need opinions for LED's in Automotive CANBUS applications

[ashepher]

Hey EEV Blog folks,

Im a mechanic and always get asked about running led's on CANBUS error checking circuits in cars. From what I have tested in the past this is pretty much fraught with issues and its about time I get some opinions of more qualified people to give there thoughts and I could really find another topic that covered this problem exactly.

Issue 1:
non can bus led's don't turn off dash cluster warning lights.

Issue 2:
can bus "error removing" globes have simply a resistor in what looks to be parallel. in applications such as indicator lights, the resistor is able to cool down enough between each time the circuit is powered however if the light is on constantly it burns out.
there are alternatives such as a Phillips "led control unit", which is pretty much again a load resistor and usually has the same overheating and burnout issues if constantly on.

My taking on these problems is simply the current is too high for too long and results in too much heat. while I can easily devise ways to cool down the resistors such as better heat sinks, cooling fans or mineral oil cooling (which has limited practicality in hot engine bays) I have been wondering if there is a better method to avoid most the issue in the first place.

Its possible to turn off the CANBUS globe detection system in some cars but that would require having access every in house diagnostic tool.
Had some thoughts about maybe trying a linear regulator or pwm but figured I would ask you folks first

cheers Shepherd

[garethw]

Are you talking about headlamps LEDs? The can bus has nothing to do with LEDs, it is a communication network between separate modules in the car. Faults detected by one module regarding LEDs will be transmitted across the can bus as a message, nothing more.
If you’re trying to trick the module into thinking there is an LED present when actually it’s a resistor then you will struggle. The current and voltage characteristics are programmed into the LED driver by the manufacturer. Anything other than an LED with the same specifications will probably raise a fault code.
These aren’t as simple as “fixing” airbag warning lights with a resistor [emoji3]


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[techman-001]

Hey EEV Blog folks,

Im a mechanic and always get asked about running led's on CANBUS error checking circuits in cars. From what I have tested in the past this is pretty much fraught with issues and its about time I get some opinions of more qualified people to give there thoughts and I could really find another topic that covered this problem exactly.

Issue 1:
non can bus led's don't turn off dash cluster warning lights.

Issue 2:
can bus "error removing" globes have simply a resistor in what looks to be parallel. in applications such as indicator lights, the resistor is able to cool down enough between each time the circuit is powered however if the light is on constantly it burns out.
there are alternatives such as a Phillips "led control unit", which is pretty much again a load resistor and usually has the same overheating and burnout issues if constantly on.

My taking on these problems is simply the current is too high for too long and results in too much heat. while I can easily devise ways to cool down the resistors such as better heat sinks, cooling fans or mineral oil cooling (which has limited practicality in hot engine bays) I have been wondering if there is a better method to avoid most the issue in the first place.

Its possible to turn off the CANBUS globe detection system in some cars but that would require having access every in house diagnostic tool.
Had some thoughts about maybe trying a linear regulator or pwm but figured I would ask you folks first

cheers Shepherd

Hi Sheperd, I did automotive electronics for many years, but always hated any automotive electrician work, those guys earn their money!
In those days car's didn't have CANBUS but it seems to me that the current CANBUS system has been designed for safety and lower cost and that there are only two ways to deal with this issue properly. Note I've never seen a current CANBUS bulb and holder with inbuilt circuit so I'm making some assumptions.

1) replace the blown bulb with one of the same exact OEM bulb, This is the most legal and safe method.
2) Replace the bulb with a LED and reprogram or replace the CANBUS module so it actually talks to the CANBUS master and only raises the alarm when the LED fails. This method may break the law if the LED is the wrong color, brightness or if it doesn't meet the applicable legislation for any reason. It also may break copyright and be very hard to do. It may result in the FBI shoving a M14 in your face at 3am while you sleep and screaming "DMCA BREAKER YOU'RE GOING TO GITMO"

The popular method of replacing the bulb with a LED and adding a nice hot LED shunt resistor so the LED/resistor combination draws the same power as the bulb .... in order to save power compared to a bulb and not upset the CANBUS error circuit  seems to be a contradiction?