Get UI Slider Value

I have a UI slider set to react to information from an Arduino. Is there a way to read in the value of the UI slider so that when the slider reaches a certain value I can then use that information in my script to trigger something?

UPDATE: I added the whole code so you can see what it is I may be messing up.

    using UnityEngine;
 using UnityEngine.UI;
 using System.Collections;
 using System.IO.Ports;
 using System.Threading;
 
 
 public class Sending : MonoBehaviour {
 
     //int sysHour = System.DateTime.Now.Hour;
     
     //Random Clips
     //public AudioClip[] darknessDetectedVoices;
     //public AudioClip[] brightnessDetectedVoices;
 
     public AudioClip[] BrightnessAudioClips;
     public AudioClip[] DarknessAudioClips;
 
     //DTMF Tones
     public AudioClip DTMFtone01;
     public AudioSource source;
 
     //UI Text Reference
     //public Text MessageCentreText;
 
     //_isPlayingSound is true when a sound is currently playing - just as the name suggests.
     private bool _isPlayingSound;
 
     public GameObject LightSlider;
     public Slider slider;
     Slider lightSlider;
     public static Sending sending;
 
     //public static SerialPort sp = new SerialPort("COM4", 9600, Parity.None, 8, StopBits.One);
     public static SerialPort sp = new SerialPort("/dev/cu.wchusbserial1420", 115200); //115200
 
     public string message2;
 
     //Button States
     bool button01State = false;
 
 
     void Awake () {
         if (sending == null) {
             DontDestroyOnLoad (gameObject);
             sending = this;
         } else if (sending != this) {
             Destroy (gameObject);
         }
 }
 
 
     float timePassed = 0.0f;
     // Use this for initialization
     void Start () {
         OpenConnection();
         lightSlider = GetComponent<Slider> ();
         if(slider == null) slider = GetComponent<Slider>(); // search slider in this object if its not set in unity inspector
         if(source == null) source = GetComponent<AudioSource>(); // search audiosource in this object if its not set in unity inspector
 
         }
     
     // Update is called once per frame
     void Update () {
 
         //timePassed+=Time.deltaTime;
         //if(timePassed>=0.2f){
 
             //print("BytesToRead" +sp.BytesToRead);
             message2 = sp.ReadLine();
             //print(message2);
         //    timePassed = 0.0f;
         //}
 
         /*if (message2!="") {
             print("called");
             lightMeUp(message2);
             //MessageCentreText.text = "LIGHT VALUE CHANGED";
         }*/
         ///////////////////
         string message = sp.ReadLine(); //get the message...
         if(message == "") return; //if its empty stop right here
         // parse the input to a float and normalize it (range 0..1) (we could do this already in the Arduino)
         // I dont know if a higher value means darker, if so add a "1 - " right after the "="
 
         float input = /* 1 - */ float.Parse (message) / 100f;
         // set the slider to the value
         slider.value = input;
         // after the slider is updated, we can check for the other things for example play sounds:
 
         if (source.isPlaying) return; // if we are playing a sound stop here
 
         // else check if we need to play a sound and do it
         if (slider.value > 0.8f)
             source.PlayOneShot (BrightnessAudioClips [Random.Range (0, BrightnessAudioClips.Length)]);
         else if (slider.value < 0.2f)
             source.PlayOneShot (DarknessAudioClips [Random.Range (DarknessAudioClips.Length)]);
         
 
         //////////////////
 
     }
 
     public void OpenConnection() 
     {
        if (sp != null) 
        {
          if (sp.IsOpen) 
          {
           sp.Close();
           print("Closing port, because it was already open!");
          }
          else 
          {
           sp.Open();  // opens the connection
           sp.ReadTimeout = 16;  // sets the timeout value before reporting error
           print("Port Opened!");
         //        message = "Port Opened!";
          }
        }
        else 
        {
          if (sp.IsOpen)
          {
           print("Port is already open");
          }
          else 
          {
           print("Port == null");
          }
        }
     }
 
     void OnApplicationQuit() 
     {
        sp.Close();
     }
 
     //Movie Player Toggle
     public static void sendYellow(){
         sp.Write("y");
     }
 
     //Analyzer Toggle
     public static void sendYellow2(){
         sp.Write("A");
     }
 
     //Pod 7DLA Toggle
     public static void sendYellow3(){
         sp.Write("D");
     }
 
     //Pod PENG Toggle
     public static void sendYellow4(){
         sp.Write("P");
     }
 
