Hi Wayne, You series as many LED's as required to drop the voltage from the supply. If you need more LED's than in one string, parallel more strings...
The regulator keeps brightness constant anywhere above 8 or 9 volts (low battery condition) and protects the LED's from overvoltage during charging or when connected to shore power. A common problem is "shore power" derived from 3-phase, which comes out to 208V, versus the usual 220V. Unless your hookup is completely automatic, you *will* eventually juice the system with 220 when it's configured for 208. > You could use a carefully calculated ( or measured ) resistor and use > the 12 VDC. You should have 12 VDC, and ample current capacity. The problem is the lack of regulation. If you design for the likely maximum voltage deviation your brightness will be low at normal voltage and dim at low voltage. Since these are navigation lights, it's a considerable virtue for them to be designed to be full bright until the batteries are nearly dead... Always planning for worst-case scenarios. Any small loss of efficiency from regulator power dissipation is nothing compared to the improvement you're already getting over incandescent lamps. > I think the 7805 has only a one amp output. A heavier duty model does > exist. I can't imagine needing more than 60ma for my application. That may not be as robust a safety margin as you could want, but probably sufficient. The thing I'm most concerned with is power dissipation at max design voltage. If the LED's are going to be full brightness down to, say, a 9V supply (low battery), then at 16V (oversupply condition) the regulator would have to drop 7V. That'd be 140 milliwatts for every string drawing 20 milliamps... Doesn't sound too bad, I think. > You can use heat sinks and fans. Heat sink, maybe, but there's not going to be a fan inside these tiny light fixtures! <grin> > Still, I would consider using the 12 VDC. It is already there. I am, but it's not that well regulated. Or, at least, you can't *count* on it being that well regulated. Thanks, Mike D. [Mike Devour, Citizen, Patriot, Libertarian] [[email protected] ] [Speaking only for myself... ] -- The Silver List is a moderated forum for discussing Colloidal Silver. Instructions for unsubscribing are posted at: http://silverlist.org To post, address your message to: [email protected] Address Off-Topic messages to: [email protected] The Silver List and Off Topic List archives are currently down... List maintainer: Mike Devour <[email protected]>
