by bdring » Sat Nov 26, 2011 2:11 am
I had to do a little work on my laser so I decided to install my new LightObject 2012 DSP controller. I wanted to get it to work with my 4 axis controller too.
The 2012 controller has a much simpler stepper driver interface. It has just three pins per axis. These are ....
DIR (Direction)
PUL (Pulse or Step)
DC5V
Just by looking at the pin names, I assumed it was designed to go into a transistor or optical isolater. These devices invert the signal. The pulse would go from +5V to ground and back.
The stepper drivers trigger on an edge so they would work either way, but timing issues on the DSP cause engravings to slowly walk off to one side if this is not right. The DSP has some options regarding rising/falling edge pulses, but these were not fixing the walking problem.
Fortunately I use a Schmitt trigger on my 4 axis, so that gave me some flexibility. The normal Schmitt trigger I use is a non inverting type. I selected this type for best compatibility with parallel ports, Arduinos, etc. The normal Schmitt trigger is inverting, so I bought I bought a few of those to test. It worked perfectly.
74HC14N Inverting
74HC7014 Non-Inverting
I can supply it either way now. Anyone with a 4 axis who needs to change it can get the 74HC14 from me for the cost of postage. It is a $0.40 part.
Bart
"If you didn't build it, you will never own it."