Why resistor and LED is in place in this schematic?

Discussion in 'The Projects Forum' started by quintaar, Apr 28, 2016.

  1. quintaar

    Thread Starter New Member

    Apr 28, 2016
    7
    0
    Hi.
    I'm trying to understand this module, and I cant figure out why R1 and L1 is on the board. Forgive me use of DA1 as I was not able to find the 3pin bi-colour LED, common cathode. (I'm able to use it but can't figure out the design choice.)

    r1 =1000ohms (102 SMD)
    initially I thought this is linked parallel between one anode and a cathode, I have no access to the module right now, so cannot confirm the layout of the back of this PCB.
    If someone could break this down for me I would appreciate!

    LED-006 (1).jpg

    schemeit-project.png
     
  2. TheButtonThief

    Active Member

    Feb 26, 2011
    219
    38
    I'm finding it difficult to understand what your question is.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,139
    3,054
    Those components are likely part of a boost circuit allowing the LED to operate off a low voltage. Can only guess without seeing more.
     
  4. quintaar

    Thread Starter New Member

    Apr 28, 2016
    7
    0
    Hi again.
    I have checked the back PCB which confirmed the diagram being done correctly. Middle pin from the schematic is a ground one. I'm trying to Figure out the purpose of L1+R1 loop, my understanding is if V is too low to meet forward V of DA1 it will illuminate the L1, but then it will treat the opposite 'anode' as GND?
    (not having data sheet for the module sucks)
    If FV of DA1 is met, I assume resistance of the DA1 is lower than R1, and L1 is no longer emitting light - for either of the anodes being used, and the same goes for supplying Fv sufficient to power DA1 and enable the 3rd colour?
    Am I incorrect?

    Thanks for your input
     
  5. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    1. Please take two clear pictures for double sides of PCB, I want to check the details.
    2. I can't see the R1 and L1.
    3. The three pins LED could be the common cathode, so the middle pin connecting to GND, and other two pins in series a current limits resistor for each pin and connecting to +Vcc.
     
  6. quintaar

    Thread Starter New Member

    Apr 28, 2016
    7
    0
    Here is the back of pcb.
    (im unable to run the multimeter tests till Sunday) as I'm not home same goes for high quality pictures but there was enough detail to figure out the layout and schematic. I'm 99% sure I did it correctly. Thanks for looking into it.

    received_1319908041358679.jpg
     
  7. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    You just bought this product or it has other device?
    The circuit looks like used for some ac signal as pulse or special indicator, for a +5V application, normally the loop1 is Vi1 Rled1 CR(common resistor) to GND and the loop2 is Vi2 Gled1 CR(common resistor) to GND, when the Vi1 = high(5V) and the Vi2 = low(0V) then the L1 will be light up, the colors of led just for explanation.

    received_1319908041358679_new.jpg
     
    quintaar likes this.
  8. quintaar

    Thread Starter New Member

    Apr 28, 2016
    7
    0
    Excellent breakdown of this thank you.
    It was one of the modules from 37in1 arduino/RPI kits available at chinese resellers, and before I obliterate my board or a module by trying it blindly i wanted to check if i understand whats going on correctly.
    Actually - nvm about the follow up question. Got that figured out. Thanks again for taking the time
     
  9. hp1729

    Well-Known Member

    Nov 23, 2015
    1,956
    219
    R1 and L1 are the SMD components.
     
  10. hp1729

    Well-Known Member

    Nov 23, 2015
    1,956
    219
    It looks like it was intended for more than one exercise. R1 and L1 is one exercise. The other LED is a different exercise.
     
  11. quintaar

    Thread Starter New Member

    Apr 28, 2016
    7
    0
    I think the L1R1 loop is just an 'info' loop to indicate the power draw. the main purpose of course being bi colour LED
     
  12. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    Thanks.
    When I checked all the details that I already found out the two parts.
     
Loading...