POV (Persistence of Vision) Display With IRled

Today I will introduce POV (Persistence of Vision) Display with WIZwiki-W7500ECO board.

Did you ever heard about POV before?

You can check detail of POV here.

https://www.instructables.com/id/ATtiny8545-POV-Dis... (See Step 1)

It is really funny project.

I will let you know how to make it. Just follow me.

Let's start

Step 1: Hardware Requirement

For this project.

We need below components.

1. 2ea WIZwiki-W7500ECO board (mbed platform)

https://developer.mbed.org/platforms/WIZwiki-W7500...

2. any LEDs

I used RGB led, smd type

3. IRled (TX, RX[photosensor])

http://forums.parallax.com/discussion/138272/ir-led-receiver-circuit

4. Phototransistor (SG-23FF)

http://pdf1.alldatasheet.com/datasheet-pdf/view/78838/KODENSHI/SG-23FF.html

5. any DC motor

I used small DC motor (I dont know part number exacly)

6. any Li-ion Battery (3.7V)

https://www.sparkfun.com/products/341

Step 2: Hardware for Basic POV Display

I will introduce basic POV first and add some functions later.

In this step I will show you how to design hardware for basic function.

Picture shows you how connect WIZwiki-W7500ECO and one LED only.

You can duplicate other LEDs ealily.

To control these LEDs, LED must be connected with and port of WIZwiki-W7500P.

DigitalOut LED1R(P5);
DigitalOut LED1G(P6);
DigitalOut LED1B(P7);
DigitalOut LED2R(P15);
DigitalOut LED2G(P16);
DigitalOut LED2B(P17);
DigitalOut LED3R(P18);
DigitalOut LED3G(P19);
DigitalOut LED3B(P20);
DigitalOut LED4A(P25);
DigitalOut LED5A(P22);
DigitalOut LED6A(P23);
DigitalOut LED7A(P24);
DigitalOut LED8A(P21);
DigitalOut LED9R(P27);
DigitalOut LED9G(P28);
DigitalOut LED9B(P29);
DigitalOut LED10R(P26);
DigitalOut LED10G(P31);
DigitalOut LED10B(P32);

As you see. it is very simple.

For connect LED, any port is OK.

And you can check that which port is used for LED control in source code as below.

And I used DC motor and Just connected with Li-ion Battery and Switch.

So it will run with full speed when SW is ON.

Step 3: Software for Basic POV Display

Point of POV is LED control for display.

And here is a chraracter display library for POV and I found it from other POV projects.

I also used it in my source code.

