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P a g e
J Tech Photonics, Inc.
Pic-
Convert™ Board Instructions V2
.7
Copyright 6/13/17
If the G Code program says now to go to -
0.0128” then the DIRECT
ION pin will go positive. This tells the
DAC to INCREMENT the count. Then, the controller will put out 128 pulses on the STEP pin. The DAC
will increment the count 128 levels. This will change the duty cycle on the PWM output by 50%.
If you make the range in the controller more than 255 levels then the digital potentiometer on the DAC
board will get to the end and stop, even though the controller might still be sending steps to
it. Example: If you set the range from Min = 0 to Max = -
0.075”, and y
ou keep the steps per inch in
mach3 at 10,000, then your controller will think your range is set to 750 levels. So, your picture will
come out mostly black and white because 495 levels will have the DAC board at the complete maximum
of its range. So, let
’s say the program says to go to
-
0.075” from a starting position of 0.
The DIRECTION
pin will go high which will INCREMENT the count. The controller will put out pulses on the STEP pin. The
DAC will increment and increase the DUTY CYCLE (increasing laser power) with each step pulse. After
256 pulses, the digital potentiometer on the DAC board is MAXED out and the DUTY CYLCE is now 100%
(laser at FULL power). Now it continues for another 495 more pulses. The digital potentiometer is still
MAXED out for all of it.
Then, let’s say the next pixel is slightly less dark at 0.065”.
It will set the
DIRECTION pin low (DECREMENT the count) and put out 100 steps on the STEP pin. Now the digital
potentiometer will DECREASE the duty cycle by 100 levels, which puts the DUTY CYLCE now at 61%
(almost at half power). This pixel was just supposed to be a little lighter than the last, but it is now 39%
lighter than the last pixel.
Now, let’s say the next pixel is supposed to be a little lighter again, maybe at
0.04”
. The DIRECTION pin is still low and another 250 steps go out on the STEP pin. The digital pot will
DECREASE the count until it hits ZERO after just 155 steps because it is already at 155 level from the last
pixel move. It continues to put out steps even though the DAC is at 0. The laser is now OFF even though
the pixel was supposed to be just slightly lighter than the last.
So, if you set the min and max values in Pic Laser Lite without adjusting your steps per inch, your picture
will be mostly black and white because your machine is operating on a different range than the DAC
board.
Why do I need to make the acceleration so fast?
You are not really moving any axis, so it can be super-fast. You are just trying to get the step and
direction signals to the Pic-
Convert™
board fast. The faster the computer thinks the axis is moving the
faster you can get the signals.
Why is my machine pausing after each pixel?
It needs to be in “constant velocity” mode. In Mach3 this is the G64 command.
Why does it sometimes come out darker for different materials?
Each material will need its own federate settings because of the different material properties. Some
wood is softer and burns easier and some are hard and burn slower. Grain patterns are especially hard
to engrave and will come out with “lines” where the grain is lighter. Try engraving at a 45 degree angle
to help with this effect.
