Cabin Light addition

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.
 
thataway":30sdouqb said:
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.
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AC vs DC: It all depends, doesn't it? Explain that DC is safer to a lighting strike victim, or to someone who throws a 300 AMP DC breaker that explodes in one's face. Yes, high energy AC breakers explode, too, but I have had master electricians (whom I greatly respect) tell me that they are more afraid of high energy DC breakers. I read a journal article many years about micro DC voltage accidentally killing many people with heart conditions. It all depends upon the situation. To me however, the debate between the two at the levels we are talking about, and assuming that necessary precautions are taken -- the difference between the two is nil. I leave that discussion for experts.

No, I did not measure the current draw of my power supply. And yes, I do understand the concept of Wattage. I actually think it draws less than 2 amps, but there is no doubt about it: you do bring up a valid point, as I conceded, that a DC to AC power supply is very inefficient relative to just using straight DC. That's why DC/AC power supplies give off so heat.

Believe it or not, I like your idea, and I'm going to give it a try, because it is a far better alternative to what I'm doing today. It certainly is far cheaper at 1/3 of the cost, uses less energy (I'm converting DC to AC, then back to DC again within the bulb) and it is safer than using a DC/AC power supply. It's all good.

You are also right about boating cabins being different. I don't remember the cabin configuration and coatings on C-Dory roofs. However, on our Marinaut, the cabin roof is concave (as viewed from the inside,) and it is painted with enamel paint that is highly reflective. So this evenly disperses the light throughout the cabin.

Thanks!

Rich
 
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.
 
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
 
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