lighting a room with array of LED's on 9v

[William Gaatjes]

So 20 mA x 10 LED's = 200, and the battery is about 570. About 2, almost 3 hours. Not really good.

Try putting them in series as well. That increases efficiency.

It all depends on the forward voltage of the led.
If 1 led works on 3,5V, you can put 2 in series for 7V. You have 9 Volts to begin with.
9V-7V = 2V left. Now the forward current limiting resistor is just 2/0.02 = 100 Ohm.
That will double the amount of lightning time you have compared to one led.
Try choosing a battery as a source with the highest voltage close to N x led forward voltage.

With 1 led it is 9V - 3,5V = 5,5V. 5,5 / 0.02 = 275 Ohm.

It is all about power draw and efficiency. You want all the power in the led and not in the resistor.
P=U*I .

 

[Mark R]

First thing to do is get decent LEDs. The LEDs in the original post are low-efficiency garbage grade LEDs. They are not specified in light output (only intensity, which is near meaningless - but I would estimate that the total light output from this type of LED is less than 1 lumen - my calculations from the spec sheet is 0.2 lumens). With a power consumption of 66 mW, the luminous efficacy is a tragically bad 15 lumens/Watt an absolute best. That's about as good as a low quality incandescent lamp.

If you want to light a room, you need illumination grade LEDs, designed for high efficiency and high light output. I'd suggest looking for something like premounted luxeon rebel LEDs.

Just one of those LED boards linked above will be close to 100 times more powerful than one of the original LEDs, while being close to 5 times as energy efficient.

In practice, it would be easier to get 12V GU6.3/MR16 low-voltage halogen retrofit LED bulbs. This would save effort in building heatsinks and ballasts.

 

[Murloc]

you'd have to invest so much money in this that you'd maybe not even repay the investment through the energy savings before the stuff ends its lifecycle.

Buy a more efficient fridge and shelve the AC.

 

[rudeguy]

Didn't read the thread but let me help:

We just bought a ton of these for work:
http://www.amazon.com/dp/B00ENX0VUE/...I326RLP2A6PB1Z

Low wattage, bright as all hell and can be trimmed every 3 lights with no soldering needed. They run off straight 12 Volt, no transformer needed. So if you wanted to do a room in them, you could just get a cheap 12V power supply and you would be done.

 

[Gillbot]

That's what I get for being a diode head and reading his OP as wanting to light an entire room and run it on rechargable solar cells. I admire his ambition, but he's in for some serious energy scavenging, harvesting and efficiency issues to achieve his goal.

Yeah, that's what most of us were getting at in a non-tech-head kind of way. What he wants to do isn't really easy to accomplish within his limitations. It it were that easy, we'd all have free lights in our house by now. 20ma draw LED hooked to a 20ma output solar cell = perpetual free light machine right!!! :hmm:

 

[feralkid]

Didn't read the thread but let me help:

We just bought a ton of these for work:
http://www.amazon.com/dp/B00ENX0VUE/...I326RLP2A6PB1Z

Low wattage, bright as all hell and can be trimmed every 3 lights with no soldering needed. They run off straight 12 Volt, no transformer needed. So if you wanted to do a room in them, you could just get a cheap 12V power supply and you would be done.

Coolzo!

 

[Harvey]

Yeah, that's what most of us were getting at in a non-tech-head kind of way. What he wants to do isn't really easy to accomplish within his limitations. It it were that easy, we'd all have free lights in our house by now. 20ma draw LED hooked to a 20ma output solar cell = perpetual free light machine right!!! :hmm:

Throw in an auxiliary generator powered by solar sails on the walls an ceiling, and we might be able to generate more power than we had at the start.

Nicola Tesla would be so proud! <== Shades needed in the bright light.

 

[Gillbot]

Throw in an auxiliary generator powered by solar sails on the walls an ceiling, and we might be able to generate more power than we had at the start.

Nicola Tesla would be so proud! <== Shades needed in the bright light.

My next project!

Ceiling fan with a windmill generator, perpetual free whole house air movers! :whiste:

 

[mikeford]

You should ask your question in an "off grid" forum where they do this type of stuff all the time.

You need a decent small solar array, charge controller, scavenged 12v car batteries or laptop cells, an LED driver circuit and some good LEDs. Likely no reason to make the room glow, so 5w might be enough with a couple spots for a reading area etc.