LED driver and switch advice

Discussion in 'The Projects Forum' started by supakpow, Sep 3, 2008.

  1. supakpow

    Thread Starter New Member

    Sep 3, 2008
    4
    0
    Hi, I'm an extreme novice with electronics so some help would be really great. I have avoided posting in any forums, trying to figure this out on my own but I think I need to throw in the towel and get help!

    Here's my project:

    I'm putting together a light using (3) luxeon V stars (5w, 6.84vf, 700ma to 1000ma if pwm),
    in series, (Would it be better to run these in parallel instead, given the battery specs)
    14.8v or 11.1v LiPo battery (1500mAhr 8C max discharge),
    Barantec piezo switch.
    (see attached spec sheets)

    My goal is to be able to dim from 100% to 75% to 50% to off. 4 states, (0-100%-75%-50%-0) Using the piezo like a momentary switch to scroll to each setting with another click.

    From the research that i've done I think that I can use the Luxdrive 3021/3023 LED driver to at least drive it at 100% (see luxeon spec sheet)
    Could this driver be turned on/off and/or be made to dim using a piezo switch? I'm using the piezo because it's waterproof and extremely durable. (waterproof light)

    I know that a potentiometer can be used with this driver but is there anything that can take the place of the potentiometer (hard to waterproof vs piezo ip 68), such as a microcontroller or PIC, so that I would still have the benefit of the features designed specifically for high power LEDs, (such as voltage regulation and auto current shutoff when the battery drops below the batteries discharge limit) and accomplish the 4 states (0-100-75-50-0) that I would like to have?
    It would be preferable to have the driver reduce voltage to accomplish the reduced power states so as to lengthen the life of the battery instead of using resitors etc...

    Here is the page from luxdrive that shows all their drivers and features.
    http://www.leddynamics.com/LuxDrive/faq_how-do-i-choose-a-driver

    If the Luxdrive driver isn't capable of doing this, does anyone know of a driver that would be on/off dimmable with a piezo?
    I found another company that makes a large variety of drivers but I am having trouble narrowing down the choices for the configuration I want. I simply don't have enough knowledge presently to choose correctly.
    http://para.maxim-ic.com/results.mvp?fam=hbled

    I would like to avoid having to try to make a pcb circuit if I can use a LED driver that already exists. I wouldn't mind incorporating one with the driver. I would even settle for simple on/off if I have to.

    I have a head lamp that is a single 3w luxeon III that dims in this configuration using a momentary switch in an extremely smallformfactor, so I know it can be done. I just don't have a clue how. I could post a picture of the circuitboard if it would help.

    Isn't a momentary/tactile switch basically the same as a piezo in the way it functions?

    Also, what is the lowest input voltage for (3) v stars(6.84vf) in series? 24v?
    verses 7.4v in parallel?

    I have the desire to learn more about this topic and am trying, but I don't have enough time to learn everything it seems I need to be able to understand some of this or where to start with PCBs and PICs etc...

    I know this is a lot to ask so I really appreciate any help given. Remember your talking to a neophyte, so please dumb it down if you can. :D
    Thanks for any input!

    KP
     
    Last edited: Sep 5, 2008
  2. kammenos

    Active Member

    Aug 3, 2008
    127
    0
    Only these 3 states? You do not want for example potensiometer?

    Some Luxdrive have dimming capabilities but only with potentiometer. Not switch.

    If you want only 3 states, you may use for example a 555 with 2 different resistors or capacitors to generate 2 PWM signals. You may choose using this calculator:
    http://pcbheaven.com/handbook/calculus/index.php?calc=555astable

    The output of the 555 (that is pin No.3) will be connected to a transistor driver. The driver is shown here:
    http://pcbheaven.com/handbook/trans_circuits/
    Of course you will not connect a relay as an output, but instead, you will connect your LEDs.

    You should also choose a transistor suitable for the application. If each LED draws 1Ampere, then you need a transistor that can handle IC more than 3 amperes. You may choose a transistor using this transistor selector:
    http://pcbheaven.com/handbook/transselect/
    Put for example collector current>=3 and colelctor emitter voltage >20.

    How many switches will you use? Because i really do not understand how you intend to use one piezo switch. You want to click each time and scroll 0-50-75-100 and back again 0?


    Parallel of course
     
  3. supakpow

    Thread Starter New Member

    Sep 3, 2008
    4
    0
    Correct, except from 0-100-75-50-0, using one piezo switch for the four states.

    What advantage is there to running parallel over series? I don't completely understand the difference.

    Do I need to be able to program the 555? I have ZERO knowledge of how to do this.

    Sorry, I know I sound lame but I don't understand more than the very basics of the info about transistors and calculating the resitors. I am a window cleaner by trade wishing I had a degree in electrical engineering.:D

    I have several led resistor calcs but they seem to apply to a LED setup that doesn't have a designed LED driver.
    I would like to avoid having to try to make a pcb circuit if I can use a LED driver that already exists. I would even settle for simple on/off if I have to.
    I really appreciate your reply and will continue to try to understand the ideas you shared!
    KP
     
    Last edited: Sep 3, 2008
  4. iONic

    AAC Fanatic!

    Nov 16, 2007
    1,420
    68
    I guess that before offering any suggestions I'd need to know how "water-proof"
    does it need to be. Are you swimming with it?

