High color fidelity approaching an ideal is a common feature of „high CRI“ Osram LEDs with CRI up to 96.
When you recall to lessons of physics from your basic- or grammar-school, probably you´ve heard a term „black body radiation”. As we know, each object with a given temperature radiates in a wide range of wave lengths, while a maximum of a radiation depends on its temperature. We mention it because the Sun also operates on this “principle” and its spectrum (light) depends mainly on its surface temperature. Temperature of an object is also the most important factor influencing whether the light will be “warm” or “cold”, that´s why a term color (chromacity) temperature CCT is used.
Even though a portion of radiation (some wave lengths) is absorbed in atmosphere, it can be said that it is very near to a black body spectrum and it´s ideal for us in respect to a pleasant and true color perception.
There are several methods to evaluate color fidelity and one of the most important is so called CRI (color rendition index, maximum = 100). To an ideal light source with CRI =100 is very near a classic incandescent bulb, even though it´s spectrum is shifted towards warmer tones. Unfortunately a light spectrum gained from hot surfzce object also contains a large portion of thermal (infrared) radiation, what causes a low efficiency of incandescent bulbs. However LEDs deploy emission of photons on an other principle (change of electrons energy), so their surface is in fact “cold” in comparison to what temperature a black body radiator should have to gain a similar spectrum.
Modern LEDs have a high CRI, usually over 70. But among LEDs we can find types with even higher CRI (above 80) , as well as “color champions” with even higher CRI. To such champions also belong LEDs from the OSLON Square series, which we introduced to you in our article New LED OSRAM OSLON Square withstands up to 1.5A. Since then company Osram advanced in development and was able to make types with a typical CRI 96 (!), for example LCWCQAR.CC-MPMR-5J7K-1 (4500K).
Light fidelity of this LED is extremely high and such light is very suitable for lighting of areas with high requirements for a light quality, like for example: galleries, museums, shops, photographic ateliers as well as for an everyday work. Despite a high CRI, this particular type also features a considerable efficiency of 180-224 lm/700 mA and a max. current up to 1500 mA.
Among novelties from company Osram can also be found the Oslon Square 2nd generation with even betterthermal features increasing lifetime and efficiency at high temperatures. Moreover this new 2-nd version is sorted (binning) at 85°C, what ensures minimum color in a real operation.
Almost perfect light from the Oslon Square LED – [Link]
Lee Zhi Xian writes:
I was always fascinated with LED Matrix Display because it makes a good and clear display. I always saw LED display used as advertisement signboard. It can be programmed with variety of animations. So I decided to make myself a 48×8 LED Matrix Display. Of course, I start off with a smaller one by soldering LEDs on stripboard, making a 8×8 LED Matrix. I tried to understand how the LED Matrix works and how to deal with the programming part.
Development of 48×8 Led Matrix Display – [Link]
ZXLee built a simple sensor for Arduino which allows him to detect colors. The idea lies behind using red, green, blue LEDs and Light Dependent Resistor (LDR). Lee Zhi Xian writes:
Previously I have made a colour sensor using Arduino but don’t have the time to update it on my blog. Today I am going to share the details of this mini project. Basically, the sensor consists of three LEDs and Light Dependent Resistor (LDR). The LDR will detect the colour and display it to another RGB LED. Besides display it on the RGB LED, the colour will also display on PC. RGB LED is commonly used in display colours on LCD or OLED such as the monitor and television.
Simple technique of sensing colors using Arduino – [Link]
This relatively simple circuit uses a 6-V DC supply with a PWM current-source configuration to provide efficient, adjustable dimming of a white LED over a wide range, needed to accommodate the unique lighting needs of an optical microscope over its magnification range from 40× to 1000×. by James Campbell
When the built-in incandescent light source of my venerable Olympus microscope failed after many years of use, I decided to design a reliable modern replacement. A 1-W white LED (SEOUL X42182, 350 mA max, Vf = 3.25 V) was the obvious choice to provide high brightness and full-spectrum light without the heat of incandescent or xenon arc lamps. The microscope lamp brightness needs to be adjustable, however, to accommodate the different objective lenses, which offer magnifications from 40× to 1000×.
