Highest safe voltage

Of course, if you don't ground (or do I mean water) either side of the battery...

Sylvia.

Reply to
Sylvia Else
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You do not know what you are talking about at all. I'll wet you down with a hose and had you a live 115 AC and watch you dance. In fact why don't you take your plugged in toaster and you in the shower, and turn them both on, if nothing happens you win.

Reply to
Haliima Awil Samow

All of the examples he cited above are absolutely true, as is the explanation he gives for why it works. Who is it that doesn't have a clue???

In fact, if you have a rubber mat on the floor, and keep your body from touching the faucets, *nothing* will happen. Just don't try to turn the water off...

A lot of years (40+) ago I was in High School, and was part of a group that decorated the gymnasium for a dance. They had this big circular metal tub, about a dozen feet across that was set up as a fountain, with a foot or so of water in it. But alas, when the lights were turned down low it just didn't look like much. So I took a standard drop light (with a regular 60w bulb) and put the lamp on the bottom of the tub (under a foot of water)... and was about to plug it in when everyone told me I was nuts in the head, that it would electrocute people at worst, and at best would simply blow up. I laughed, and plugged it in. Of course it worked perfectly, and lit up the water in the tub in an eerie way that was just great. Everyone else was in awe that I could also lean right on that metal tub, and even put my hands in the water, and live to tell about it.

Reply to
Floyd L. Davidson

Realistically, there is NO absolutely safe voltage. This is somewhat of an urban myth based on what is generally accepted as safe (< 30 V) due to the resistance your skin has to current flow which reduces the amount of current your heart sees when your body becomes a conductor.

If for instance you have a cut, the resistance is dramatically reduced, so a lower voltage could create enough current flow to cause your heart to stop.

Reply to
Bob Peterson

Actually in some respects a smaller wire might be more of a danger since it might result in a higher potential for the wire to penetrate the skin, which dramatically reduces the voltage required to produce the amount of current required to kill you.

The 120V inverter idea is just plain STUPID and highly dangerous for what this guy plans. A better choice is not to do this at all, but if you insists, best solution is a 12V battery and 12V light strings.

Reply to
Bob Peterson

Reply to
Bob Peterson

A 24 volt class 2 circuit supplied through a Class 1, Div 1 intrinsically safe module probably is about as safe as you can get for supplying these lights. The intrinsically safe module limits the power so that there is not enough power to ignite a flammable mixture of gasoline vapors and air. I have worked on these circuits while damp and in hazardous locations and shorting the wires together or to yourself has minimal effect. There simply is not enough energy available to do anything. But from a practical and Code stand point, 12 volts DC supplied by a common battery is used on boats for lighting on a regular basis. However, wiring on boats and ships do not fall under the National Electrical Code but under Coast Guard Standards. The link below should take you to the coast guard standards that are quite extensive. From a liability stand point, I would avoid installing the lights on your Kayak unless you are the only one using it.

Ref: NEC 90.2 (B) Not Covered. This Code does not cover the following: (1) Installations in ships, watercraft other than floating buildings, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles FPN: Although the scope of this Code indicates that the Code does not cover installations in ships, portions of this Code are incorporated by reference into Title 46, Code of Federal Regulations, Parts 110-113.

Marine Electrical Regulations Overview: The principal Coast Guard office responsible for the development of marine electrical standards is the Systems Engineering Division (G-MSE-3). Electrical regulations are provided to set forth uniform minimum requirements for electrical equipment and systems aboard vessels in accordance with the intent of various statutes, the International Convention for Safety of Life at Sea (SOLAS), and other treaties that contain requirements regarding electrical installations. These requirements are services necessary for safety under both normal and emergency conditions and protect passengers, crewmembers, and other persons from electrical hazards.

Federal regulations for marine electrical systems: The principle Federal regulations governing marine electrical systems are found in Title 46, Code of Federal Regulations (CFR) Subchapter J, "Electrical Engineering" (parts 110 thru 113). The CFR is available online; a link to the CFR is on the left side banner. However, additional requirements apply to specialized vessels in other subchapters (such as small passenger vessels or OSVs), and Subchapter Q pertains to equipment approvals.

Ref:

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Reply to
Gerald Newton

Chris - F.Y.I. An LED will attempt to draw as much current as the circuit can provide - which will cause it to burn itself out if it is allowed to draw that current. (It will burn out at a relativly low amount of current.) As a very general rule of thumb, keep the current to about 10 mA. Most LEDs will be just fine if the current is limited to roughly .01 amps (10 mA). That is well below the maximum current they can handle, yet still yields plenty of brightness.

