I have a sketch, which runs without issues, when i start it while the PC is connected. I have some serial outputs and everything is fine.
Then i have removed all the serial prints and transfer the sketch to the arduino in order to run it without the pc.

#include <ThingSpeak.h>
#include <SPI.h>
#include <WiFi101.h>
#include “arduino_secrets.h”
char ssid = SECRET_SSID; // your network SSID (name)
char pass = SECRET_PASS; // your network password (use for WPA, or use as key for WEP)
int status = WL_IDLE_STATUS; // the WiFi radio’s status
//für ThingSpeak können nur daten alle 15s übertragen werden
#define SpeedTime 1000
#define SendIntervall 15000 //15000 für Thingspeak
#define NumberofPulses 2
#define Max_speed 200 //km/h
unsigned long myChannelNumber = 1234;
const char * myWriteAPIKey = “xxxx”;
WiFiClient client;
//Arduino anemometer sketch*************
const byte interruptPin = 1; //anemomter input to digital pin(3 mega und 1 mkr)
volatile unsigned long sTime = 0; //stores start time for wind speed calculation
unsigned long dataTimer = 0; //used to track how often to communicate data
volatile float pulseTime = 0; //stores time between one anemomter relay closing and the next
volatile float culPulseTime = 0; //stores cumulative pulsetimes for averaging
volatile bool start = true; //tracks when a new anemometer measurement starts
volatile unsigned int avgWindCount = 0; //stores anemometer relay counts for doing average wind speed
volatile unsigned int myInterrCount = 0; //stores anemometer relay counts for doing average wind speed
float aSetting = 70.0; //wind speed setting to signal alarm
float HSF = 3.013;
float LSF = 1.761;
float Max = 0;
float Min = -1;
float Average = 0;
int iNumAverage = 0;
unsigned long aTime = 0;
void setup() {
delay(2000);//Delay to let system boot
pinMode(6, OUTPUT); //setup LED pin to signal high wind alarm condition
pinMode(interruptPin, INPUT_PULLUP); //set interrupt pin to input pullup
attachInterrupt(interruptPin, anemometerISR, RISING); //setup interrupt on anemometer input pin, interrupt will occur whenever falling edge is detected
dataTimer = millis(); //reset loop timer
aTime = millis();
// check for the presence of the shield:
// attempt to connect to WiFi network:
while ( status != WL_CONNECTED) {
// Connect to WPA/WPA2 network:
status = WiFi.begin(ssid, pass);
// wait 10 seconds for connection:
// wait 10 seconds for connection:
// you’re connected now, so print out the data:

void loop() {
unsigned long rTime = millis();
if ((rTime - sTime) > 2500) pulseTime = 0; //if the wind speed has dropped below 1MPH than set it to zero
if ((rTime - dataTimer) > SpeedTime) { //See if it is time to transmit
detachInterrupt(interruptPin); //shut off wind speed measurement interrupt until done communication
float aWSpeed = getAvgWindSpeed(culPulseTime, avgWindCount); //calculate average wind speed
if (aWSpeed >= aSetting) {
digitalWrite(6, HIGH);// high speed wind detected so turn the LED on
} else {
digitalWrite(6, LOW);//no alarm so ensure LED is off
culPulseTime = 0; //reset cumulative pulse counter
avgWindCount = 0; //reset average wind count
float aFreq = 0; //set to zero initially
if (pulseTime > 0.0) aFreq = getAnemometerFreq(pulseTime); //calculate frequency in Hz of anemometer, only if pulsetime is non-zero
// Min/MAX/AVERAGE bilden
Average = Average + aWSpeed;
if (aWSpeed > Max) {
Max = aWSpeed;
if (aWSpeed < Min || Min < 0) {
Min = aWSpeed;
start = true; //reset start variable in case we missed wind data while communicating current data out
attachInterrupt(digitalPinToInterrupt(interruptPin), anemometerISR, RISING); //turn interrupt back on
dataTimer = millis(); //reset loop timer
// Daten an Thing speed alle SendIntervall schicken
if ((rTime - aTime) > SendIntervall) {
Average = Average / iNumAverage;
// schicke Daten
// Daten an Thingspeak
ThingSpeak.setField(1, Max);
ThingSpeak.setField(2, Min);
ThingSpeak.setField(3, Average);
ThingSpeak.writeFields(myChannelNumber, myWriteAPIKey);
//Reset der Zähler
Max = 0;
Min = -1;
Average = 0;
iNumAverage = 0;
aTime = millis();

//using time between anemometer pulses calculate frequency of anemometer
float getAnemometerFreq(float pTime) {
return 1 / ( pTime * NumberofPulses); //*2 wegen der Anzahl der Signale pro Umdrehung
float getWindMPH(float freq) {
return LSF / (1 + freq) + HSF * freq;
//Calculates average wind speed over given time period
float getAvgWindSpeed(float cPulse, int per) {
if (per) return getWindMPH(getAnemometerFreq((float)(cPulse / per)));
else return 0; //average wind speed is zero and we can’t divide by zero

void anemometerISR() {
unsigned long cTime = millis(); //get current time
if (!start) { //This is not the first pulse and we are not at 0 MPH so calculate time between pulses
pulseTime = (float)(cTime - sTime) / 1000;
if (pulseTime > 0.007) {
culPulseTime += pulseTime;
sTime = cTime;
start = false;
} else {
sTime = cTime;
start = false;

It does not work? Can you please help!!!

how are things powered ? and (important) make sure grounds are connected between your board and external devices

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