looking for some help with an LED project for a costume

Discussion in 'The Projects Forum' started by dandufaur, Jul 16, 2014.

  1. dandufaur

    Thread Starter New Member

    Jul 16, 2014
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    Hi all. Could anyone help with my costume LED problem? I need to set up a line of LED'S that will come on in sequence until they are all lit then they all go out together and start again on its own. Its for the power cell lights of my Ghostbusters proton pack. The lights start at the bottom then rise in a line coming on until they are all lit. They all then go off and start again. This would be activated by a toggle switch supplying power to the circuit and ramp on its own until turned off. I have seen "kits" for sale but they are extremely expensive. Any suggestions or help would be very welcome.

    Thanks

    Dan
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    How many LED's, color, brightness, available power
    Might use a CD74AC164 for direct drive of 8 LED's, 8 more LED's for each additional IC.
     
    Last edited: Jul 16, 2014
  3. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Bernard has asked some questions that need to be answered, but a general approach can be discussed.

    First, you'll need a clock circuit that runs at a speed which you want the LEDs to light. A 555 astable circuit will likely be sufficient, as you're not timing a critical dangerous application.

    Next, you'll need a counter to count for the number of cycles equal to the number of LEDs in your prop. (I refer to the number of LEDs meaning the number of bars to be lit on your prop; if you need 2 or 3 LEDs per "bar", this is an important detail, but can be decided later in the design)

    After the counter, you'll need a decoder. This will decide the binary output of the counter to one output in "n". A CD4028 BCD to Decimal decoder is one such IC. Or a CD4017 will do BOTH the counting and decoding.

    Then you will need OR gates, so that each subsequent level lights up the previous levels. This might be possible with diode OR gates, depending upon the important answers to Bernard's questions.

    Finally, transistors will be required for driving the LEDs.

    So, we're waiting for your answers.
     
  4. elec_mech

    Senior Member

    Nov 12, 2008
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    Welcome to AAC. For future reference, at least for movie props, it helps immensely if you post a link to a video showing what it is you're trying to re-create. Based on your description, I assume you're talking about the blue LED's on the back as shown here at 0:50 and 2:20. Is this correct?

    If so, it looks like 16 blue LED's, probably 5mm through-hole. The ones shown in the video appear to be clear domes which are very bright and ideal for daytime. If this is going to be used at night or in a mostly dark environment, I'd suggest using diffused blue LED's which will still be plenty bright without blinding people. :)

    Taking Bernard and djsfantasi's suggestions, I think this circuit will do what you want with a few modifications. Take a look at the video at the bottom. Each LED lights up and stays lit until all are on. I don't know offhand if the 74HC164 can provide enough current to the LED's, but if not a ULN2803 could be used.

    How much experience do you have making circuits? Can you solder? Put a PCB together from a schematic?
     
  5. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Using the shift register is a good idea. Do you have a video of the desired effect?
     
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    elec-mech's # 4 post," here", gives a 16 LED bar graph on the " Proton Pack Lights With Sound Card" video.
    I believe the 74AC164 can drive 20 mA with all 8 on at the same time. Add a 555 clock, & possibly a buffer to give delayed reset from # 16.
    No more 'till OP comes back.
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    If 10 LEDs will suffice, then an LM3914 plus a ramp generator should do the trick.
     
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