pulse lenght

[danut1234]

Hello. Is there a way to change the step (pulse) lenght for motor? Now it depends on the frequency of the Kernel. 20us for 25khz, 1us for 400khz. Some stepper motor drivers do not like such a short pulse. I have some drivers that barely work at 20us, at 50khz and up they do not work at all. It might be because of the cables, i should check... But i have checked with another type of drivers and they work up to 400khz. Another thing is, if i remember correctly, the firmware used for talking to Mach3 generated much longer pulses...

Dan

[danut1234]

I have searched more about this problem and it seems i am correct in my assumptions. For example ST-M5045 driver. Here you can find the documentation http://s3.amazonaws.com/s3.image.smart/download/101-80-109/2-Phase_stepper_Motor_Driver_ST-M5045.pdf Have minimum of 10us for step pulse 5、PUL+、PUL -：Stepping pulse input+5V (Rising edge effective , rising edge duration >10μS
I can attach a photo with the oscilloscope that shows a 1us step pulse length for 400Khz Kernel if it is needed
I have some stepper drivers from Longs motors, and i know for sure that they are not working from 50khz and up.

Dan

[danut1234]

it seems that for 25khz kernel mach3 outputs same 20us pulse length.
is 20us because 1/25000 equals 40us and20for on time 20 for off time.
the documentation for the above driver is fake, because they state a 300khz maximum step frequency and a step length of more than 10us... it should be 1.6us...

A recommendation is to make available a speed of 10khz for kernel. To work with garbage stepper drivers.
An interesting thing is that Mach3 on parallel port at 45khz kernel speed works pretty well with garbage stepper drivers. This is either that they are not running at 45 khz or they use some adaptative pulse length depending on the motor speed. I don't have anymore a computer with parallel port to investigate....

[formantjim]

i'm glad someone posted this question because I've always wanted to know what the pulse length was for a given kernel frequency.

I've been running UCCNC and the ETH300 for at least 4 years without issue except I've had to reduce the pulses per revolution on my Clearpath Steppers. I originally purchased the enhanced versions that give 6400 pulses per revolution as the plan for the CNC machine was to do PCB work with SMD devices so small tracks so my thoughts were to get the highest accuracy I could get. However I found that once calibrated on my machine I would get approx 32,000 pulses per inch and it was fantastic but if I tried to cut at speeds greater than 60 inches per minute the machine would halt especially when cutting circles it would cut the circles fine but would just stall for no apparent reason.
To overcome this I dropped down the pulse per revolution to 2400 and this alleviated the issue and I've been running like this quite happily. I know this is not the same topic but since I saw some knowledgeable person answer the original poster I thought I'd jump in and ask.
I'm using by the way a little stick PC to control the CNC and have no issues at all but the limited speed.