Using constant current to drive LEDs is a good practice, but turning them on instantly can be dangerous for both the LED and the LED driver. Harmful spikes are generated when large currents are instantaneously turned on. This app note from Maxim describes how to soft start LEDs to increase overall lifetime and performance. [via]
An incandescent bulb requires some time to reach full brightness after you switch it on, and that delay gives the eye a comfortable interval for adjusting to the bright light. LED-based lights lack this property. Instead, their brightness goes from zero to 100% almost instantly. That property is welcome in a camera flash, but rather annoying for general lighting.
App note: Soft-Start in LED lighting - [Link]
High luminous intensity and a low height of Kingbright LED KA-3529 series will enable you to use them for displays backlighting and production of various indication panels.
Nowadays, for a backlight of displays or various panels, there are very often used white LEDs. However there are still a lot of reasons why to use a color backlight. In many applications a color backlight can increase contrast ratio or visibility of a display in a given environment, or it is simply more aesthetic.
Advantages / Features:
- high luminous flux 4.2-22 lm/ 150mA, according to a type
- small, only 1.3 mm high PLCC2 package
- low power consumption
- 120° large radiation angle
LEDs Kingbright KA-3529 with a high luminous intensity, maximum current up to 150 mA and small dimensions are very suitable for these purposes. In only 1.3mm high PLCC2 SMT package they require only a minimum of space. KA-3529 are available in blue, green, orange and red version.
LED in a PLCC package not only for a display backlight - [Link]
Steven Keeping writes:
LEDs for mainstream lighting are much brighter and are capable of being driven at higher drive currents than the devices of just a few years ago. That means fewer chips are needed for lighting fixtures (luminaires) taking the pressure off designers who previously had to come up with complex power units (“drivers”) to supply long strings of dim LEDs.
This article demonstrates how power requirements have changed and then investigates a new generation of integrated, efficient, and compact LED drivers that are perfectly suited to powering modern luminaires.
High Current, High Brightness LEDs Simplify Power Supply Solutions - [Link]
We create an application based on Arduino, that allows you to control brightness and color of a RGB strip LED via local network or Internet through a WiFi or Ethernet shield. The system that we propose is based on the Arduino UNO, on which are mounted two shield: the Ethernet or WIFI Shield, which provides the connection to LAN, and the RGB shield which mounts three power drivers to control the LED strip.
Arduino WiFi RGB Lamp - [Link]
I found a small project at another site about fading an LED in and out smoothly, without a microcontroller. I changed it a bit. In my version I removed one of the transistors and changed some resistor values. This is supposed to result in lower costs and smaller footprint. I know it’s a very small difference, but still.
LED Fade in / Fade out - [Link]
I’ve been meaning to make something cool for my dorm room this coming semester and decided that some custom closet lights would look great. In this Instructable, I’ll show you how to make some nice-looking LED lights that will turn on automatically using a hall effect sensor and a magnet.
Edit: I’ve noticed a lot of people are hating on the excessive control used in this project so I just wanted to clarify a few things:
- This instructable was also meant to be a lite introduction to actual AVR programming for those people who are used to only Arduino programming. I had a bit of trouble finding useful information when I was learning so I figured it would be nice to help out some others. That is why I posted the basic tutorials along with my AVR code.
- Yes I’m aware I could have simply used a reed switch to switch the LEDs when the door opened and closed. I wanted to leave room open for myself to add different light modes, maybe using more wires and pins to create nice fading effects, possibly a remote control sensor, and maybe even an auto-shutoff routine.
Door Activated LED Lighting using Hall Effect Sensors - [Link]
Will Lyon writes:
I wanted to do something unique and special this year for my wife for Valentine’s Day. I was browsing the web and came across this Instructable and I knew I had to make one! I decided to make one, but put my own special twist on it. Read more…
I decided to make it do a color rainbow with some RGB LEDs rather than sit a single color for all eternity. In addition I wanted a speed control to adjust the speed of the rainbow cycle and also a manual mode where the user can manually change values for red, green and blue to get any color they so desire.
I pieced together some code I found (here – analog rainbow code) and edited it to my liking, adding the analog read for the manual values and also analog read for the speed in auto mode. You can download the finished code here (.ino – Arduino 1.0 or later – not compatible with the PDE system). It works very well.
Valentine’s Day RGB LED Mixer - [Link]
The 8bi8 is a small self contained 8×8 bi-colour LED matrix toy. It has emerged after various prototypes. From here I want to create a new revision building on what I have learn from building this version.
8×8 bi-color LED matrix toy - [Link]
A very popular type of LED that has finally come about is the tri-color, RGB LED. The RGB stands for: red, green and blue since the LED is capable of displaying all three colors, independently. This means that an RGB LED can display any color of the rainbow. This is a powerful capability, but it also requires more control.
In this article, we shall look at how to build an RGB LED controller so that we have accurate and independant control over all three colors at any instant. The method of Fading LEDs via PWM will be leveraged for this design, since our goal here is quite similar, but with more control paths.
RGB LED Controller - [Link]
Ordinary LED flashers turn the LED on and off abruptly, which can get a little irritating after a while. The circuit shown here is more gentle on the eyes: the light intensity changes very slowly and sinusoidally, helping to generate a relaxed mood. The circuit shows a phase-shift oscillator with an adjustable current source at its output. The circuit is capable of driving two LEDs in series without affecting the current. The frequency is set by three RC networks, each of which consists of a 100 microF capacitor and a 22 kohm resistor. Operation is largely independent of supply voltage, and the average LED current is set at about 10 mA. The circuit adjusts the voltage across the emitter resistor so that it matches the base voltage of the first transistor (around 0.6 V). The phase shifting network gives rise to the oscillation around this average value. In the prototype of this circuit we used an ultra bright red LED.
Smooth Flasher circuit - [Link]