I want to perform the most basic possible check to test parts that I have bought: make the motor turn via manual control of the x axis in repetier. I don’t have a machine to connect to yet (building the MPCNC).
Symptoms:
Board is plugged in and recognised by repetier. I see messages from the board in the console. I can connect and disconnect using the green/red button at the top left. Red led comes on when board starts. There is no resistance in the motor, I can turn it as freely as when not plugged in to anything.
Nothing happens when I do manual control of the x axis. Motor does not turn.
I get the status “3 commands waiting” in the upper right area after trying to perform manual control, and this eventually resolves to the message “Idle” after 30s-1min.
Hardware/setup:
Arduino Mega 2560 (genuine board). Running Marlin firmware, I download the Marlin-MPCNC_Ramps_T8_16T_LCD_32step package that is directly linked here: https://github.com/Allted/Marlin. It is connected to the correct serial port, and I used the 115200 baud rate (for compatibility with mac, but I have tried a windows machine also) set in software and Configuration.h
Ramps 1.4 board, ebay, very low quality board (main reason for testing!) .It has shoddy soldering, some sort of residue all over the board, very poor part alignment etc. Nothing connected to the thermistor jack, I read that a dummy resistor was not needed.
Link: https://www.ebay.com/itm/223201408851
3x DRV8825 driver boards, seem ok quality but I had to file them a little to remove a jagged pcb edge that prevented them being able to mount beside each other, no components or traces were damaged. 3x jumpers installed under each board. Have not adjusted trimpots yet, I understand this is a later step. These are installed on the lower locations on the board, i.e. the ones marked for x/y/z axes.
Link: https://www.ebay.com/itm/252715006826
ATX PSU (rated >10A on 12V rail). Connected via the green connector on the ramps board, not the arduino barrel jack. Polarity and voltage is checked with a multimeter.
A single stepper motor connected to X axis (I have tried all xyz ports and connector orientations).
You really should adjust these before connecting the motors. The location of that pot determines how much current goes to the motors and the initial values could definitely be too high for your motors. The more likely scenario is they will just overheat the drivers, but it doesn’t take long to adjust them and you have to do it anyway.
So now, the motor turns for about 0.1 seconds, before the power supply cuts out (fan stops spinning and no voltage, so I presume some sort of safety circuit kicking in). Progress of sorts, and a completely different problem to solve! Any ideas?
Ok, I will do this. I thought it was a later step because you were supposed to activate the motors while taking the measurements. Will report back, thanks!
Thanks, I had not heard of this. It seems to work ok now, but it definitely explains why the PSU cut out since the currents being pulled can’t have been that high. It will eventually have a raspberry pi on the 5V line, which should fill that role.
I’m kind of surprised it works at all without a base load. It’s been years while since I set up that power supply, and at the time it was a 3d printer, but I remember that it just didn’t work at all until I plugged in the drive. Maybe my PSU is more finicky, or maybe the hotend drew enough to trigger the shutdown back then.
I’d still consider putting something on there to be safe. You don’t want your machine to shut down halfway through a job.
That does seem like a good place to connect a Pi. I might have to try that, too!
On an ATX power supply and a RAMPS board, you can connect the 5V stand by to the 5V of the arduino, and connect the power signals to the ramps board. Then there are configurations for enabling gcode to start and stop the 12V. You could also do that with a pi, and power it by the stand by power, and have it turn on the CNC with some commands from octoprint.
