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I am trying to use the official arduino wifi shield, It works occasionally, but most of the time (when running the WiFi web server example code, or my derivitave program, it outputs WiFi shield not present on the terminal. I have tried updating the firmware several times, but it has not fixed the problem. Is the wifi shield always this unreliable? What can I do to fix it?

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Are you using a Uno rev3? See arduino.cc/en/Main/arduinoBoardUno for differences between Revs-1/2/3 – ForgeMonkey Jul 3 '15 at 19:55
    
yes, I got an r3 Uno just for use with this project (although I also got it intermittently working with an r2 uno (using wires to compensate for missing pins, before the firmware update). – Patrick L Jul 3 '15 at 19:58
    
also, it seems to be getting worse, I haven't been able to get it to detect the shield at all for the last hour :( – Patrick L Jul 3 '15 at 19:59
    
Ok, what are you powering the setup from? The other main possibility I can think of is that the WiFi shield is drawing too much power for your USB port (some PCs can limit to 100mA). You could try a wall adapter. – ForgeMonkey Jul 3 '15 at 20:01
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Connecting the LEDs to Vin while powered from the USB is not good. You are feeding power backwards through the 5V regulator. You should be running the LEDs from the +5V pin of the Arduino. – Majenko Jul 3 '15 at 20:25
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Be sure the shield is not shorting out on the metal USB socket on the Arduino board. I don't know if this is still an issue but I've seen many Arduino boards with black electric tape on the top of the USB socket to insulate it from shorting out the shield.

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