Need help designing a circuit

Discussion in 'The Projects Forum' started by summertime, Nov 17, 2010.

  1. summertime

    Thread Starter New Member

    Nov 17, 2010
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    0
    I am needing some help designing a circuit. My ultimate goal is to have a battery powered string of LED's that is remotely controlled on and off. the attached diagrahm is for 4 LED's but i am thinking i will need 20. I realize the resistors will most likely need to be different with 20 LED's.

    So would someone tell me how to wire this circuit.

    I have a remote already that has a corasponding IR receiver and would like to utilize that. Any questions let me know.

    Thanks in advance

    P.S. this is for a non profit i am volunteering at, and the deadline is 11-20-10.
     
  2. blueroomelectronics

    AAC Fanatic!

    Jul 22, 2007
    1,758
    98
    If you want to use IR you'll need a microcontroller or some sort of preprogrammed IC (not aware of one) that can decode IR data from your remote.
     
  3. Audioguru

    New Member

    Dec 20, 2007
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    If your LEDs are 1.8V red ones then the 68 ohm resistors limit their current to 40mA and they will quickly burn out.

    We don't know if your remote receiver switches the positive side or the negative side.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
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    Hobby/Surplus places have premade solutions for stuff like this. Here is one for 12V Supply, for example.

    Would need info on the IR Receiver and Transmitter that you already have to give any advice.
     
  5. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    Constant current limiters are the way to go.

    [​IMG]

    If you want variable...

    [​IMG]

    Use 27Ω or 30Ω resistors as shown in the previous schematic.

    A simple transistor will work with your IR unit to turn the power to this circuit on/off. It is an easy project for an experienced user. Do you have a protoboard, something that looks like this?

    [​IMG]
     
  6. summertime

    Thread Starter New Member

    Nov 17, 2010
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    i do have a bread board/proto board - but an experianced circuit builder i am not -


    thatoneguy - thank you for the link - i will be ordering one today - i really appreciate all the input - i can't thank you all enough - i will upload a diagram of what i think the circuit should be with one of these remote switches -

    let me know your thoughts of whether it will work

    they will be white leds
     
  7. summertime

    Thread Starter New Member

    Nov 17, 2010
    4
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    also i will be using regular household batteries - what is the easiest configuration and size battery to acheive 12 volts?
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Radio Shack has various battery holders, some with wires, and some that connect to a snap-on 9v type battery harness, which they also sell.

    See this page: http://www.radioshack.com/family/index.jsp?categoryId=2032264

    You could use a pair of the 4-battery AA or D size wired in series, or one of the 8 AA battery size to get 12v. You'd get somewhat less voltage out if you used NiMH batteries, but using rechargeable batteries is preferable to having to buy fresh alkaline batteries frequently.
     
  9. Audioguru

    New Member

    Dec 20, 2007
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    Repeat: We don't know if your remote control unit switches the positive side or the negative side.
    We also don't know it it can switch the total current of your seven strings of LEDs.

    Post the detailed datasheet of the remote controlled switch so we can see if we must add a switching transistor and where the transistor must be connected in your LEDs circuit.
     
  10. summertime

    Thread Starter New Member

    Nov 17, 2010
    4
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    this is the one i will be using - i ordered it today - the remote i had went to a LED circuit for a pumpkin light and i think that would be too much for me to rewire - so i ordered Here is one for 12V Supply
    this one
     
  11. Audioguru

    New Member

    Dec 20, 2007
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    The remote controlled receiver is not a switch!
    Instead it is switched +12V (from its white wire). It has plenty of output current (6A) to power your LEDs.
     
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