The working principle of light cube _ based on 74hc573 8*8*8 light cube LED control method

The light cube is built in cube form by a number of diode led lights, 4*4*4, 8*8*8, 16*16*16 or even more, and is driven by electrical components such as a single chip microcomputer, a latch, and a decoder. Form a three-dimensional animation effect. Among them, 8*8*8 light cubes are the most common.

For example: 8*8*8 light cube is constructed by 512 LEDs in a cubic way. There are two schemes: a common yin beam and a common anode and a total yin, each layer has 8*8 Light-emitting diodes, a total of 8 layers. Compile the MCU program with C language to realize the custom animation effect.

The light cube is simply to use a single-chip microcomputer to control the brightness and extinction of many regularly arranged LEDs.

1, the control mode of a single LED

First understand the control mode of a single LED, you can connect the positive pole to the power supply, and the negative pole is connected to an IO port of the MCU through a current limiting resistor. When the IO port outputs a low level, the LED will be on. Otherwise, the LED will be off.

If we want to drive the LED in any position, we only need to connect the column line used by the LED at this position, and connect the line to +V.

The friends who have studied the MCU know how the digital tube is lit. Among them, there are points and segments. Scanning is used to realize that all the digital tubes can work normally to display the numbers we want.

The dot matrix is the same. Although it is an 8*8 dot matrix, if we let the whole display the pattern at will, it needs to be scanned. Otherwise, it can't achieve precise control.

The so-called scanning, that is to say, we can only make one row or one vertical row of lights at a time. Only this time, 8 times for a cycle, click from left to right, then loop, we see the complete image.

2, each layer of LED control

According to the control mode of a single LED, each LED needs to occupy one IO port of the single chip microcomputer, and 100 IO ports are required to control 100 LEDs. So, is there a way to control more LEDs with fewer IO ports? The answer is yes, this method is the scan drive circuit.

2*2 scan drive circuit

So in general, each layer of the light cube has 64 lights, but we will have 64 lines connected to these lights, so that one-time control of 64 lights, usually with fewer pins. Generally, chips such as 74hc573 and 74hc595 will be used for expansion.

3, (based on 74hc573) 8 * 8 * 8 light cubic LED control

The data is entered into each 74hc573 in parallel, and the controller stores the data, thereby realizing a layer of 64 lights simultaneously. The following describes the display of a fixed picture, the process required by the hardware.

1) Pass the data of the first layer of 64 points into 8 74hc573, control the uln2803 layer control chip to open the first layer switch, so that the first layer is lit. At this time, the other layers are off.

2) Waiting time t.

3) Extinguish the first layer, start transmitting the data of the second layer to 74hc573, latch, turn on the second layer of the total control switch, and illuminate the second layer.

4) Waiting time t.

. . .

Extinguish the first layer, pass the data of the eighth layer into all 74hc573, latch, turn on the eighth layer of the main switch, and light up the eighth layer.

Go back to the first step and loop. .

In this way, the display of a periodic picture is realized. Due to the persistence of the human eye, as long as the refresh is fast enough, what we see is that the light cube is bright overall. It achieves the effect we want. In order to stabilize the picture, the above interval lighting t must be consistent, otherwise uneven brightness will occur.

When actually using the above circuit, it is better to add a current limiting resistor to the 64 pins of the 74hc573 output, which can achieve good diode protection and overall power consumption limitation and brightness adjustment.

Careful analysis of the above control process can reveal ways to further save the number of IO ports.

Take the whole column of 16 & TImes; 16 as an example. If only 16 columns are defined, only one column is highlighted at a time, and four IO lines plus one 4~16 decoder can be used instead. In this way, it becomes 16+4 with only 20 IO ports. The line still retains 16 lines, because by doing so, it is possible to control multiple LEDs in one column at a time to be illuminated at the same time. Speed up the scanning process.

8*8*8 light cube circuit diagram based on 74hc573

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