     //Pod 6RM Toggle
     public static void sendYellow5(){
         sp.Write("6");
     }
 
     //Pod Laser Toggle
     public static void sendYellow6(){
         sp.Write("Z");
     }
 
 
     //Auto Phone Toggle
     public static void sendGreen(){
         sp.Write("g");
         //sp.Write("\n");
     }
     
     //Oil Slick Toggle
     public static void sendRed(){
         sp.Write("r");
     }
 
     //Surveillance Mode Toggle
     public static void sendBlue(){ 
         sp.Write("b");
     }
     
     //Scanner Toggle
     public static void sendRed2(){
         sp.Write("1");
     }
 
     //Fog Lights Toggle
     public static void sendGreen2(){
         sp.Write("f");
     }
 
     //Head Lights Toggle
     public static void sendGreen3(){
         sp.Write("h");
     }
 
     //Hight Beams Toggle
     public static void sendWhite(){
         sp.Write("H");
     }
 
     //Rear Hatch Popper
     public static void sendPulse1(){
         sp.Write("p");
     }
     
     //Grappling Hook Launch
     public static void sendPulse2(){
         sp.Write("q");
     }
 
     //Auto Doors Right Pulse
     public static void sendPulse3(){
         sp.Write("R");
     }
 
     //Auto Doors Left Pulse
     public static void sendPulse4(){
         sp.Write("L");
     }
 
     //Startup and Shutdown Pulse
     public static void sendPulse5(){
         sp.Write("S");
     }
 
 
 
     /*void lightMeUp(string message){
         //If there is a sound currently playing, return immediately so we don't play another sound simultaneously.
         //if(_isPlayingSound) is shorthand for if(_isPlayingSound == true), in case you where wondering.
         if (_isPlayingSound)
             return;
         print (message);
         float fl = float.Parse (message) / 100.0f;
         fl = 1.0f - fl;
         LightSlider.GetComponent<Slider>().value = fl;
         //Do something Here if Light Value / UI Slide on the LDR is near Darkness
 
 
         if (LightSlider.GetComponent<Slider> ().value <= 0.1) {
             Debug.Log ("DARKNESS DETECTED");
             //Pick a random sound.
             AudioClip randomClip = darknessDetectedVoices [UnityEngine.Random.Range (0, darknessDetectedVoices.Length)];
             //Play that sound.
             GetComponent<AudioSource> ().PlayOneShot (randomClip);
             //Flag that we are currently playing a sound.
             _isPlayingSound = true;
             //Start a coroutine that will set the flag to false once the sound stops playing, so we can start playing a new sound.
             StartCoroutine (RunResetIsPlayingSoundFlag (randomClip.length));
             if (_isPlayingSound)
                 return;
         }
             
         //Do Something Here if the Light Value on the LDR is near Daylight brightness
         else if (LightSlider.GetComponent<Slider> ().value >= 0.6) {
             Debug.Log ("NEAR DAYLIGHT DETECTED");
             //Pick a random sound.
             AudioClip randomClip2 = brightnessDetectedVoices [UnityEngine.Random.Range (0, brightnessDetectedVoices.Length)];
             //Play that sound.
             GetComponent<AudioSource> ().PlayOneShot (randomClip2);
             //Flag that we are currently playing a sound.
             _isPlayingSound = true;
             //Start a coroutine that will set the flag to false once the sound stops playing, so we can start playing a new sound.
             StartCoroutine (RunResetIsPlayingSoundFlag (randomClip2.length));
             if (_isPlayingSound)
                 return;
         }
         //BONUS if Possible Do something if the LDR is deliberately played with like waving hand over or blocking and un blocking the sensor.
 
     }
     private IEnumerator RunResetIsPlayingSoundFlag(float soundDuration)
     {
         //Wait until the sound finishes playing.
         yield return new WaitForSeconds(soundDuration);
         //yield return new WaitForSeconds(10.0f);
         //Disable the _isPlayingSound flag, so we can play a new sound since this one is over.
         _isPlayingSound = false;
     
     }    */
 
     //Comlink Clock Close Button
     public void  GoMainScreen(){
         StartCoroutine(LoadT3());
         GetComponent<AudioSource>().PlayOneShot(DTMFtone01);
     }
     
     IEnumerator LoadT3(){
         yield return new WaitForSeconds(0.0f); // wait time
 
     }
 
 
 }