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General discussions. For specific printers / electronics / fabrication methods / softwares, please see other sections.
Re: Fix for Skipping Steps - 5 years ago
try again, I had issue with domain register.by trampas - Mechanics
Re: Fix for Skipping Steps - 5 years ago
Yeap, over the last 3 year I have improved the Smart Steppers such they work really well. They do a really good job of preventing missed steps and turns stepper motors into closed loop servos. The real value is in large prints that take a long time. Specifically if your prints are short and mess up you can just reprint. If you have prints that run 12 hours or more and they mess then you looby trampas - Mechanics
Re: Mechaduino Closed-loop Stepper - 7 years ago
This is not true on the NZS. The firmware constantly reads the encoder so it knows where the shaft is such that it can calculate the correct phase of the current to move. For example see this video So even if the motor is way of say 1000 degrees (yes more than full rotation) the unit will recover. You will also notice in the video the LCD shows you the error...by trampas - General
Re: Mechaduino Closed-loop Stepper - 7 years ago
It depends on the feedback controller on the Nano Zero Controller it will correct even if 1/16 of step off, however it will not assert the error line unless error is more than 1.8 degrees (1 step for a motor with 200 steps per resolution). The NZS check the error 6,000 times a second and will attempt to fix the smallest of error. This means that with the NZS your positional accuracy can improve.by trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
Well as the designer of the Nano Zero I am biased... The Nano Zero Stepper has an additional level shifted pin for and Error signal. That is a pin that can interface with the 5V logic of the MEGA/RAMPS hardware. I added this extra pin such that if the stepper misses a step it can signal the host (Marlin firmware in your case). However I will say that for your problem neither one is an off thby trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
For a given motor and current the torque of the motor (ie power) is going to be the same. However often people run stepper motors well under their maximum operating current to keep the noise and heat down. If this is the case then the controller might give you more power. Specifically the controller can drive the motor at maximum current when moving, but then lower the current when not moving toby trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
I was confused over what you were calling phase advance, I think I understand now. I do not do this currently as my goal was not maximum motor speed, but rather positional accuracy. Is there a need for such speeds? I had figured most people would be happy with full stepping speed, and microstepping accuracy.by trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
LoboCNC, I am changing the current on the Vref1 and Vref2 pins such that I have 256x microstepping at the A4954 driver level. Thus I can can adjust the motor for very small errors, less than 0.01 degrees, the A4954 driver also lets me change the current (torque) (ie magnatude) going to motor. So I can move with a lot of current one microstep or a small amount of current one microstep. From aby trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
That is correct, using the motor for Z homing would be hard with a delta. Trampasby trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
Currently the motor controller knows nothing about home position. To gain perspective on this think about the motor sitting on a bench, it has no idea which way is zero degrees, all it knows that from where it is now it can move xxx degrees. Hence the controller right now arbitrarily sets a position as zero degrees and then measures all angles relative to this starting position. Homing is uniby trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
The code does implement phase advancement which in simple terms, allows dynamic step size on the stepper motor. That is the driver code for the A4954 implements 256x microstepping, while I have normally been running the external interface at 16x microstepping. So what happens is when a user requests a step internally the firmware calculates what the desired angle is, then it measures the currentby trampas - General
Re: Whether it’s good to replace DRV8825 with A4982 on MKS Sbase. - 8 years ago
Here is an example of the DRV8825 error during 16x microsteppingby trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
Thanks, it has taken me months to get everything working. There is still more work to be done but I am happy with the results. Trampasby trampas - General
Re: Whether it’s good to replace DRV8825 with A4982 on MKS Sbase. - 8 years ago
Yes sorry about thatby trampas - General
Re: Fix for Skipping Steps - 8 years ago
So the advantages come down to few things: 1. Faster prints - turning down acceleration, jerk and speed to keep from missing steps means slower print times. 2. Increased reliability - external items like bumping machine in operation will have less effect, or extruder hitting bump in work piece causing missed step ,etc. 3. Improved print accuracy - see below 4. Less heat and noise from steppersby trampas - Mechanics
Re: Whether it’s good to replace DRV8825 with A4982 on MKS Sbase. - 8 years ago
The DRV8825 are junk! I when I started on the stepper motor controller I was using step sticks and testing with the A4988, and then tested with the DRV8825 and found it had large errors on 16x microstepping. I contacted TI and asked them if I was doing something wrong and they recommended buying their new chip as it was suppose to be better... Here is some graphs and details of the error.by trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
I forgot to mention that with the error pin and ability to change the motor current on the fly it is possible to have Marlin tell the NZS to lower the drive current on the motor. Then run the extruder head into the plate until the error pin is asserted. This would basically allow homing of the Z axis using the head, which then in turns makes bed leveling easy. Here is a test I was doing on a Pby trampas - General
Re: Mechaduino Closed-loop Stepper - 8 years ago
I have made a stepper controller like the mechaduino but with some additional features . First off there is a error pin. If an motor skips a step then the error pin is asserted until the NZS fixes the problem. This could be used by Marlin to stop the other motors until the error has been fixed. For example if the extruder binds and misses a step then error pin is set and Marlin could stop theby trampas - General
Re: Fix for Skipping Steps - 8 years ago
The NZS does not try and reduce acceleration and jerk, but does fix missed steps if you do accelerate or jerk too high. The issue with acceleration and jerk is that it is a multiple axis problem. For example if I am moving in a diagonal line and the two axis involved in the diagonal movement have different accelerations then you do not get a diagonal line. Hence acceleration has to be controlleby trampas - Mechanics
Fix for Skipping Steps - 8 years ago
Having faced the problem of slowing down my printer to keep from skipping steps I finally gave up and added a rotary encoder to my steppers such that I never miss a step again, see Basically you glue a magnet on the back of the stepper motor shaft and then attach the PCB, see The PCB has a built in driver, thus you remove your step sticks. I have noticed my stepper motors are much quieter andby trampas - Mechanics