2m542 source or sink current help?

[irving2008]

I just edited my post having re-read the datasheets. The leadshine 16mA is a max value when using > 5v sources, used to calculate the additional external resistor, its not relevant here. On a true 5v drive with an open collector sink, the current will be 10mA. Using the existing BOB as a sink should work as would your additional output transistors (messy though). Timing isn't going to be an issue...

Hi,

I check through the bearings yesterday and there were some bearings that were too tight indeed. Not sure what optical isolators are without opening the drive but the drive datasheet gives max 16mA per channel and the bob Schmitt gives a little over 7mA sourcing current.

I have a transistor system built to sink current from the ena-, dir- and step- such that I can wire the ena+, dir+ and step+ on drivers directly to 5v using the bob step dir ena to trigger the gates. Between the two I think I should have solved things but need to test it, I also ditched my mach3 machine and built a new rapid linuxcnc box that should help, my other machine was borderline. I scoped the output yesterday from the parallel port and it is putting out 5v.

The current sink arrangement was just confusing to me, I'm more used to working with n channel circuitry vs p channel I guess. the transistors gating the ground should solve things with minimal re-wiring and they are able to rise in 80-90ns and fall in 32ns so shouldn't impact timing.

thanks for the help, appreciate it, il report back when I get things tested,

[Evengravy]

Thanks Irving, just for reference then the sinking arrangement I posted is correct?

[irving2008]

Your first picture, yes... I'd try that first before making an intermediate driver.. or change the BOB for one with better output drivers...
.
And don't connect motor supply and BOB supply grounds else you'll lose the isolation.

Thanks Irving, just for reference then the sinking arrangement I posted is correct?

[Evengravy]

K, so can I just leave the BOB xn (GND) unconnected, that had me confused mainly

[irving2008]

yes., assuming BOB xn(GND) and 5v GND are connected (I'd be surprised if they're not)

K, so can I just leave the BOB xn (GND) unconnected, that had me confused mainly