With any sort of reflector surface you can widen or narrow the angle of the beam of an LED.
This drawing portrays a 30˚ viewing angle LED with a curved reflective surface, be it a white piece of paper or a piece of tin or aluminum foil. Any kind of reflective surface will disperse the beam. In this case the beam angle after reflection turned out to be 90˚. I don't have a mathematical explanation of why 30 became 90 degrees, it just did. A tighter bend would result in a wider beam and a lesser bend would turn out to be less than 90.


I think this is what others are saying about using a reflective defuser.

In that case, do I need to enclose the LED with white cards?

No. Just something for the LED to point at. Of course you'll have to make something to hold it all together, but I'm confident you can figure that out.

EDIT: After wondering why 30˚ became 90˚ is because I used a 3.5" radius. And to be more precise, the 90˚ angle is actually 90.1˚

 

Or you could just hold the LED close to the page on a 45 degree angle. You don't need to point the LED directly at the page. More of a skimming across the page sort of lighting.

 

I have had great success in diffusing the light beam from an LED, shaped like the one in post #42, by simply roughening the curved surface with a bit of fine abrasive. Of course, that effect is permanent, so it is not suitable for experimenting.

 

want to make a book reading LED light

((((F**)))) the first honest reaction - it's because if you don't have a precise voltage/power source for your gizmo the regulation and thermal designs will be a head ache . . . but if not -- there is a slim chance for #6 will not "explode to your face"/"set anything on fire"

without the data on long term effects on your sight https://www.amazon.com/Leylix-Light-Reading-Night-White/dp/B0GR56XML9?th=1 (. . . at least it's affordable to buy !!!!)

 

A possibly interesting consideration is the use of a different color of light. Some specific colors allow much faster recovery to seeing in more brightly lighted areas.
AND, tolearn about different LEDs, I suggest looking in a DIGIKEY CATALOG!! It used to be that their catalog contained a great amount of information about the LEDs that were for sale. That might have changed, but looking at an on-line catalog is not expensive, usually it is free.

 

The user started a new thread on electronics-lab.com :
https://www.electronics-lab.com/forums/threads/book-light-improvement.313309/

 

I built a fixture and tested 5mm red, green, blue, and yellow ultrabright LEDs with clear lens. Currents were 9.5mA, 6.2mA, 6.4mA, and 6.5mA. LED was held 8-10 inches from the paper.

Text was readable with all colors. Any focus issues were due to taking pictures in the dark. I used a supply set to 4.09V to simulate a Li-ion battery.

LED specifications:

AliExpress purchase.

 

There has been a VAST amount of research already done, and the results adequately verified, as to what colors,(wavelengths) of light allow the best viewing with the least fatigue. and with the least electrical power requirements.
That means that there is already a great amount of information available.
The question as to which cheap 5mm LED is best may already have been answered. Not by me, though.

The question I see relative to this thread is the relative color response of the light intensity measuring system. Certainly this is an interesting question!
Do we know what color of lighting is used in submarine control rooms?? Probably that has been optomised quite well.

 

Hello,

You could also use a joule thief circuit:
https://www.evilmadscientist.com/2007/weekend-projects-with-bre-pettis-make-a-joule-thief/

Bertus

 

Did tests with the AliExpress USB book lights and a homemade one. All from 4.09V, held 6-8" from the paper.


Commercial with 39 ohm resistor:


Commercial with 281 ohm resistor:


Homemade with 221 resistor:

 

Did tests with the AliExpress USB book lights and a homemade one. All from 4.09V, held 6-8" from the paper.
View attachment 369588

Commercial with 39 ohm resistor:
View attachment 369589

Commercial with 281 ohm resistor:
View attachment 369590

Homemade with 221 resistor:
View attachment 369591

Did you use a benchtop DC power supply here?

 

Did you use a benchtop DC power supply here?

Yes. But the voltage was set to emulate a nearly fully charged Li-ion battery.

The homemade white light was designed for something like 6V. I made up several of them years ago. It was fine as a reading light at 4V.

 

The homemade white light was designed for something like 6V. I made up several of them years ago. It was fine as a reading light at 4V.

When you used your home-made light for reading, how did you power that up? With two coin cell batteries in series?

 

When you used your home-made light for reading, how did you power that up? With two coin cell batteries in series?

AA cell battery packs. Usually 3-4 NiMH cells, but also alkaline cells.

I also made up some that operated from 6V or 12V. I had some 12V lead acid gel cells. I used a jumper to switch between voltages. Two LEDs in parallel for 6V and 3 LEDs in series for 12V. Can't find any of them now.

EDIT: I didn't use them for reading. I used them as flashlights.

 

Does any of you have any experience in using the LED shown in the picture? This is an SMD LED Pure white Super Intensity 20W Light. The supply voltage is 12-14V as written in the website where I found it. I am curious to know, if I try to turn it on with a 9V battery, won't it turn on at all or lit dimly?

 

Without a part number, datasheet, link to a vendor page, or any other information, it is impossible to say. But note that operating on 12 V and dissipating 20 W, but part is drawing over 1.6 A. A 9 V radio battery cannot supply that.

ak

 

Without a part number, datasheet, link to a vendor page, or any other information, it is impossible to say. But note that operating on 12 V and dissipating 20 W, but part is drawing over 1.6 A. A 9 V radio battery cannot supply that.

ak

The vendor site has no datasheet. Only these specs-

Parameter	Specification
Power Consumption	20W
LED Type	SMD (Surface Mounted Device)
Light Color	Pure White
Color Temperature	6000K – 6500K
Luminous Flux	Approx. 1800 – 2000 lumens
Input Voltage	12V – 14V
Material	Aluminum + Plastic
Dimension	46mm X 52mm
Operating Temperature	-20°C to 50°C

 

Quite probably, the 12 volt LED will produce a bit of light at 9 volts. BUT not close to the rated intensity. Diode conduction is not at all linear, nor simply predictable, outside of the intended operation range, which is why it is seldom shown on data sheets. BUT just because it is not shown does not mean that it does not exist, but rather that it is not consistent enough to be specified.

 

Its great if you want to light the whole room brightly with your book light.