Thanks Thanks:  0
Likes Likes:  0
Dislikes Dislikes:  0
Results 1 to 1 of 1

Thread: Is there any pitfall to using resistors in series AND parallel for an LED array?

  1. #1
    Junior Member
    Join Date
    Nov 2017
    Posts
    1

    Is there any pitfall to using resistors in series AND parallel for an LED array?

    The first post.Having a little nervous.I'm understanding for series and parallel compensated resistance, however as my title I am confused that Is there any defect in series resistance and LED array parall.
    I've seen a lot on LEDs and series vs parallel resistor usage, but found nothing regarding the combination of both, so here goes.

    I am working on a watch of sorts, that will work similar to a 7-segment display, where different LEDs are lit simultaneously depending on the driver's output (sometimes 2, sometimes all 7), so I will use that as an example.
    In order to conserve battery, I am looking to have a low brightness during "normal" operation, with a momentary high brightness option. Since this needs to be rather small to be wearable I am, of course, looking to minimize component count. Cost is relevant, but much less of a factor than attaining a small size that can be hand soldered.
    It is widely understood that running parallel LEDs on a single resistor is not the best approach, and I have allowed for a resistor-per-LED arrangement in my design, but I would like to be able to bypass SOME of the resistance temporarily.
    What I figured I could do is put the Resistor-LED series pairs in a parallel array that feeds to a single resistor with a bypass, as in this schematic:
    Click image for larger version. 

Name:	1.png 
Views:	37 
Size:	20.3 KB 
ID:	691

    So, the question: Would placing a single resistor in series with a parallel LED.html array be as bad if the LEDs also had dedicated series resistors, and if so, are there other alternatives for the dim/bright outcome I am looking for?
    Additional Info
    - I am planning on a 3v (2xAAA) battery source running LEDs with a Vf of 2-2.2.
    - Once I have my LEDs, I intend on testing different resistance values for brightness yield, but am hoping for around 2-4 and 7-10 mA for the low & high respectively.
    - The actual array will have 12 LEDs, with a maximum of 9 lit at one time.
    - There will be 4 "digit" arrays in total.
    - I am comfortable working with SOIC and 0805 (and some 0603) packages.
    - If there is a risk of (slightly) uneven brightness from one LED http://www.kynix.com/Detail/738157/LEDto the next, that will be ok, as it will give a "battle worn" look that will work with the design.

    Thanks all advices.
    Attached Thumbnails Attached Thumbnails 2.jpg  

Similar Threads

  1. three MS-OPS2 in parallel
    By pauloeuvray@hotmail.com in forum Design Assistance - Controls
    Replies: 1
    Last Post: 02-27-2017, 11:47 AM
  2. HW 4 series processor
    By bitza89 in forum General Discussion - Legacy HW
    Replies: 5
    Last Post: 09-01-2015, 09:33 AM
  3. Replies: 5
    Last Post: 08-28-2015, 12:42 PM
  4. Help plz with HW 4 series
    By techniquesmethodes in forum Troubleshooting - Legacy HW
    Replies: 3
    Last Post: 06-12-2015, 05:29 PM
  5. 4 series question
    By danluke1640 in forum Troubleshooting - Legacy HW
    Replies: 1
    Last Post: 05-27-2015, 04:00 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •