Hey guys,

New to this forum, but I've been brainstorming a project for some time now.

I recently developed a set of LED taillights for the IS300, but there is one obvious problem. The current from the LEDs is substantially less than the standard bulbs, so it trips a rear bulb failure light.

I am against load resistors wired in parallel because others who have done the same thing have melted taillights.

Essentially, I'm just looking to have a small circuit to tell me when a LED module has failed (or fuse has blown, etc).

I've been eyeing the zetex high side current monitor, but I wonder if i'm missing something much simpler here.

ANyone have any other suggestions, I'm so deep in this perhaps a fresh look at the problem might yield better results. Also, modding the original sensor circuit is out of the question, since the chip was manufactured by Denso, and they won't release datasheets about the chip tothe public, but i do have part numbers if anyone has access or thinks they can help.

Thanks,
Nick

 

...perhaps the trick is to determine the "trip point" for the rear bulb failure circuit in the IS300's body monitoring computer. You could do this with successively lower wattage bulbs... it may be that just a trickle of current is all you need so a low-watt (and cool) resistor will do the trick.

Other than that it would help to understand how the various body computers test bulb presence/function... for instance, do they only check on initial switch-on, versus continuously? The former might allow you to place the resistor in-circuit at the beginning of a lighting cycle... the switch it out with a MOSFET.

LED failure is a much lower likelihood than for bulbs... perhaps it's worth ignoring? Silly observations aside, just put a low-ohm resister/shunt in series with the LEDs so you can use an a/d channel across it to measure the LEDs drawing current. Other ways to do it might be to use a phototransistor to monitor LED light output.

I think your main issue is turning off the damn dashboard light that's already there... short of disconnecting it from the dash... as I know it would annoy the hell out of me ;-)

P.