20 Compact I/O High-speed Counter Module
Publication 1769-IN030B-EN-P - October 2010
Output Operation
The four output terminals must be powered by a user-supplied external source. User-power range
is from 5…30V DC. See Output Specifications on page 27 for voltage and current levels.
There is no isolation between the outputs, but the outputs are isolated from the inputs and the
1769 Compact bus.
Electronic Protection
The electronic protection of the 1769-HSC module has been designed to provide protection
from current overload and short-circuit conditions. The protection is based on a thermal cut-out
principle. In the event of a short circuit or current-overload condition on an output channel, that
channel will turn off within milliseconds after the thermal cut-out temperature has been reached.
When this occurs, the module’s fuse status indicator will turn on. You have the option to allow
the protection device to automatically reset, or to be reset under program control. The automatic
reset function occurs after the thermal protection device cools. If the current overload or
short-circuit condition still exists, the automatic reset cycle repeats until it is removed.
Figure 8 - Timing Diagram for Over-current and/or Short-circuit Shutdown
and Restart
Under-voltage Condition
If the field supply voltage falls below a value of approximately 4V DC, all of the 1769-HSC
module’s outputs shut down and remain off until the field supply voltage returns to a value
within the module’s normal operating range.
Correct short-circuit and overload conditions as soon as possible. If short-circuit
and overload conditions occur for extended periods, damage can occur.
IN1
I
L1
Other Channel: Normal Operation
I
L(SCp)
I
L(SCr)
t
off(SC)
IN1 – Commanded state of output channel
I
L1
– Output current due to short-circuit overload
I
L(SCp)
– Peak short-circuit or overload current
t
off(SC)
– Time before shut-off occurs. This may
take up to 11 ms depending on external
conditions.
I
L(SCr)
– Recurring short-circuit or overload
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