Posted by michael Jul 25, 2017 01:52:11
Posted by michael Dec 02, 2015 03:44:50
AT+CNMI=2,2,0,0,0 so messages will be forwarded to the serial port instead of stored. You also need to set Text mode with AT+CMGF=1 to make sending and reading messages easier....
I also needed to select a provider to log on to from the ones that were available since my module did not 'connect' automatically. Maybe this has to do with the settings in my (prepaid) SIMcard.
I applied the same recipe to the next units I purchased off ebay. To my surprise they seemed to be bricked after flashing the same firmware. The status LED refused to flash and no response to AT commands.......
After trying various firmware versions it still did not work, in spite of the download apparently finishing successfully. Finally, I found out (by using the uplaod feature of the flash tool) that my first units contained a 32k ST flash and the stubborn units sported a 128k flash by SPANSION. So I tried flashing a firmware version with SPANSION in the filename from Muhammad's repository. Only one available, an Italian version, but after downloading finished it functioned as I had hoped for. Conclusion: Not only the size of the firmware should match the flash memory size, but the firmware should also be made for a specific flash vendor. Bigger is not always better!
Posted by michael Jul 13, 2014 01:08:25
Anyway, the decision was made to rebuild the machine with Linuxcnc and Mesa boards.
For the motor drives, Granite Argon drives were obtained. Really great drives, with the ability to find the commutation points by wiggling the motors at startup. That feature comes in very handy as the Aciera has Fanuc motors which do have rather odd commutation signals. On the Web you can find boards that use these signals for initial commutation and switch over to encoder position after one revolution. Quite nice, but that solution would have added another $500 to the project cost. So we decided to let the Argon drives sort it out themselves.
The actual rebuild started with taking out the original Fanuc controller parts. Patiently we traced all the external wiring, plugs and terminals and drew up diagrams of that part in order to facilitate the wiring of the MESA cards later. Then we wired up one of the motor drives and started testing the lot. Disappointment was our reward. The first axis moved rather strange. It turned out that the signals from the encoder were erratic. Closer examination learned that the line driver had gone bad (accidental supply line reversal?). Replacing the line driver chip in the encoder (Fanuc Pulsecoder) cured the problem. The next test with the Argon Granity tool went successfully. We succeeded in tuning the x-axis so there was virtually no overshoot or following error. So far I am very happy with the Argon drives. Configuration of the drives could be documented a bit better though. However, in practice, it turns out to be easy: check the right boxes and the drive 'knows' how to behave. (the z-axis will present a challenge since the motor also has to support the weight of the table and I haven't found a torque offset parameter yet)
Next came tsetting up of the computer and MESA cards and doing some preliminary testing. We will discuss this in the next posting. I'll also will make put in some pictures.
Posted by michael Jan 29, 2008 02:00:54
In the junkbox I found a BUX10 (RdsOn<0.05 Ohm) and a heavy Schottky diode, fit for the purpose. A TL494 was chosen as controller. Driving the FET presented a challenge. The FET being in the 'high side', needs 10V gate drive to get into the low resistance range. Eventually, a bootstrap circuit consisting of one diode and one cap turned out to be enough to create the drive voltage. Since switching off the FET was still a bit slow, an extra transistor was used to discharge the gate when the FET was supposed to stop conducting. Success! Even at 2.5 A output current the FET hardly heats up. I measured an efficiency of 75% at 1.8A and even better at higher loads. Not bad, compared to 40% for a linear solution.
To make sure that the computer would not get roasted in case the supply would malfunction, an SCR crowbar was added which shorts the input in case the output voltage becomes too high. When that happens, the fuse in one of the supply lines will prevent draining the ship's battery really fast!
The complete circuit was transferred from the breadboard to a PCB which fits in the original case. Since my PCB milling machine is not ready yet, I more or less milled the tracks freehand after creating a layout on the computer and transferring the hole pattern first.
A new label on the cover, for the professional look completed the project.
Posted by michael Dec 16, 2007 21:50:20
As a last resort I can always disassemble the firmware, but of course I am not looking forward to such an exercise!
Posted by michael Aug 17, 2007 03:15:01
The ruler which can be seen in this disassembled HP deskjet was taken out and will be mounted on my MiniMill. An AVR tiny2313 is big enough to hold the software for a 3-axis position display plus a few extra features.
The picture shows a test version of the software. The two columns will eventually display absolute and relative position, while the bottom line will show the functions of the 4 keys mounted directly below the display. Functions will include zeroing abs and rel position display, An uncommon but handy feature I want to include is a display of the position of the 'edges' of the mill-bit. Normally, a DRO shows the center position of the mill, which makes it necessary to (mentally) subtract or add the mill radius from the position shown, which is bound to go wrong sometime causing too much material being removed.
Posted by michael Aug 17, 2007 02:45:43
Eventually I'd like to be able to do more with this robot than just make it execute simple oneliners that only contain one command. My goal is to write a g-code interpreter which runs on the controller. Programs are written in a Basic-like dialect, which also has some string functions. Interpreting g-codes shouldn't be too difficult to program.....
Posted by michael Aug 17, 2007 00:30:24
Now before moving on, I tried some of the commands in the book. Finally I managed to make the controller send some important files to the PC. Having a backup of the configuration files on my PC now gave me enough peace of mind to call it a day (or rather night) and use the (little) remainder of it on catching some sleep.