Use an Arduino UNO. Program and upload a simple blinking:

// We will connect 5V of the big wireless coil here
int my_led =7;

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(my_led, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(my_led, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(my_led, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}

You can also use Analog:

// We will connect 5V of the big wireless coil here
int my_led =A0;

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(my_led, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  analogWrite(my_led, 255);   // turn the LED on (255 is the max voltage level)
  delay(1000);                       // wait for a second
  analogWrite(my_led, 0);    // turn the LED off by making the voltage 0  
  delay(1000);                       // wait for a second
}

Conect big Coil of the charger like this:

GND -> GND

5V -> pin 7 or pin A0

We will be talking about big coil and small coil. Spot the difference before start!

Solder the tip of the GND and 5V with conductive thread.

If you are using a sewing machine, choose a line pattern, in order to make it work as best as possible without wasting too much thread.

But you can also use a needle! this is encouraged.