Watlow CPC400 - Manual (Page 50)

Chapter 2: Installation CPC400 Series User’s Guide
36 Watlow Anafaze Doc. 0600-2900-2000
Digital Inputs
All digital inputs are transistor-transistor logic (TTL) level
inputs referenced to controller common and the internal
+5V power supply of the CPC400.
When an input is connected to the controller common, the
input is considered on. Otherwise, the input is considered
off. Most features that use the digital inputs can be user-
configured to activate when an input is either on or off.
In the off state, internal 10 k Ω resistors pull the digital in-
puts high to 5V Î ( dc) with respect to the controller com-
mon.
Table 2.4 Digital Input States and Values
Stored in the Controller
1 Read these values through serial communications and LogicPro pro-
grams.
External Switching Device
To ensure that the inputs are reliably switched, use a
switching device with the appropriate impedances in the on
and off states and do not connect the inputs to external
power sources.
When off, the switching device must provide an impedance
of at least 11 k
Ω to ensure that the voltage will rise to
greater than 3.7V Î (dc). When on, the switch must provide
not more than 1 k Ω impedance to ensure the voltage drops
below 1.3V Î (dc).
To install a switch as a digital input, connect one lead to the
common terminal on the TB50 (terminals 3 and 4) or TB18
(terminal 2). Connect the other lead to the desired digital
input terminal on the TB50 (terminals 43 to 50) or TB18
(terminals 16 to 18).
Figure 2.26 Wiring Digital Inputs
State Value 1 Description
Off 0 Open circuit
On 1
Digital input connected to controller
common
External
Switching
Device
TB50
Input
Control Com