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Dan McCosh
02-23-2011, 10:48 AM
I have an anchor light that I converted to use a 4.5 v. LED from a Maglite flashlight. The problem has been the batteries--I would like to use a 6V. lantern battery--easier to find--but don't know if a: this would fry the LED, or b: the voltage could be cut with a resistor. If the latter, what should the resistance be?

willmarsh3
02-23-2011, 12:48 PM
This would depend on the current rating of the diode. You could measure it while hooked up to the 4.5v source with a multimeter.

Once you have that then you can use any number of online diode calculators.

http://led.linear1.org/1led.wiz

to find the required resistor.

Dan McCosh
02-23-2011, 01:58 PM
Now I'm looking at installing a voltage regulator, after a little research. What I can find out about the bulb is it won't take the high voltage.

gibetheridge
02-23-2011, 02:03 PM
How about if you use 3 of 1.5V in series. For more time use banks of 3 in parallel. You could use the flashlite body(s) to hold the 3.

Dan McCosh
02-23-2011, 04:22 PM
How about if you use 3 of 1.5V in series. For more time use banks of 3 in parallel. You could use the flashlite body(s) to hold the 3. I've tried several ways to use 1.5 v. cells. The problem is that the light is an antique originally designed for a dry cell, and while I can fit a 6V lantern battery in it, the 1.5 cells are a pain.

Dan McCosh
02-24-2011, 03:45 PM
FWIW, after consulting with numerous technology consulting firms, I calculated that a 37.5 ohm resistor in the circuit would provide the correct voltage. I purchased a 33 ohm resistor from Radio Shack. Close enough. It works. The thing is supposed to run for 300 hours, but I'm not sure it will work that well. Looks kind of pretty, though. W've used this light for about 20 years or so, and it was in an antique store when we found it. Ain't technology great?

Dan McCosh
02-25-2011, 11:14 AM
Oops. The 33 ohm resistor was way to small. Cut-and-try, along with measuring the current, reveals about 100 ohms is more like it. The high-tech consulting firms didn't know what they were doing.

paladin
02-25-2011, 01:26 PM
Dan, post me a piktoor of the light.....if it's similar to mine (I saved mine when I sold the boat) there are other ways to skin the cat. Open the thing up and use a multimeter to measure the current drain.

Dan McCosh
02-25-2011, 01:46 PM
Here's what it looks like, if this works:

http://i242.photobucket.com/albums/ff159/dmccosh/92ecbddc.jpg

Dan McCosh
02-25-2011, 01:51 PM
http://i242.photobucket.com/albums/ff159/dmccosh/29e1073c.jpg

PhaseLockedLoop
02-25-2011, 05:05 PM
I have an anchor light that I converted to use a 4.5 v. LED from a Maglite flashlight. The problem has been the batteries--I would like to use a 6V. lantern battery--easier to find--but don't know if a: this would fry the LED, or b: the voltage could be cut with a resistor. If the latter, what should the resistance be?

I don't know about the Maglite LED, but many LED flashlights nowadays use flux LEDs that have integral constant-current circuits. If that's not the kind you have, it's probably the kind you should have, and they're not too expensive.