Or to borrow a golfing reference, that's not a drive, just a putt.

Sure that's not a hole in one?

 

Here's a relay solution with resistor that detects the three states -- Off, PWM, and full-on:
(I believe it's similar to what MB2 suggested.)
When the PWM signal is detected, a relay bypasses the PWM and connects the LEDs to 12V through a resistor.
With a steady 12V, the relay directly connects the 12V to the LEDs.

Below is the LTspice sim of a circuit to do that:
With a PWM signal from the lights (green trace) the relay is energized (red trace) and the LED is connected to 12V through R3 (yellow trace).
With a steady lights signal, the relay is turned off, and the lights' 12V is applied directly to the LEDs (at about 425ms here).
With no signal (at the start) no voltage is applied to the LEDs.

At the start of the PWM signal there is a short delay due to the relay operate time (about 40ms here).

The value of R3 value and power rating must be experimentally determined to give the desired LED DRL brightness.

View attachment 351469

This is awesome. Quick questions: Can you explain function of D4 here? Grounding R2 through the stock wire back to the BCM seems reasonable /preferred but I'm assuming all other grounds are safer going to the chassis. This circuit assumes the PWM is on the positive side, not the ground yes? I'm assuming ground side sensing would be similar. I will verify which side is being controlled in my case (2014 GM) and report back. The only suggestion I would offer would be it would be nice if the relay wasn't energized during DRL/PWM just from a longevity standpoint (most people have many more hours spent on DRL/day driving than lo/night) but that would probably be cumbersome and a solid state relay would probably do the trick.

Assuming this circuit works I can't believe its not been packaged/marketed yet by aftermarket companies like iJDMtoy. I'm in a similar but different situation as OP... Many GM cars were equipped with good projector housings designed for HID bulbs but low spec models received halogen bulbs/no fancy DRL instead. Its a common mod to source the higher spec OE DRLs/HIDs and retrofitting but separating out DRL/low beam function (critical for HID longevity) and maintaining OE like operation is always an issue.

Thanks!

 

Re: legal issues... That 'no brighter than OE' law would be fun to argue in my case: I seem to remember the NTSB was investigating GM for the abysmal light output of halogens being put in HID projector housings causing accidents in a bunch of models.

Putting LEDs/HID in halogen housings doesn't seem to be much of a problem anymore in my area - everyone figured out the light output sucks. Even the lifted pickup guys around here generally have their lights re-aimed sufficiently and rely on light bars for deer spotting etc. I think the OE laser/LED lights are a far bigger issue.

 

Can you explain function of D4 here?

It's to provide reset current to C2 when the lights voltage returns to zero.
When the light signal goes high, current goes through C2 and D1 to turn on the relay.
When the light signal goes low, current goes through D4 to resupply the current to C2 that went through D1.

This circuit assumes the PWM is on the positive side, not the ground yes?

Yes, but it can easily be reconfigured if it's not.

it would be nice if the relay wasn't energized during DRL/PWM just from a longevity standpoint

A relay's longevity is mainly determine by its number of operations, not how long its been on.

 

I am late to the thread, but let me share my experience.
I have a Mazda CX5 which has separate bulbs for the low and high beams. The high beams are used as DRLs and are PWM-dimmed when operating that way.
A couple of years ago, I also installed LED lamps on both low and high beams, and had many issues. Long story short, I kept the LED on the low beams only and reverted to stock halogen on the DRL/high beams.
I weighed several options, and that ended being the safest one.
Hope that you can succeed where I failed.

 

It's to provide reset current to C2 when the lights voltage returns to zero.
When the light signal goes high, current goes through C2 and D1 to turn on the relay.
When the light signal goes low, current goes through D4 to resupply the current to C2 that went through D1.
Yes, but it can easily be reconfigured if it's not.
A relay's longevity is mainly determine by its number of operations, not how long its been on.

Thanks for the quick response. I guess I need to break out the old electronics books and brush up. Signal goes high, current flows through C2 (because there is a voltage differential) through D1,not through D2 (obvious), into/charges C1 and powers the relay. Signal goes low, C1 discharges powering relay, D1 prevents current from back feeding to source /charging C2. Not sure where current comes from to flow through D4 (triangle is ground yes?), not sure why C2 needs resupply while signal is low when C1 is doing the work. I figured inline C2 was there to help even out the delivery a bit (PWM Hz vs capacitor charge/discharge speed), couldn't figure out D2.

 

not sure why C2 needs resupply while signal is low when C1 is doing the work.

The charge that went from C2 to C1 when the input goes high, has to be replaced when the input signal goes low, otherwise there will be no charge available when the input again goes high.
That charge comes from ground through D4, when the input goes low.

I figured inline C2 was there to help even out the delivery a bit (PWM Hz vs capacitor charge/discharge speed)

No.
C2 is there to pass the AC PWM signal, and block DC when the input is steady-state high so the relay will then become deenergized.

couldn't figure out D2

I see no D2 in my circuit in post #24, so what are you referring to?

 

I just read thru this thread again. I will make no comments at all. On this thread. EVER.

 

The Thread Starter is no longer a member of AAC.

 

I just read thru this thread again. I will make no comments at all. On this thread. EVER.

??

 

The Thread Starter is no longer a member of AAC.

Which means??

 

??

Second those question marks.

 

Which means??

It means my cousin TonyR1084 has left AAC.

 

It means my cousin TonyR1084 has left AAC.

Well, we will miss your cousin.
But I don't see how that affects this thread (?).

 

No, I guess it doesn't.

 

No, I guess it doesn't.

Update. Confirmed positive PWM control. Bread board tested the circuit and it does not seem to work as intended. Connecting constant +14 dc yields a barely detectable low voltage at the relay (.04). Connecting to the car/PWM yields zero volts. I'm thinking only 'correct' way to do this would be to find the operational hz of the PWM and use a counter IC.

Attached setup to verify correctness.

 

Update. Confirmed positive PWM control.

Sure you got the right thread?