The value of the resistor that limits the current can be computed by subtracting the voltage needed by the LED(s) from the supply voltage, then dividing that by .01. As an example, say you have

12 red LEDS in series (each one needs about 1.6 volts) and a 24 volt source: (24 - (12*1.6))/.01 = 480 A 470 ohm resistor (the closest standard value to 480) would limit the current through the LEDS to just about 10 mA.
Reply to
ehsjr

| Chris - F.Y.I. An LED will attempt to draw as much current as | the circuit can provide - which will cause it to burn itself out if it | is allowed to draw that current. (It will burn out at a relativly low | amount of current.) As a very general rule of thumb, keep the current | to about 10 mA. Most LEDs will be just fine if the current is limited | to roughly .01 amps (10 mA). That is well below the maximum | current they can handle, yet still yields plenty of brightness.

There's only a tiny whisker wire which I believe is what will burn out first. Regardless, the LED is a very small device, and once burned out, the full voltage is applied across it (unless others have burned out at the same time which I suppose can happen). If the full supply voltage exceeds the breakdown voltage of the burned out point, then it can jump across, creating all new problems. Imagine wiring up 100 light bulbs of the 120 volt variety, in series, powered by 12000 volts. As soon as one burns out, watch the fun. At least with a current limiting resistor, it shouln't be too much on the LEDs. But as the LED stack voltage approaches the supply voltage, and the resistor gets smaller, one's luck is getting pushed. What would you suggest as a maximum percentage of supply voltage for the LED stack? How could you optimize the system and eliminate power loss heating the resistor? Would an electronic ballast of the proper parameters be usable for large scale LED lightning?

Reply to
phil-news-nospam

This is a follow-up post to my previous message. Placing lights on a water craft seems like a simple task. However let me write of my experiences in this area. You may find it of interest. In July of 1989 I was assigned as a State Electrical Inspector to Valdez, Alaska. The Valdez Exxon oil spill cleanup activity was administered at this time from Valdez and there were many local construction projects in process to support this activity. The Prince George ferry was towed into the Valdez Port and docked at he city dock to be used to supply housing to workers. The local businesses resented this outside threat to the local economy and called the State of Alaska to see if something could be done to shut down this new housing threat.

The Prince George had been used in Southeast Alaska to ferry passengers to and from ports for some 30 or 40 years before, but was now without its own power and engines.

Shore power was supplied by a 3-phase 208 volt wye grounded generator.

As such the ferry fell under the floating dwelling unit category of the National Electrical Code. Of course the ferry had been originally wired under Coast Guard standards. I proceeded to inspect this ferry to the 1987 NEC and found that there was no way this ship could become compliant to the NEC without major rework.

Ships are wired using an ungrounded system. However shore power was connected into the ships existing electrical system using a grounded system. XO was connected to a handrail and the individual XHHW phase conductors were run alongside the ship hanging by ropes then through a port hole into the engine room then connected to three single phase ungrounded transformers. I suppose the ships hull acted as a grounding electrode conductor and grounding electrode for the supply from the on shore generator . It is not uncommon to use a copper wire hanging in the water as a grounding electrode conductor for wye transformers used on floating docks. From my research, ships are wired ungrounded because of the corrosion problem.

In the end between myself and the State Fire Marshall, we found enough safety violations to limit the use of the ship to only 2 of its 5 decks, as I recall. It was too bad, too. The ship had beautiful wood work in it and was truly a classic. I had rode aboard this ferry from Ketchikan, Alaska to Prince Rupert, British Columbia when I was only 15 years old. I will never forget the dining room sets with crystals and real silver utensils.

Reply to
Gerald Newton3

or use a voltage regulator. set it to 2.1 volts out (or whatever makes the particular LED happy). the advantage here is that the brightness stays the same until the battery is completely exausted. disadvantage is 90% of the watts are wasted as heat.

i would use blinking LEDs to extend battery life and for the cool visual effect. maybe even use a "light chase circuit"

i have been involved in setting up boats for light parades, however these were larger pleasure craft. generators, PA systems, rope lights, police beacons, stage lighting with controllers, sirens, oscillating lights and other effect lighting is used. sometimes even fog machines.

Reply to
TimPerry

I don't know if there is a very general rule of thumb for maximum percentage of supply voltage for the LED stack as there is for LED current, nor do I think there would be. For example, suppose the supply voltage is 1000? Wouldn't there be a FAR greater chance of the arc-over you mentioned in a burned out LED , regardless of percentage, than in a circuit with a supply voltage of 48 volts? I just don't see it making sense to have a rule of thumb for that percentage.

The two other questions clearly don't apply to rule of thumb. When you are trying to optimize and eliminate power loss in the resistor, you are not using rule of thumb computations. There are electronic controls available for LED lighting.

Reply to
ehsjr

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