRL, applying the turn signals will cancel out the LED on the side that's activated.

I'm thinking that maybe (?) because in DRL mode the LED runs at about half voltage that might be messing with things.

Guess I'll have to look into installing resistors or other adapters. Fun, fun, fun.

They use PWM on the DRL/high beam when in DRL mode, capacitors should help. Resistors won’t help for that problem.

I’m like 99.9% sure the drop out when the DRL’s are on and then you activate a turn signal is normal, I’ll double check on our 2018 Grand Caravan though.