[BKS72]

I was at Radio Shack today and picked up some red and green LEDs to make nav lights for my boat project. The only ready made ones I could find were around $40 and I'm too cheap to pay that. And I also wanted to fool around with wiring up some LEDs since I've never done it before:smile2:

The housing is a plastic cap off of the wife's laundry detergent. I just drilled 3/16 holes and pushed the lights through. They fit nice and snug. The calculation for the resistor for the 5 lamps called for a 68 ohm resistor, but with Radio Shack's limited selection 100 ohm was the closest I could get. The lights won't be quite as bright but should give me a little more protection from voltage spikes:wink:

All the connections were soldered as you can see in the pics and I'll mix up a tablespoon or so of fiberglass resin and fill the back to seal it up and make it stronger. I've checked the lights and they lit up fine. I'll hold off on the red marker for the other side till SkipEye posts up and lets me know what I did wrong on this one so I can fix it on the other side:smile2:

 

[DANZIG]

If it were me, I would go over the exposed leads with liquid electrical tape.

Other than that, it looks good. Will it be bright enough?

 

[mandingo]

that looks pretty slick branden,curious to know where you 're gonna mount it.post a pic after the install.i have been thinkin about some led's for lighting but also cant force myself to pay what they want, i dont care what color it is or if its as bright as the sun.i might have to try something like yours,if you have'nt pattened it yet:big_smile:

 

[GaryF]

Brandon

I'm a little surprised you would need a resistor, as LED's typically need 3.2-3.7 voltage for native operation. Five LED's in series like that would be considered under driven at anything under about 15-16 volts. Perhaps the resistor does add some spike protection though.

I would run the lights for about 10 minutes and make sure the resistor doesn't heat up. If everything stays cool and it's bright enough you should be in good shape. Cool idea!

 

[GaryF]

Of course I may have spoken too soon, I just found some green, red, and yellow leds that are rated for 1.8-3.0 volts. :embarassed: Bottom line, if they are bright enough with the 100ohm resistor then you should be in good shape.

 

[BKS72]

Thanks guys! Yeah, Gary, I used an online calculator for the resistor values, and they seem ok - thanks for the tip on checking the heat, I never thought of that.

I checked them in the garage with the lights off and they seem as bright as the regular nav lights with the old 1157 taillight bulb in them:wink:

I talked with SkipEye about running them in series and eliminating the resistor and his advice was to include it to help clean up the spikes.

 

[BoxxerBoyDrew]

So what is the total cost for the settup? I am wanting to run BLUE LEDs inside my boat for Night Fishing Lights. I found some at Wally World that are strips around 6" and have Chrome ends on them, and they only cost around $10! I am thinking of running 3 Around the Lower Deck. BUT if your Idea is Cheaper I might Borrow it from you!!! :wink:

Looks like they will work out fine!!

Drew

 

[metalman]

If I had done this project I would have wired them in parallel; I don't know why, as I have never worked with LED's. I guess it just seems more logical to me.
Is there a reason that they should be wired in series? Thanks...W

 

[SkipEye]

Thanks guys! Yeah, Gary, I used an online calculator for the resistor values, and they seem ok - thanks for the tip on checking the heat, I never thought of that.

I checked them in the garage with the lights off and they seem as bright as the regular nav lights with the old 1157 taillight bulb in them:wink:

I talked with SkipEye about running them in series and eliminating the resistor and his advice was to include it to help clean up the spikes.[/quote]

Branden, tsk, tsk. Are you misquoting me? LED's require a resistor in the circuit for current-limiting. Overcurrent is a sure death for an LED. Once the semi-conductor junction is biased into conduction its resistance will be very little. It's not just a matter of 'spikes'.:wink:

I would be concerned about the visibility. There are super-bright LEDS available now that might do the trick for Nav Lights but a lot has to do with the design of the globe. The LED NAV lights I looked at had a concentrated area of glass around the LED that I think was there to focus or concentrate the light.

I'd start off playing around with interior lighting first as that won't get you a ticket on the water for non-compliance with Coast Guard regs on visibility.

 

[AwShucks]

I would suggest you google search for the USCG Rules and Regulations. Depending upon the size of you boat, the navigation lights must be visible for a distance of 1 to 2 miles. Be a shame to put all that effort into the project if they won't meet the base requirements.

 

[metalman]

Once the semi-conductor junction is biased into conduction its resistance will be very little.

Darryl,
I love it when you talk technical!
Now, explain the series vs parallel thing to me in words I can understand:big_smile:
...W

 

[SkipEye]

Branden, I am coming up with more like a 130 ohm resistor for your 5 LED series circuit. Of course I am assuming some values to be 2v per LED and a desired current of 15 milliamps.

LED's vary widely in their voltage drop and optimum operating current. You need to know these values to correctly size your resistor. White LED's will differ from Blue, which differs from Green, which differs from Red etc.....

Basically you need the specs off of the package on the LED's you are using.

In your example, you had a source voltage of 12v, I assumed a voltage drop of 2v per LED. This leaves 2v for the unknown resistor to dissipate. Assuming you want your LED's to conduct at 15 milliamps, you will calculate as follows, E/I=R or Voltage/Current=Resistance, this will then be 2v/15ma(or .015)= 133.33 Ohms.

