Christmas LED decoration design help for a Newbie DIY

Discussion in 'The Projects Forum' started by DifferentIce, Dec 6, 2010.

  1. DifferentIce

    Thread Starter New Member

    Dec 6, 2010
    2
    0
    Hello all,

    I just signed in here, looked around a bit and did not see an obvious answer to my question so if I should have looked better I apologize.

    I just started studying electronics this fall and after the semester of fiddling with stuff and learning text I decided to try a bit of a DIY to get more of a hands on feel and see if I can begin a project and find my way to it's end.

    The project I have in mind is a simple Christmas LED circuit attached to some batteries and a switch, self sustainable except for a battery change.

    I already found some neat LED's both 3mm and 5mm in diameter and according to the shop assistant 2V all of them. After one died unexpectantly I feel I should maybe test this further. So question 1. How does one test them?

    I first attached the lot into a bread board and to a 9v battery (I only had that one, but none of them died). Then I started experimenting a bit, since I really need to use either 1,5V or 3V batteries, just cause they are smaller and cheaper. I couldn't get the 3mm yellow one to work in 1,5v and two of them together (3v) killed her. The green and red one lived fine, and all of the 5mm ones. What are the best steps in testing and trying these things? And when I have, do you have any great ideas on the circuit? I'm having a bit of a brain twist on how many LED's per leg and how to connect the batteries.

    I really want to try and make this project only out of LED's, switch batteries, some wire and home made housing, without using resistors or anything else, just to save on materials and also to understand the principles.

    I've thought about creating some pole endings for the batteries from metal from cans (aluminium is the way to go right?) since it seems that battery holders are either too big or too expensive.

    The big picture is LED's of three colours, 5-10 pcs ca, leaded together and to the batterie connectors and switch and then housed in a pearl plexglass frame with a bottom from an aluminium profile for excample.

    I do realize this is a bit of a "do your research yourself" maybe, but I thought the people with the experience could maybe save me some of the stupid first timer mistakes, as you can see I'm quite the novice.
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    LEDs, 555s, Flashers, and Light Chasers

    Using electronics always involves some reading and learning. I wrote the above article as a tutorial for beginners. You will need to learn Ohm's Law though, to be able to calculate currents and voltages for any given situation. If you have a specific question you will find folks here very helpful in filling in the blanks.

    What is your background? Are you comfortable with Ohm's Law for example?

    Chapter 2: OHM's LAW

    This is the appropriate section from the text book that is a core part of this site.

    Welcome to AAC!
     
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    The LEDs probably failed due to too much current. You shouldn't run over 20mA through a clear lens LED, or over 5-10mA through a colored lens LED.

    "Clear Lens" or "Water Clear" LEDs are the type where you have no idea what color it will be until you power it up.

    For testing them, some multimeters can test LEDs, others cannot supply enough voltage (many will only go to 1.5V). If your DMM has a diode check setting try that, but it may not be a guarantee.

    A CR2032 "Button Cell" works great for testing LEDs without a resistor, as the battery is taxed to put out more than about 20mA. Simply put the leads of the LED on either side of the coin cell for a very short time to see if it is good, and get the color.

    Putting too much current through an LED will cause it to die, and a resistor limits the current (see Ohm's Law link above). For a 6V supply, something around 220 ohms should be fine to keep them from dying on you.

    This Site will calculate a schematic for you All you need to do is add source voltage, LED Voltage drop, current through LEDs, and how many LEDs you want in your string.
     
    Last edited: Dec 6, 2010
  4. DifferentIce

    Thread Starter New Member

    Dec 6, 2010
    2
    0
    Thank you, these two answers seem a good start :) I do have the Ohm on my side. I'm going to sit over these posts tomorrow when I have time and then answer what I have probably missed here. Thank you for taking the time to answer.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    If you have any problems you can hand sketch a schematic, scan it, and post it for review.
     
Loading...