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Emergency Vehicle Lights

Discussion in 'LEDs and Optoelectronics' started by CDork, Jul 4, 2013.

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  1. CDork

    CDork

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    Jul 4, 2013
    Hey guys,

    This is my first post and I'm not all too knowledgeable about electronics. I have basic info about some components from electronics classes in high school (two years ago) but really the only thing I got out of the class was how to solder...

    A little bit of info about me to have this project make sense:
    I'm a volunteer firefighter/EMT with my local company. I think our average response time (time from when the dispatch comes out to when we're in the truck leaving the station) is between 5 and 10 minutes. Most often, the most time wasted in getting to the station is sitting in traffic because people don't realize we're in a hurry :p so we're allowed to have blue emergency lighting on our personal vehicles. Most of these lighting set ups you can buy are pretty darn expensive considering I'm a college student working two jobs outside of my volunteering.

    So, I want to make my own lights to put in my car.

    I need some help deciding what circuit to make/build.
    A few restrictions:
    1) These lights have to be BRIGHT. They need to be clearly visible during the day to the guy driving 15 below the speed limit in front of me.
    2) I want four groups of 2 or 3 LEDs and I want them to light in a specific order (see attached picture)
    3) I want to be able to run it from my cigarette lighter if possible (car batteries end up putting out a bit more than 12v
    4) A switch to be able to turn it on and off so I can leave it plugged in, also if possible.

    Now I'm a Biomedical Technology major in college here in Pennsylvania so I need electronics at some point and I prefer sooner than later :D

    I've seen a ton of schematics that use astable multivibrators or 555 timers but they were all designed for voltages ranging from 1.5v to 9v, not the almost a car battery can end up putting out.


    The lights (four banks of 2 or 3 LEDs each) are arranged in a row. The outside left (OL) will light up first, then the outside right (OR), then OL and OR again. Then it switches to the inner lights (left, right, left, right) and then back to the outer lights. I want it to switch from outer to inner every half second with the lights switching from left to right quickly (doesn't necessarily matter how quickly).


    I appreciate the help, guys
    Thanks!
     

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  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    If your lights are A, B, C, D (L to R), you could use a 4017 with steering diodes to get a flashing order of A, D, A, D, B, C, B, C, A, D, ...

    So, your circuit consists of several modules:

    1) A power supply. Car electrical systems have voltage spikes which can kill electronics. This will reduce the voltage and eliminate the spikes.

    2) an oscillator. This determines the frequency of the flashing. You could use a 555, or some other oscillator.

    3) a 4017 This converts a string of pulses from your 555 into pulses on 10 outputs. Only one output is ON at any one time, with the outputs going on in the order 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 1, 2, 3, ... Because you only have 8 states (I'll explain later) then output 9 goes to clear so the output goes 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, ...

    4) steering diodes. This is a bit of magic that allows you to combine the outputs of the 4017 together. Using these diodes outputs 1 and 3 connect to A, 2 and 4 connect to D. 5 and 7 to B, and finally 6 and 8 to C.

    5) LED drivers. OK A through D above are going to be outputs to 4 circuits that will actually turn on the high power LEDs. These things are called LED drivers.

    Some or all of this may be unclear. Let me know *how* unclear, and I'll continue...
     
  3. CDork

    CDork

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    Jul 4, 2013
    I didn't think of using a decade counter! That makes life a whole lot simpler!

    What would an LED driver circuit look like? I assume relatively simple. Also, what kind of LEDs should I use? The biggest LED Radioshack has is a 10mm that will produce 8000mcd. I'm not sure if that would be bright enough to be seen during the day. What are some good high power LEDs?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    For LEDs visible during the day, you're probably going to be looking at 5W or higher LEDs, like this.

    A LED driver is typically a switchmode constant current source like this.

    I haven't checked those drivers, but it may be possible to switch them on and off with a logic signal.

    Also these have a bridge rectifier onboard. For driving then with DC, you can remove the diodes for additional efficiency.
     
  5. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    You do know that what you're attempting is illegal in PA and most, if not all, of the States?
    It's a gnat's a$$ away from installing a siren.

    Chris

    Edit: Oh sh!t I missed that you're a VFF! :eek:

    Never mind......:eek:
     
    Last edited: Jul 5, 2013
  6. CDork

    CDork

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    Jul 4, 2013
    Loopholes :D


    How do these RGB LED's work? Could I buy some RGB lights and just connect up the blue leads to just have them light up blue? The only reason I ask is because these RGB lights are much cheaper than the Blue's.
     
  7. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    I think it's likely that any emergency lighting would be required to be approved by the state or federal government which would preclude any DIY solution.
     
  8. CDork

    CDork

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    Jul 4, 2013
    The lighting that gets regulated by the government is generally the permanent fixtures you see on police cars/fire trucks/ambulances. Otherwise, the PA code doesn't mention lights for POVs (personal vehicles). The guidelines say that the emergency vehicles (as defined by the PA code) must follow SAE guidelines and must be permanently wired into the vehicle but I know for a fact most of the lights the other guys at the station have are cigarette lighter flashers.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Yes, RGB LEDs could be used, but a 3W RGB LED is going to contain a 1W red, 1W green, and 1W blue LED (or thereabouts).

    It's hard to know if they're going to be bright enough as the brightness depends on efficiency, power and beam width. The last is critically important because a LED with a 10 degree beam width is going to look about ten times brighter than one with a 30 degree beam width.

    However, a LED with a 10 degree beam width will not be visible at 30 degrees off axis where one with a 30 degree beam width most likely will be. (And a lot of this depends on how the brightness falls off with angle too)
     
  10. CDork

    CDork

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    Jul 4, 2013
  11. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
  12. Larzman

    Larzman

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    Nov 29, 2012
    The Marlin Jones site is way expensive compared to eBay. I have about 100 3W LEDs in various colors and never paid more than $1.50 per piece, most are under a dollar, for 3W.
     
  13. hzuiel

    hzuiel

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    Jan 8, 2012
    You might want to recheck the PA codes, but typically any lighting of any sort on a vehicle is supposed to be DOT approved. You can usually get away with such non-dot approved items like fog lamps, or non-dot headlight or turn signal bulbs. Police don't usually look that hard at them unless they really stand out in some way(like blindingly bright or using emergency colors. Accent lighting like the neon glow under cars also draws cops like a bug zapper draws moths. They love to write tickets for those.) I'm guessing that since you're a volunteer with the fire department, no local PD are going to bust your chops about having non-DOT approved emergency lights, but still, it's something you need to be aware of.
     
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