replace electronic board ?

Discussion in 'General Electronics Chat' started by organic, Feb 27, 2017.

  1. organic

    Thread Starter New Member

    Feb 27, 2017
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    Recently the left tail led light from my car stopped working and I soldered the defective R750 resistor which had bad contact . It had worked a few days and now it doesn't work any more.
    I took a clear picture of the electronic board here https://goo.gl/gcozXI , the output voltage from the board is 4.4 Volt after measuring the right side led board, the working one.
    DSC_3707_RFS.JPG

    Now I would like to ask you guys if I replace the faulty electronic board with lm2596S module (input 3 - 40 VDC max 2.5 A , output 1.25 - 35 VDC) will this work (of course after adjusting the potentiometer to the right voltage) ?
    On the housing of the led light I see some data like 13.5 and 2.6W; 13.5 is probably the input voltage and 2.6w the wattage.
    Here is the link to lm2596S module https://goo.gl/ArsGVa

    Thank you for your time

    Mod edit: resized image and posted here.
     
    Last edited by a moderator: Feb 27, 2017
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    The board for your LED tail lights provides constant current (not voltage) and brightness is adjusted via an external PWM circuit..
     
  3. wayneh

    Expert

    Sep 9, 2010
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    It's unlikely that the purpose of the board is to provide a regulated voltage. It's more likely a current controller. [too slow on typing!]
     
  4. organic

    Thread Starter New Member

    Feb 27, 2017
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    Last edited by a moderator: Feb 27, 2017
  5. organic

    Thread Starter New Member

    Feb 27, 2017
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    When measuring the grey and rose wires I get the 4.4 Volt ( this is the one that is working the faulty one is 0)
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Does not matter that you measure voltage or not...
    The board you show provides constant current to the LEDs as they do not have their own form of current limiting (resistor,etc..).
    As such a replacement would need to function identically..

    #1-A constant current power supply varies the voltage to maintain a fixed output current..
    #2-A constant voltage power supply outputs a fixed output voltage..
    You need #1 or you will more than likely burn up the LEDs..
    LEDs are not like regular lightbulbs (incandescent,etc..)
    The filament of a regular lightbulb is a resistor that ensures that only the needed current is being drawn from the power source..
    An LED needs to be "fed" a proper current or it goes "pop".. That is typically done with a resistor in series (for low power) or via a constant current power source (LED driver)
     
    organic likes this.
  7. wayneh

    Expert

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    The voltage you measure is a side-effect of whatever else the controller is doing. It's not the targeted, main effect, which is controlled current.
     
  8. organic

    Thread Starter New Member

    Feb 27, 2017
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    The problem is they don't have spare parts only the full package led with housing, the board and that is about 200 euros so that's why I am looking for an alternative...
     
  9. JohnInTX

    Moderator

    Jun 26, 2012
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    If it worked awhile after the repair then failed I think I would investigate whether the repair itself failed before going to heroic measures. Not to pick on you but the soldering on the 750 ohm resistor looks a little cold.
     
  10. wayneh

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    I get that, and the good news is there should be options available. If you look on eBay you'll find plenty of constant current LED drivers.

    The big question is what current is required – that's the key specification you need to find a replacement.
     
  11. organic

    Thread Starter New Member

    Feb 27, 2017
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    and how to I get to know that "what current is required"?
     
  12. Kjeldgaard

    Member

    Apr 7, 2016
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    The soldering on the R750 resistor looks very suspicious, especially the lower pad.

    It seems to be a TLE4242 driver circuit, as with the 0.75 Ω resistor and a reference voltage of 177 mV would provide a nominal of 236 mA LED current (At 100% duty cycle, if used).
     
    absf likes this.
  13. organic

    Thread Starter New Member

    Feb 27, 2017
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    Thank you for all your answers!
    As far as i understand I need a led driver with constant current of 236 mA or am I wrong ? If the driver is like 200mA would that be a problem ?
    Where can I buy one ? this one would be ok ? https://goo.gl/J9l1N8
     
  14. KeepItSimpleStupid

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    Mar 4, 2014
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  15. wayneh

    Expert

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    It would be 36/236 or 15% less bright. This would be tough to see without a side-by-side comparison.

    I believe that device you linked would work.

    I'm not 100% comfortable we are sure about the current level. @Kjeldgaard seems to have a good idea about it but it would really be great to confirm it. Do you know anything about the LEDs? Maybe a picture.

    Or, if you have some supplies you could experiment with different current levels – starting low and working up – to see what current level is appropriate. You would need different power resistors to place in series with the LEDs. Or you could use the ammeter function of your multimeter to measure the current of the working LED panel.
     
  16. organic

    Thread Starter New Member

    Feb 27, 2017
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    no it's not dimmable
    the led's are enclosed in the housing so only if I break the hosing, I will be able to see them...
     
  17. KeepItSimpleStupid

    Distinguished Member

    Mar 4, 2014
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    You said that R750 had a bad contact. This really suggests that that IC could be bad.

    I suppose that swapping the boards worked?

    The IC is not very expensive. http://www.digikey.com/product-deta...gies/TLE4242GATMA3/TLE4242GATMA3CT-ND/6560019 and is probably obsolete.

    Removal could be a real pain. Cut the leads first. Remove the conformal coating and use hot air. The large pad on the rear is the issue.

    There is an evaluation board available, but there is no info about it. http://www.infineon.com/cms/en/prod...nel=db3a304319c6f18c011a154646852706#ispnTab4 You may be able to get it from digikey. < $50.00 USD The evaluation board MIGHT be a good replacement.

    The unmarked components look like capacitors. The two others may be diodes and could be confirmed on the working module.

    Surface mount soldering is done with a solder paste. Non-lead solder has a higher temperature and therefore more difficult to work with.

    A uk source for the IC is: http://uk.farnell.com/webapp/wcs/st...me=All&selectedCategoryId=&gs=true&st=tle4242

    Some solder removal could be done with a solder braid: http://uk.farnell.com/webapp/wcs/st...tegoryId=700000006483&langId=44&storeId=10151
     
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  18. wayneh

    Expert

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    If it was me, I'd check the current to the LEDs on the good side and try to replicate that on the dead side. Start with your meter on its 10A ammeter setting and be double, triple sure you connect it in series with the LEDs, not across (parallel to) the connector. Otherwise you'll immediately blow something, a fuse in your car or your meter. If the reading you get (maybe 0.24A) is less than the next lower scale, you can move it to a lower scale. My meter only goes from 10A down to 200mA, so I'd be unable to use the lower scale.
     
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  19. organic

    Thread Starter New Member

    Feb 27, 2017
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    I just measured the amps from the right side and I get 236 mA as Kjeldgaard said. Aren't there any led boards with adjustable mA ? Because if I start soldering I don't have the tools like hot air gun, solder braid...
     
    wayneh likes this.
  20. Kjeldgaard

    Member

    Apr 7, 2016
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    Have you tried to repair the solder joints on the 0.75 Ω resistor?

    Because if the resistance increases or disconnect completely, then the LED current decreases or go to zero.
     
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