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Author Topic: My Arduino Doesn't Connect to the Computer  (Read 825 times)
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Please help!
I've been using Arduino for a while now (3 months) and recently I was trying to control some motors with the arduino via serial connection (aka USB).  The code was fine and without an external powersource the motors responded fine, but didn't move fast.  So I hooked the arduino up to an external power source (18v) and controlled the motors via the computer and USB.  It worked, however after a couple minutes the computer crashed and after I rebooted it, when I plugged the Arduino in again the power went on, but the computer did not read the Arduino.  I thought it was the cable so I got a new one, but the second cable didn't work either.  Can someone please help.  I can't do anything if I cannot upload code onto my arduino!
Thanks a lot for your help!
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Dee Why NSW
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It could be a power problem, or the results of one. Try running the Arduino with  some simple hello world example, not involving any motors or the like, and off another USB port.

I had several power problems when I changed the mother board. The new one was less tolerant about USB power.
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My arduino doesn't connect to teh computer at all.  I cannot upload any code to it what so ever.  So unfortunately I cannot follow your advice.
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Dee Why NSW
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Does the PC do d-ding when you connect the Arduino? If not, do other things work OK in that USB port?
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No, the PC doesn;t do the sound.  But other devices work on the USB ports.  Evry port is functining fine, but my arduino doesn't work on any.
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OK, I guess there no point in asking about any lights then, it looks pretty dead from here and I guess the 18 volts is the villain. My Etherten says it will work 6 - 20v maximum but I wouldn't be game to go over 12v.  It gets quite hot enough with 9v applied.
If it is dead, it may be only the regulators and immediate peripherals that are fried. You might therefore be able to salvage it by applying 5v to the 5v pin, thereby bypassing the damage. There should be something on this forum about that.
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What lights are you talking about? It still turns on when it is connected to the computer.  And does this mean that I cannot upload any more code onto tmy arduino.
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Dee Why NSW
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I was referring to the lights on the Arduino.

I assumed your problem was power, like me but perhaps with a sadder ending.

I asked about the d-ding because, if you hear it, it confirms the most important thing - the PC can see the Arduino.  We know it can't so, with all other things being kosher, it is dead.

Still assuming that power is the cause of death, I would not have expected to see lights on the Arduino.  If you can see lights on the Arduino, I assume it is a power light and this simply proves that a dead Arduino can still have a power light on.  I find this surprising but I think you need someone with more experience than me for further analysis. 

On reflection, I think the absence of d-ding and the presence of lights, is probably the worst combination.
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Thank you for all your help.  Well that stinks. Are you sure that that's it?  Do u know another resource that I can go to to potentially fix this problem or is that it. Furthermore is there anyway to self diagnose a dead arduino. Are there any "symptoms" so that I know the arduino is completely dead?
Thanks and if anyone else has insight into this problem please share.
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I just thought of something. Do you think that I fried my bootloader or USB port?  That could explain why the computer isnt reading it... just a thought...
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Dee Why NSW
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No, I not sure that's it. As I said
Quote
I find this surprising but I think you need someone with more experience than me for further analysis.
and I bet somebody has been through this before.

What I understand is:

1. The lights are on. This suggests power is getting through and the electronic components most likely to fail haven't.

2. The PC cannot detect the Arduino, no d-ding. This could be due to a failure at the Arduino USB port which indeed was caused by a power problem, but the power supply itself has survived.

I guess the second only makes sense if the damage was done when you tried to power everything through the USB, but you did have some results after you went to the 18v supply.

In the lack of better advice, I would closely examine the USB port, sight and smell. You should be able to test for continuity. If it is a USB "B" terminal, you might consider replacing it. That should be cheap and easy, but I think a mini port would be a very different proposition. You might even just wire an old USB cable to the board, bypassing the port.

Nothing vetured  = nothing gained.......


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Thanks for all your help. About "bypassing the USB" what do you mean? I have an arduino UNO and I don't know if that means I have a USB b port. Furthermore how would I replace the port on the arduino?  Sorry for all the quetions but i am a bit short on money and do not want to have to buy a new arduino.
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Thanks for all your help. About "bypassing the USB" what do you mean? I have an arduino UNO and I don't know if that means I have a USB b port. Furthermore how would I replace the port on the arduino?  Sorry for all the quetions but i am a bit short on money and do not want to have to buy a new arduino.

I am assuming the power is actually OK and the fault lies in the USB port, thereby offering a small chance of salvation. If the problem lies elsewhere, I assume there is no chance of salvation.  Wiki USB. The type "B" port is the square one and common  on Arduinos. It should be easy to unsolder it and a replacement should be about a dollar.  It should be easy to cut the plug off a cable and solder the cable to the board on the four USB holes, thereby saving the cost of the port. You could even wire the cable to the underside connections and leave the dead port in place, but it would be better to remove it. 

On the underside of the board, you may see near the USB port two pairs of little gold patches about 1x1.5mm. Both my Mega and my EtherTen have them.  I don't know what they are but I bet they are test points. They might even be fusible links.  You should inspect them closely for damage. If they are clearly damaged, soldering a new track over them may fix your problem.
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