Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mount a circuit with timer and led

  1. Nov 8, 2013 #1
    Hi there,

    I'm a material's design student and I have an idea to a project.. This idea needs an electrical circuit , with a led and a timer, but it has to be really really small, because it is for small objects.

    How can I mount this type of circuit, with a timer that will fire a red light in the led, after long datas ( from 3 to 12 months).

    I don't have any experience in this area , so I need to know the materials i need to use, how to mounth and program them.. Can you help me?

    Thanks !!
  2. jcsd
  3. Nov 8, 2013 #2


    User Avatar

    Staff: Mentor

    What kind of battery do you plan to use -- that may determine the minimum size of the LED unit. Why the long delay? Is the delay something that will be programmed into the LED device, or will some external event tridder the LED flash?
  4. Nov 8, 2013 #3
    its better explain the real problem of the project:

    Imagine a Coca-Cola bottle. It has a validity period! The led will turn red when this period expires ;-)
    That's why i really need the smallest possible circuit.
  5. Nov 8, 2013 #4


    User Avatar
    Science Advisor
    Gold Member

  6. Nov 9, 2013 #5
    I already knew this kind of process, it's done by the chemical process.
    I want to adapt the idea to put a led that fires a red light when the product becames out of date. Thats why I need a small circuit with a timer .
  7. Nov 10, 2013 #6


    User Avatar

    Staff: Mentor

    But in Engineering, we focus on realism and optimization. There is a reason that the folks in Ultrafast's link did not choose to use a battery-powered LED circuit to show the expiration -- it is too costly and bulky to be practical. It is possible to make a battery-powered long-term timer and LED flasher, but the volume will be at least a 5mm per side cube (depending on how long the LED has to be able to flash), and the cost will be several tens of cents. None of that will be attractive to food packaging companies.

    Think practicality and optimization in your designs! :smile:
  8. Nov 10, 2013 #7


    User Avatar
    Science Advisor
    Homework Helper

    There is another basic problem with the idea. How long will an LED flasher continue to show that the product is out of date, before the battery runs flat?

    The chemical change indicators continue to show the product is out of date "for ever", or at least for the whole life of the product packaging.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook