App note: 12Vac LED Driving without smoothing capacitors


Application note from Diodes Incorporated on driving 12Vac LED without smoothing capacitors with their Zetex ZXLD1360 LED driver IC and SBR2A40P1 super barrier rectifier. Link here (PDF)

LED based architectural lighting is now coming of age, but there are still some problems to be considered when designing luminaires to be fitted into existing installations.

This Application Note discusses some of the challenges and shows that the omission of the traditional smoothing capacitors has advantages in saving cost, space and PFC problems.

Driving a 48-segment RGB LED bar graph with a Teensy 3.2


Glen Akins writes:

In my post Driving a SparkFun 48-Segment RGB LED Bar Graph, I stated that the hardware built there could be used to drive the LED bar graph with any combination of hardware and software that could drive one of the common 32×32 or 32×16 RGB LED matrices. Today I’m back to prove that point. In this post, I ditch the FPGA and drive the 48-segment RGB LED bar graph using a Teensy 3.2 board and the Pixelmatix SmartMatrix 3 library.

More details at Glen Akins’ blog.

App note: Flash for “Selfies”


Effective front facing camera flash discussed in this white paper from Lumileds. Link here (PDF)

Smartphones are ubiquitous in everybody’s daily lives, a trend that shows no sign of slowing. A key component of the smartphone is the camera, which has gained market share over Digital Still Cameras due to its convenience.

As the demand for smartphone cameras increases, sensor makers are continuously working to improve the resolution and while 20MPix capability gained in importance for the main camera of the smartphone, the resolution race has begun for the front camera. With the rise in popularity of “selfies” and the 5 to 8 Mpix resolution for the front camera, it is not surprising that camera flash is starting to be more readily implemented for front cameras also. However, to make a successful front flash that captures an ideal “selfie,” there are certain illuminance requirements and shorter flash pulses that are recommended.

Creating custom 3D printed LED bar graphs


Glen Akins has a nice build log on his 3D printed LED bar graphs:

While building my zombie containment unit, I decided I wanted some LED displays or bar graphs to complement the containment status video running on the smaller secondary video monitor. Some other containment units used LED air pressure gauges from eBay. I wanted to achieve a similar look, but I also wanted my gauge to be software controllable so I could change the number of segments lit in response to events in the playback of the two videos. I decided it was time to build my own LED bar graphs.

More details at Glen’s blog.

Programmable LED dimmer


Programmable LED dimmer from Soldernerd:

Around one and a half years ago I’ve designed and built various LED dimmers for both white and RGB LEDs. Then late last year someone approached me asking if I could make an RGB dimmer for him, too. But my designs were really tailored to their specific applications and built with home-made, i.e. milled PCBs which are time-consuming to make. So I decided to make a more universal version based on a proper, etched board which could be built in a small series and used for all kind of applications, both white and RGB. The result is this versatile, programmable 4-channel dimmer.
The design is based on my previous RGB dimmer but with a number of improvements.

Project info at Soldernerd homepage and the GitHub repository here.

Individually addressable incandescent lamps


Michael wrote an article on controlling a bunch of lamps individually with WS2811 drivers and Arduino:

I simply used the same technology as LED strips to allow communication between lamp modules. LED strips have RGB LEDs with an embedded driver chip which uses PWM (pulse width modulation) to control the duty cycle on the red, green, and blue LEDs. This combined LED/chip is called WS2812 or WS2812B. On older LED strips, the driver chip was not embedded into the LED itself, but was a separate chip called WS2811. These standalone driver chips are somewhat obsolete now which means they are cheap! I got 50 of them on eBay for $5.00. Since these modules use the same technology as LED strips, the same code can be used. Adafruit’s NeoPixel library is a very simple way to control LEDs, so we can control each lamp easily. The lamp is controlled by the “blue” pin on the WS2811 so that is the value to set.

More details at Project Lab.

Check out the video after the break.


An Arduino Knight Rider Rainbow dice that uses WS2812B RGB LEDs


An Arduino Knight Rider Rainbow dice built using a clock by Davide Gironi:

This project implements a Knight Rider / Rainbow effect Random Selector.
It uses an Arduino UNO and a WS2812B RGB led strip.
A friend of mine needs a random selector for train scale model.
I’ve developed this using the Arduino framework, because he would like to modify the sketch “the Arduino way”.
Unluckly I have not any picture or video of his build. So I’ve built a dice selector by using an old clock frame. I would like to thank my friend Matteo for cutting vinyls out for this project.

Check out the video after the break.

Programming an 8 digit 7-segment display, the easy way, using a Max7219


Allan Schwartz shows off the easy way to interface 7-segment displays using the MAX7219:

Previously, in part 1 of my blog posting Programming a 7-segment Display, using just Arduino digital pins (the hard way) we had demonstrated how to hook up a pair of 7-segment displays to an Arduino, treating each individual segment as a separate LED. There was a bit of tricky logic to translate each digit into the segments A, B, C, D, E, F, G plus additional logic to turn the digital pins on or off. Although I tried to code it as efficiently as possible, the logic may have been difficult to understand.
Also, constructing the project was fairly tedious, with dozens of resistors and hook-up wires.
Instead, lets do this the easy way. A typical MAX7219 module comprised of a single MAX7219 chip and eight 7-segment displays.

More details at

Comfort Thermometer display built with 517 individual LEDs

Richard wrote in to tell us about a ‘Comfort Thermometer display built with 517 LEDs’ that he has just finished building:

Comfort Thermometer Display built with 517 individual LEDs and the following microprocessors:
1) PiC24FV16KA301 – controlling outer 36 RGB LEDs
2) PIC16F886 – bargraph and pink LEDs animations
3) ATmega328 – controlling 7-segment display
4) PIC16F57 – rf transmitter and receiver

The bargraph LEDs are current sinked with LM3914 LED display drivers, and current sourced via the PIC16F886 and transistors

Via the contact form.