Stop or SlowDown on external input

Hi there,

I'm new to this forum so please excuse if I posted at the wrong spot an feel free to move the post do a better category.

We are currently working on a Laser engraving machine using stepper motors. For optimal reliability we would like to control the speed of the X and Y axis with an external sensor. Two szenarios would be possible:

1. digital HIGH / LOW Sensor: when Sensor is LOW, process job as usual, when Sensor is HIGH, stop X and Y axis with usual decelaration and wait for sensor to turn LOW, then accelerate and proceed as usual.
2. analog Sensor (eg. 0 - 12V)
: adjust speed of X and Y axis according to value on Sensor PIN. The mapping might not be linear. When a sudden value change occurs, no steps should be lost, this could also be achieved by an analog filter of the sensor signal

If anyone has experience with this kind of application, I would be glad to know! I assume it could be a very basic functionality or easy to implement but I haven't found anything likewise in the documentation or when searching the web. We would have some financial ressources if a special implementation is needed and are willing to put it back in the opensource software.

Kind regards,
Felix

See here in the manuals linuxcnc.org/docs/html/gui/halui.html
for #1
halui.program.pause (bit, in) - pin for pausing a program
halui.program.resume (bit, in) - pin for resuming a paused program
for #2 probably
halui.feed-override.scale (float, in) - pin for setting the scale for increase and decrease of feed-override.

piflixe wrote:

Hi there,

I'm new to this forum so please excuse if I posted at the wrong spot an feel free to move the post do a better category.

We are currently working on a Laser engraving machine using stepper motors. For optimal reliability we would like to control the speed of the X and Y axis with an external sensor. Two szenarios would be possible:

1. digital HIGH / LOW Sensor: when Sensor is LOW, process job as usual, when Sensor is HIGH, stop X and Y axis with usual decelaration and wait for sensor to turn LOW, then accelerate and proceed as usual.
2. analog Sensor (eg. 0 - 12V)
: adjust speed of X and Y axis according to value on Sensor PIN. The mapping might not be linear. When a sudden value change occurs, no steps should be lost, this could also be achieved by an analog filter of the sensor signal

If anyone has experience with this kind of application, I would be glad to know! I assume it could be a very basic functionality or easy to implement but I haven't found anything likewise in the documentation or when searching the web. We would have some financial ressources if a special implementation is needed and are willing to put it back in the opensource software.

Kind regards,
Felix

Thanks for your quick reply! I think if reading an analog signal is hard to realise, we would start off with digital. Is there a documentation of how to get started with the hal interface? - I am quiet new to linux cnc and not especially good in programming. Would you be willing to help us with the inital setup? As I mentioned, we have some financial ressources and I think it would be more effective to have someone at hand who is familiar with linuxcnc.

piflixe wrote:

Hi there,

I'm new to this forum so please excuse if I posted at the wrong spot an feel free to move the post do a better category.

We are currently working on a Laser engraving machine using stepper motors. For optimal reliability we would like to control the speed of the X and Y axis with an external sensor. Two szenarios would be possible:

1. digital HIGH / LOW Sensor: when Sensor is LOW, process job as usual, when Sensor is HIGH, stop X and Y axis with usual decelaration and wait for sensor to turn LOW, then accelerate and proceed as usual.
2. analog Sensor (eg. 0 - 12V)
: adjust speed of X and Y axis according to value on Sensor PIN. The mapping might not be linear. When a sudden value change occurs, no steps should be lost, this could also be achieved by an analog filter of the sensor signal

If anyone has experience with this kind of application, I would be glad to know! I assume it could be a very basic functionality or easy to implement but I haven't found anything likewise in the documentation or when searching the web. We would have some financial ressources if a special implementation is needed and are willing to put it back in the opensource software.

Kind regards,
Felix

can you explain your reason for this ? or the problem you are trying to solve ?
i have a number of lasers , and not had to resort to adjusting the speed in this way .

so i wonder if it is the style of explaination
any way let us know and lets see if we can solve your problem .
is this a height focus issue , or rasterising error etc

The reason for this is that due to very limited laser power and fragile surfaces, we have to reduce engraving speed when laser is not "burned in". The surface is normally white, turning black when being burned therefore absorbing more light therefore a much higher engraving speed is possible. We can observe that process using the light being reflected.