In the previous part, we have told about RGB multi-color LED Strips.
We have begun explaining different kinds of controlling devices.
With today’s tutorial, we will continue explaining them.
SCH. 1 For You, Dear Explorers – Working Schematic by the Author
We develop a special “working” schematic – SCH. 1, for a better understanding and explanation of the topic.
The mechanical switches are replaced by N-Channel MOSFET transistors and they are working as electronic switches.
Also, we add an MCU – Microcontroller UNIT. It has configured three I/O Pins as outputs, named and related associatively with the same Color’s first letters:
- OUT-R = SW-R – Controlling signal for RED Color segment.
- OUT-G = SW-G – Controlling signal for GREEN Color segment.
- OUT-B = SW-B – Controlling signal for BLUE Color segment.
Type and Level of Controlling signals:
- Squire Pulses with CMOS logic 0-5V amplitude.
The logic of using electronic switches is quite simple. With some “weak” signal outputs, we can manage and control 1 and above Amperes output currents. It is a way to create interactive lighting solutions with flexible control and the best dynamic parameters.
Many of today’s known controllers for managing RGB Tapes use almost the same type of control circuits. The effect of whole strip color controlling is good, used to create a beautiful interior lightening solution.
These controllers are good, BUT, here is a large “BUT” – they can control the tape’s color as a whole.
Sometimes in the practice, the goal is other. If the wanted effect is another: we want to control each RGB LED “Pixel” with its own color – the solution is very, very different.
1.) On PIXEL-Level Controlling
PIC. 1 On Pixel-Level Controlling RGB LED String
As the words songs, we need to use a controlling IC (integral circuit) for every single RGB Light Emitting Diode.
Many manufacturers create different ASICs (Application-Specific Integral Circuit) to control RGB LED parameters – Intensity of Red-Color, Intensity of Green-Color, Intensity of Blue-Color ON-OFF the device, and Flashing patterns (for future usage).
The single pixel has different parameters for each color. In the common case, the color is with 8-bit (255 steps or gradations) depth.
Imagine that you have 1000 different RGB Pixels connected to each other, and You need to set the 100-th with green color.
How that amount of information will go into the right PIXEL – the right member of the Pixel’s'”string”?
That is possible with the special technique, named addressing (you can see the SCH. 2 ).
You easily can see the controlling signals and a cascading connection between different RGB-Pixels.
With only two powering Wires and only two signal wires, You make speed SPI (Serial Peripheral Interface) communication between the PIXELS. Each Pixel translates and remakes the signal levels, who allows You to insert large amount of Pixels into the development project
For our explanation, we will use the real member of addressable RGB PIXEL’s division – well known by many hobbyists and professionals – IC – WS2801.
Our main goal is to extend the count of users, who like and understand this nice circuit.
We are sure that at the end of the topic, you will be more reach, than at the beginning.
SCH. 2 WS2801- Typical Example of usage
For a Better understanding of the principle, see the details in Time Diagram 1.
Time Diagram 1. RGB Pixel WS2801 – COLOR Data Format and Timing Diagram
VIDEO 1. How_to_Build_an_LED_Display_Wiring_and_Setup_of_WS2801
VIDEO 2. RGB_Led_Strips_in_action: DMX_Controlled_LED_STRIPs_by_SIRS-E
Don’t stop to Create!