Help with understanding if leds and voltage can change on a basic circuit

Discussion in 'The Projects Forum' started by Andrew Antill, Oct 17, 2015.

  1. Andrew Antill

    Thread Starter New Member

    Oct 17, 2015
    2
    0
    Hi

    I have had a search but couldn't find what i needed. My skills are pretty limited, hence my asking.

    I'm also not asking for anyone to do this for me, i'm just looking for a point in the right direction really and hopefully i can do the research when i know what to look at to get the job done.

    ultimately i am looking to improve this wireless brake light, its running 3v worth of LEDs but i would like it to run 12v LEDs...

    So, i have found one of these wireless brake and indicator lights which fit on your helmet on ebay, the transmitter part looks good but the leds look pretty weak, probably not much use in the day time. (please see link below)

    http://www.ebay.co.uk/itm/TRACKBIKE...659701?hash=item4199b524b5:g:Mb4AAOSwPcVVgUNQ

    this is a pic i have found of the circuit board if it helps
    [​IMG]

    I would like to take out the circuit board and modify it to fit better LEDs, like this:

    http://www.ebay.co.uk/itm/Tail-Rear...314059?hash=item3ab2874a8b:g:8OMAAOSwuTxWA6cs

    i am thinking putting the circuit in a little box to protect it, attach the light strip to the back of my jacket with a 12v battery pack of 8xAA batteries in a pocket to power it. and perhaps add a couple more indicators to have them further apart on my shoulders. this is in the interest of safety after all, not fashion!

    is it possible just to unsolder the original LEDs and splice in the new ones and power them off the battery pack? im guessing not, thats why i ask...

    thanks in advance
     
  2. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
    1,016
    You first need to determine if those existing LEDs are wired in serial or parallel. Then you have to know your supply voltage.

    LEDs work off of voltage. Each type of LED has a different voltage drop. Or forward voltage. A white LED can have a VF between 2.9V to 4.2V.

    Basically the total vf of LEDs wired in series cannot exceed the supply voltage.

    You could probably add LEDs in parallel with appropriate current limit resistors. But remember the more LEDs you add the shorter your battery life.
     
  3. Andrew Antill

    Thread Starter New Member

    Oct 17, 2015
    2
    0
    Ok cool, they use 2 batteries so i am guessing theyre running off 3v as a supply.
     
  4. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,887
    1,016
    That would be correct, so you will need to find a white LED that has a vf lower than 3V.
     
  5. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    What does "better LEDs" mean?

    LEDs are operated by current; not by voltage. To make LEDs brighter means passing more current through them. More current means better drivers, and shorter battery life or bigger batteries...

    Unlikely that the electronics on that board will supply more current, so you can change the LEDs, but probably will not improve anything...
     
Loading...