Re: [CAD_CAM_EDM_DRO] Has anyone ever had trouble driving a G201 w/ an unbuff...

In a message dated 5/9/2004 2:40:14 PM Central Standard Time,
sciciora@... writes:
I have no problem adding a 74ACT245 buffer to drive the LEDs, but I'm afraid
that this will un-do the majority of noise immunity that the opto-isolators
provide. It's my understanding that optos work on current, not voltage.

Steve: I use the 74HC541 NON-inverting buffer. It has 8 bits, and can sink
OR source 25 mA per bit, so can handle ALL the "LED's" (inputs to the
opto-isolators) with NO problem. The ACT may be different, and I am too lazy to dig
out a spec-manual and look.

One point had me going for a short time: The Gecko specs DO say that the
input loading is 16 mA, but I found only 8 mA, so for a few femtoseconds, I was
wondering where I was thinking wrong. Then (Mariss explained?) I was told that
"16 mA" was only "worst-case". In any event, the 'HC541 buffer can handle
the "worst case" with ease.

FYI: I have an OLD '386 "mini-tower" running DOS-only out in my lab, running
GWBASIC to test "CNC stuff", and I find that the 8 printer-port data-lines
CAN handle opto-isolator loads with no difficulty. However, I STILL insert an
'HC541 as I say for "isolation purposes"---just to make [deleted-] sure!

Jan Rowland


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