Yes, that worked... I downloaded master.zip and replaced the current Liquid Crystal folder with the new one. Restarted IDE and was able to compile and upload the sketch. Thank you!

Here is my first prototype of a working solution for a timing light: ( neopixal timing light):https://youtu.be/b3TDGKUS05I

Thank you for direction @mfalkvidd !

I am attempting to set up a moisture sensor, using the diagram and included sketch (https://www.mysensors.org/build/moisture). The diagram shows pin 3 for data but the sketch references d6 and d7. I don't see any reference to pin 3 there. I am not clear why there are references to d6 and d7 when my sensor only has a single data pin.

Thank you for your reply. I did resolve the problem and wanted to share what I did, in hopes of helping other newbies.
Firstly, I double checked the wiring, compared it to the working gateway and it seemed to be fine but still did not work.

I ran across this post and it turned out to be ideal for my situation:
https://forum.arduino.cc/index.php?topic=421081.0

Got the two radios communicating in a simplistic configuration and once working, uploaded mysensors sketches and the radios continued to work correctly. Maybe dismantling and reconnecting was the fix. Not sure, but things are working now. Thank you for a great resource of information and projects!

@bjacobse That seems to be the ticket! I will update the project as I learn more and develop a prototype.

Version 0.94.4

Thank you for the recommendation. I learned to look there through trial-and-error but the relay does not show up.

However, everything works as expected (4 relays show up in Unused Entities) when I use the following sketch:

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// Override Setting for Manual Node ID to 2
#define MY_NODE_ID 2

// Enable debug prints to serial monitor
#define MY_DEBUG 

// Enable and select radio type attached
#define MY_RADIO_NRF24

// Enable repeater functionality for this node
#define MY_REPEATER_FEATURE

#include <SPI.h>
#include <MySensors.h>

#define RELAY_1  3          // Arduino Digital I/O pin number for first relay (second on pin+1 etc)
#define NUMBER_OF_RELAYS 4  // Total number of attached relays: 4

// Opto Relay Module I was using Active Low - Low (0):ON, High (1): OFF
#define RELAY_ON 0          // GPIO value to write to turn on attached relay
#define RELAY_OFF 1         // GPIO value to write to turn off attached relay

bool initialValueSent = false;

//Init MyMessage for Each Child ID
MyMessage msg1(1, V_LIGHT);
MyMessage msg2(2, V_LIGHT);
MyMessage msg3(3, V_LIGHT);
MyMessage msg4(4, V_LIGHT);

void before() { 
  for (int sensor=1, pin=RELAY_1; sensor<=NUMBER_OF_RELAYS;sensor++, pin++) {
    // Then set relay pins in output mode
    pinMode(pin, OUTPUT);   
    // Set relay to last known state (using eeprom storage) 
    digitalWrite(pin, loadState(sensor)?RELAY_ON:RELAY_OFF);
  }
}

void setup() {
  
}

void presentation()  
{   
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Relay", "1.0");

  for (int sensor=1, pin=RELAY_1; sensor<=NUMBER_OF_RELAYS;sensor++, pin++) {
    // Register all sensors to gw (they will be created as child devices)
    present(sensor, S_LIGHT);
  }
}


void loop() 
{
  if (!initialValueSent) {
    Serial.println("Sending initial value");
    send(msg1.set(loadState(1)?RELAY_OFF:RELAY_ON),true);
    wait(1000);
    send(msg2.set(loadState(2)?RELAY_OFF:RELAY_ON),true);
    wait(1000);
    send(msg3.set(loadState(3)?RELAY_OFF:RELAY_ON),true);
    wait(1000);
    send(msg4.set(loadState(4)?RELAY_OFF:RELAY_ON),true);
    wait(1000);
    Serial.println("Sending initial value: Completed");
    wait(5000);
  }
}

void receive(const MyMessage &message) {
  Serial.println("=============== Receive Start =======================");
  if (message.isAck()) {
     Serial.println(">>>>> ACK <<<<<");
     Serial.println("This is an ack from gateway");
     Serial.println("<<<<<< ACK >>>>>>");
  }
  // We only expect one type of message from controller. But we better check anyway.
  if (message.type==V_LIGHT) {
    Serial.println(">>>>> V_LIGHT <<<<<");
    if (!initialValueSent) {
      Serial.println("Receiving initial value from controller");
      initialValueSent = true;
    }
     // Update relay state to HA
     digitalWrite(message.sensor-1+RELAY_1, message.getBool()?RELAY_ON:RELAY_OFF);
     switch (message.sensor) {
        case 1:
          Serial.print("Incoming change for sensor 1");
          send(msg1.set(message.getBool()?RELAY_OFF:RELAY_ON));
          break;
        case 2:
          Serial.print("Incoming change for sensor 2");
          send(msg2.set(message.getBool()?RELAY_OFF:RELAY_ON));
          break;
        case 3:
          Serial.print("Incoming change for sensor 3");
          send(msg3.set(message.getBool()?RELAY_OFF:RELAY_ON));
          break;
        case 4:
          Serial.print("Incoming change for sensor 4");
          send(msg4.set(message.getBool()?RELAY_OFF:RELAY_ON));
          break;                    
        default: 
          Serial.println("Default Case: Receiving Other Sensor Child ID");
        break;
     }
     // Store state in Arduino eeprom
     saveState(message.sensor, message.getBool());
     Serial.print("Saved State for sensor: ");
     Serial.print( message.sensor);
     Serial.print(", New status: ");
     Serial.println(message.getBool());
     Serial.println("<<<<<< V_LIGHT >>>>>>");
   } 
   Serial.println("=============== Receive END =======================");
}```

