Help please. Dip switches and mach 3 settings

[john swift]

combining the circuit of one of the BOB outputs with the circuit f the stepper driver inputs :-


when the printer port or motion controller goes high
the output of one of the inverters in the 74HC14 goes low and
about 10.6mA flows through the opto isolators LED
the light turns on the NPN photo transistor that in turn pulls the
stepper driver negative input down to ground
(- step in the circuit example)

about 16mA flows through the stepper drivers input LED

the problem is when the BOB input goes LOW
the BOBs opto isolator LED is turned off but the NPN transistor takes a while to turn off
the square edge of the step pulse gets rounded off
delaying when the stepper driver LED is turned off

while I expect a faster opto-isolator is used inside of the stepper driver
the NPN photo transistor inside the drivers opto-isolator will further degrade the step pulse


John

PS
propagation delay through a high speed opto-isolator



not only is the signal delayed but the edges are rounded - see page 4


PPS

in another thread to use surplus Tormach stepper drivers

https://www.cnczone.com/forums/torma...ml#post2107952
from the above post




you can see the Tormach / Leadshine stepper driver uses a HCPL 2531 dual high speed opto isolator for the step & direction inputs

a slower FL817 opto-isolator being used for the enable input
the "817" being the opto-isolator I expect your BOB to have