Okay, will re-think my power-side E-Stop section. I believe I
understand what you are saying and it seems to coincide with what
actions I have used to power up big machines. Too bad I wasn't into
electronics when I worked for the machine builders, I could have
learned SO MUCH at that time :-(
Thanks Richard
Chris
There are standards. The normal Start-Stop circuit begins with a
normally closed Stop switch from one power rail to the junction of
a
normally open Start switch and one side of the holding contacts.
The
other side of the holding contacts connects to the other side of
the
Start switch (they are in parallel, the holding contacts hold the
Start state) and this junction connects to one side of the coil.
The
other side of the coil goes to common or ground. You really don't
want to switch an emergency circuit with a ground connection. Any
short circuit can simulate a ground connection.
The point is, it takes a specific action (pressing the Start
button)
to get power but even the loss of power will cause the Stop
function
to work. And the system won't restart.
A not particularly useful schematic is in Figure 7-16 here
Richard
