D8 Series User’s Guide
Chapter 2: Installation
38
SSR
+ 5VDC
Watchdog Timer
(Terminal 1)
(Terminal 6)
TB50
+
-
Figure 2.21
– TB50 Watchdog Timer Output
SSR
+ 5VDC
Watchdog Timer
(Terminal 1)
(Terminal 3)
TB18
+
-
Figure 2.22
– TB18 Watchdog Timer Output
Digital Inputs
All digital inputs are transistor-transistor logic (TTL) level inputs referenced to controller common and
the in5V power supply of the D8.
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 4.7kΩ resistors pull the digital inputs high to 5VDC with respect to the
controller common.
Table 2.6
–
Digital Input States and Values Stored in the Controller
STATE
VALUE
1
DESCRIPTION
Off
0
Open circuit
On
1
Digital input connected to
controller common
1
Read and write these values through communications.
External Switching Devices
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 swiching device must provide an impedance of at least 14kΩ to ensure that the
voltage will rise to greater than 3.7VDC. When closed, the switch must provide not more than 1.7kΩ
impedance to ensure the voltage drops below 1.3VDC.
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).
Содержание Controller Series D8
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