How much is 'less than 5mW' ?

[duggybuggy]

Hi, I have just bought some 12v LED map-reading lights rated at less than 5mW each. there is just one little yellow square LED in each lamp. Clearly they are,of course, less than 5 amps, but how much less? I am supposing that a mW is a fraction of a watt, but what fraction. If so, how many mW in a watt? Cheers.

[Cockeye429]

The current I in amps (A) is equal to the power P in watts (W), divided by the voltage V in volts (V):

[four winds]

duggy, it's five thousandths of a watt. .005 watt

1w equals 1000mw

[h20man]

a mW is used to display milliwatts, which are 1/1000 of a watt. So. If they truly are less then 5mW @ 12V they should be pulling (from the formula Watts=Volts*Amps; solving for Amps yields: Amps = Watts/Volts, substituting gives (0.005watts/12volts = 0.000416666667 amperes. (and knowing you use LESS THEN 0.005 watts, it must DRAW less then 0.000416666667 amps....


(not a lot.. ) Hope that helps and Best of Luck

[four winds]

A lot of light for so little current flow. Shows what a vampire heat can be, as in incandescent lighting.

[duggybuggy]

Wow, much less than i could have imagined, and I was expecting real low, but that......amazing. It is very good news as it will be much help and much used; light, so important to the job. Brill.

I will right down that formula. I remember we did it in Physics at college, as a triangle with power, current, and voltage, but I couldn't remember what went where with it. Cheers. I'm staggered with that LED current.

[TrentePieds]

Duggy:

The "m" (pronounced "milli", like the old-fashioned girl's name) put in front of any unit of measurement means "a thousandth part" of the unit it is put in front of.

Similarly, 'k" (pronounced "KEE-lo") put in front of any unit of measure means "a thousand times more than" the unit it is put in front of.

Since you are talking about lamops and light, presumably to read by, the power consumption in watts is no the critical parameter for you. Go here to learn the basics of "strength" of light - the ability to illuminate an object, say a page in a book, or the chart on your navigation table.

https://en.wikipedia.org/wiki/Lumen_(unit)

Once you've determined that a given lamp will give you "enuff" light, you can begin to worry about how many amperes it will draw from your battery, because that is the critical parameter for designing (and monitoring) your electrical system.

TrentePIeds

[pcmm]

Originally Posted by duggybuggy

Wow, much less than i could have imagined, and I was expecting real low, but that......amazing. It is very good news as it will be much help and much used; light, so important to the job. Brill.

I will right down that formula. I remember we did it in Physics at college, as a triangle with power, current, and voltage, but I couldn't remember what went where with it. Cheers. I'm staggered with that LED current.

LED is awesome light tech! we rewired our 41 sailboat completely this past spring and with all the LED lights we were able to use 16AWG cable everywhere and stay withing 3% voltage drop (overkill) saved a lot of cost in cabling etc! best part is when we have ALL the interior lights on ( 15 fixtures) we draw less than 2 amps! we used to draw more than that with 1 light on!

[Bulawayo]

The other postings have given the response......what I should like to know is what did you buy with such low consumption and how does it perform? Cost and from whom? You could leave this chart light on all night and not even notice the 'drain' from your battery.

Originally Posted by duggybuggy

Hi, I have just bought some 12v LED map-reading lights rated at less than 5mW each. there is just one little yellow square LED in each lamp. Clearly they are,of course, less than 5 amps, but how much less? I am supposing that a mW is a fraction of a watt, but what fraction. If so, how many mW in a watt? Cheers.

[jeepbluetj]

Originally Posted by duggybuggy

....

I will right down that formula.....

No need. It's the law. Ohm's law. That and google is all you need.

[Cockeye429]

There's the triangle for u.

[SteveSails]

I question the 5mW rating, LEDs are efficient but not that efficient. Sure the specs didn't say 5mA or 5 milli Amps? Even an indicator LED, not bright enough to read by, would draw a couple of milli amps and even 1mA at 12V would be 12mW (.001A x 12V = .012W).
The seller may not be trying to deceive, often specs get lost in the translation. Ohm's law and the power formula are good things to memorize, helps to raise ???? when something seems too good to be true.

Any link to the specs? We can help make sense of it for you.

[Cadence]

Originally Posted by four winds

duggy, it's five thousandths of a watt. .005 watt

1w equals 1000mw

I came up with.004 something.

[MarkJ]

Originally Posted by h20man

it must DRAW less then 0.000416666667 amps....

For a reading lamp?

Bloody useless for Penthouse.



.

[four winds]

Originally Posted by SteveSails

I question the 5mW rating, LEDs are efficient but not that efficient. Sure the specs didn't say 5mA or 5 milli Amps? Even an indicator LED, not bright enough to read by, would draw a couple of milli amps and even 1mA at 12V would be 12mW (.001A x 12V = .012W).
The seller may not be trying to deceive, often specs get lost in the translation. Ohm's law and the power formula are good things to memorize, helps to raise ???? when something seems too good to be true.

Any link to the specs? We can help make sense of it for you.

I think you are on to something here.

Also curious to know the product purchased.