LED lightbar

Discussion in 'General Electronics Chat' started by garye5007, Mar 20, 2009.

  1. garye5007

    Thread Starter New Member

    Mar 20, 2009
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    Hello.
    I'm a fire police and i want to build a LED lightbar like a police car with red & blue ultrabrite LEDs. i plan to use around 30 LEDs per board probably 12 arrays. i would like to control the flash patterns. can anyone point me in the right direction to start? will i need to learn to program a microcontoller?
    I attended electronics training 20 years ago so i'm a bit rusty:)
    is this a doable project? LED lightbars are VERY expensive and i saw a homebuilt one on a emergency light forum but they didn't go into detail.
    any opinions?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    What's a fire police? :confused:

    I've heard of firemen, I've heard of policemen, sherriffs, etc - but never a fire police.

    Besides, doesn't your department provide lightbars? I wouldn't think that FD/LEO's would have to provide their own.

    If you're not really fire/law enforcement, you can wind up in some mighty hot water using FD- or LEO-like lightbars on public roads.

    But to answer your question, a microcontroller driving logic-level MOSFETs to control the LEDs would be the way I'd approach it.
     
  3. garye5007

    Thread Starter New Member

    Mar 20, 2009
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    fire police control traffic at wrecks and fire scenes. i have a permit for emergency lights. i have a dept. provided strobe lightbar i like the LED bars better you can have lower profile and very eye catching patterns.
    thanks for the reply! Gary
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Hey Gary,
    Thanks for the explanation - makes more sense now ;)

    There have been a number of schematics posted on here for various types of emergency lighting, but they are usually some variation on a theme of using a 4017 Johnson counter IC; this is a 1-out-of-10 counter IC that always has one output at a logic high, the remainder at a logic low, and each time the 4017 counter receives a clock pulse, the counter advances by one.

    You can make some pretty impressive displays using such a device, but the problem is that once it's wired up, you have to re-wire it to change the pattern.

    This is what's great about microcontrollers; you can program them with a bunch of pre-set patterns, and have the pattern change at the push of a button. The parts count is also reduced considerably.

    The big problem is the "learning curve"; just how does one program those things, anyway?

    There's an absolutely bewildering array of microcontrollers on the market nowadays. Some of the stronger players are Microchip and Atmel. Parallax is out there, for mainly the educational market; their microcontrollers have a relatively low learning curve due to the Basic language they're programmed in, but are prohibitively expensive.

    Microchip sells a kit called "Pickit 2 Debug Express" for $50 that includes a programmer, microcontroller (PIC16F877) mounted on a development board, and a software package that contains a number of lessons and tutorials. You could actually incorporate the development board into your finished lightbar if you wanted to, I suppose - or just use it to experiment with the patterns that you wish to create. A few nice things about the PIC16F877 is that it has a LOT of I/O pins, it has it's own internal clock (so that you don't have to fool around with external crystals or resonators if you don't want to) and it's cheap, at a couple of bucks each.

    The biggest complaint I've heard about Microchip's offerrings is that the various uC's have different architectures, which makes portability (trying to take an application from one uC to another) an issue, along with the associated learning curve for the new uC. Of course, if you stick with one family of uC's, you won't run into that problem.

    I haven't used Atmel's offerrings, but I've heard (basically) that once you learn one of their uC's, you pretty much know how to program all of them.
     
  5. garye5007

    Thread Starter New Member

    Mar 20, 2009
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    thanks for the reply stwookie! you definitely answered my question....
    i want to get into uCs and this might be a good way to start. i'll look into that "Pickit 2 Debug Express" i could wire-up some arrays and experiment. there are other LED applications that that would work for.
    direction arrows ect.
    thanks again, Gary
     
  6. bill l

    Member

    Oct 11, 2009
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    i know this thread is older than dirt, but i found it 7 months after the fact as i peruse my way through each page all the way back to page 335.

    but i promise, i won't resurrect a lot. :)

    thought i'd bring it back as it seems that i have seen threads of similar nature on other boards as well.

    there are many manufacturers of emergency lighting equipment such as code 3, sound off, whelen, and etc. these manufacturers have modules designed to do a lot with l.e.d.'s and have many random flash patterns available.

    i believe there are federal codes regulating the duty cycle and frequency of flash patterns and this is due to possible negative side effects of unregulated flash pattern frequency and duty cycles.

    anyways, thought you guys might want to be careful about suggesting this kind of stuff.

    here is a link to a pdf from ford discussing this:

    https://www.fleet.ford.com/showroom/CVPI/pdfs/BRP_Report_Out_Countermeasures.pdf
     
  7. Wendy

    Moderator

    Mar 24, 2008
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  8. bill l

    Member

    Oct 11, 2009
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    who is the "knowledge" question directed to?

     
  9. Wendy

    Moderator

    Mar 24, 2008
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    I missed it first time around, and missed the date. This is why we don't really like to resurrect old threads, if you miss the start date then people will treat it as new. I don't think I had this article finshed back then either.
     
  10. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    You know, I DO wonder if he did try to build this thing! I know they are expensive, but modern light bars are very water/wind proof; they provide an easy way to change or modify the flash pattern, and meet all federal and state codes.

    Then, there is the problem of mounting it to the vehicle - manufacturers spend a LOT of money coming up with all the brackets and pieces to make these things fit as best they can. But that process takes time!


    Besides:
    Gall's sells some rather inexpensive stuff targeted to the volunteer and low-budget department that takes little work to maintain.

    I just wonder if he ever did try to complete this project - and what it looks like, how he mounted it, etc.
     
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