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    #21
    Re: Car LED Headlights dimmer?

    If it is boost/buck type circuit inside to maintain constant current then I do not expect it to dim down when placing resistor (or MOSFET) in series to cause it to dim down, and if you lower the input Voltage to the regulated circuit then input current will go higher to maintain the same output power.
    His second picture shows dimmer lights and lower current draw.
    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


      #22
      Re: Car LED Headlights dimmer?

      A picture of the pcb inside the LED lamp would help.
      BigClive did a teardown of one with a fan on the end and datasheets of QX9920 IC and sch.
      https://www.youtube.com/watch?v=CX_uFs5vKc0
      Last edited by redwire; 02-11-2019, 06:01 PM.

      Comment


        #23
        Re: Car LED Headlights dimmer?

        Originally posted by redwire View Post
        I think we're assuming the LED headlamp is like a light bulb, a linear load.
        But inside is most likely a boost/buck converter.

        So supplying the LED lamp with 10V or 15V should give the same (constant) power to the LED's and not really dim it.
        The led light dimmer worked very good wild range adjustment, the very good linear adjustment from very dark to maximum brightness.

        When I pulled the led light out, no heat dissipation, led overheat right away, not enough time for meter to read. Pic1, 2, 3
        Attached Files

        Comment


          #24
          Re: Car LED Headlights dimmer?

          You can lower the buck-converter output current by removing one or two of the three sense resistors R2, R3, R4 that are 0.25R each.
          If the 6-pin IC is QX9920, roughly... all three = 3A, two = 2A, one =1A current to the LED's. The fan is 9V so it might be a 9V LED array.
          I'm guessing:
          9V 3A to the LED's is 12V 2.25A input
          9V 2A to the LED's is 12V 1.5A input
          9V 1A to the LED's is 12V 0.75A input
          Last edited by redwire; 02-11-2019, 07:21 PM.

          Comment


            #25
            Re: Car LED Headlights dimmer?

            Your inference is very correct.

            BigClive, He explained very well. I can add a little bit more here.

            COB LEDs are 3 in each row and 10 in each line. Total 30 in my case. If leds are 3.3v then driver voltage will be 9.9v.

            This is like putting all the LEDs of a 50-inch TV on two sides of one stick. That's why the stick is so hot. I have been using it for half a year, so far so good maybe is because of the fan.

            One thing I don't understand is why they don't use 12 volts directly.
            Attached Files
            Last edited by capwizard; 02-12-2019, 08:40 AM.

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              #26
              Re: Car LED Headlights dimmer?

              because a car is not 12v, it's as low as 11 when stopped with a low battery and as high as 14.8 when charging (or worse if the alternator is shit)

              Comment


                #27
                Re: Car LED Headlights dimmer?

                Originally posted by budm View Post
                The Voltage reading of 12.17V @.177A, is it the Voltage reading on the LED terminal or on the input feeding Voltage to the circuit. What is the Voltage between S and D pin of the MOSFET? Once you know that then you can calculate the Power dissipation of the MOSFET.
                The Voltage reading of 12.17V @.177A is it the input feeding Voltage to the circuit.

                What is the Voltage between S and D pin of the MOSFET?

                Sorry took a long time to answer this question because of pic1. As sti predicted, the breadboard is melted.
                So I added a heat sink. Circuits are too simple to be true. Let's test for 3 days.

                Next, I gonna put two led headlights to one MOSFET see what's going on?
                Attached Files
                Last edited by capwizard; 02-12-2019, 11:22 AM.

                Comment


                  #28
                  Re: Car LED Headlights dimmer?

                  I cannot tell from the pictures as to what Voltage you have between the S & D pin of the MOSFET.
                  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


                    #29
                    Re: Car LED Headlights dimmer?

                    I soldered Fluke test leads on S and D pins of mosfet already.

