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
    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 ( 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.

  2. Solar shock

    Thread Starter New Member

    Dec 4, 2014
    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;


    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
    Just use CR2012 battery + any VQFN (or smaller) package MCU.
  4. dannyf

    Well-Known Member

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

    Thread Starter New Member

    Dec 4, 2014
    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
    Ne555 can fit in 50mm package without any problems especially if SMD.
  7. DickCappels


    Aug 21, 2008
    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.