user11019: I am working on an esp8266 and I am connecting it with Arduino Uno. I have programmed the Arduino but when I write AT command on the serial monitor it doesn't show anything.The connections which i have made are:
tx uno - rx esp
rx uno - tx esp
gnd uno -gnd esp
vcc and ch_pd - 3.3v supply

I am using an external supply and not the 3.3v from the Arduino.
I need help with this.

user7628: Be careful, you could fry your ESP like that.  You need to get the signal lines down to 3.3V, not the 5V used by the Arduino Uno.  There are many ways to do this, from voltage dividers, to transistors, or you can use a 3.3v Arduino Pro Micro.  I would also recommend starting out with just a 3.3v FTDI board, and interface that directly to the ESP to remove the Arduino and its code from the picture.  
I would also make sure that your grounds on the external supply and the Arduino are tied together, or just power the ESP from the 3.3v out of the Arduino.  
Other than that, double check your baud rate, some come shipped at 9600, some at 115200, and i'm sure that there are others out there too shipping at different baud rates.  

11019: <p>I am working on an esp8266 and I am connecting it with Arduino Uno. I have programmed the Arduino but when I write AT command on the serial monitor it doesn't show anything.The connections which i have made are:</p>

<pre><code>tx uno - rx esp
rx uno - tx esp
gnd uno -gnd esp
vcc and ch_pd - 3.3v supply
</code></pre>

<p>I am using an external supply and not the 3.3v from the Arduino.
I need help with this.</p>
 7628: <p>Be careful, you could fry your ESP like that.  You need to get the signal lines down to 3.3V, not the 5V used by the Arduino Uno.  There are many ways to do this, from voltage dividers, to transistors, or you can use a 3.3v Arduino Pro Micro.  I would also recommend starting out with just a 3.3v FTDI board, and interface that directly to the ESP to remove the Arduino and its code from the picture.  </p>

<p>I would also make sure that your grounds on the external supply and the Arduino are tied together, or just power the ESP from the 3.3v out of the Arduino.  </p>

<p>Other than that, double check your baud rate, some come shipped at 9600, some at 115200, and i'm sure that there are others out there too shipping at different baud rates.  </p>
