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Topic: Need Help, strange serial failure (Read 537 times) previous topic - next topic


Sep 21, 2008, 12:44 pm Last Edit: Sep 21, 2008, 12:58 pm by Eliaspe Reason: 1
I tried to connect a motor with a transistor to the arduino. The C pin of the transistor I connected to the 3v3 pin the B pin  to Pin 11 and the E pin I connected to the motor. the other Motor-pin I connected to Ground.
Now I send PWM signals to the B pin of the transistor. The motor works. put during the moter turns, the serial port doesn´t work. That´s my code:

void setup(){

void loop(){
 static int v = 0;
 if (Serial.available()){
   char ch = Serial.read();
   switch (ch){
      case '0'...'9':
       v = v * 10 + ch - '0';

after the motor stops, I can´t send a second command to let the motor tun again.   :question :question :question

please answer

I mostly send "120s" or "180s"



I'm surprised the motor turns at all, and I'm also surprised you haven't burned out the USB chip.

The Arduino power supply is not designed for high current devices (like motors).  The 3.3V supply is from the FTDI USB adapter IC and is only capable of supplying a few tens of mV IIRC.  The 5V supply is typically from USB, where you have at most 500mV total.

I suspect the behavior you are seeing is because the excessive current draw of the motor is causing the ATmega and/or the FTDI to brown out and lock up.

You need a separate power supply for high current loads.  Check out this tutorial for more info.


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