DNF Controls Universal Switch Panel (USP-8, USP-8D, & USP-16) - Manual (Page 38)

36 OF 41 Universal Switch Panel (USP) User Manual
7. APPLICATION NOTES
A. GPI
1) USER DEFINED "ON" STATE.
a) Opto ON
When the unit is going to be used with the external source supplying
power, the "ON" state should be defined as "opto ON". Since the opto
circuit is
normally off, it
will be turned
on by the
application of
the external
signal.
Connection of power = ON
No connection of power = OFF
b) Opto OFF
When the unit is wired using the internal power supply (wet mode), the
"ON" state should be defined as "opto
OFF. Since the internal power supply is
supplying power to the opto circuit we
are acctually turning it on, but since we
want it to be off, we need to tell the GPI
state to be off. When we short the GPI
input to ground by the external signal,
we will be turning it off, but then we
invert the signal and make the GPI state
be ON. So an external short to ground
will cause the GPI state to turn ON.
Connection to ground = ON
No connection to ground = OFF
2) USER DEFINED "ON" MODE.
a) Latched
The user defined "ON" mode as LATCHED, means that the GPI state will
follow the external signal. When the signal is
'on' the GPI state is on, when the signal is 'off'
the GPI state is off. This, of course, is
conditioned by the above "user defined 'ON'
state".
The GPI state follows the input signal