Spring is only 60 days or so away. Time to plan ahead for some maintenance and long due enhancements for Brunnhilde. Many are small projects that I wanted to do for a while. Some of these are due to mission changes such as towing of a car trailer, as well as the types of camping.
I finally got around to modify the CF light fixture in the bathroom into LEDs. LEDs have come a long way since 2004. In the past the biggest problem were light spectrum, efficiency, as well as availability of the variety of designs that lend themselves to different applications. The time is ripe to perform this fixture modification and I have all the needed material on hand. I bought this spool of LED tape light that I have yet find a use for it. I looked into if it can be used for the bathroom light fixture.
I referred to my older post how the modification was done
the bathroom's fixture differs from the one in the cabin that it is moisture proof gaskets and membrane over the on/off switch
the CF bulb is 11 watts so the entire fixture probably consumes 12 watts
strangely the cabin fixture is branded as Westfalia but obvious both are made by Rensch Lichttechnik; I only notice the "ply marks" on the back plastic cover exist on both fixtures
I like fixture that the designer thoughtfully label the correct type of replacement bulb at the most prominent place
For this fixture I took a different route in the LED lights I used. I have a spool of LED light strips which you can cut to length and it has much better color rendering than the one I used on the cabin fixture 4 1/2 years ago. I was going to place three strips side side to fill the flat surface of the fixture but fortunately I didn't.
The reason is I want just enough light and keeping the fixture cool and low power consumption is paramount. Each strip of this LED lights has 15 LEDs for the length of the fixture. I compare the light output side by side with a 20W MR16 halogen light and they are comparable. For such a small space I reckon one strip should be enough.
there is enough space for 3 strips of LEDs side by side
I used single strand teflon jacket wire-wrapping wire
The tape light has pressure sensitive adhesive tape on the back marked as 3M, but obviously it is Chinese knockoff counterfeit. It is my biggest concern that the adhesion is adequate and of quality that will not deteriorate prematurely. This concern is my main reason not wanting more than 1 strip. I cleaned the plastic surface well with alcohol first. Despite being 3M counterfeit double-side adhesive tape the peel strength felt strong at least when new.
I am happy with the tidy workmanship
being bare SMT LEDs the angles of the emitted light is very narrow
with the cover lens on the Fresnel lens disperses the light
a different photo showing the light from 15 LEDs inside
it draws 280 mA at 12.5V
All the center console switch blanks in Brunnhilde were broken (the flimsy plastic tabs) when I acquired her. I have been wanting to replace them for years but never got around to. I secure them with silicone caulking but the one I modified to house a toggle switch invariably came loose. I have plan to add 1 or 2 more of switches so I need to buy a batch of these switch blanks.
I didn't want to deal with paying high price for these small items as most dealers use matrix pricing. I found the cheapest price on the web but took into account the shipping and handling charge. Since these are so fragile I decide to buy 10.
I was really on a tear with catchup projects; I got around to install a battery tender harness for the Porsche; this is the best option out of many unattractive options
I monitored the modified light fixture on my bench for hours to ensure nothing goes wrong. While doing so an idea came to me. Why not make it with a high/low selectable? While I am quite sure one light strip should be adequate with regular use of the bath at night, there may time that I want more light for tasks such as cleaning the bathroom, or repairing something. Unlike the cabin fixture the one in the bathroom is doubly switched. I can make use of the SPST switch on the fixture for hi/lo function.
in no time I had a second strip added
wiring was done in a jiffy too
I firmly subscribe to difficult constraints make for better design as they challenge you to explore all options over the obvious. Most best designs are the fruits of stepwise refinements and the best are deceivingly simple.
current at 13.5V => 9.4W
current at 12.5V supply => 7.1W
I was right to be conservative on the number of strips to install. The plastic housing of the fixture got quite hot during my bench testing, and the worst was at 13.5V. I would not want to set the fixture to High for extended duration in a hot summer day. The main reason these LED tape lights get so hot is by nature of their design for 12V. There is no switch mode DC/DC converter so resistors are used to drop the 12V to circa 5V the LEDs need. The resistors are just dead loads that do nothing except dissipating power.
To prove my assertion I measured the voltage across the resistors and the LEDs. The voltage across each LED is 3.14V, and across each resistor is 4.00V at supply voltage of 13.50V. My estimate was a bit high for the resistor as well for the LEDs. It is very easy to figure out the tape light topology without the need to examine the conductor traces. From my measurements across one LED and a resistor one can infer that there must be 3 LEDs sharing one resistor, and the LEDs and the resistor are connected serially. 3 x 3.14V + 4.00V = 13.42V, which is close enough to 13.50V of the supply voltage.
As a sanity check, I counted the number of resistors. There are 5 resistors for this strip length that has 15 LEDs. So what is the wasted wattage due to the current limit resistors for each strip of LEDs? 4.00V x 360 mA = 1.44 W. 1.44 W is not a lot of power dissipation in this fixture. However the 15 LEDs also create modest amount of heat due to inefficiency. Any power not converted to light output is converted into heat.
The proof is in the pudding and to prove the success is to replace the fixture into the intended location. Many things can go wrong, such as adequate brightness, and most important the correct light color rendering. When trying to capture this in a photo most common mistake is without a use of reference. With camera especially the dumbed down point and shot smart phone you can make the color and brightness anything you want, or worst not intended as you didn't tend to the task.
Without much effort here are what I captured.
color rendering and brightness - the problem is there is no reference; the diffusion and dispersion are quite good
here with a reference of LED galley light that I have compared to 20W halogen that is very close in color spectrum; the bathroom light is warmer with without the dreaded green tint of the early warm light LEDs
The Low setting of the bathroom light fixture is adequate and comparable to the original 11W CF bulb. The color spectrum is slightly cooler which is good as warm CF is too pink to my taste.
Since I am quite please with the newer LED tape light I went ahead and replace the LED replacements that I did back in 2015.
the LED conversion that I did in 2015; I don't like the green tint
to show the green tint I placed it side by side to a 20W halogen
here is the old LED (green tint on left) and the newer LED light tape (right)
just 10 minutes later I have the LED lights swapped and back into the cabin
here is a photo of it against the galley LED lights which has more blue; all are good as I expected
As the main motivation of switching to LED is to conserve batter charge only the current consumption at 12.5V matters. Here is a comparison to the older LED that I swapped out.
the old LEDs that I swapped out - consist of 9 LEDs
the new strip light consists of 15 LEDs is 280mA at 12.5V
the power consumption has increased by 40% but it emits more light
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