Ordbot Stopping Mid-Print. Help Please?

Topics Related to the ORD Bot Printer

Re: Ordbot Stopping Mid-Print. Help Please?

Postby cvoinescu » Fri Oct 25, 2013 8:28 pm

It is quite possible that the USB and the heaters don't go together well. If your PSU connects GND (V-) to earth, a voltage drop on the GND between the Azteeg and the supply could cause a significant voltage difference between the ground of the USB at the Azteeg end and that at the PC end. Such a voltage drop could occur when heaters turn on, and could randomly interrupt USB communication, or even latch up the processor on the Azteeg.

Isn't there a way to auto-print from the SD card w/o a controller? I wonder what that would do, heaters on but no USB.
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby fma » Fri Oct 25, 2013 8:42 pm

As said on the Azteeg X3 thread, I tried 2 working solutions: using a pure RS232 connection, with a RS232-TTL converter on the printer side, connected to J2 connector. The other solution is using a USB-TTL converter as FTDI cable, where the entire USB is in the computer's side connector; the other side (TTL) is also connected to J2. I can switch on/off what ever I want, no problem.

I prefer the RS232 solution, as TTL signals could be jammed by something more easily than RS232... But, again, with a shielded, short cable, it should also work.
Frédéric
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby evil2002usna » Sat Oct 26, 2013 1:20 am

So i have now seen two prints with the heaters off where the machine has stopped mid print as well. The second print I was also using the new 3ft shielded cable w/ferrite core I received today. I am at a loss at this point. I cant believe that my power supply doesn't have enough power to run the motors for at least two hours. I wasnt even running the extruder motor during any of these tests. Is it possible that I just have a bad board. It doesnt make sense to me that I would have to jerry rig some kind of alternative serial connection to my computer to get this thing to run consistently. There are plenty of people out there including countless Bot Farms that are printing 14 and 15 hours at a time and I cant even make it through two. How is this possible? These boards were designed with certain types of connections in mind, I should be able to use the connections the board was designed with.
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby fma » Sat Oct 26, 2013 7:15 am

USB is evil, period! You'll never see any industrial long time running process based on USB... RS232/RS422/RS485 is still one of the most used serial transmission used.
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby cvoinescu » Sat Oct 26, 2013 10:44 pm

USB is fine for small devices, but stuff with big power supplies causes problems. To me, this seems to be caused by ground problems more than anything else. Other systems either have galvanic separation (Ethernet), have very high noise immunity (RS232) or are much more tolerant to common mode noise (RS485). I've managed to get continuous uninterrupted prints via USB by using optoisolators. It is possible to isolate USB itself, but it's much cheaper to isolate the TTL-level serial signals between the USB-to-serial adapter and the microcontroller. I connected a cheap USB-to-TTL-serial adapter to two 6N137 optocouplers, with no electrical connections between the USB and the rest of the printer. That completely eliminated my random interruptions. I used an Arduino, which has resistors between its on-board USB-to-serial adapter and the respective pins, so an external adapter overrides the on-board one. I'm not sure what the situation is on the Azteeg; worst case, you may have to cut a trace.
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby jammer » Sun Oct 27, 2013 4:53 am

cvoinescu wrote:USB is fine for small devices, but stuff with big power supplies causes problems. To me, this seems to be caused by ground problems more than anything else. Other systems either have galvanic separation (Ethernet), have very high noise immunity (RS232) or are much more tolerant to common mode noise (RS485). I've managed to get continuous uninterrupted prints via USB by using optoisolators. It is possible to isolate USB itself, but it's much cheaper to isolate the TTL-level serial signals between the USB-to-serial adapter and the microcontroller. I connected a cheap USB-to-TTL-serial adapter to two 6N137 optocouplers, with no electrical connections between the USB and the rest of the printer. That completely eliminated my random interruptions. I used an Arduino, which has resistors between its on-board USB-to-serial adapter and the respective pins, so an external adapter overrides the on-board one. I'm not sure what the situation is on the Azteeg; worst case, you may have to cut a trace.


I have read several threads here on people that are using an STL- interface with their controllers but it would be great if there was an USB to STL for dummies guide that explains how to use this connection. I have an Azteeg as well but haven't completed my printer yet so I haven't experienced the issue. I have read enough threads talking about how sensitive the USB connection (especially the mini-USB cables) to know that it is a somewhat serious problem. I have also read that someone used the J2 connection on the Azteeg board to connect using the STL but I would have no idea how to figure that one out.
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby fma » Sun Oct 27, 2013 7:25 am

TTL, not STL ;) TTL is an electric spec, defining the levels used for 1 (+5V) and 0 (0V), and other stuffs.

You need to know that the µ-controller used in the X3 does not have a integrated USB line. Communication is done through a serial line: TX/RX/GND. So, the X3 also has a chip which converts USB line to serial (TTL levels).

The J2 connector is connected to the µ-controller TX/RX/GND lines, so you can send datas there (there are resistors on the USB chip side, so there is no problem, but don't try to send datas from both sides!). The 2 solutions are keeping the USB on the computer side (in the FTDI connector), so it is not jammed, and have the TTL signals from the computer to the X3. The other solution is to use RS232 serial line (higher level signals for RX/TX), and convert levels on the X3 side, before connecting to J2. RS232 signals are less sensitive than TTL.

The FTDI USB-TTL cable is a simple solution: just buy one of these refs:

- TTL-232RG-VSW5V-WE
- TTL-232R-5V-WE

and solder +5V/GND/RX/TX directly on J2 connector (crossing RX/TX).

To upload firmware, just use the standard USB connector (and unplug the FTDI cable).
Frédéric
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby cvoinescu » Sun Oct 27, 2013 2:23 pm

In my case at least, the external USB-to-serial (TTL level) converter made no difference compared to the one on board. The difference came when I had them isolated -- the problem went away completely. With the optocouplers in place, I connected the USB ground to the controller GND, and the problem re-occurred.
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby fma » Sun Oct 27, 2013 5:24 pm

Strange. I made more tests, yesterday, and it really works fine without optos. Electric noise and all that stuff can be really annoying and very difficult to fix...
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Re: Ordbot Stopping Mid-Print. Help Please?

Postby cvoinescu » Sun Oct 27, 2013 7:26 pm

Lucky you, then! :)
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