NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
FW: Lights etc.
From: Doug Royer
Date: 2003 Oct 10, 14:41 -0700
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@verizon.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.