Yet another 555 fading LED - how small can i make this?

Discussion in 'General Electronics Chat' started by Solar shock, Aug 23, 2016.

  1. Solar shock

    Thread Starter New Member

    Dec 4, 2014
    17
    1
    hey Guys,

    first, apologies for once again drawing on the vast and deep knowledge contained on AAC to solve....... A FADING LED!!! .... your favorite past time im sure ;)

    So, ive had a good play with a 9v 555 circuit and ive read through bill's blog (http://forum.allaboutcircuits.com/threads/leds-555s-flashers-and-light-chasers.19075/#post-117641) which has given me some good starting points as to where to take this next, but i was hoping for a friendly shove in the right direction!

    I need to make a battery powered fading LED that all included fits within a circle about 50mm in diameter with as small as possible height.

    my thoughts on options:
    1. To use something like the 7555 as detailed in bill's blog to create a PWM connected to the fade RCnetwork?
    2. to use a 'joule thief' to boost the battery - thinking a coin cell is going to be the only viable option for my size issues? so 1.5-3.3v at best?
    3. or by this point is some sort of microcontroller going to be viable? i have some experience with arduinos, which i am sure i could transfer over to other microcontrollers; as the arduino mini pro (smallest form factor arduino i believe) is still a little large/overkill/costly for what i want?

    do you guys have any advice as to which avenues are going to be the best for achieving as small as possible circuit? Or am i chasing ghosts?:D
    i should be getting a few circuit simulations going in a few hours once im back from work.

    Rob
     
  2. Solar shock

    Thread Starter New Member

    Dec 4, 2014
    17
    1
    well Last, i appreciate that you looked :)

    I think ive found a reasonable solution. I could use a multivibrator circuit rather than a 555. After a little searching i actually found something that supposedly will do exactly what i want; https://www.axiris.eu/en/index.php/project-corner/breathing-led

    [​IMG]

    All ill need do is see if i can lower the supply voltage to say 3.3v, then adjust the component values as required. I'll have a simulation when i get home and maybe build a test circuit if i have the right values kicking about.
     
  3. bug13

    Well-Known Member

    Feb 13, 2012
    1,208
    38
    Just use CR2012 battery + any VQFN (or smaller) package MCU.
     
  4. dannyf

    Well-Known Member

    Sep 13, 2015
    1,825
    364
    A MCU can get it done with minimum parts and small size.
     
  5. Solar shock

    Thread Starter New Member

    Dec 4, 2014
    17
    1
    I'm not overly familiar with MCU's other than tinkering with an arduino.

    Would something like the PIC10F be a the right sort of ballpark?
     
  6. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    527
    Ne555 can fit in 50mm package without any problems especially if SMD.
     
  7. DickCappels

    Moderator

    Aug 21, 2008
    2,659
    632
    A PIC10F would be an excellent solution. You only need to add a power supply decoupling capacitor and a current limiting resistor for the LED. I've done something similar with the Atmel ATTINY12, and it was pretty easy.
     
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