const unsigned char font[95][5] = {
  {0x00,0x00,0x00,0x00,0x00},   //   0x20 32
  {0x00,0x00,0x6f,0x00,0x00},   // ! 0x21 33
  {0x00,0x07,0x00,0x07,0x00},   // " 0x22 34
  {0x14,0x7f,0x14,0x7f,0x14},   // # 0x23 35
  {0x00,0x07,0x04,0x1e,0x00},   // $ 0x24 36
  {0x23,0x13,0x08,0x64,0x62},   // % 0x25 37
  {0x36,0x49,0x56,0x20,0x50},   // & 0x26 38
  {0x00,0x00,0x07,0x00,0x00},   // ' 0x27 39
  {0x00,0x1c,0x22,0x41,0x00},   // ( 0x28 40
  {0x00,0x41,0x22,0x1c,0x00},   // ) 0x29 41
  {0x14,0x08,0x3e,0x08,0x14},   // * 0x2a 42
  {0x08,0x08,0x3e,0x08,0x08},   // + 0x2b 43
  {0x00,0x50,0x30,0x00,0x00},   // , 0x2c 44
  {0x08,0x08,0x08,0x08,0x08},   // - 0x2d 45
  {0x00,0x60,0x60,0x00,0x00},   // . 0x2e 46
  {0x20,0x10,0x08,0x04,0x02},   // / 0x2f 47
  {0x3e,0x51,0x49,0x45,0x3e},   // 0 0x30 48
  {0x00,0x42,0x7f,0x40,0x00},   // 1 0x31 49
  {0x42,0x61,0x51,0x49,0x46},   // 2 0x32 50
  {0x21,0x41,0x45,0x4b,0x31},   // 3 0x33 51
  {0x18,0x14,0x12,0x7f,0x10},   // 4 0x34 52
  {0x27,0x45,0x45,0x45,0x39},   // 5 0x35 53
  {0x3c,0x4a,0x49,0x49,0x30},   // 6 0x36 54
  {0x01,0x71,0x09,0x05,0x03},   // 7 0x37 55
  {0x36,0x49,0x49,0x49,0x36},   // 8 0x38 56
  {0x06,0x49,0x49,0x29,0x1e},   // 9 0x39 57
  {0x00,0x36,0x36,0x00,0x00},   // : 0x3a 58
  {0x00,0x56,0x36,0x00,0x00},   // ; 0x3b 59
  {0x08,0x14,0x22,0x41,0x00},   // < 0x3c 60
  {0x14,0x14,0x14,0x14,0x14},   // = 0x3d 61
  {0x00,0x41,0x22,0x14,0x08},   // > 0x3e 62
  {0x02,0x01,0x51,0x09,0x06},   // ? 0x3f 63
  {0x3e,0x41,0x5d,0x49,0x4e},   // @ 0x40 64
  {0x7e,0x09,0x09,0x09,0x7e},   // A 0x41 65
  {0x7f,0x49,0x49,0x49,0x36},   // B 0x42 66
  {0x3e,0x41,0x41,0x41,0x22},   // C 0x43 67
  {0x7f,0x41,0x41,0x41,0x3e},   // D 0x44 68
  {0x7f,0x49,0x49,0x49,0x41},   // E 0x45 69
  {0x7f,0x09,0x09,0x09,0x01},   // F 0x46 70
  {0x3e,0x41,0x49,0x49,0x7a},   // G 0x47 71
  {0x7f,0x08,0x08,0x08,0x7f},   // H 0x48 72
  {0x00,0x41,0x7f,0x41,0x00},   // I 0x49 73
  {0x20,0x40,0x41,0x3f,0x01},   // J 0x4a 74
  {0x7f,0x08,0x14,0x22,0x41},   // K 0x4b 75
  {0x7f,0x40,0x40,0x40,0x40},   // L 0x4c 76
  {0x7f,0x02,0x0c,0x02,0x7f},   // M 0x4d 77
  {0x7f,0x04,0x08,0x10,0x7f},   // N 0x4e 78
  {0x3e,0x41,0x41,0x41,0x3e},   // O 0x4f 79
  {0x7f,0x09,0x09,0x09,0x06},   // P 0x50 80
  {0x3e,0x41,0x51,0x21,0x5e},   // Q 0x51 81
  {0x7f,0x09,0x19,0x29,0x46},   // R 0x52 82
  {0x46,0x49,0x49,0x49,0x31},   // S 0x53 83
  {0x01,0x01,0x7f,0x01,0x01},   // T 0x54 84
  {0x3f,0x40,0x40,0x40,0x3f},   // U 0x55 85
  {0x0f,0x30,0x40,0x30,0x0f},   // V 0x56 86
  {0x3f,0x40,0x30,0x40,0x3f},   // W 0x57 87
  {0x63,0x14,0x08,0x14,0x63},   // X 0x58 88
  {0x07,0x08,0x70,0x08,0x07},   // Y 0x59 89
  {0x61,0x51,0x49,0x45,0x43},   // Z 0x5a 90
  {0x3c,0x4a,0x49,0x29,0x1e},   // [ 0x5b 91
  {0x02,0x04,0x08,0x10,0x20},   // \ 0x5c 92
  {0x00,0x41,0x7f,0x00,0x00},   // ] 0x5d 93
  {0x04,0x02,0x01,0x02,0x04},   // ^ 0x5e 94
  {0x40,0x40,0x40,0x40,0x40},   // _ 0x5f 95
  {0x00,0x00,0x03,0x04,0x00},   // ` 0x60 96
  {0x20,0x54,0x54,0x54,0x78},   // a 0x61 97
  {0x7f,0x48,0x44,0x44,0x38},   // b 0x62 98
  {0x38,0x44,0x44,0x44,0x20},   // c 0x63 99
  {0x38,0x44,0x44,0x48,0x7f},   // d 0x64 100
  {0x38,0x54,0x54,0x54,0x18},   // e 0x65 101
  {0x08,0x7e,0x09,0x01,0x02},   // f 0x66 102
  {0x0c,0x52,0x52,0x52,0x3e},   // g 0x67 103
  {0x7f,0x08,0x04,0x04,0x78},   // h 0x68 104
  {0x00,0x44,0x7d,0x40,0x00},   // i 0x69 105
  {0x20,0x40,0x44,0x3d,0x00},   // j 0x6a 106
  {0x00,0x7f,0x10,0x28,0x44},   // k 0x6b 107
  {0x00,0x41,0x7f,0x40,0x00},   // l 0x6c 108
  {0x7c,0x04,0x18,0x04,0x78},   // m 0x6d 109
  {0x7c,0x08,0x04,0x04,0x78},   // n 0x6e 110
  {0x38,0x44,0x44,0x44,0x38},   // o 0x6f 111
  {0x7c,0x14,0x14,0x14,0x08},   // p 0x70 112
  {0x08,0x14,0x14,0x18,0x7c},   // q 0x71 113
  {0x7c,0x08,0x04,0x04,0x08},   // r 0x72 114
  {0x48,0x54,0x54,0x54,0x20},   // s 0x73 115
  {0x04,0x3f,0x44,0x40,0x20},   // t 0x74 116
  {0x3c,0x40,0x40,0x20,0x7c},   // u 0x75 117
  {0x1c,0x20,0x40,0x20,0x1c},   // v 0x76 118
  {0x3c,0x40,0x30,0x40,0x3c},   // w 0x77 119
  {0x44,0x28,0x10,0x28,0x44},   // x 0x78 120
  {0x0c,0x50,0x50,0x50,0x3c},   // y 0x79 121
  {0x44,0x64,0x54,0x4c,0x44},   // z 0x7a 122
  {0x00,0x08,0x36,0x41,0x41},   // { 0x7b 123
  {0x00,0x00,0x7f,0x00,0x00},   // | 0x7c 124
  {0x41,0x41,0x36,0x08,0x00},   // } 0x7d 125
  {0x04,0x02,0x04,0x08,0x04},   // ~ 0x7e 126
};