P=IE Power = Current times Voltage. In this example your power dissipated= 15ma or .015 x 2v= .03 watts, in other words not squat. A 1/8 watt resistor for example will handle .125 watts, a 1/4 watt resistor will handle .25 watts etc. Although it is not a good idea to use a resistor at its full power rating. Once you get past around 60% of a resistor wattage rating just bump up to the next size. You can put your finger on your resistor all day long, it will not get warm in this case. I guess thats one way to 'test' your circuit but it's easier to just do the math!:smile2::smile2::smile2:


Metalman: We could get into a lengthy discussion over LED's in parallel but basically it just isn't a good practice. You can in fact run strings of series LED's in parallel and that works great, as long as each string has their own series limiting resistor.

Class over!:wink:

 

[GaryF]

An advantage of parallel would be redundancy. If one fails, the others continue to shine. LEDs are often rated for up to 100,000 hours, but failures do happen. Wired in series, if one LED fails, the entire light goes out.

Disadvantages of parallel would be that it's a lot less efficient, as a bigger resistor would have to be used for the step down from ~13 volts to ~2 volts. And variations in the vf (voltage forward) of the individual LEDs could cause big variations in brightness between them. That takes care of itself a little better when they are wired in series.

Using a resistor isn't the most efficient way to reduce voltage for an LED, but it tends to be the simplest, which is an advantage in harsh environments such as a boat.

 

[GaryF]

In your example, you had a source voltage of 12v, I assumed a voltage drop of 2v per LED. This leaves 2v for the unknown resistor to dissipate. Assuming you want your LED's to conduct at 15 milliamps, you will calculate as follows, E/I=R or Voltage/Current=Resistance, this will then be 2v/15ma(or .015)= 133.33 Ohms.

15mA seems pretty low, I figured he was calculating at 30mA and 2 volts. Those little green and red LEDs are usually rated for a fairly wide voltage range, but you wouldn't want to push the voltage and current too high above rating.

 

[BKS72]

My, how quick we all are to assume I'm too dense to check the specs on the lights and plug the numbers into a simple formula using my cell phone calculator while standing at the parts cabinet in the store. Something like Ohms = (Source Voltages- LED Forward Voltage)/Current and then to double-check them on the online calculator when I get home:smile2: Those calcs were for single lamps because I wasn't sure how exactly I was going to run them, but at 99 cents a pack I could splurge and buy a range of resistors to accommodate different implementations:smile2:

So everyone can stop saying I'm dead wrong based on their guesses as to the requirements for the lights, the greens are 2.1V at 25mA and the reds are 2.6v at 28mA. :wink:

Darryl, I didn't mean to misquote you and I apologize - I thought you had recommended including the resistors to limit spikes, even if my voltage was close running them in series. I know about enough about electronics to fill the bottom of a thimble, so any misquotes were due solely to my misunderstanding and/or innatention.

As far as the distance they need to be visible, I'm not sure, but again, they're as bright as my old ones based on my very unscientific method of looking at them next to my old ones. If the Coast Guard really feels the need to check the lumens, candlepower, or whatever they rate the lights by some dark night on the MO river, I guess I'll just take the chance and learn my lesson:smile2:

Thank you guys for all the input and suggestions!

Branden

 

[SkipEye]

Sorry Branden, hope I didn't offend you. I was just trying to post a little info on how to calculate for the correct resistor. I see that you did a fine job.

Forgive me, brother from the West!:big_smile:

 

[GaryF]

If the Coast Guard really feels the need to check the lumens, candlepower, or whatever they rate the lights by some dark night on the MO river, I guess I'll just take the chance and learn my lesson:smile2:

They will probably bust you for having 5 little green lights instead of 1 big one, and then ticket you again because the one green one they deem to be your legal light isn't bright enough by itself. :0a26:

Seriously though, it's a cool idea.

 

[BKS72]

No worries, Darryl, I didn't mean to come off as a (complete) wisea#$ a minute ago and I'M the one that owes you an apology for the misquote. I should have gone back and read the PM before I did that but I didn't take the time.

I appreciate all the suggestions and I know my little project isn't perfect - but it was a fun way to kill an hour or so for a $5 investment at Radio Shack and I learned something while I did it. I appreciate you guys taking the time to share some of your expertise to make sure I learned it the right way

Not at all offended by anything on the thread, I just thought it was funny the way it was kind of inferred that I hadn't checked the specs on the lights or anything:smile2: I don't take offense to very much at all on here, especially in the boats forums since I know y'all were just looking out to help make sure I did it right, legal, and didn't waste my money by installing them wrong.
:smile2:

 

[BKS72]

OK, I realized version 1.0 of the nav lights got cheesier and cheesier the more I looked at them.

Took the lights out of the bottle cap, wired them in series, sharpened my pencil on the calcs, eliminated the resistor.

Cut up a castnet box to get a mold, cut up a beer can to get some nice, shiny aluminum. Put the nice, shiny aluminum and LEDs in my cut up cast net/duct tape mold and poured it full of clear, non-yellowing, non-blushing epoxy.

pulled it out of the mold, sanded the edges, scuffed up the top, and shot a coat of silver paint, then a coat of black paint on the top to get more reflection and brighter light.

Painted the back to cover up the Bud Light logo on the reverse side of my soon-to-be patented light-intensifying refractory unit:crazy:

Scuffed up the front so the lights would have more surface to shine on and minimze the appearance of "dots" that the LEDs had through the block of epoxy. Pix attached are what I would up with. Sorry about the pic quality, camera batteries are dead and I had to use my phone:big_smile: I now have enough time, material, and aggravation in them to have bought 3 or 4 sets of nav lights.:smile2: But I FEEL betteroooh:

 

[BKS72]

And here it is lit up - too lazy to climb in the boat to get to the battery so they're powered off a 12vdc adapter for something:smile2: