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    Help with LED brake lights

    Good day folks. I'm having an issue which has been driving me nuts for the past few days: I CANNOT get some LED brake/parker lights to work on my car. I managed to track down the issue and THOUGHT I solved it, but when I tried it again, it STILL doesn't work....it's one of those "how the hell does this work?" type of deals. *LONG STORY WARNING*

    Let's explain some stuff so we're on the same page: I don't know if I'm calling them by their right name to begin with...these bulbs have two intensities: a dim one for the parker and a bright one to indicate braking. They achieve this by employing two separate filaments inside the same envelope, nothing special or amazing there, we've all seen this. The socket is a BAY15D, so it's got two contacts on the end for the + of each filament and the shroud is the -. They look almost identical to these.

    Now the LED ones I picked up also have a BAY15D socket and claim they do exactly the same thing: light up at full brightness when braking and dim down when you've got the parker lights on...fair enough I thought - should be a direct replacement and work like a charm, but no.... These weren't cheap either, so I MUST get them going or else this will be a disaster of automotive modding

    When I first got them, I first tried them out on the bench, just to ensure they work before I start taking things apart: negative clamp around the base and then touched the positive to each of the terminals and sure enough they worked. Red light came on at two different levels as advertised...no problems there so it was time to try them out on the car.

    After installing just one, I immediately faced unwanted behavior: I first tried the "parker mode", since it was easier to just turn the lights on and have a good look around the back, whereas with the brake I'd have to find something heavy to place on the pedal and....anyway. I got nothing on this first try: no light at all...I tried wiggling the socket around, tapping it, cleaning those contacts...it was useless...the light simply wouldn't come on. Adding to my frustration was the fact that inserting the original classic bulb which had been on the car for 10 years, resulted in immediate light, so why the hell wasn't the new one which I just tested on the bench 10 minutes ago not working ? After many many hours of tinkering and measuring, I managed to identify what the issue was...it's the brake circuit that's killing the light when installed...how do I explain this, since this is a wall of text already ?

    Check out the crude schematics I drew: when the brake is "off" (foot NOT on pedal, the car is rolling so to say), the brake wires aren't left floating: they're actually pulled low to GND, which isn't a problem for the dual-filament lamp, since the two filaments operate individually, but these LED lamps don't have two different sets of LEDs to achieve the same effect. I THINK they most likely use a simple resistor in line with the "parker" contact to achieve the dimmer light, so even though 12v were going into the lamp, they were immediately sank back into the GND through that internal resistor and the brake switch...hope that makes sense.

    Ok, so what now ? Are we just gonna leave it here ? Of course not. What I tried so far (but failed) was installing a diode in series with the brake wire (not figured in the schematics), hoping that when the brake is "off" (NOT pressed down), I'd get no current flow from the parker wire back through the resistor and into GND through the brake switch. I first simulated the setup on the bench: ground clamp around the base again and sure enough, when the parker is lit and the other contact is grounded, it immediately kills it. Installing a diode in series with the brake contact worked: grounding the wire no longer shut the light off and when it was the brake's turn to light up it did. With high spirits, it was back at the car again, where frustration resumed: with the diode in place, the parker light does come on, since the diode indeed blocks the current from going into GND, but now the BRAKE doesn't come on....UUGH ! WHY ?! Again, it worked on the bench, why not the real deal ?! When I touched the "enabled" brake wire with the diode to the corresponding contact, it made no difference: the lamp didn't come on any brighter.

    My only guess is that the brake lamp on the other side has something to do with it, since I haven't tried changing both at the same time - I only tried one so I wouldn't have to do twice the work if it didn't work *pun intended*....what now ? Is the diode to blame ? It's an SB5100 I reckon. I shall try unplugging the opposing light to see if it changes anything...if it doesn't then God knows what we'll do...looks like we'll have to build a little transistor switch or something....Cheers guys and thanks for your patience.
    Attached Files
    Last edited by Dannyx; 04-04-2018, 09:50 AM. Reason: Correction
    Wattevah...

    #2
    Re: Help with LED brake lights

    Verify the Polarity of the lamp socket?
    BTW, is the Brake switch really SPDT as shown in your drawing? Your drawing is confusing, I do not see why the Brake switch has to go to GND.
    Last edited by budm; 04-04-2018, 10:08 AM.
    Never stop learning
    Basic LCD TV and Monitor troubleshooting guides.
    http://www.badcaps.net/forum/showthr...956#post305956

    Voltage Regulator (LDO) testing:
    http://www.badcaps.net/forum/showthr...999#post300999

    Inverter testing using old CFL:
    http://www.badcaps.net/forum/showthr...er+testing+cfl

    Tear down pictures : Hit the ">" Show Albums and stories" on the left side
    http://s807.photobucket.com/user/budm/library/

    TV Factory reset codes listing:
    http://www.badcaps.net/forum/showthread.php?t=24809

    Comment


      #3
      Re: Help with LED brake lights

      It's standard like I said: negative on the outer shell, positive on each leg and it works straight off the battery or a 12v supply like that...
      Wattevah...