I will explain how does it works with

{0x14,0x7f,0x14,0x7f,0x14}, // # 0x23 35

You can know well as represent it to binary.

0x14, 0x 7f, 0x14, 0x7f, 0x14

0 1 0 1 0

1 1 1 1 1

0 1 0 1 0

1 1 1 1 1

0 1 0 1 0

You can know "#" character.

Now we can control led and diaplay characters by keeping led display sequence with this libarary.

As below source code.

void printletter(char ch) {
    if (ch < 32 || ch > 126) ch = 32;
    ch -= 32;
    for (int i = 0; i < 5; i++) {
        unsigned char vertical = font[ch][i];
        if (vertical & 0x01) led1(1); else led1(0);
        if (vertical & 0x02) led2(1); else led2(0);
        if (vertical & 0x04) led3(1); else led3(0);
        if (vertical & 0x08) led4(1); else led4(0);
        if (vertical & 0x10) led5(1); else led5(0);
        if (vertical & 0x20) led6(1); else led6(0);
        if (vertical & 0x40) led7(1); else led7(0);
        wait_us(columnDelay);
    }

(Where, ch : ASCII number, ledx(1) : on, ledx(0) : off, delay control : columnDelay and letterDelay)

Step 4: Demo Video of Basic POV Display

Now we can make basic POV display.

And you can see demo video of POV display working.

As you see this video.

There is a problem need to fix.

First one is flowing of character position.

Motor speed is different every time.

So it is impossible to fix character position with software only.

And Second one is it cannot change displayed string freely with remote.

It is not funny display only fixed characters.

Step 5: Hardware for Upgraded POV Display

For fix character position,

I used Photo interrupter.(SG-23FF)

You can check detail of phototransistor in below link.

http://www.electroschematics.com/10494/arduino-opt...

Anyway this photo interrupter make our system know the position to start display.

Now our character of POV display will be not flow.

You can check the hardware connection photo interrrupter between WIZwiki-W7500ECO board in picture.

For display character freely,

I used IRled TX, IRled RX (photo sensor) module.

It is very simple to connect. and very cheap component.

You can see more detail of how does IRled communication work in below link.

https://learn.sparkfun.com/tutorials/ir-communication

I used irled as a UART communication.

And we need one more WIZwiki-W7500ECO board which connected to PC and send character string to display.

Step 6: Software for Upgraded POV Display

For fix character position,

I used ADC function for sensing photo interupter value.

Here is a source code

displayString(buf);
while(1) {
    if (myanalog.read_u16() < 2000) break;
}

After display, board check analog value of photo interrupter.

When sensor value is under 2000, System will display again.

That is all for using photo interrupter.

For display character freely,

We need one more WIZwiki-W7500ECO board which connected to PC and send character string to display.

Here is a receive side source code.

if (uart0.readable()) {
            char ch = uart0.getc();
            if (ch == 13) {
                pc.printf("%s\r\n",buf); 
                for (int i = 0; i < index+1; i++) buf[i] = 0;
                index = 0;
            }
            else {buf[index] = ch; index++;} 
        }

Until receive "Enter" save received character to buf2.

And it will update buf from buf2 when revcive "Enter" (ASCII number : 13(decimal))

That is all.

Here is a transimit side source code.

if (pc.readable()) {
            char ch = pc.getc();
            char ch2 = ch;
            pc.putc(ch2);
            if (ch2 == 13) pc.printf("\n");
            uart0.putc(ch);
        }

Transmit code more simple.

It works just transfer PC to UART0 which connected with IRled TX.