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    FW: Lights etc.
    From: Doug Royer
    Date: 2003 Oct 10, 14:41 -0700

    Jared,this is good stuff.I'm going to FW it to the group.I do hope that is
    ok with you.Thanks for the info.I'll write Mon. about what I find out
    reguarding these.
    
    -----Original Message-----
    From: Jared Sherman [mailto:jared.sherman---.net]
    Sent: Friday, October 10, 2003 14:32
    To: Royer, Doug
    Subject: Re: Lights etc.
    
    
    Doug-
     
    
    That's the theory, somewhere between 32 and 60 cycles and the eye thinks
    they are always on. There's more of a debate about subjective/objective
    brightness, but also apparently a real time factor that an LED takes a mucj
    longer fraction of a second to come to full brightness. That is, it is "on"
    right away, but it doesn't reach full brightness for something like 1/10th
    second--way longer than the blink.
    
    I don't know, I've just heard "he said she said" on this.
    
    The main spike that gets thrwon in a boat is from the starter motor. When
    you stop cranking the starter, it continues to spin for a short time and in
    that time it is acting as a generator, so it can add +14V to the 14V on the
    power lines, spiking 28VDC for less than a second--but that's eternity for
    some solid state devices. Those caps &tc you have are good protection. I'd
    batted this around with some ham operators and electronics techs and there
    was some debate, especially since a boat may be running 10VDC (low battery
    limping home and hoping the lights are still on) to 12.8V (full battery) and
    13.8-14.4 when the alt/generator is running. In order to get optimum light
    from the LED's they want a specific voltage, not a range. So...
    
    The jury was out on whether to use a single-chip DC regulator at the LED's
    (more expensive, best controller), or just spike protection (zener diode or
    other simple device) with resistors to limit current. I was cleaning up the
    instrumentation power lead on a boat last year and wound up building a small
    box with a circuit board in it. One external fuse for the instrument power,
    two sets of overvolt protection (fast spike protection + zener diodes since
    no one would swear which one was best, and the spike protectors DO wear out
    over the years) and then a tiny buzzer that should only sound if there is an
    overvoltage, allowing us to shut the instruments manually if the electronics
    all go out or the alternator goes berserk.
    
    Unfortunately I could only find an aluminum mounting box, and LORD! does
    that shop-grade aluminum get pitted fast in a salty atmosphere.
    
    
    

       
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