Power LED Residential Lighting

[transistance]

These are the LED's I'm planning to order.

I don't know where to start with the circuit design besides the fact that I will be using inverted LED's in parallel to benefit from each half cycle and the whole fixture will be controlled with a rotary dimmer.

How many power LED's will be enough to light up a room of this size behind a rice paper light diffuser? Will I have overheating problems? Any safety issues i should look into? Any ideas about the circuit design?

Thanks in advance

Note: Power Source is 220 VAC 50 Hz - not 60 Hz

 

[Hero999]

Rice paper?

That sounds like a fire hazard.

You'll probably need 20 to light a whole room.

Connecting LEDs in parallel isn't a good idea, perhaps yould should consider connecting them in series?

 

[Willbe]

1W in an LED is probably 4 to 5 W in an incandescent.
Lighting load estimate from the NEC is roughly 15A at 120V for each 600 sq.ft.

 

[transistance]

Rice paper?

That sounds like a fire hazard.

You'll probably need 20 to light a whole room.

Connecting LEDs in parallel isn't a good idea, perhaps yould should consider connecting them in series?

There are a lot of rice paper lamps sold, if I insulate the circuit well (no sparks), i doubt that rice paper will catch on fire from ambient heat generated by the LEDs.

also here is what I mean by my series-parallel mambo-jambo in the first post.

Lighting load estimate from the NEC is roughly 15A at 120V for each 600 sq.ft.

What is NEC?
could you give me an estimate of many 1 W diffused LED's it will take to light up a 6.5m² or 70 ft² room?


Any inputs on my circuit design?
LEDs are 75 mA, 3.8 V

220Vac scares me

 

[blueroomelectronics]

Use compact fluorescent, LED bulbs are a fairly focused beam compared to CFLs.
**broken link removed**

 

[transistance]

Use compact fluorescent, LED bulbs are a fairly focused beam compared to CFLs.
**broken link removed**

I use a lot of CFL in in my apartment but I think to achieve the desired effect, I need very bright light sources like LEDs so they can diffuse through rice paper. The fixture will look like a lighted panel and has to be thin.

 

[blueroomelectronics]

You may find the LED beam will create bright spots even when diffused. Frosted LEDs might help but that will reduce their brightness.

 

[transistance]

Is this circuit for 20 75mA 1W LED's safe?
Any values I should change?
How can I implement a heat related circuit breaker?

 

[Willbe]

What is NEC?
National Electrical Code.
could you give me an estimate of many 1 W diffused LED's it will take to light up a 6.5m² or 70 ft² room?

15A at 120V = 1800w for 600 sq. ft. = 3w/sq.ft..
Incandescents for 70 sq. ft. = 3x70=210w.
210w/4 = 50w for LEDs.

If you want special effects you might want to peek into one of those 800 page lighting handbooks you find in bookstores. It can get pretty complex.
Also you may want to control
https://en.wikipedia.org/wiki/Color_temperature

For your posted circuit, if you give me the tolerances on the AC voltage, LED voltage, cap value and resistor value, I can probably tell you the expected brightness variation for your LED circuit.
LEDs prefer constant current, and your design seems to pretty much fly in the face of that guideline.

 

[wayne2056]

Any inputs on my circuit design?
LEDs are 75 mA, 3.8 V

220Vac scares me[/QUOTE]

I don't have a lot of hands on experience with this but my first thought is

that across R2 you have ( 220 - 10*3.8 ) volts = 182

Power = (V^2 / R2 ) = 182^2 / 2.2K = 15W so I think R2 gets fried.

Also I don't think your LEDs can withstand the reverse voltage.

I know they are doing this sort of thing with Christmas tree light strings but there are many more LEDs in the series.

Regards
Wayne

 

[Hero999]

Go for CFLs they're more efficient than LEDs especially if you want a diffuse light source.

 

[nickelflippr]

Here is yet another LED driver IC. It has either a PWM or linear dimmer mode. I am sure there are other IC's out there that do the same.

P.S. The 5600K color temp on the 1W led you spec'd is going to be on the blueish side. A neutral white would be better. Suggest a few high watt leds over the work counter area, and leave the diffused rice paper for the rest of the space.

 

[philba]

Is this circuit for 20 75mA 1W LED's safe?
Any values I should change?
How can I implement a heat related circuit breaker?

I suspect that circuit is safe but probably wouldn't pass UL muster.

Another point about the circuit you posted - it's a waste of LEDs since only half will be on at any one time. You are much better off building a constant current power supply. There are numerous chips made to drive LEDs for lighting -natsemi, linear, maxim, ... I'd design in blocks of 4-8 LEDs. Modular is a good way to go.

The problem with a heat related breaker is you will need to have one next to each LED. The manufacturer's datasheet should tell you a lot about thermal engineering for the part.

 

[Hero999]

Sorry but I think the whole idea is silly.

Power LEDs just aren't designed to be diffuse light sources and they're less efficient and more expensive than existing technologies such as fluorescent tubes.

 

[on1aag]

Hi Transistance,

Although the circuit will work the blinking of the leds at a
rate of 50 hurts will drive you, me and everyone else nuts.
I think you should "fry" something else.

on1aag.

 

[nickelflippr]

Sorry but I think the whole idea is silly.

Monetarily, it is kind of silly, but shouldn't deter people from being early adopters if they choose to. But from an industry standpoint, it seems pretty serious, LEDs Magazine. Companies seem intent on, putting their hat in the ring, suing each other, making latest lab report claims as if their results will be on your doorstep tommorrow, etc. etc.

There is another http://search.digikey.com/scripts/dksearch/dksus.dll?pname?site=us;lang=en;name=475-2594-1-ND with a clear lens, warm white that has twice the lumens for same price. Best to experiment, and try out a couple, before loading up with one that will disappoint you. Increasing depth of box could give the right combination on the diffusion issue.

 

[Willbe]

50 hurts

Heinrich Hertz is rolling over in his grave!

 

[on1aag]

Hi Wilbe,

It hurts 100 times a second !

on1aag.

 

[Ubergeek63]

I suspect that circuit is safe but probably wouldn't pass UL muster.

There are two problems with this statement:

1. UL does not apply in Europe. and

2. UL is NOT a law, it is a clever deception. A testing house set up themselves as a defacto safety standard and convinced everyone that it was a law. They get $5000 dollars if you so much as change a letter in the documentation and want to keep their mark. An exaggeration, but you get the point. It actually has a lot in common with M$ in that respect

That said the LEDs under consideration are crumby and beyond the capabilities of a simple experimenter to mount.

 

[philba]

There are two problems with this statement:

1. UL does not apply in Europe. and

2. UL is NOT a law, it is a clever deception. A testing house set up themselves as a defacto safety standard and convinced everyone that it was a law. They get $5000 dollars if you so much as change a letter in the documentation and want to keep their mark. An exaggeration, but you get the point. It actually has a lot in common with M$ in that respect

That said the LEDs under consideration are crumby and beyond the capabilities of a simple experimenter to mount.

I never said UL was a law so please don't put words in my mouth. It sounds like you have an axe to grind about UL. I think they provide a decent service - what would have in their place - nothing? Note that when assigning blame for fires and such, the lack of UL certification has a lot of weight. I'm pretty sure there are similar bodies (governmental or not) in most countries. Whether they are "deceptions" or not they get to say if a product meets safety criteria.

Also, I know a number of experimenters that are using much more powerful LEDs than that. I don't think it is beyond them.