Cabin Light addition

C-Nile · Posted: Fri Mar 07, 2014 10:25 am Post subject:

I use an EcoSmart, 60W-Equivalent, Soft White, 2700K lumens, A19 LED bulb that consumes only 10 watts and has an output of 2,700 lumens, and it draws less than 2 amps in a portable lighting fixture with a heavy cord. Obviously Dr. Bob is right, because electricity and water don't mix. I should point out that electricity is dangerous regardless as to whether or not it is AC or DC. Yes, my power supply draws less than 2 amps. It's really the amperage that can harm you. It is true that a 9 volt radio battery can cause an arrhythmia in heart patients; I have read that micro amperage has been responsible, in fact, for many hospital patient deaths. What I'm doing is no more dangerous than using my power supply in my car, provided I exercise caution and keep everything dry. My Marinaut has a dry cabin, and has 12 Volt outlets inside the cabin. The power supply is placed in a dry spot. I find that any inefficiencies involved in converting DC to AC for my temporary usage is acceptable for me. Personally, involving electricity, I don't want anyone to do what I do. My comment was made to describe what I do, and should not be taken as advice. Further, I don't want the liability. I should not have mentioned it in the first place.

There is a clear warning on my power supply: "Keep the power supply dry. Do not expose it to moisture." I don't use lamp cords. I can see it now, someone wires an internal circuit in their boat with ungrounded, cheap lamp cord to a 1,000 watt power supply that does not know what they are doing. That's a disaster waiting to happen.

As for Dr. Bob, he generally knows what he is talking about, and he tends to be very conservative. One can't go wrong following his advice on this matter.

Rich

yukonjbishop · Posted: Fri Mar 07, 2014 11:10 am Post subject:

An A19 60w equivalent LED will generally provide 800 to 900 lumens, not 2700. The reference to 2700k refers to the kelvin number which describes the "temperature" of the light. 2700k provides a "warm" light similar to an ordinary incandescent 60w.

C-Nile · Posted: Fri Mar 07, 2014 12:06 pm Post subject:

thataway · Posted: Fri Mar 07, 2014 2:18 pm Post subject:

This is not the place to debate DC vs AC power as a danger, but AC is considerably more dangerous for multiple reasons from a medical standpoint.

I assume that Rich has actually measured the current draw of his 200 watt inverter powering the 810 lumen equivalent 60 watt light bulb. If one was to use 12 volt LED's to give 800 lumens, the current draw would be just under 1 amp at 12 volts. Thus he is using twice the current necessary. (The 2 amps Rich cited also fit with the efficiency loss of an inverter, and converting AC to DC to power this size LED.) The footprint of the 12 volt LED package would be a fraction of the size of an inverter, fixture, equivalent size 110 volt bulb. I suggest that Rich look into the use of 12 volt LED's to give the indirect light he requires.

If indirect light were a desired feature for other C Brats, it would be very easy to design a light to do this. For example, a 10W 3000-3300K 800-Lumen Warm White Light LED Emitter(9-12V,850mA ) is $6.50 (less if bought in bulk) The fixture could be made to be less than a 2" cube. However, each of our boats is different, and the place we want the unit put will also be different.

C-Nile · Posted: Fri Mar 07, 2014 3:57 pm Post subject:

thataway · Posted: Fri Mar 07, 2014 6:44 pm Post subject:

An easy mount for this light if you want to put it on the inner hand rail, is to make the back of the holder concave, the same as the diameter of the hand rail, and use either clips, or small shock cords to hold it in place. I would also mount the LED at least slightly off the mounting material--since there is some heat (I have a 36 LED cluster over my bunk in the RV, and it is running about 40 degrees over the ambient temperature. But it does have an open design which allows for heat dissipation. Also you may want to make a diffusing lens over the LED--since the light bulb which you like so well is well defused as a feature of its design.

As to the DC current which you describe is very high amperage and not germane to this discussion. (Lightning is some where between 30 Kilo-amps (negative lobe) to over 300 Kilo-amps (Positive lobe) Voltage dependent on the length of the bolt--temp is somewhere near 20,000 °C. Yes, I mentioned about 100 micro amps being enough to cause an issue with a cardiac patient, and it can be less, but you are getting into an area where I have some expertise--but how and and under what circumstances--again--beyond the comprehension here.

As for measuring power consumption--it is also a good idea to have a device such as the Link 10, or one of several comprehensive battery monitoring systems to manage the power on your boat. It is also easy to measure small current (under 10 amps) with most digital volt meters--my apology, I assumed that since you said it used 2 amps--you had measured the current draw. However, theoretically your guess is close.

C-Nile · Posted: Fri Mar 07, 2014 8:28 pm Post subject:

Thank you Dr. Bob. I like the idea of the concave mount. One thing that got me intrigued with your suggestion was the small size of your proposed LED solution relative to the to large and clunky shop-type light I use. With our size of boats, space is a premium, and anything we can do to maximize space is beneficial. Thanks again,

Rich