Gina Roos writes:
One of the biggest challenges faced by solid-state lighting designers is reliability. Electrical and thermal conditions are two major factors affecting device life and lighting output and, while long life is a key benefit of LEDs compared to incandescent and fluorescent light sources, all bets are off if the LEDs exceed their temperature ratings.
Thermal management continues to vex LED lighting designers, particularly for high brightness LEDs that continue to escalate in forward current while decreasing in package size. Couple this with potentially high-temperature applications such as streetlights and high-bay lighting in warehouses, and it becomes apparent that there is a major hurdle to overcome.
With an estimated 20 percent of global energy used for lighting, LED driver suppliers are more than aware of these challenges and are starting to integrate thermal foldback control into some of their designs to protect LEDs from failure and reduced lifetime due to high-temperature environments. Thermal foldback limits the LED temperature to protect against failure by reducing the LED current as the ambient temperature increases; this arrangement continues to decrease the current until the LED junction temperature returns to a safe operating temperature. The result is higher reliability, longer operating life, and, in some cases, increased safety.
How Thermal Foldback Improves the Reliability of LED Lighting Fixtures - [Link]
janw @ instructables.com writes:
A few months ago, I saw an instructable by fjordcarver on how to build a coloursensor with an RGB led and an LDR. It inspired me to try whether I could improve his design.
Here are the things that I wanted:
The sensor should have as few pins as possible.
It should work as a stand-alone device. All calculations should be done on the device.
It should have a triggered mode and a continuous mode.
All parameters should be programmable.
Calibration parameters should be stored in the EEPROM of the microcontroller.
Firmware updates should be made possible
And finally: size does matter ⇒ The smaller the better.
I did choose an smd attiny85 as the brain of the sensor. It has a small footprint but a large enough flash for the calculations. It also has just enough pins for the project (all eight pins are used).instructables.com
Build your own (at)tiny colour sensor - [Link]
by Abhijeet Deshpande:
Properly maintained rechargeable batteries can provide good service and long life. Maintenance involves regular monitoring of battery voltage. The circuit in Figure 1 works in most rechargeable batteries. It comprises a reference LED, LEDREF, which operates at a constant current of 1 mA and provides reference light of constant intensity regardless of battery voltage. It accomplishes this task by connecting resistor R1 in series with the diode. Therefore, even if the battery voltage changes from a charged state to a discharged state, the change in current is only 10%. Thus, the intensity of LEDREF remains constant for a battery state from a fully charged state to a fully discharged state.
Simple battery-status indicator uses two LEDs - [Link]
Aurora 48 is a compact and thin profile full-color LED sequencer. It’s built entirely with surface mount components, so the profile is nice and clean.
Aurora 48 – 48 RGB LED Sequencer - [Link]
Ivan Creations made this ReCoMonB (Real Computer Monitoring Block) and wrote a detailed explanation on his blog describing the build:
I managed to de-virtualize the CPU/MEM/HDD/NET stats and now I have them physically represented on my desk. The device that does that is named ReCoMonB – Real Computer Monitoring Block. I have also made the device driverless and working on Liunx and Windows.
ReCoMonB – Real Computer Monitoring Block - [Link]
DanNixon @ instructables.com writes:
I just happened to see some large strips of LED lighting when I was picking up some parts at Maplin which were on sale (if I remember correct they were around £12 per approx. 2m strip) however the controller/driver was still around £40, so I thought I would just build a better one myself.
I wanted it to be a web enabled controller as there are a lot of cool things that can be done with a device once it is accessible over HTTP, and I am working on a home automation server project so it would be good to have some devices which I can test this with.
Arduino Web Enabled RGB Lighting - [Link]
Professor John A. Rodgers has previously taught us what the future has in store by way of flexible, stampable microelectronics that adhere to the surface of human skin. As revolutionary as those devices can be – providing critical health-related information from real-time physiological monitoring of the human body – they are limited in their ability to penetrate the depth of human tissue for an even greater understanding. A recent study by Rodgers and his team from UIUC alongside Professor Michael R. Bruchas of Washington University has found a unique solution to the tissue issue – injectable LEDs that can stimulate and monitor brain activity.
Studying the brain with micro-injectable LEDs - [Link]
No-name GU10 LED lamp teardown @ kuzyatech.com
In the usual Kuzyatech fashion, when something breaks, we must take it apart. Today, one of the ”early adopter” GU10 style LED lamps decided to fail mechanically.
No-name GU10 LED lamp teardown - [Link]