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Extra Led Light In Car Headlight Switch

Discussion in 'LEDs and Optoelectronics' started by wilf58, Oct 2, 2017.

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  1. wilf58

    wilf58

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    0
    Oct 2, 2017
    Untitled.png Untitled.png

    i need to know if i put the resistors 911=910ome where it says on pic top left and if i follow the circuit what else would i need to use to make it work
     

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    Last edited: Oct 2, 2017
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    11,284
    2,583
    Nov 17, 2011
    Welcome to EP.

    Without more info on the module and your purpose we can hardly help.
    What are you trying to achieve?
    Why do you think the LED and resistor should go where indicated?

    P.S.: The poll you activated was kind of useless, I therefore removed it.
     
  3. wilf58

    wilf58

    3
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    Oct 2, 2017
    well i was hopeing for some help in achieveing on how to put an extra led bulb into a headlight switch so i can iluminate a new window for the front pannel all the circuit is there but no led bulb and i was hopeing seeing as im a novice at electronics that at least someone might take a look at the pics and maybe point me in the right direction as what resistors to fit and hopefully get the extra led up and working ... its a bit unfair to say my poll was useless as im new to your site and just wanted some help
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    11,284
    2,583
    Nov 17, 2011
    I'm sorry if my P.S: sounds a bit unsensible, but the idea of a poll is to collect responses from forum members what they think about some topic.

    You're free to put your questions in the body of your post.

    This should in principle be no problem. However, without knowing this specific PCB it is hard to tell whether these unpopulated pads (or lands as they are also called) are prepared to take the components required for the additional light/led.
    These pads could be for an additional LED, they could be for an entirely other purpose as well.

    I suggest you check the suitability of these lands:
    1. Measure the voltage between the two pads that are indicated by the two left arrows in the picture, i.e. the top pad of the supposed LED position and the bottom pad of the supposed resistor position. If you measure a steady DC voltage when the switch unit is powered, these pads could be suitable for the proposed purpose.
    2. It looks like there are pads for two resistors in parallel. This is not clearly visible in your image. Check whether the 2 top pads and the 2 bottom pads for the resistors are electrically connected in pairs. You may be able to see this by close visual inspection (if you see a copper trace between them) or by using a multimeter in Ohm range. If these pads are connected, then this is an indication that 2 parallel resistors should be used. This is to distribute the power dissipation.
    3. Check the pass voltage and the operating current of the LED you want to use (see the datasheet). From these values and the voltage measured in step 1 calculate the required series resistor as
      Rtotal = (Vtotal - VLED)/ILED. I'd expect the result to be somewhere around 450 Ω.
      Then use Rsingle= 2*Rtotal (910 Ω would be a good value if the previous result was ~450 Ω). By using 2 resistors in parallel the effective resistance is 1/2*Rsingle.
    Observe the polarity of the LED. Other than an incandescent lamp an LED has a defined anode (+, long wire) and cathode (-, short wire). When reversed it will not light up.

    When you encounter problems while proceeding as described above, come back here and report what you have achieved (and measured) so far, then we will try to guide you along.
     
  5. wilf58

    wilf58

    3
    0
    Oct 2, 2017
    yes the top and bottom pads arrowd are connected ...i measurd them with multimeter and they are defo connected .so there should be the 910 ome sresistors in parallel in them two positions that are arrowd ?
     

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