Chuck, Be nice or I will lead you astray. :-) Wait til you see the ideas I came up with for navigation exercises after Matt's talk.... we might discover the hyperlink between Mille Lacs and the Bermuda Triangle. The calculations you present worked for me for 2 LEDs in series. The problem I had with multiple green LEDs is the maximum light output I found at Radio Shack was around 600 mcd. The high output orange red LEDs I used to illuminate my compass have 13000 mcd output. To get the equivalent mcds in green I would need more than 40 of the green LEDs and more of a power source than I would care to add to my boat load. In practice, I found that 4 of the green LEDs provided enough illumination, if they were put above the compass card. The problem was that I could not get them to go with a 9 volt battery. 4*2.1= 8.4 <9 and the circuit should work without a resistor, but it did not. Maybe low battery voltage was the problem, they lit with a 12 volt battery. I tried wiring the green LEDs in a mix of parallel and series and managed in one configuration to get no illumination and when I reduced the size of the resistor I toasted the LEDs. Dana Dickson > -----Original Message----- <snip> > > This LED business is all Dana Dickson's fault; next month he's > leading a weekend Inland Sea Kayakers trip to a large lake in > central Minnesota (Lake Mille Lacs) that will include a night > paddle under the nearly new moon. I'm just trying to get ready > for it. ;-) > > Chuck Holst > <snip> > From what I have read on the Web, you get more even brightness by > wiring multiple LEDs in series than in parallel. Here's how: > > The LEDs should have a forward voltage and a forward current marked > on the package. Add up all the forward voltages and subtract them > from the voltage of your power source. What remains is the voltage > drop across your series resistor. To find the size of the resistor > in ohms, divide the voltage across the resistor by the forward > current in amps. <snip> *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
Dana Dickson wrote: >I tried wiring the green LEDs in a mix of parallel and series and >managed in one configuration to get no illumination and when I reduced >the size of the resistor I toasted the LEDs. Did you have the resistor running in series with the parallel LEDs or was the resistor on one of the "legs" of the parallel circuit? In series: voltage drops, amperage is constant parallel: voltage is constant, amperage drops or you might have already known that :) Shawn -- 0 ____©/______ ~^~^~^~^~^~^~^~^\ ,/ /~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^ Baker Brothers 0 Brews & Boats http://www.missoulaconcrete/shawn/ Shawn W. Baker mailto://baker_at_montana.calm --Fix the obvious to send email *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.paddlewise.net/ ***************************************************************************
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