Another application note from OSRAM on different LED circuit design failure mode. Link here (PDF)
In recent years, Light Emitting Diodes (LEDs) have become a viable alternative to conventional light sources. The overriding advantages long life, high efficiency, small size and short reaction time have lead to the displacement, in ever increasing numbers, of incandescent bulbs. One of the markets where this change has become most evident is Automotive, where LEDs are used now not only for backlighting dashboards and switches, but also for exterior illumination in Center High Mounted Stop Lights (CHMSL), Rear Combination Lamps (RCL), turn signals and puddle lighting.
Despite the long life and low failure rates of LEDs, cars can be found, on occasion, with failed LEDs in their CHMSL. Most often this is due to a flawed circuit design wherein the LEDs were allowed to be overdriven. It is with that supposition in mind that this application note is written: to identify, characterize and comment on LED behavior and failure modes in serial and matrix circuits.
App note from OSRAM describing the behaviour of LEDs in respect to brightness by varying the current and to suggest solutions for avoiding negative influence for the application. Link here (PDF)
In the design of a driving circuit for LEDs, the dimming behaviour is an important topic to fulfill the end customer requirements. The behaviour of the LEDs in respect to brightness is investigated by varying the current and solutions for avoiding negative influence for the application are suggested.
Here is the finished Seven Segment Tester. All of the available Arduino Nano pins, except for analog input pins A6,A7 and Serial Port pins D0 and D1 are connected. This leaves us with 18 pins to bring to the 3M Zero Insertion Force (ZIF) socket. Any display up to 9 pin DIP can be tested.
Here are some pictures of the device testing a 16 segment display, a 7 segment display and a 3 digit 7 segment display. The common cathode and common anode versions are programmed as test patterns.
Once the Arduino is programmed, the device can work standalone using a 9v battery.
I’ve always been fond of the popular Nixie clocks made from old surplus Soviet nixie tubes. Nixie tubes are no longer made, so they’re hard to acquire. Instead, I took inspiration from “Lixie” displays and made my own Nixie-inspired, LED-powered display. And in an unusual twist (for me, anyway), I didn’t make a clock this time! It’s a weather/temperature display. I made the parts myself, starting with the electronics. These circuit boards were created on the CNC machine. The “brains” are an ESP8266 chip, which grabs the current weather from the Internet.
Controlling LED brightness through digital potentiometer and a LED driver from ON Semiconductor. Link here (PDF)
Light-emitting diodes (LEDs) require a regulated current, and their brightness is proportional to the current that flows through them. Some LED drivers use an external resistor to set the LED current. A digital POT can replace a discrete resistor with the advantage of providing an adjustable value allowing the LED brightness to dynamically change. Most digital POT circuits have the ability to store permanently the resistor value in non-volatile memory.
Driving 300 WS2812B RGB LED’s with “the 3 cent microcontroller” – the Padauk PMS150C.
The 3 cent Padauk PMS150C is.. Interesting to say the least. First of all there’s a lot this little MCU doesn’t do. It doesn’t have a lot of code space (1K Word), it doesn’t have a lot of RAM (64 bytes) and it doesn’t even do hardware multiplication. It doesn’t have an instruction for loading data from ROM either(Though there are ways of getting around this – but that’s a subject for another post). And of course – you can only program it ONCE.
In the first post in this series, we built a miniature LED bicycle traffic signal using 3D printing, laser cutting, a sticker, and an Adafruit Neopixel Jewel. In this post, we’ll look at bringing the signal to life using a Particle Photon. We’ll start with basic code to blink the traffic signal green, yellow, and red then add code to control the color over the web using the Particle Cloud or locally using an iPad and the Art-Net protocol.
This build combines small dozens of small laser-cut acrylic pieces which fit together with very tight tolerances. It uses skinny (4mm wide) LED strips which must be soldered, bent, and then slotted in between those acrylic pieces. When assembling the parts you must be willing to force pieces into place, even though it feels like you are stressing the brittle acrylic. You must also be willing to remove and re-seat said pieces and LED strips when it turns out they *can’t* actually be forced into place. At some point during the assembly there is a strong likelihood that you will have to remove everything and re-solder your LED strip when you realize that forcing everything into place broke one of the wires away from your LED strip or created a short circuit.
This project is a small DMX-512 controlled, color-changing RGB LED light. The light can be controlled via the DMX512 protocol or it can run a number of built-in programs depending on how the software is configured. The light incorporates an advanced 16-bit PIC24 microcontroller with PWM capabilities, a 3D printed enclosure, a laser cut acrylic lid, a custom switching power supply, and a MEMS oscillator. The light measures roughly 2.25″ square by 1.25″ high. This light is the evolution of my RGB LED light designs that span back over a decade.
Pulsed LED application like flash LEDs requires adequate thermal management to counter the heavy heat caused by larger current, here’s an app note from OSRAM discussing on thermal management of LEDs. Link here (PDF)
This application note focuses on how to develop an adequate thermal management for LEDs in camera flash applications. It provides information on critical factors and the thermal properties of LEDs during a range of operation modes as well as information on how to develop an adequate thermal management in flashlight applications.