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Canon Canola L1211's display unit controlled by ESP32 to display a single digit number.

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Each segment of the display unit of Canon Canola L1211 can be turned on and off by ESP32. For more information about JRC (Japan Radio Co., Ltd.) SEPTANIX J4923A, the display unit for Canon Canola L1211, please see here.

The SEPTANIX J4923A needs to perform two controls: segment control and digit control.

This time, I would like to make a control circuit for the segment.

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Controlling segments with transistors

The pins of each segment are connected across a resistor, and the current is passed to GND using a transistor to light up the segment.

Here is the driver circuit for the segment. It uses the high-voltage transistor MPSA42, which was previously used to control the lighting of Nixie tubes. For more information, please see this article.

I made a transistor circuit on a small PCB.

Program

I made a simple program to display numbers from 0 to 9.

const int a_PIN = 5; //7
const int b_PIN = 16;  //5
const int c_PIN = 2;  //2
const int d_PIN = 15; //1
const int e_PIN = 0; //3
const int f_PIN = 17; //6
const int g_PIN = 4;  //4
const int dp_PIN = 18;  //8
const int com_PIN = 19; //9
const int SEG_PIN[9] = { a_PIN, b_PIN, c_PIN, d_PIN, e_PIN, f_PIN, g_PIN, dp_PIN, com_PIN };
const int SEG_NUM = 9;

//                            a  b  c  d  e  f  g 
const bool CHAR[10][7] =   { {1, 1, 1, 1, 1, 1, 0},{0, 1, 1, 0, 0, 0, 0},{1, 1, 0, 1, 1, 0, 1},{1, 1, 1, 1, 0, 0, 1},{0, 1, 1, 0, 0, 1, 1},{1, 0, 1, 1, 0, 1, 1},{1, 0, 1, 1, 1, 1, 1},{1, 1, 1, 0, 0, 0, 0},{1, 1, 1, 1, 1, 1, 1},{1, 1, 1, 1, 0, 1, 1} };

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  Serial.println("start");
  for( int i=0 ; i< SEG_NUM ; i++)
  {
    pinMode(SEG_PIN[i], OUTPUT);
    digitalWrite(SEG_PIN[i], LOW);
  }
}

void loop() {
  for( int i=0 ; i< 10 ; i++)
  {
    for( int j=0 ; j<7 ; j++ )
    {
      digitalWrite(SEG_PIN[j], CHAR[i][j]);
    }
    Serial.printf("%d\n",i);
    delay(500);
  }
}

The program has also been written and is now ready to go.

The numbers are showing up!

I turned on the power, and the numbers appeared on the display tube without a hitch! The color is similar to that of a Nixie tube, but it is a 7-segment indicator. It has a very beautiful color with a warm feeling that LEDs do not have.

The segment control worked well. In the next article, I would like to add digit control.

Added on April 2021.4.11 2021 Click here to continue.

End of addition

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