LED Light Construction and Power Management

[Bob Schwartz]

In my last post, Texas to Key West with Pictures, I discussed LED lights and several people on and off the board ask for more information. Unfortunately, this post is a bit tedious, but so is the process of making LED navigation lights.

For those who want the bottom line, I find that LED lights appear much brighter than incandescent bulbs; and they burn about one-fourth the power of incandescents. With a bit of power management, I could run all the electrical appliances I needed while consuming less power than it takes to run one incandescent bulb. My 20-watt solar cell was sufficient to provide all the power that I needed under sail, and it was not necessary to use the engine to charge batteries. I will start off with some pictures, and then discuss a bit of electrical theory.

I have a CD-27 on the Gulf Coast and a Typhoon on the local lake and have installed LEDs in both boats. I have made 2 bi-color bow lights, 2 stern lights, a steaming light, and an anchor light and I have not made any two lights the same. To start out, I physically remove the light fixture and take measurements. Then, I go to an LED supplier and check out LED availability and look at the scale drawings to get measurements. I have been able to make all the lights. The one failure is the deck light on the CD-27. The space in the Perko fixture is just too small to install a high intensity LED. I have purchased all my LEDs from superbrightleds.com and will refer to that website.

Bow Light on Typhoon

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I cut 2 brass plates to the same shape as the interior of the fixture and drilled 6 holes, top and bottom so that the tip of the festoon fixture protruded through. Then, I soldered the festoon bulbs to both plates. I then soldered this arrangement into the festoon light socket.

Solder and construction notes: I have been in ham radio for over 35 years and have done much soldering. This is a difficult solder job. The festoon base does not easily accept solder. I had to lightly sand the base and apply a liberal amount of resin flux (not acid) and I used a 140-watt solder gun. I do not think a soldering pencil would have hacked it. LEDs are polar devices, which means positive must be attached to positive and negative-to-negative or they will not work. I marked the positive with a red marker so as to not get the poles reversed. I found it very challenging to clamp this in place while soldering – it was a real struggle. To add to the challenge, the face of the bulb should tangent with the curve of the fixture (i.e. pointed directly out) Finally, on a bi-color light, be sure to use red and green, not white. The reason for this is explained in the Superbright website as follows: “For best results the LED color should be the same as the lens color. As an example: a red lens will filter out all but the red portion of the light so if the light is all red, none or very little light will be blocked by the lens. The light from a White LED contains very little light in the red portion of the visible spectrum so most of the light would be filtered out by a red lens.”

The CD-27 has an identical bi-color light, but I constructed a different type of fixture. I cut a half inch ID piece of PCV pipe exactly the length of the inside of the fixture and mounted 4 green and 4 red LEDs on it. My CD-27 is 200 miles away and I have not been down there since my last post, so I have no pictures. I think the Typhoon fixture is probably a better arrangement since I removed the bulb holder on the 27. On the Typhoon, I could de-solder the LED fixture and revert to using an incandescent.

I used 3910/4211-R6 (red) and 3910/4211-G6 (green) festoon lights on the bow. I would strongly recommend buying several extra bulbs of all types in case some bulbs are destroyed in the soldering process.

The stern light on the CD-27 is quite similar to the bow light, so construction of the LED is the same, except for the white color of course. I believe I used 6 bulbs. The bulb is 3910/4211-W6 (white)

The stern light on the Typhoon quite small, so I used the 4 LED bulb fixture instead of a 6. 3022/3610-W4


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The steaming light on the Typhoon has a similar light holder as the stern light – perpendicular. I did not want to lower my mast to take pictures, but I believe I soldered 4 or 5 bulbs in a circle in a similar fashion to the stern light so as to get 360-degree coverage. I do not remember the size. I mounted the bulbs vertically, in the same fashion as the stern light.

I used 1142 LED bulbs for the conical interior light fixtures in the cabin, which are over the bunks and in the head. They come in 12 and 19 LED sizes. I tried both and they both work well. If you buy the 19, it comes in narrow and wide. I would suggest wide. Bulb numbers: 1142-W12 White LED bulb; 1142-W19 White LED.

There are 4 ceiling dome lights in the CD-27. An 1142 bulb will fit, but they do not work well because the light is pointed sideways and not down. For these I used LED lights attached to a square circuit board that points down. (T10-PCB-Wxx White LED Lamp) I used the 24 LED version. When installing these, I would recommend putting electrical tape across the backside of the board to prevent electrical shorting if the board contacted metal. I attached the board to the light fixture to keep it from moving when under way.

This pretty well covers the subject of LEDs. For those who are interested in delving into the minutia of power measurement and power management – read on.

Shortly after I bought my boat, I did a test to see how long the batteries would last. I turned on the running lights and most of the cabin lights. I could almost see the voltmeter drop. The next morning, the battery was dead as a hammer.

