Need help with multiple mode LED strings

Discussion in 'The Projects Forum' started by N0ctrnl, Aug 14, 2009.

  1. N0ctrnl

    Thread Starter Member

    Aug 14, 2009
    14
    0
    I'm in the process of trying to build a LED "staff". It's essentially going to be a clear PVC pipe with multiple strings of LEDs. Right now I'm thinking maybe 3 different strings of 7 - 5mm LEDs each. (The first run is going to have blue, green and red LEDs - nothing too crazy)

    The problem I'm running across is coming up with a flashing circuit that I can use to switch modes. I'd really like to stick a momentary switch in one end of the pipe to be able to switch it and be able to toggle modes that way. I was thinking maybe an "always on" setting, a "strobe" (alternating flashing of all 3 strings) setting, and a "fade" setting (where one color stays on until the next lights up, then the first goes off).

    Clearly I can figure out the always on. I can even figure out the flashing, though I've not yet found anything that seems practical for what I'm after. What I'm wondering is if anybody has come across a design for a circuit that will switch between modes and is relatively easy to build. I've done quite a bit of looking, but haven't yet found anything that seems workable for what I'm doing.

    The constraints of what I'm doing are this:
    - The electronics have to fit inside a 3/4" ID PVC pipe
    - No longer than 3 or 4 inches - This has to be mostly concealed by the cap on the end of the pipe
    - The battery is a 1300mA, 3.7V rechargeable battery

    I'd even be willing to pay somebody to design the circuit for me if that's what it takes. It's been 15 years since I did much with designing circuits, and I'm not sure I'm up for picking it up now to design this.

    Thanks!
     
  2. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
  3. N0ctrnl

    Thread Starter Member

    Aug 14, 2009
    14
    0
    Essentially it's this http://www.scavengeinc.com/led-lightstick-poi-stick-p-6065.html but with many more LEDs on it. Those light sticks just have 3 LEDs in a cluster on the end (red, green, blue) that have the different modes. That's what I'm after. In face, I've even toyed with taking the LEDs off and soldering a string on it their place. I'm just real sure that the actual circuitry on those things isn't equipped to handle 5-7 LEDs in the place of a single one, and I don't want to burn them up unnecessarily.

    I've found many designs as far as an individual circuit goes. There are plenty for chasers, "random" flashers, mood lights, single flashing, etc. The problem I'm having is that I'm not at all equipped to design a circuit that does them all.

    It's entirely possible that there's a design or 10 out there I haven't come across yet. I just know I've been searching for a week and haven't found exactly what I'm looking for in any one place and thought maybe somebody would have some insight. :)
     
  4. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    First I can tell you, you can build any mode individually. Like a simple flasher requires an IC or sometimes just a transistor. But if you want a chaser or a random flasher, you will need sperate circuits for each as all involves different Ic's or atleast the same IC in different modes. So you can't have all in one with one 1 IC, but with many.

    The only way to achieve multiple modes of flashing, blinking and chasing is using microcontrollers.

    However, if you have a toy that flashes according to your needs, you might be able to hook up lots of LED's onto it using a few transistors, provided you know how to measure their output voltages.

    The products you see in market for multiple effects use specialized IC's from that manufacturer. I havent seen much of multiple effects in 1 Ic, but 2 might be possible using the commonly available ones.
     
  5. Amberwolf

    Member

    May 2, 2008
    28
    2
    It is pretty likely that someone has already done the basic thing you want using a microcontroller, most likely with a PIC or an Arduino. You could check over at the ladyada.net forums to see if anyone there has done this and would share the code for it.

    You'd probably just have to modify the code and hardware to adapt it to the total number of LEDs you want on there.


    Optionally, if you are going to series-wire the LEDs and use a fairly high battery voltage (enough to cover the LED voltage drops for however many you have in series), then you could easily build a separate control circuit out of discrete components (555s and transistors would work, or op-amps, probably stuff in the archives here you could adapt) for each function, and have your switch just change which function is operating.

    Then the pushbutton switch can either be a click-to-select type switch that switches between each of them, like the pull-to-select chain switches on a cieling fan, or it could be a simple momentary NO switch that triggers a shift register of some type (or a counter like the 4017) whose outputs are wired to enable the power to each of the individual control circuits.

    If you parallel-wire the LEDs, then you can still use individual control circuits, but the output stage of each one grows greatly in component count, and that means you need NumberOfColorsOfLEDs x NumberOfLEDs x NumberOfFunctions output stage components, instead of just NumberOfColorsOfLEDs x NumberOfFunctions components.


    Optionally, you could simply amplify the output of that device you linked, tapping off the existing LEDs there, using a MOSFET or transistor amplifier to drive your series strings of LEDs. That is the simplest in terms of hardware design and component count. You only have to ensure that you limit the current for the LEDs you use, and that you have a separate power supply for the original device vs your much-higher-voltage series strings of LEDs.
     
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