Help please. Dip switches and mach 3 settings

[Radu_Andrei]

This is the one. Db25 1205. https://www.ebay.com/itm/CNC-6-Axis-...sid=m570.l1313
I don.t know any more details that it says in the lower side of this webpage.

The multimeter reads 5v at the VDD terminal, without bridging it.
I did it like in the photo you.ve sent, but bridged ENBL+ as well.

Thanks for your reply. :)

[john swift]

going by the photo linked to in post 38

it looks like the BOB is as I expected with pull up resistors on the outputs



unless you connect the - enable to a BOB output
having the + enable connected to +5V will have no effect

what could be a problem is having the BOB's output optoisolator being connected to another optoisolator inside the stepper driver

having the step signal passing through two optoisolators could distort the pulses too much at high step rates

John

PS
in the photo of the BOB you can see two links that connect the +5V in to Vdd and connects the two GND's together so you don't need the external wire link as in post 37

PPS
a while ago I produced this circuit diagram from photos taken from the net



what I need to confirm is the connection of the 10K resistor connected to the 74HC14 input
it was not clear from the photos if the resistor was a pull up to +5v or pull down to GND

[Radu_Andrei]

Hi John,
ˇˇwhat could be a problem is having the BOB's output optoisolator being connected to another optoisolator inside the stepper driver/having the step signal passing through two optoisolators could distort the pulses too much at high step ratesˇˇ - does this mean I should remove the bridge from enbl+?
ˇˇwhat I need to confirm is the connection of the 10K resistor connected to the 74HC14 input/it was not clear from the photos if the resistor was a pull up to +5v or pull down to GNDˇˇ - how exactly can I help in confirming this?

P.S. although I have some general knowledge about diodes, capacitors and resistors, I.m struggling to wrap my head around schematics, so I.m sorry if my replies are quite banal. I very much welcome reading material to avoid pushing the limits of anyone.s patience. :)

[Clive S]

. I very much welcome reading material to avoid pushing the limits of anyone.s patience. :)

Don't worry about this. I believe John is very experienced in electronics. Just go through it with one small step at a time.

Also have you disabled all the crap like screen savers and stuff in the bios that is not needed on the pc.

[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

[Radu_Andrei]

Clive: yep, no such thing on this 12+ years pc, has a built in parallel port, windows 7 32 bits, no aero theme or screensaver. I don.t know what are the bios things which I don.t need.

John: ok, got the point a light and a sensor which acts like a switch and this one does not work fast enough. Now changing the drivers (wantai) is not possible, and buying others costs a bit.
Changing or upgrading the optoisolator in drivers or bob is I guess problematic. Like chancing the tiny chip on a pcb, is doable, and I have some tools for that, but not the skills just yet.
I can buy another Bob, if it helps. Should I, and if yes, which one?

[john swift]

I would try another BOB that does not have opto-isolated outputs
and either has 74HC14 HEX inverters connecting the printer port outputs to the stepper driver inputs or 74ACT245 octal transceivers as used on the C10 BOB


the C10 has no opto-isolators on either the inputs or outputs


note this BOB

has a design flaw

if you look at the 74HC14 used for the inputs
the supply pi 14 is not connected !!!

see top left hand corner of the circuit diagram



John

[cropwell]

Has the enable been connected up yet ?

I would common all the +v inputs to the drivers and use -ve pulses to drive enable, step and direction. There again, I wouldn't use that BoB as it has no relay output (though these can be added with a cheap board) and no 0-10v speed control.

I happily use this board https://www.dropbox.com/s/gfq4isvihn...rd-EN.pdf?dl=0 and have only blown one of them so far (my own stupid fault). At least they are cheap