                    Full lightness is 11.9v at 2.478A.
                    12.4v at 0.178A
                    12.18v at 0.102A
                    Last edited by capwizard; 02-12-2019, 11:35 AM.

                    Comment


                      #30
                      Re: Car LED Headlights dimmer?

                      https://www.badcaps.net/forum/attach...1&d=1549771216
                      That cannot be right since the MOSFET is in series with the load, so if you have 11.9 V at full brightness between S and D then the load will barely has any Voltage on it.
                      And at 11.9V @ 2.478A that will be lots of Wattage.
                      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


                        #31
                        Re: Car LED Headlights dimmer?

                        I connected two led lights together, reading is from a 12v power input at full brightness. Pic 1
                        Attached Files

                        Comment


                          #32
                          Re: Car LED Headlights dimmer?

                          I connected two led lights together, reading is from a 12v power input at full brightness. Pic 1

                          12.24v @ 4.825A for two lights. Mosfet is 50A that means OK.
                          Attached Files
                          Last edited by capwizard; 02-12-2019, 12:47 PM.

                          Comment


                            #33
                            Re: Car LED Headlights dimmer?

                            But as you know in series circuit, if you have 12V between S and D pin then how can you have any Voltage left for the LED?
                            BTW, it is not just the current rating, you have to consider the power dissipation also to keep the junction temperature at the safe level so proper heatsink is required.
                            Right now you are operating the MOSFET in linear region.
                            https://cdn.badcaps-static.com/pdfs/...f668f60e6d.pdf
                            https://www.powerelectronics.com/dis...mode-operation
                            Last edited by budm; 02-12-2019, 01:55 PM.
                            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


                              #34
                              Re: Car LED Headlights dimmer?

                              My bad, I am so Inteligente, series the meter leads to S and D, it should be parallel.

                              I used a more simple circuit and in the future only use one resistor.
                              Attached Files

                              Comment


                                #35
                                Re: Car LED Headlights dimmer?

                                My bad, I am so Inteligente, series the meter leads to S and D, it should be parallel.

                                I used a more simple circuit and in the future only use one resistor. Because potentiometer is not easy to find in Africa.

                                My idea is car has dim lights during the day. At night auto turn on and switch with full or half full light.

                                Pic 4 is at full brightness.
                                I double posted again...cellphone.

                                I have a dream......can we use this idea applies to the tv led backlight, forced to the people who refuse to reduce their brightness.
                                Last edited by capwizard; 02-12-2019, 01:50 PM.

                                Comment


                                  #36
                                  Re: Car LED Headlights dimmer?

                                  Well, when Data does not make any sense then you know something is not done right. Data is important to me.
                                  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


                                    #37
                                    Re: Car LED Headlights dimmer?

                                    MOSFETs Withstand Stress of Linear-Mode Operation....in this article I can't find fig. 1 ,2, 3, 4, 5 ?

                                    an extended forward-bias safe operating area (FBSOA).

                                    MOSFET is subjected to high thermal stress due to the simultaneous occurrence of high drain voltage and current resulting in high power dissipation. When the thermo-electrical stress exceeds some critical limit, thermal hot spots occur in the silicon causing the device to fail.
                                    Attached Files

                                    Comment


                                      #38
                                      Re: Car LED Headlights dimmer?

                                      yes, so use PWM like it already does.

                                      Comment


                                        #39
                                        Re: Car LED Headlights dimmer?

                                        Or, a big heat sink? PWM IC is not easy to find in Africa.

                                        I used half brightness, mosfet is not hot at all.
                                        When I used full brightness, mosfet is getting hot, still touchable, the way to solve this problem is full brightness just bypass it.

                                        No needs mosfet just use a coil from a hairdryer make 2.5A x 12v=30w current limit resistor.
                                        Attached Files
                                        Last edited by capwizard; 02-12-2019, 04:06 PM.

                                        Comment


                                          #40
                                          Re: Car LED Headlights dimmer?

                                          you think africa cant get arduino nano's??

                                          Comment

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