Lenze TCF Series - Manual (Page 68)

B APPENDIX - INPUT ASSERTION LEVEL
B.1 GENERAL
Digital inputs on VFDs are asserted or activated by either applying a voltage level to the input
(active-high) or by pulling the input down to a common or ground potential (active-low) . This
is an important issue when using solid-state outputs (from an external device) to interface
with the VFD, but is less of an issue when using dry contacts . Most VFDs are set up for either
active-high or active-low, but the TCF can be configured for either type .
The TCF digital inputs (TB-1, 13A, 13B, 13C and 13D) are configured for active-high as
standard . Refer to section B .2 to determine if the assertion level must be changed, depending
on the type of solid-state circuit being used (PNP/sourcing or NPN/sinking) .
NOTE
If dry contacts (from relays, switches, push buttons, etc), or PNP/sourcing
circuits are to be used to activate the digital inputs, the assertion level does
not need to be changed, and this Appendix can be ignored . Also, the label
that covers the control terminal strip can be discarded .
Parameter 79 - INPUT ASSERTION LEVEL shows the assertion level of the inputs, and is
either HIGH (01) or LOW (02) . This parameter can also be used to change from active-high
to active-low during initial set-up using the procedure described below in section B .3 .
When set for active-high (P79 set to HIGH), TB-4 is configured as a +12 VDC source and
the digital inputs are activated when they are at +10 VDC or higher (24 VDC max) relative
to TB-4 .
When set for active-low (P79 set to LOW), TB-4 is configured as a 0 VDC common and the
digital inputs (which will be at +12 VDC) are activated when they are at +2 VDC or lower
relative to TB-4 .
B.2
SOLID-STATE CIRCUITS
The digital inputs were designed to work with dry contacts (refer to NOTE above), as well as
PNP and NPN type open-collector circuits .
PNP OPEN-COLLECTOR CIRCUITS
If PNP (current-sourcing) outputs are to be
used to activate the drive's digital inputs, the
assertion level does not need to be changed
from the factory default of HIGH .
NPN OPEN-COLLECTOR CIRCUITS
If NPN (current-sinking) outputs are to be
used to activate the drive's digital inputs, the
assertion level must be changed to active-
low . Refer to section B .3 for the procedure to
change P79 to LOW .
TB-4 (+12 VDC)
TCF DIGITAL INPUT (0 VDC)
(ACTIVE-HIGH)
PNP
TB-4 (0 VDC)
TCF DIGITAL INPUT (+12 VDC)
(ACTIVE-LOW)
NPN
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