Apologies!! I kept getting errors when using that board, so used another. I am on a new worksation and it turns out python was not installed. The error ceased after I installed. The sketch works fine now.

Looks like I will need to tone things down a bit because of time limitations and complexities. I will revisit my original concept after the upcoming concert, when I will not be under time restraints.

I have decided I will use the following lights: WS2812B LED Strip DC 5V Black White PCB Smart Addressable Pixel WS2812 IC 30, controlled wirelessly.

My plan would be to create a single control unit (rather than a sensor triggered by frequencies) that will send a wireless signal (numeric value 1-30) back to my Homeassistant control box which in-turn will signal each sensor device to execute a corresponding light show event. Homeassistant would be configured to execute code commands similar to what I have below.

Code
void startShow(int i) {
  switch(i){
    case 0: colorWipe(strip.Color(0, 0, 0), 50);    // Black/off
            break;
    case 1: colorWipe(strip.Color(0, 43, 0), 50);  // Green
            break;
    case 2: colorWipe(strip.Color(34, 34, 0), 50);  // Yellow
            break;
    case 3: colorWipe(strip.Color(43, 0, 0), 50);  // Red
            break;
    case 4:
          theaterChase(strip.Color(127,   0,   0), 450); // Red
          break;

That all seems doable, correct? Couple questions: I need to run this all by 9 volt (needs to last 2 hr). What would be the best board to use (Still a nano?) ? Is the NRF24L01+ 2.4GHz radio the best wireless solution to use in this case? We will be lighting up 25 violin bows as per the pic
Pic link

Apologies!! I kept getting errors when using that board, so used another. I am on a new worksation and it turns out python was not installed. The error ceased after I installed. The sketch works fine now.

Those are the ports I am using on my ESP8266 NodeMCU

I'm confused. That is from my sketch. Do I add another reference?

Isn't that what this is for?

// Select SDA and SCL pins for I2C communication
const uint8_t scl = D6;
const uint8_t sda = D7;

Are you speaking of a comment made on the tutorial? I don't see that instruction in the sketch. I did try to change to numerical values for D1 & D2 but the error followed.

I am starting to ding around with my project, using the following tutorial sketch but getting an error and not finding how to fix it. Is it just a coding error?

exit status 1
'D6' was not declared in this scope```

#include <Wire.h>

// MPU6050 Slave Device Address
const uint8_t MPU6050SlaveAddress = 0x68;

// Select SDA and SCL pins for I2C communication 
const uint8_t scl = D6;
const uint8_t sda = D7;

// sensitivity scale factor respective to full scale setting provided in datasheet 
const uint16_t AccelScaleFactor = 16384;
const uint16_t GyroScaleFactor = 131;

// MPU6050 few configuration register addresses
const uint8_t MPU6050_REGISTER_SMPLRT_DIV   =  0x19;
const uint8_t MPU6050_REGISTER_USER_CTRL    =  0x6A;
const uint8_t MPU6050_REGISTER_PWR_MGMT_1   =  0x6B;
const uint8_t MPU6050_REGISTER_PWR_MGMT_2   =  0x6C;
const uint8_t MPU6050_REGISTER_CONFIG       =  0x1A;
const uint8_t MPU6050_REGISTER_GYRO_CONFIG  =  0x1B;
const uint8_t MPU6050_REGISTER_ACCEL_CONFIG =  0x1C;
const uint8_t MPU6050_REGISTER_FIFO_EN      =  0x23;
const uint8_t MPU6050_REGISTER_INT_ENABLE   =  0x38;
const uint8_t MPU6050_REGISTER_ACCEL_XOUT_H =  0x3B;
const uint8_t MPU6050_REGISTER_SIGNAL_PATH_RESET  = 0x68;

int16_t AccelX, AccelY, AccelZ, Temperature, GyroX, GyroY, GyroZ;

void setup() {
  Serial.begin(9600);
  Wire.begin(sda, scl);
  MPU6050_Init();
}

void loop() {
  double Ax, Ay, Az, T, Gx, Gy, Gz;
  