      Comment


        #4
        Re: Help with LED brake lights

        Yea, but did you actually verify it is actually connected like you think?
        BTW, is the Brake switch really SPDT as shown in your drawing? Your drawing is confusing, I do not see why the Brake switch has to go to GND.
        You can also try connect your new LED lamp in parallel with the OLD lamps to verify.
        Last edited by budm; 04-04-2018, 10:11 AM.
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment


          #5
          Re: Help with LED brake lights

          It's not on the CAN Bus is it and you have the wrong bulb ?

          Comment


            #6
            Re: Help with LED brake lights

            No CAN bus on the car as far as I know.

            I checked it with a multimeter and it's also clearly visible how the traces are laid out, since the GND trace is shared by all bulbs on the lamp holder, so you can't possibly get it wrong. Every other trace is +. THIS is how the bulb holder looks like BTW. The bulb in question is at the top (far left of the picture), easily identified by the BAY15D twin-blade connector. The one in the middle is the indicator and the bottom one is the fog light - no problems on either of those.

            The switch may not be EXACTLY a SPDT switch like I drew it, but that's how it operates nonetheless: it DOES connect to GND when not in use. If I place my meter's negative probe on the brake line when not pressed and the positive end to the parker light (switched on), I get a positive 12v readout, so the brake line is grounded, otherwise I would get 0v if it was floating. The behaviour is also confirmed by the LED light not turning on at all if one of its pins is grounded (whether on the bench or on the car).

            The drawing's pretty messy indeed - it was done for me to better follow what's going on and not really intended for sharing The first one with the squiggly filaments is meant to represent the two bulbs with two filaments each (so 4 filaments) and how they're connected in parallel to each other (left side and right side, since they're symmetrical on either side of the car), that's why I put an L and R there (left right). The second one is the same thing, but with the LED lamps and how I believe they look on the inside: series resistor for low intensity (parker) and the other connection straight onto the LEDs for high intensity (braking) bypassing the resistor entirely. Hope that clears it up a bit.
            Last edited by Dannyx; 04-04-2018, 10:29 AM. Reason: Added picture
            Wattevah...

            Comment


              #7
              Re: Help with LED brake lights

              The contacts in the socket not reaching the bottom contacts of the bulb. The LED bulb shank could be a 'tad' shorter and so not reaching to make contact in the socket.

              Comment


                #8
                Re: Help with LED brake lights

                Wish it were that easy TBH, however I doubt it because if I do the opposite and power JUST the brake line, the light does come on, so it is touching the blade underneath no doubt.

                On that topic: if I have both the brake on and the parker on at the same time (12v going to both wires), we've already established that touching the cathode side ("output") of the diode I tried putting in series with the brake line to the brake contact on the socket itself doesn't change the intensity at all (it should glow brighter and it friggin' DID on the bench !), however if I touch the wire directly (without the diode), it does glow slightly brighter, so it's an electronic issue/mismatch somewhere, not a mechanical one. All the while, the lamp on the right side (this was the left side I messed with) still had its regular, ordinary, run of the mill filament bulb in it, so that's what's on my mind next: try and unplug the right side to see if it makes any difference on the left.
                Last edited by Dannyx; 04-04-2018, 10:43 AM.
                Wattevah...

                Comment


                  #9
                  Re: Help with LED brake lights

                  nice wall of text... yow.

                  What if you have diodes on both brake and parking inputs?

                  Comment


                    #10
                    Re: Help with LED brake lights

                    One difference between the bench and the car is the other light bulbs in circuit.

                    So park lights OFF means that wire is almost grounded due to the other park lights in the car. They act like pull-down resistors.

                    Your LED lights, maybe draw the schematic because they should have a few diodes inside. If you brake and park lights are on, they would be super bright if only a resistor or two was involved.

                    Comment


                      #11
                      Re: Help with LED brake lights

                      Less headache solution......Get the original filament bulbs and forget LED light

                      Comment


                        #12
                        Re: Help with LED brake lights

                        I can't open them up to inspect the insides sadly...at least not without breaking them and they were expensive as I said Yes, there could be other components inside indeed. My schematic is not complete, since there should be another set of two parkers for the front....which I forgot about and further complicate matters since they pull down as well, however parker OFF and brake ON does work (with or without the external diode), so there's most likely a diode inside the LED lamps.
                        Wattevah...

