Arduino Uno troubleshooting

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Hapka
 
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Arduino Uno troubleshooting

Post by Hapka »

I have a set of arduino uno (real ones from Adafruit not fakes), all have been heavily used in robotics class and one is misbehaving.

When I connect it to a windows 7 pc with arduino open, the green power LED lights continuously, and the orange LED blinks slowly, but the serial port option on the tools menu is greyed out. I checked the usb cord with another board and that works, I tried the board on three different windows 7 machine with the same result, but the board works perfectly on my macbook pro. I loaded blink and changed the timing to verify that.

Any suggestions for getting it to work again with the windows computers?

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Franklin97355
 
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Re: Arduino Uno troubleshooting

Post by Franklin97355 »

Which version Arduino is it?

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Hapka
 
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Re: Arduino Uno troubleshooting

Post by Hapka »

Revision 3

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adafruit_support_bill
 
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Re: Arduino Uno troubleshooting

Post by adafruit_support_bill »

If you open up Device Manager and plug in the problem UNO, does any new device appear? If so, what kid of device does it show up as.

You might also try a different cable. With repeated plugging and unplugging, it is possible that the contacts on either the cable or the board can get worn or bent. Sometimes a different cable will solve the problem.

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Hapka
 
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Re: Arduino Uno troubleshooting

Post by Hapka »

Thanks! It seems to be a weak contact, I tried different cables but just seems flakey. It either shows normally in device manager or not at all. Do you think resoldering the usb socket on the board might help? I have a kid in class who is very good at surface mount soldering. Do you know if there is reference for using test points on the back of the board to diagnose if that is the problem?

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adafruit_support_bill
 
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Re: Arduino Uno troubleshooting

Post by adafruit_support_bill »

In most cases, it is not the soldering, it is the contacts inside the plugs and/or the jacks. I coach several HS robotics teams and have observed that the students tend to be pretty rough when plugging and unplugging cables. As a result, they have had lots of connection problems.

In some cases swapping cables will solve the problem. But once the jack is worn out, even a good cable won't help. If you have someone that is good at surface-mount soldering, you could have them try soldering a new jack onto the board.

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Hapka
 
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Re: Arduino Uno troubleshooting

Post by Hapka »

I wiggled some cords and cautioned the group to be gentle when plugging and unplugging their boards and all has been well since.

Now we have added motor shields (1438) and DC motors. The group is currently working on following a colored line on the floor using photoresistors (161) some with LED lighting and some without lighting and another error has cropped up. At first there was no consistent set of symptons but I think I have it narrowed down to a cause and effect.

We are using dell optiplex 780 desktops with windows 7 and arduino with the adafruit motorshield library added in. The group successfully drove in a straight line earlier in the semester so all systems were operational recently.

Here is the problem: When the group plugs in their arduino uno, even just to load blink to set the setup, under the tools menu, port, there will be port 1 and port 9, but they get an avrdude connection error. We try unplugging and reconnecting the board, switching usb ports (our computers have two on the front and two on the side of the monitor), and when the board is disconnected the menu still offers port 1 and port 9. Normally when the board is not connected the port menu is greyed out.

I striped the unos down to just them and a usb cord and they load blink fine on other computers, but once a computer gets "confused" about finding the device it never seems to be able to go back to finding the board.

Could the problem be that the circuit is connected incorrectly to power, ground, or a pin and somehow that is affecting their ability to connect to the computer? The robots are powered by two 9V batteries, one connected to the power of the arduino uno and one to the motor shield to power the motors. I have a dell latitude laptop with windows 7 and it never seems to have the permanent lack of connection issue that the desktops have.

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Re: Arduino Uno troubleshooting

Post by adafruit_support_bill »

What ports do you see in DeviceManager when you plug them in?

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Hapka
 
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Re: Arduino Uno troubleshooting

Post by Hapka »

I see port 12 in device manager, and port 12 is listed on the tools menu under ports but I get an avrdude error when trying to load a program.

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Re: Arduino Uno troubleshooting

Post by adafruit_support_bill »

I see port 12 in device manager
What kind of device is port 12 identified as?

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Hapka
 
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Re: Arduino Uno troubleshooting

Post by Hapka »

It correctly identifies as an arduino uno. I explained the issue to one of my robotics team students and we found that the lack of connection is directly caused by some sort of "bad wiring" on the motor controller but we thought we had it wired correctly. Connecting and disconnecting the power and ground wires allowed and prevented connection to the computer. We had three photoresistors connected one end of ground the other to 5V and a pin through a 330 ohm resistor. No external power connected at the time. Two DC motors were wired to the motor controller in M3 and M4 and the bypass was connected so the motors were powered from the board (the small plastic clip that comes with the motor shield).

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Re: Arduino Uno troubleshooting

Post by adafruit_support_bill »

Interesting. I cold see possible grounding issues if you were using an external supply. But from your description, I don't see anything that should cause a communication problem.

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Hapka
 
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Re: Arduino Uno troubleshooting

Post by Hapka »

I found part of a solution, the "bad" computer that was not communicating turned out to have a teeny tiny piece of paper stuck in its USB port so that helped a lot.

I think a have a few damaged motor shields, which I suspect was due to either my "expert" soldering of stacking headers or rough handling by the kids. I'm going to desolder them, clean them up, and see if that saves them. I'm testing the shield just by connecting a DC motor and running the test program that comes with the library, is that the most efficient way? If nothing else it will give me soldering practice.

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Re: Arduino Uno troubleshooting

Post by adafruit_support_bill »

The example program is a good test for basic shield operation. Other than assembly issues the majority of motor shield problems are due to overloads. Sticking with smaller motors avoids most of those, but it is still possible to damage a bridge by short-circuiting the outputs.

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