Re: [CAD_CAM_EDM_DRO] Re: breakout board and diode question

In a message dated 1/31/2004 7:20:10 PM Central Standard Time,
ja_erickson@... writes:
did you ever build a breakout board that utilizes the 74LS541?
do you have or know of any diagrams of how to build a breakout
board using that octal driver, keeping in mind i'm not an E.E.
but a really good assembler. haha
I have. Tie each input-line to gnd. with a 4K7 resistor, then another 4ky
resistor in series with each gate. Then tie each gate to +5 with a 1N4148, and
from ground with another 1N4148. Total 16 diodes and 16 resistors. The first
one ("to" +5) prevents the gate being forced higher than about +5.6 VDC. The
second one ("from" ground) prevents the gate input from going below about
-0.6 VDC. These diodes WILL save your '541 if there are "electrical nasties"
(bad emi, etc.), and in normal use, will have NO effect on signal (unless you
have severe ringing, and then they will "help"). I have also added a couple of
74HC4538 monostables on the "pulse pins" to stretch the pulses to at least 2
µS, when indicated; many stepper drivers will "ignore" input pulses shorter than
1µS or so.

Jan Rowland


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