I have a bit of an electronics background, so I decided to do a power survey. I wanted to know how much amperage all the devices on the boat drew. Measuring amperage is normally not an easy task. I found that the easiest way to do it was to take a 1 ohm precision (1%) resistor rated at 5 or 10 watts and put it in series with the battery. Disconnect one of the battery cables and with alligator clips, connect the battery to one end of the resistor and the battery cable to the other end. One must have a precision voltmeter, capable of measuring within a few thousands of a volt (millivolt). These meters are available for under $50.

The test is based on Ohm’s law. Voltage (E) is equal to Current (I) times Resistance (R). Or, E = I*R. A one ohm resistor works well because the small resistance creates a negligible effect on the overall load, and, with a resistance of 1, the voltage equals the current. (E = 1 * R, or E = I). Hence, one can take a voltmeter and measure the voltage between one end of the resistor and the other end of the resistor and that reading will also be the amperage. Hence, if the voltage reading is .577, the current is .577 amps. The current through the resistor is the same as the current through the load device being measured. I measured the current draw of every electrical device on the boat and posted it to an Excel spreadsheet.

An alternative way to measure current drain is to take the power rating of the various devices in watts, and calculate current draw. The formula is: Power (P) is equal to Current (I) times Voltage (E). Or, P = I * E. Also, to determine current the formula is: I = P / E. One obviously has to know the power consumption rating of the device, but this is commonly shown in the owner’s manual or etched on light bulbs.

To illustrate: if your battery voltage is 12, and you have a 7.5 watt bulb burning, the current draw is .625 amps. (.625 = 7.5 / 12) Each of the two running lights on the CD-27 takes a 7.5 watt bulb.

The running lights on the CD-27 consist of 10 festoon bulbs – 4 red, 4 green and 6 white. The current draw of the red bulbs is 35 milliamps, or .035 amps. The green and white bulbs draw .032 milliamps. So, the total current draw of the running lights is .46 amps ((10 x .032) + (6 x .035) = .46.

All I need for sailing are running lights, a cabin light, and reasonable use of my Chartmaster GPS – charting unit. The 1142 LED cabin lights draw 36 milliamps and the Chartmaster draws 7.5 watts or .625 amps. If I restrict my GPS use to 2 and a half hours a day, I am using it only 10% of the time, so my overall current draw is one-tenth, or .063 amps. Adding all this together, my minimal power requirements consist of running lights .46 + cabin light .036 + Cartmaster .063 = .559 amps, which is less than the .625 current draw of one running light!

One final note on equipment and LEDs, LEDs are very sensitive to voltage. If they get higher than their rated voltage, they will either burn up immediately, or their useful life will be greatly diminished. The festoon bulbs and other 12 volt bulbs are designed to operate between 9 and 14.8 volts. According to the service manual, my Yanmar 1-GM alternator has a regulated voltage between 14.0 and 14.6 volts. Sometimes alternator regulators malfunction, and if the voltage gets too high, the LEDs won’t last long.

While sailing, I was keen on measuring charge voltages of my solar panel and alternator, as well as static battery voltages. I was frustrated because the installed voltmeter is so inaccurate as to have little utility. I found a neat little voltmeter, which is pictured below. You can find these at places that sell equipment for recreational vehicles. The reading is quite accurate. It plugs into a cigarette lighter type receptacle. Since the great majority of 12-volt devices plug into these receptacles, I installed 4 receptacles in the cabin - 2 on each side.


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So, after this long-winded dissertation, I think I will give my fingers a rest and raid the reefer for a brew.

Happy sailing,

Bob

[John Ring]

Bob,

Thanks for sharing that wonderful technical detail! That has to be one of the best posts of the year!

Thankyou!
John Ring
CD28 Tantalus

[neil]

This is exelent.
All my running lights are LED clusters, I like yours better but I lack the skill to make them.
Mine came from a guy named Steckman (or something like that) who had his boat in the yard I work at, they were rather expensive but WAY more than worth it in the long run, they use almost no electricity compared to the old ones I had.

Here ishis website if you are interested:

http://www.stecktronics.com/index.html

Great post! Thanks!


Cheers,
Neil

[Dean Abramson]

Bob,

Wow! Thanks for all of the effort that went into your post. I am going to copy it and save it.

We recently installed a white/red LED light in our galley, and are very happy with it. Just bought it, didn't make it!

Dean

[Cathy Monaghan]

Bruce is writing a few articles for the CDSOA's newsletter, Masthead, detailing some of his LED conversion projects as well. The first article describes the conversion of a marker light and will probably appear in the "Yard Talk" section.


Cathy
CD32 Realization, #3
Rahway, NJ
Raritan Bay