Current Source For LED Microscope Illuminator Provides Full-Spectrum Light – [Link]
LANp combines an LED RGB Bar from an old scanner, an Arduino and Ethernet/SD Shield to make a full RGB Lamp.
It has a built-in webserver that has an RGB colour picker, which changes the LED bar in real-time.
There is some photos and a YouTube video to show it all working.
LANp – A DIY Arduino network controllable RGB lamp made from scanner parts! – [Link]
µ-Wire: USB on ATtiny10 controlling a WS2812 LED. cpldcpu writes:
I tried to push the ATtiny10 to its limits and succeeded – I implemented a seriously gutted version of V-USB on an SOT23 ATtiny10 with just 1kb flash and 32b of RAM. It implements a subset of the little-wire protocol to control a single WS2812 LED.
µ-Wire: USB on ATtiny10 controlling a WS2812 LED – [Link]
bogdan informed us about his latest post on electrobob.com. It’s about a level translator for WS2812 LEDs. He writes:
WS2812 LEDs are one of my favourite toys. Apart from all the things that you can do with them in terms of lighting, displays or even light painting you can also use them for your projects as indicator lights.
The great advantage comes from the fact that you can use a single pin to drive so many of them and it takes just 3 wires ran across the whole box for practically any number. This in turn comes with the disadvantage of more complex control and problems driving them (5V devices) from a 3.3V microcontroller.
WS2812 level translator – [Link]
LED drivers are electrical devices that regulate the power of LEDs. What makes them different from conventional power supplies is their ability to respond to the ever-changing need of LEDs in a circuit by supplying a constant amount of power as electrical properties change with temperature.
The PCA9622 is an I2C-bus controlled 16-bit LED driver optimized for voltage switch dimming and blinking 100 mA Red/Green/Blue/Amber (RGBA) LEDs. Each LED output has its own 8-bit resolution (256 steps) fixed frequency individual PWM controller that operates at 97 kHz with a duty cycle that is adjustable from 0 % to 99.6 % to allow the LED to be set to a specific brightness value. An additional 8-bit resolution (256 steps) group PWM controller has a fixed frequency of 190 Hz and an adjustable frequency between 24 Hz to once every 10.73 seconds with a duty cycle that is adjustable from 0 % to 99.6 % that is used to either dim or blink all LEDs with the same value.
These LED drivers are based on system-centric, mixed-signal LED driver technology for backlighting and solid-state lighting (SSL) applications. This broad-based and rapidly growing market includes LCD TVs, PC monitors, specialty panels (industrial, military, medical, avionics, etc.) and general illumination for the commercial, residential, industrial and government market segments. LED drivers utilize a proprietary and patented combination of analog and digital circuit techniques and power control schemes.
- PCA9622 I2C-bus controlled 16-bit LED driver
- 2C-BUS/SMBus MASTER
- Resistor 10kΩ ( 27 units)
- LED (88 units)
- Voltage Source 40Vdc
- Voltage Source 5Vdc
I2C Bus Controlled LED Drivers for backlighting and SSL applications – [Link]
There is a new 8mm RGB LED introduced to the WS2812 family of LEDs. cpldcpu writes:
There is a new addition to the popular WS2812 family of RGB LEDs with integrated controller: A 8mm through hole version. Right now they seem to be in pilot production stage. The only place that has them is Soldering Sunday where they are called PixelBits. My understanding is that they will also be available at the usual sources later this year. I got a couple of them to test for compatibility with my light_ws2812 library.
New member of the WS2812 RGB LED family – [Link]
This project is a simple LED tester and LED polarity checker. It can be used to check 1206, 0805, 0603 and 5mm LEDs. All parts are readily available and they are very cheap. Usage is very simple. Just press the tack switch to first check the battery is good. The blue led will turn on. Now you are ready to test your leds and check their polarity.
Simple SMD LED tester – [Link]