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Hooking up a 12v DC LED strip box to Automotive wiring?

Discussion in 'Automotive Electronics' started by electricview, Jan 11, 2012.

  1. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Yes it should have been 11.60 at the solder pads on the board. May be you have a bad wire or connection to the car.
    Test your red and black wires going to the car.
     
    Last edited: Jan 13, 2012
  2. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    11.6 V may indicate car electrical problems. I would check the voltage at the car battery.
     
  3. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    My guess is you should have seen around 12.5 volts into the board minimum and 5 volts at the 7805 output. I would start by replacing the 7805. Assuming you had a good ground when you took the measurements you should have seen 12,5 to 14.5 or greater in and 5 volts out. Depending on your location a 7805 can be had at any Radio Shack or parts house for a few bucks or less.

    Ron
     
  4. dave

    Dave New Member

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  5. electricview

    electricview New Member

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    Okay so i did another test and the results are the kind of things that confuse me..

    I hooked up my multi meter to the wires from the car for this intended to power this box (I use a pair of aligator clips) and get a solid steady 13.60, when the car is running its 14.80 ish or so. then when i hooked up this defunc box to the aligator leads (that are connected to the car power for this project), i this time for the hell of it put my multimeter leads into the aligator teeth that were clamped onto the wires coming out of this defunc box and it was again registering the 3.60 ish watts.. so i didnt even have to touch the soldered leads on the board, it's somehow making the voltage at the aligator teeth drop to 3.60 ish volts.. I dont understand that? I tried this with both the car running and not running, and the results where the same... As soon as i remove the box from the aligator teeth , the multimeter registers 13.60 (car off) volts.

    also i was testing the output end of the box (That would normally plug into the led light strips) and it was measuring 3.05 ish volts for each color. (not that this is neccessarily any useful info or not).
     
    Last edited: Jan 14, 2012
  6. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Sounds like something in the box is drawing the power down or you have a bad power input wire.
    Did you do all your tests with the LEDs disconected?
     
  7. Reloadron

    Reloadron Well-Known Member Most Helpful Member

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    I assumed, maybe wrongly that in post #20 you were running off the automotive system when you got the voltages you got. Does the 7805 get real hot to the touch? If not a bad 7805 maybe, as mentioned, it is being loaded down? I would think it was getting hot?

    Ron
     
  8. electricview

    electricview New Member

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    4pyros: Yep , the led's are disconnected each time i've done the test. If i need to connect and re-test let me know.

    Relaodron: I'm not sure- I didn't touch it while it was on, I can definately try it. How long do you think it would take to get warm? (in my intial testing it certainly wasn't putting out enough heat to feel any rising eminating heating at least since i didn't smell anything or notice any warmth and it was 39 degress out there, my guess is its not getting hot.) Should i connect the 1 meter of LED lights in order to see if it heats it up? or leave them disconnected?

    And sorry for the vagueness, any tests that resulted in 11.60 where just with the car engine off, when the car is start its up near 14.60-14.90 ish (depending on idle speed)

    A possible problem here is that this that this unit is turned on and off by an IR remote that came with it, but trying to turn it on or off, doesnt seem to change any of my test readings i've posted. I'm not sure if it should or not, but since i was at least getting 3volts on the output leads for the leds i'm kind of asuming it is at least on.
     
    Last edited: Jan 14, 2012
  9. electricview

    electricview New Member

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    I did a few tests again today, after being on for about 3-5 minutes there was absolutely no heat on the 7805 it was cold to the touch the entire time actually. I also tried hooking up the LED strip to the box and seeing if that changed voltages or heat, nothing changed. I even attempted to clip the aligator clips directly to the solder globs on the board itself (bypassing its wires) and still got the same voltage readings..

    I tried testing the Diode, i'm still new to them, but when i put the black Multimeter test lead on the side of the dide with the solid white bar, and the red lead on the other end, i got a reading of .60 when i reversed these leads on the diode i got -.61 i'm not sure if thats correct or not, but i thought i'd take a reading and mention it in case it has any bearing.

    Also the new box came today, i'm not so sure its gonna work, its half the size of the other box, and i dont believe i see a voltage regulator on this one.. Here's a few pictures.. (clickable for bigger size)


    [​IMG] [​IMG] [​IMG]
     
  10. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Its thare just smaller. its U# on the board labeled 78L05.

    Its the same thing as the old one only using surface mount components.

    The power input curcits look almost exactly the same. A diode, regulator and some filter caps.
     
    Last edited: Jan 14, 2012
  11. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    The new one you got was repaired once, see the new solder on Q3?
     
  12. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    OK Does the red power input wire go the the diode?
     
  13. electricview

    electricview New Member

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    4pyros : On the old box, yes it goes to the diode, non white stripped side, then the white stripped side goes to the 7805 's first lead as far as I can follow the PCB.


