The LED module with the Max7219 must be considert being a RF-transmitter.
When touching the metal plate underneath the breadboard it works as it should.
Obviously this is the same story when I had it attached to the DIY PIC-controller board.
I’m not an Radio amateur.
But I know this is exactly the effect when making a capacitive counterwight to an antenna or operating high resistive high impedance amplifiers (tube or MOSFET) I made earlier.
Touchsensitive device long before the stupidly small touchscreen phones came up.

Cheers

http://www.whatimade.today/programming-an-8-digit-7-segment-display-the-easy-way-using-a-max7219/

Only drawback with the Raj-display, they light up ALL segment FULL brightnes on power up.
This sucks much current!
This happens all the time you power up the circuitry, regardless of having placed the Iset-resistor or having set the brightness register to “1”.
Please, read the notes regarding placing and modifying the rinkydinky libraries carefully.

The code (Fahrenheit portion removed):

/**
* Display (Date) Time Temperatur on 2*4 Max7219 Raj LED-Display
* used those with the Max7219 SMD SO chip soldered on
*
*
* RTC DS3231 (read the clock and temp sensor)
*
*
* Rinkydinky “DS3231” and “HW_AVR” libraries used
* Copy both the DS3231-library files AND the HW-Library files into the same DS3231-folder!
* They have to be placed manually to the library folder structure.
* Remove the hardcoded links /avr/hardware/… from both files HW_AVR_defines.h and HW_AVR.h !
* Let the library manager scan and by doing this way rebuilding the datase of installed libraries!
* In case the compiler mocks about having found many DS3231 libraries, move those unwanted libraries *temporarily out of the libry folder!
* Let the library manager scan and rebuilding the datase of installed libraries again!
* Let the IDE “correct and reload the code”.
* Thereafter I have successfully compiled on Arduino IDE 1.6.5
*
* @file max7219_DS3231_temp_clock.ino
*
* @brief view DATE/TIME/TEMPERATURE using an 8-digit
* 7-Segment display
*
* @history Feb 6th, 2017
*
*
* @author Allan Schwartz
* Michael Diamond
*
* @maker/editor April 7th 2019 changed for using Raj 2*4 digit I2C Max7219 LED display
*
*
* @notes The following Arduino Pins are attached:
*
* name Arduino 7 Segment display
* —– —- —–
* +5V VCC
* GND GND
* DIN D10/MOSI DIN
* CS D11/SS Load/CS
* CLK D12/SCK CLK
*
* name Arduino RTC module
* —– —- —–
* nc 32K
* nc SQW
* SCL SCL/A5 SCL
* SDA SDA/A4 SDA
* 5V VCC
* GND GND
*/

#include // import library from rinkydink.com

// define pins attached to MAX7219 (and also see notes above)
#define MAX7219_DIN 10
#define MAX7219_CS 11
#define MAX7219_CLK 12

enum { MAX7219_REG_DECODE = 0x09,
MAX7219_REG_INTENSITY = 0x01,
MAX7219_REG_SCANLIMIT = 0x0B,
MAX7219_REG_SHUTDOWN = 0x0C,
MAX7219_REG_DISPTEST = 0x0F };

enum { OFF = 0,
ON = 1 };

const byte DP = 0b10000000;
const byte C = 0b01001110;
const byte c = 0b00001101;

DS3231 rtc(SDA, SCL);

void setup()
{

// Serial.begin(115000); // initialize serial communication
// Serial.println(“max7219_7segment_date_time_temp”);

// define type of pin
pinMode(MAX7219_DIN, OUTPUT); // serial data-in
pinMode(MAX7219_CS, OUTPUT); // chip-select, active low
pinMode(MAX7219_CLK, OUTPUT); // serial clock
digitalWrite(MAX7219_CS, HIGH);

resetDisplay(); // reset the MAX2719 display

rtc.begin(); // init. the DS3231 RTC interface

// Uncomment the following lines to set the RTC initally ONLY!
// nur zum Stellen der RTC ( mit Batterie) einmalig aktivieren

//rtc.setDOW(WEDNESDAY); // Set Day-of-Week to WEDNESDAY
//rtc.setTime(3, 40, 0); // Set the time to 4:20pm
//rtc.setDate(7, 4, 2019); // Set the date, adjust this to the time you compile and send the code over!
}

void loop()
{
String str;
// … display Date, dd.mm.yyyy
// read the date as a string from the RTC
// str = rtc.getDateStr(FORMAT_LONG);
// Serial.println(str); // debug
// displayDate(str); // display on the 7-segment
// delay(5000);

