"Static" print lapse for polar...

CNCModeller

Hi Folks,
Is there any way to detect when my polar bed is at 0 degrees and going clockwise, then trigger an output pulse? I'm thinking in principle using parameters conditional gcode and a macro, but I'm not sure where to get real time bed position in rotation coordinates.

I'd like to trigger a camera to do a static time lapse of the print.

At the moment my prototype is two additional separate home sensors on the bed that are read by an Arduino and trigger a camera on the second sensor pulse when in the correct order. I.e trigger on b if a triggered before b within a small time window.

The direction is important as it helps to compensate for lag in the camera after the trigger event.

Obviously if I could do this on the duet it'd be one less Arduino to buy etc...

Any constructive thoughts would be much appreciated.

All the best
Barry M

OwenD

@cncmodeller
I would think that you could use two inductive sensors close to the table, and attached a piece of metal just wide enough to trigger both senors on the table, such that one triggered at say 350 degrees and one at 360/0 when rotating clockwise.
Then it would be simply a matter of using a trigger on the duet assigned to the second (360/0) sensor. See M581
That trigger just uses an IF statement.
If both sensors are triggered then the table MUST be rotating clockwise, so execute your code to trigger the camera shutter.
If it's going counter clockwise the the 350 degree sensor wont be triggered

mrehorstdmd

@cncmodeller I use an old cell phone camera to capture images while printing in my corexy printer. When I want layer synchronized time lapse sequences, I use a bluetooth shutter button that talks to the camera. I mounted the button on the printer's frame and put a "pusher" on the Y axis. I then use custom gcode in the slicer at every layer change to send the Y axis to the back of the printer which pushes the bluetooth button. I would think that you could make a similar arrangement with a bluetooth button at one end of the radial axis and the pusher mounted on the extruder carriage. When there's a layer change, just send the extruder (and table) to specific (rho, theta) coordinates where the extruder carriage will bump the button, then resume printing.

https://drmrehorst.blogspot.com/2020/04/fancy-no-hack-layer-synchronized-time.html

https://vimeo.com/411137542

A cellphone camera can produce much higher resolution images than a RPi camera, so when you turn the sequence into a video you can crop and still have high def video.

I have the camera set to immediately upload photos to Google Photos, so I can check print progress anywhere I have internet access, and with the high res photos I can see details of what's going on with the print. I run OpenCamera in the phone to get the controls I need (focus and exposure lock). OpenCamera can also do time lapse if you don't care about layer synchronization.

CNCModeller

@mrehorstdmd thanks for the thoughts, the trick is that all of my prints are continuous spiral vase mode so I don't have print artifacts at a distinct layer change. That's why I'm looking to trigger at a consistent bed rotation point rather than layers.

I do like the idea of the remote and a phone which I will look into more.

CNCModeller

@owend said in "Static" print lapse for polar...:

@cncmodeller
I would think that you could use two inductive sensors close to the table, and attached a piece of metal just wide enough to trigger both senors on the table, such that one triggered at say 350 degrees and one at 360/0 when rotating clockwise.
Then it would be simply a matter of using a trigger on the duet assigned to the second (360/0) sensor. See M581
That trigger just uses an IF statement.
If both sensors are triggered then the table MUST be rotating clockwise, so execute your code to trigger the camera shutter.
If it's going counter clockwise the the 350 degree sensor wont be triggered

Thanks @OwenD that's interesting. I was hoping to just tap into the internal data of the printer so I didn't need the sensor, however your idea is one step closer than mine!

mrehorstdmd

@cncmodeller It would be easy to modify a bluetooth button with a reed switch in parallel with or in place of the pushbutton and then place a small magnet on the edge of the printer's bed. Every time the bed rotates with the magnet near the switch it will trigger a photo. I don't know how precise it would be, but with a little more effort you could use an opto interruptor instead of a reed switch. They can be very precise, so your resulting video would be very stable.