    If portability is a concern wiring them in series will require at lease a 20V source,
    which could be difficult to manage. If you wire them in parallel then you could get by with a couple of Li-Ion laptop batteries at 4.2V a piece (8.4V). Three would be even better.

    A note on the 555's, you don't have to "program" with code, but rather just use an equation to calculate values for 50%, 75%, & 100% LED brightness.
     
  5. kammenos

    Active Member

    Aug 3, 2008
    127
    0
    In series, if each load is for example 9V 2 amperes, then for 3 loads you need to provide power 27volts 2 amperes. In parallel, the same loads would need 9 volts 6amperes. Also, connecting in series, if one load fails there is a problem. If this load that fails breaks connectin, then all loads will stop working. If this load short circuits, then the other loads will get all the voltage. In our previous example, if one load short circit, then the other loads will have each one 13,5 volts instead of 9 (27/2=13,5). That may be a problem.

    You need 0 programming for the 555. As you see the link i sent you, this is all you need to do. Only you need to calculate some parts. But we can help you when you decide in your calculations.

    This is not to worry when you decide.

    Give i a shot, it is nothing difficult, you make something by yourself. If fails to work, you may have spend a couple of hours and a maybe 10-15 dollars. Worth to try:)
     
  6. supakpow

    Thread Starter New Member

    Sep 3, 2008
    4
    0
    It needs to be waterproof to 150ft. I've got the enclosure part of things figured out, so I don't need help with that.The piezo switch is completely waterproof because of the way it is made and can be attached through a waterproof dive case that will house batteries. That's why it is a ncritical prt of the design.

    That sounds reasonably easy.

    VERY helpful bit there! Now I understand the basic basic difference between series and parallel. Other than some design advantages from one to the other, that you have pointed out, the choice seems to be do I want to multiply voltage or amperage. I think amperage would be better in this design because of the battery choices.
    The drivers will limt current or voltage, but I don't think both. A seperate circuit could be made to do accomplish whichever is not regulated by the driver I believe. correct?

    I think that I have found a driver that may incorporate all the features that I want. Maybe someone could check out the link and tell me if one of these would work with
    (3) luxeon V stars (5w, 6.84vf, 700maIF),
    in parallel,
    14.8v or 11.1v LiPo battery (1500mAhr 8C max discharge),
    http://www.taskled.com/techmaxflex.html
    http://www.taskled.com/techmaxflex.html
    http://www.taskled.com/leds/nflexuni_v1.01.pdf

    Thanks for the updates ideas
    KP
     
  7. ifor

    New Member

    Aug 16, 2008
    2
    0
    You should wire the LuxV's in series so you will end up with more voltage across the leds than the battery so the maxflex from taskled would be the one. All the taskled drivers are very good I have used maxflexs and nflexs.

    Personaly I would not be using LuxVs there are a lot better leds avalible now than the old LuxV you would get considerably more light with 3 Q5 or R2 Cree XR-e's for less power. Or if you want to be realy leading edge then a Soul P7 or the soon to be released Cree MC-E.

    Lots of info here

    Ifor
     
  8. supakpow

    Thread Starter New Member

    Sep 3, 2008
    4
    0
    Thanks Ifor! I am using the luxV because I have 9 of them that I got very cheap, but would use any of the others that you recommend as long as they are not extremely expensive. Where can I get them for a good cost?

    And do you know where I can get a tripple lens with narrow spot (10deg)?
    Besides Deal Extreme?

    If i used the Q5 or Crees what taskled driver or board would you use to get the step cycle I want. The maxflex looks like it would work. But would it be a stand alone driver or would an additional component be needed?
    It looks stand alone.

    Which emiiter is the brightest of the 3 you mentioned?

    Would (1) soul P7 or Cree MC-E put out as much light as (3) of the Q5 or R2 or XR-E? If so the that would eliminate a lot of hassle for me in way of the body of the light and lenses etc...

    Thanks
    KP
     
    Last edited: Sep 6, 2008
  9. ifor

    New Member

    Aug 16, 2008
    2
    0
    Maxflex or nflex don't need anything else so they are easy to use.

    P7 or MC-E are 4 led die in one package light output will be about the same as 3 XR-E s if you drive them both flat out. (the max curent is lower on the 4 die devices). Taskled do not have a suitable driver for the P7 it has the die in parallel so about 3.5v but a max of 2.8A For the MC-E you will be able to wire it any way you want serial/parralel wise, so it will work with the task led drivers. I have three MC-Es on order with Cutters hopfully get them by the end of the mounth. Q5 and R2 are just the two highest bins for the XR-E r2 being about 7% brighter on average which you would be hard pressed to see manualy.

    best suply depends where in the world you are. I am UK based so try to get from Europe as there will be no import taxes then. I have got batteries from DealExtreme but would not use them for led's it's too easy to be ripped off as it's hard to tell what you have...

    I am no expert on optics I have used indevidual square ones myself from Ledil but don't know what I will use with the MC-E's I have some samples comming from cutters but will want to try the square ones when they are avalible.

    Good luck with your light like I said lots of infomation is avalible on cadlepowerforums

    Ifor
     
  10. harsha.ub

    New Member

    May 25, 2009
    5
    0
    Did you manage to finsh the circuit using single pushbutton/ piezo for rotary mode selction? if so can you pass on information how you went about doing it. The links in this thread for pcbheaven are'nt working anymore!
     
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