// show the time for 10 seconds, then the temperature
// … display Time: hh-mm-ss
for ( int i = 0; i < 9; i++ ) //adjust i to the amount of repeated cycles you want

{
// read the time as a string from the RTC
str = rtc.getTimeStr(FORMAT_LONG);
// Serial.println(str); // debug
displayTime(str); // display on the 7-segment
delay(1000);
}
{ // display temp in lower row
String str;
float t = rtc.getTemp();
str = String(t, 2); // format that value
Serial.println(str); // debug
displayTemp(str,c); // display on the 7-segment
delay(3000); //adjust i to the display time you want
}
} // End loop

//—– Sub routines —–

void displayTemp(String tempString, char c ) // display the temp on the lower row Centi grade value followed by a small chracter "c"
{
set_register(MAX7219_REG_SHUTDOWN, OFF); // turn off display
set_register(MAX7219_REG_SCANLIMIT, 7); // scan limit 8 digits

// decode the 3 mostsignificant Temp-digits ONLY, use the following data for control only
// have the temp output shortended to 3 digits only see the three "1" register bits below

set_register(MAX7219_REG_DECODE, 0b11100000);
//set_register(8,0); //0=Blindschalten
//set_register(8,1); 1="1"
//set_register(8,2); 2="-"
//set_register(8,DP); DP on

// Temp-Bits: 0(Zehner), 1(Einer), 2=Doppelpunkt ignorieren, 3(Zehntel), 4(Hundertstel) ignorieren

set_register(1,0);
set_register(2,0);
set_register(3,0);
set_register(4,0);
set_register(5,c);
set_register(6, tempString.charAt(3));
set_register(7, tempString.charAt(1)| DP); //DP aktivieren
set_register(8, tempString.charAt(0)); // ganz links
set_register(MAX7219_REG_SHUTDOWN, ON); // Turn On display
}

//——————-

void set_register(byte reg, byte value)
{
digitalWrite(MAX7219_CS, LOW);
shiftOut(MAX7219_DIN, MAX7219_CLK, MSBFIRST, reg);
shiftOut(MAX7219_DIN, MAX7219_CLK, MSBFIRST, value);
digitalWrite(MAX7219_CS, HIGH);

}

//——————-

void resetDisplay()
{
set_register(MAX7219_REG_SHUTDOWN, OFF); // turn off display
set_register(MAX7219_REG_DISPTEST, OFF); // turn off test mode
set_register(MAX7219_REG_INTENSITY, 0x01); // display intensity
}

// … display the DATE on the 7-segment display
void displayDate(String dateString)
{
set_register(MAX7219_REG_SHUTDOWN, OFF); // turn off display
set_register(MAX7219_REG_SCANLIMIT, 7); // scan limit 8 digits
set_register(MAX7219_REG_DECODE, 0b11111111); // decode all digits

set_register(1, dateString.charAt(4)| DP); // plus decimal point
set_register(2, dateString.charAt(3));
set_register(3, dateString.charAt(1)| DP);
set_register(4, dateString.charAt(0));
set_register(5, dateString.charAt(9));
set_register(6, dateString.charAt(8));
set_register(7, dateString.charAt(7));
set_register(8, dateString.charAt(6));
set_register(MAX7219_REG_SHUTDOWN, ON); // Turn on display
}

// display the time (hours, minutes) on the top row
// display the seconds on the second row
void displayTime(String timeString)
{
set_register(MAX7219_REG_SHUTDOWN, OFF); // turn off display
set_register(MAX7219_REG_SCANLIMIT, 5); // scan limit 6 digits

// reserve 6 digits (1-6) for the temp-Data,
// those with "0" (digit 7,8) are reserved for control data i.e. blank the digit by sending "0"

set_register(MAX7219_REG_DECODE, 0b00111111);

// Time-Bit 0,1, 2=Doppelpunkt ignore, 3,4, 5=Doppelpunkt ignore, 6,7 control data

set_register(1, timeString.charAt(4)| DP);
set_register(2, timeString.charAt(3));
set_register(3, timeString.charAt(1)| DP);
set_register(4, timeString.charAt(0));
set_register(5, timeString.charAt(7));
set_register(6, timeString.charAt(6));
set_register(MAX7219_REG_SHUTDOWN, ON); // Turn on display

}

http://alumni.media.mit.edu/~mellis/cellphone/

Thank you.
Stan Simon
ssimon333@hotmail.com

Wow !

Your majesty couldn’t just kindly ask, with a please ???