    And i do see the new solder on the new board.... interesting..
     
  14. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    OK then that is your power input circuit.
    Put your black meter lead on the black power lead where it is soldered to the board.
    Set your meter to read 12 volts DC
    With the lights disconnected and power applied, check the following points with the red lead and right down the voltages and post back.

    1 red power lead to board.
    2 diode, non white stripped side
    3 diode, white stripped side
    4 regulater, 7805 's first lead
    5 regulater, other side.
     
    Last edited: Jan 15, 2012
  15. electricview

    electricview New Member

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    4Pyros:

    Okay did as you asked.

    1. 3.53 (sometimes it would fluctuate .01 volts up or down )
    2. 3.52 (again .01 fluctuations)
    3. 2.90
    4. 2.90
    5. 1.22

    I tried hooking up the NEW box after i did a little bit of soldering (hooking up the correct pins and resoldiering the infrared wires since they were hanging on by 1 single stranded wire. After hooking it up it would not light up the lights either.

    After measuring the NEW box at the where the wires went in it was showing 4.50v I then put the black MM lead on the ground and put the red MM lead on the 12V output pin on the 4 pin OUTPUT plug that would normally go to the LED light strip, it also was measuring 4.50v. If its supposed to be 12v i dont see how its ever going to power the lights unless 1 of 2 things.. With both these boxes i've screwed something up and they are not 'on' becuase the only way to TURN them on is to use the IR remote that came with them and i just cant never tell if its on or not? OR it could be something with where i'm leaching the power it's not getting enough, neither of these boxes are..

    So I wonder now, is there another lead I could be hooking this box up to test if maybe its the power source that paticular area (leaching from the glove box light wire, which by the way did work perfectly fine for 6 months).

    My only idea is that I have a thick guage wire running to my trunk where i used to have a sub, (i dont anymore but the wire is still hooked up to the car battery directly). It does have an inline fuse box too, though i think right now it has a 20AMP fuse in there. But there's no ground wire back there, back when the amp was hooked up you could just pin the ground to any exposed bolt (which i was doing) so i dont know if i can do the same with this or if this is a BAD idea to test these boxes. so i haven't done it.

    Confused and perplexed. -Elec


    P.s. One other question i have is, this is a new idea to me, but it seems BOTh these boxes route the power supply from right when it touches the First pin of the 7805 (or in the case of this NEW box it seems RIGHT where the 12V incoming attaches to the board)- right to the output pin of the 4 pin adapter for the LED strips themselfs, which would make me think that if everything worked as it should the output pin would register 12v and the lights would light up.. Becuase of this, it must be using the other 3 leads as 'grounds' for each light strip? And somehow it can variable the ground .... Resistance? (am i close here?) to dim the lights and such? is that correct? If so is there a way i can measure this resistance to see if the box IS at least working even at low voltage? I can tap the remote controll to 'dim' the lights, which would cause the ground pins to lower or raise their resistance IF i could measure this with the MM (multimeter) I could at least tell the box was 'on' right?
     
    Last edited: Jan 15, 2012
  16. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    You have a bad power wire in the car someware.

    Does the glove box light still work???
     
  17. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Yes you are on the right track.
    The box is supplying power to the strips and switching ground to turn them on and off. Switching ground is common.
    But you will not be able to test the box without full power.
    Can you hook it up to another 12 volt DC power source? Like a battery or a wall adapter. To test it.
     
    Last edited: Jan 15, 2012
  18. electricview

    electricview New Member

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    Yes i have checked it twice now, it still lights up, though, I guess i have no checked if it lights up WHILE i have the box attached to it. I'll go test that right now, back in 3.
     
  19. electricview

    electricview New Member

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    did you see my little section about having a wire in the trunk that runs from battery directly? is that not a good idea since i dont have a ground running from the battery back there as well? I do have various 12 volt A/C Adapters around here, though i'd rather not rip off the head to test it, but maybe i could jerry rig it up with some paper clips.. 12volts at 1 or 2 amps shouldn't hurt me too bad if i mess up right? :)
     
  20. electricview

    electricview New Member

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    Okay the glovebox light stays on constantly no problems at all. even when i disconnect the box, it doesnt get brighter or flicker or anything like that.


    I also did another test, I dont know if it matters at all or not, but what i did was i hooked up the Ground wire from the car to the Black Multimeter lead, then i hooked the 12V wire from the car to the boxes 12v wire, then i used the REd multi meter lead and tested the Output pin for 12v that would normally go to the LED light strip, this time it shows 11.60 volts, I'm guessing thats probably not useful?
     
  21. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    thats what you want. with 11.60 on the LED wire you should have about that 11.60 to the regulater on the board.
     

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