SAM: reason for separate wiring for left/right lamps?

[GLK]

A question has come up during a discussion, on the best possible location for my FLASH••A••BRAKE™ unit, when a customer desires to have all three lights controlled by the adaptive brake light system, just like the OE system does.

Say, we have a SAM with three different outputs (pins) for E3e4; E4e4 and E21 - i.e. the left, right and the top stop signal lamps.

It is logical to assume that, the signals transmitted to all three are perfectly synchronised, and therefore can be intercepted by a single unit, and relayed thereafter (<0.075sec). Essentially this is saying that, the split signal is implemented for logistical and manufacturing reasons - easy to separate at the SAM, no extra soldering/joints, wiring looms clearly defined, etc.

I would love to have an informed confirmation of this assumption though, please

 

[whitenemesis]

Would the outputs be separated so the system can detect a failure in any one unit? How would connecting your unit to one and then on to the other two affect this?

 

[GLK]

Would the outputs be separated so the system can detect a failure in any one unit? How would connecting your unit to one and then on to the other two affect this?

Good point. Presumably it will report both bulbs failed, when in fact only a single one had. Something else to test

 

[richard]

As said, its there to detect single bulb failures - not just for the message but to allow a substitute light to be lit. It also means the transistors are switching less current each (good) and smaller size wires can be used

Richard

 

[GLK]

Thanks Richard, that's great - I have a clear picture now.

My adaptive brake light unit doesn't interfere with the signal, unless rapid deceleration in primary travel direction is detected, then it's re-routed and emergency flashing activated, so it will work as intended

 

[richard]

Thanks Richard, that's great - I have a clear picture now.

My adaptive brake light unit doesn't interfere with the signal, unless rapid deceleration in primary travel direction is detected, then it's re-routed and emergency flashing activated, so it will work as intended

Doesn't the factory SAM do this for all 3 brake lights (or is the car slightly older)

PS, Its the bulb failure substitution I was talking about - i.e when the the left brake light fails it substitutes in the rear fog lamp on that side, so you need to be sure that the SAM isn't thinking a bulb has failed or all kinds of other things may light up

Cheers

Richard

 

[GLK]

Doesn't the factory SAM do this for all 3 brake lights (or is the car slightly older)

Yes, older and simpler - in this case it's my 2006 A200 - exactly why I created this gadget, for my own and similar cars, with no factory Adaptive Brake Light system.

Initially, I only planned for the third brake light to flash in an emergency, but had a number of enquiries, to have the unit emulate the OE system, i.e. flash all three lights.

Not a problem for older cars, including those without a third light, but requires further testing for something like my car, which is sort of in-between - it's got the SAM and ECUs, etc, but no ABL as a factory option.

Its the bulb failure substitution I was talking about - i.e when the the left brake light fails it substitutes in the rear fog lamp on that side, so you need to be sure that the SAM isn't thinking a bulb has failed or all kinds of other things may light up

Thanks again Richard, this is precisely what I needed to know, and what the additional testing will now focus on