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Author Topic: Serial connection dropping early while drawing.
Canned
Newbie
Posts: 1
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Post Serial connection dropping early while drawing.
on: May 22, 2014, 11:03
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Hello all,
Hoping I can find an answer from the valuable experience on here!

I've built a polargraph using:
Arduino Uno
Clone Motor shield (DK Electronics - this appears to be the same design as the Adafruit motor shield [V1])
2 x stepper motors (4V, 1A, 1.8 .deg step, bipolar)
and beaded cord nicked from my mam's blinds! (I need to get some longer ones to make use of the full machine size)

I have installed all the necessary bits (controller, arduino polargraph server, processing etc) but I have a problem.

The only complete drawings I've yet managed are trace captures.

Any of the pixel drawings I have tried stop within the first 1/8th or so of the drawing. It looks like they are loosing serial connection.

I'm on Ubuntu 12.04 and have given full permissions to /dev/ttyACM* and ensured that the default.properties.txt file is linking to controller.machine.serialport=0

Here is the error I get when the machine stops while drawing:
java.io.IOException: Input/output error in nativeavailable
at gnu.io.RXTXPort.nativeavailable(Native Method)
at gnu.io.RXTXPort$SerialInputStream.available(RXTXPort.java:1598)
at processing.serial.Serial.serialEvent(Unknown Source)
at gnu.io.RXTXPort.sendEvent(RXTXPort.java:774)
at gnu.io.RXTXPort.eventLoop(Native Method)
at gnu.io.RXTXPort$MonitorThread.run(RXTXPort.java:1643)

What I don't understand is how I can get comms but it then drops.

Any ideas?
Image
kongorilla
Pro
Posts: 362
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kongorilla
Post Re: Serial connection dropping early while drawing.
on: May 23, 2014, 04:45
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Hi Canned,

Did you leave your mom's blinds open or closed?

I can't address the serial issue, so you'll have to wait for Sandy to pop his head in.

What concerns me are the specs for the motors. Are you controlling the current in some way? Or are you finding the motors, and importantly, the drivers on the shield getting very hot?

If your shield is a clone of the V1, then it's likely you've got too much current running through the drivers, unless you're limiting it in some way. I started out with a V1 motorshield and low voltage motors, and I know how hard it is to get the right amount of juice for that combo. Each driver on that shield can only withstand .6A, so if you're supplying 4V and each motor is drawing 1A, there's going to be issues with overheating and thermal shutdown.
sandy
Administrator
Posts: 1317
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sandy
Post Re: Serial connection dropping early while drawing.
on: May 23, 2014, 11:05
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Hallo, Kong makes a good point that I hadn't thought about. I think you might notice if it was going into thermal shutdown. You could test this by sticking some heatsinking onto the driver chips, or blow a fan at it or something, and see if that extends the life.

Also try re-connecting and restarting immediately after a loss, and if it reconnects and runs for another 15 minutes without problems, then I guess it's not a thermal issue.

The bad news about the serial connection is that I've never used it on linux, and all I know about the rxtx serial library is that it is not well-liked in the linux Processing community - and there is not an alternative at this time (I believe).

The good news is that I have heard of at least one other person who _has_ used the app on linux.

sn
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