                        Comment


                          #13
                          Re: Help with LED brake lights

                          Originally posted by Dannyx View Post
                          Now the LED ones I picked up also have a BAY15D socket and claim they do exactly the same thing: light up at full brightness when braking and dim down when you've got the parker lights on...fair enough I thought - should be a direct replacement and work like a charm, but no.... These weren't cheap either, so I MUST get them going or else this will be a disaster of automotive modding

                          8<

                          I first tried the "parker mode", since it was easier to just turn the lights on... I got nothing
                          When you press the break, do the (LED) brake lights illuminate properly?

                          After many many hours of tinkering and measuring, I managed to identify what the issue was...it's the brake circuit that's killing the light when installed...
                          Hence the reason to "lift that ground" (by depressing the brake pedal).

                          Once this is known to work, you can consider other ways of isolating just the ground into the brake pedal switch (so you can examine the results WITHOUT pressing the brake pedal).

                          Remove LED bulb. Use multimeter to check resistance between the parking and braking filament connections (i.e., how big is that "resistor" that's INSIDE the bulb)

                          Comment


                            #14
                            Re: Help with LED brake lights

                            I can't expect the brake light by itself not work with a diode (i.e. parking lights off) but due to voltage drop across the external SB5100 diode it may cause enough of a corresponding current drop to make it not light up brighter than the parking light input anymore.

                            Thus the idea to put diodes in series of *both* inputs, so there's now a voltage drop dimming for the parking light as well, and the additional brightness of the brake lights is now more pronounced...

                            Cheesy solution, ha. But it may just work, else you'll need to add transistors or something...

                            Comment


                              #15
                              Re: Help with LED brake lights

                              Originally posted by Curious.George View Post
                              When you press the break, do the (LED) brake lights illuminate properly?
                              Without the diode and without any other modifications, just the LED in the socket, yes, it does, regardless of whether or not the parkers are on or off, because there's nothing "sinking" the current away from the bulb. As soon as the brake is released, the brake line becomes grounded and pulls everything down.

                              Originally posted by Curious.George View Post
                              Hence the reason to "lift that ground" (by depressing the brake pedal).
                              Yes, you got it: pedal not pressed = brake Grounded (NOT floating as I originally thought). Pedal pressed = brake at VCC 12v. I placed a rock on the pedal - no joke
                              There could also be a resistor divider in there for the parker setting. I'll measure the brake terminal with the parker terminal connected to 12v (assuming the brake terminal goes straight to the top of the divider network, directly on the LEDs to light them up at maximum intensity). Something like THIS.
                              Attached Files
                              Wattevah...

                              Comment


                                #16
                                Re: Help with LED brake lights

                                Originally posted by eccerr0r View Post
                                Thus the idea to put diodes in series of *both* inputs, so there's now a voltage drop dimming for the parking light as well, and the additional brightness of the brake lights is now more pronounced...
                                I thought of that too and shall first simulate it on the bench again with an LED lamp and a regular bulb in parallel to see if that's what indeed makes a difference. When I tested JUST the LED lamp, the dimming/brightening worked even with the diode (both inputs being powered up simultaneously - parker terminal straight off the adapter and brake terminal through the diode). As I touched the diode's cathode to the brake terminal, it came on brighter indeed.
                                Last edited by Dannyx; 04-04-2018, 02:07 PM.
                                Wattevah...

                                Comment


                                  #17
                                  Re: Help with LED brake lights

                                  the diodes should work,
                                  can you post a photo of the led lamp?
                                  i'v seen some with a semiconductor based dropper,
                                  and some that use 2 groups of leds, one for low brightness and both for high.

                                  did you check resistance between the contacts in all combinations?

                                  Comment


                                    #18
                                    Re: Help with LED brake lights

                                    btw, another option is to mod or replace the brake switch - i'v never seen one do that.
                                    is it 3 wires, or grounding through the casing? obvious answer is cut the ground.

                                    Comment


                                      #19
                                      Re: Help with LED brake lights

                                      Anyone mentioned about voltage? Running car on idle supply about 12.8V-13.2V, above 1k-1.5k rpm 14.4V but with engine shut off 11.8-12.1V . If battery is bad it can be much less.
                                      I would focus on this and measure voltages in the car just at the lamp connector.
                                      Laptops and computers repair.

                                      Comment


                                        #20
                                        Re: Help with LED brake lights

                                        Nope - it's around 12.5v at the socket no problem. Didn't have the time to tinker with this project anymore, with Easter being right around the corner you know, but I shall return to it somewhere next week I expect if all goes well...
                                        Wattevah...

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