  Read_RawValue(MPU6050SlaveAddress, MPU6050_REGISTER_ACCEL_XOUT_H);
  
  //divide each with their sensitivity scale factor
  Ax = (double)AccelX/AccelScaleFactor;
  Ay = (double)AccelY/AccelScaleFactor;
  Az = (double)AccelZ/AccelScaleFactor;
  T = (double)Temperature/340+36.53; //temperature formula
  Gx = (double)GyroX/GyroScaleFactor;
  Gy = (double)GyroY/GyroScaleFactor;
  Gz = (double)GyroZ/GyroScaleFactor;

  Serial.print("Ax: "); Serial.print(Ax);
  Serial.print(" Ay: "); Serial.print(Ay);
  Serial.print(" Az: "); Serial.print(Az);
  Serial.print(" T: "); Serial.print(T);
  Serial.print(" Gx: "); Serial.print(Gx);
  Serial.print(" Gy: "); Serial.print(Gy);
  Serial.print(" Gz: "); Serial.println(Gz);

  delay(100);
}

void I2C_Write(uint8_t deviceAddress, uint8_t regAddress, uint8_t data){
  Wire.beginTransmission(deviceAddress);
  Wire.write(regAddress);
  Wire.write(data);
  Wire.endTransmission();
}

// read all 14 register
void Read_RawValue(uint8_t deviceAddress, uint8_t regAddress){
  Wire.beginTransmission(deviceAddress);
  Wire.write(regAddress);
  Wire.endTransmission();
  Wire.requestFrom(deviceAddress, (uint8_t)14);
  AccelX = (((int16_t)Wire.read()<<8) | Wire.read());
  AccelY = (((int16_t)Wire.read()<<8) | Wire.read());
  AccelZ = (((int16_t)Wire.read()<<8) | Wire.read());
  Temperature = (((int16_t)Wire.read()<<8) | Wire.read());
  GyroX = (((int16_t)Wire.read()<<8) | Wire.read());
  GyroY = (((int16_t)Wire.read()<<8) | Wire.read());
  GyroZ = (((int16_t)Wire.read()<<8) | Wire.read());
}

//configure MPU6050
void MPU6050_Init(){
  delay(150);
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_SMPLRT_DIV, 0x07);
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_PWR_MGMT_1, 0x01);
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_PWR_MGMT_2, 0x00);
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_CONFIG, 0x00);
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_GYRO_CONFIG, 0x00);//set +/-250 degree/second full scale
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_ACCEL_CONFIG, 0x00);// set +/- 2g full scale
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_FIFO_EN, 0x00);
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_INT_ENABLE, 0x01);
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_SIGNAL_PATH_RESET, 0x00);
  I2C_Write(MPU6050SlaveAddress, MPU6050_REGISTER_USER_CTRL, 0x00);
}

My violin instructor leads a strings group of mostly kids and some adults. They put on an annual concert for the community, which is always well attended. I have been speaking with him about possibly creating a small light show for their next concert and he is very interested in the idea. In the past he has strung small lights on the bows of the instruments (Violins and Cellos), which the audience really enjoyed. I would like to do something a little more advanced and either use sensors on the bows with programmable rgb lights (along the lines of a neopixal led light), that would change colors base on the frequency of the note being played by a single violin, cello, or base. (A=440hz, B=493hz, C=523hz, etc...), or I would like to use the same approach to create an LED fiber, ceiling light show. I would like to make it appear as if the lights are flowing or dancing with the music. In my mind, I imagine using a controller sending out commands to the individual sensors, based on the readings of a single sensor picking up on the note being played.
of course, there is no budget for this but I do have a HomeAssistant controller box I can use. What other sensor solutions would be required to produce this project? I do know we will want to control the intensity of the lights as well as color.
Thank you for sharing your ideas!

My sensors arrived in the mail the other day. For simplicity, I will be using the following devices:
ESP8266 microcontroller NodeMCU Lua V3 WiFi with CH340G
Wit-fancy Arduino GY-521 MPU-6050 Module 3 Axis analog gyro sensors 3 Axis Accelerometer Module

Since my dad is not very mobile and will always be with my mom when they leave the house, I have the luxury of using their home wifi to send out alert messages and do not need to be concerned about sending alerts when they are away from the house.

Hope to get started working through things in the next few days.

@bjacobse In the case of a google box, you would need something throughout the house, as well as in the garage and shop. A unit strapped to his belt that can reach wifi should work well. He does not leave the house without my mom, so she would be aware of his state while they are away from the house.