Trouble homing on version 2020-03-06-112

Dean

I recently updated to the latest version and this resolved my inch units feed issue.  I have successfully ran a g-code file that I had previously ran on LinuxCNC.  

However, I now find that I have bad behavior during homing.   The behavior is random, sometimes it homes correctly.  Other times I have an axis running into the positive direction after homing.   I must press emergency stop to prevent problems.  After attempting this many times I can eventually get it to home all three axis.

I should describe my machines limit and home switch arrangement.  I have a micro switch at the minimum and maximum travel at each axis.
My home and minimum limit are the same.   More importantly all the homes switches are in parallel and all the max limit switches are in parallel.

So I have two wires coming back from the machine.  One wire will go low if ANY HOME switch closes.  The other wire will go low if ANY MAX LIMIT switch closes.  The connection on the DDCS is the single home line goes to X,Y,Z home input.  The max limit goes to the max X,YZ limit inputs.

I have the back off distance for each axis sufficient to ensure that the home switch re-opens before the DDCS proceeds to home the next axis.

Not sure what is wrong.  The controller performs the home search correctly, and it seems to move the small back distance, but then after that it sometimes starts going in the positive direction until I hit estop.    This problem occurs if I home all three axis (sequentially) or even if I try to home an individual axis.

Dean

I have resolved this issue.  I was getting inductive coupled noise from stepper motors affecting home/limit switches wires.   
I have installed 0.47uf capacitors across the home switches and this seems to have resolved the problem

It makes sense.  The controller had no problem seeing the switches when they close to ground.   But when the homing algorithm backs off from the switches and they go open, then the line is floating and is susceptible to the stepper motor noise.

Hope this helps someone else.

我已经解决了这个问题。 步进电机的感应耦合噪声会影响限位/限位开关电线。
我在家用交换机上安装了0.47uf电容器，这似乎已经解决了问题

这说得通。 控制器在靠近地面时看到开关没有问题。 但是，当归位算法从开关退回并且断开时，则该线处于浮动状态，并且容易受到步进电机噪声的影响。

希望这对其他人有帮助。

jjae6

Dean, Excellent !!

mellbo

Yeah. I have this problems too. But in PDF's (2.6.2) say DDCS 3.1 have optocoupleur inside for the limit switches.
I think is not true, be cause with optocopleur this problem does not exist and It makes NOT senses.

I want to know...DDCS 3.1  have it or not optocoupleur.I replace switches on my machine with NC and I put 100nF capacitor in paralel with switches.
I have same problem described in first Topic...

Is my controler broken  or what ?...