About 1756-OB8
The Allen-Bradley 1756-OB8 is a ControlLogix discrete output
module. This module delivers an ouput voltage range of 10-30 VDC
with nominal value of 24VDC. It is used to energize electrical
loads that operate in DC voltages as well as AC loads, used with an
interposing circuitry.
The 1756-OB8 is a single slot module that occupies any available
slot of the chassis except the left-most slot which is intended for
the ControlLogix processor or ControlLogix communication adapter /
scanner module. It is compatible acting as a local I/O component or
as part of a distributed I/O system. It may be installed to any
available 1756- ControlLogix chassis and operate along standard or
power supply modules.
The 1756-OB8 has a backplane current draw of 165 mA at 5.1 VDC and
2 mA at 24VDC while the total backplane power is 0.89 W and power
dissipation of 2.5 W @ 60 °C (140 °F) and thermal dissipation of
8.53 BTU/hr. Each channel of this output module can deliver up to 2
Amperes @ 60 °C (140 °F) and 8 Amperes @ 60 °C (140 °F) per module.
This module uses a Removable Terminal Block (RTB) for connecting
each channel of the module to the electrical loads. Compatible RTBs
are 1756-TBNH and 1756-TBSH while appropriate RTB keying is
user-defined, mechanical keying.
It is entered in the hardware configuration where module parameters
and properties can be further modified/ Some of these parameters
are Request Packet Interval (RPI), filter time, module inhibition
and many others.
This module uses a Removable Terminal Block (RTB) which can either
be the 1756-TBNH or the 1756-TBSH (20 pins RTB). This module has
the following communication formats available: rack optimization,
listen-only - rack optimization, output data, listen-only output
data, and scheduled output data. Pilot duty is also available for
the 1756-OB8 module.
The 1756-OB8 module has a voltage category of 12/24 volts DC source
and an operating range of 10 to 30 volts DC. Its current draw is
165 mA at 5.1V and 2 mA at 24V. It has a backplane power of 0.89 W,
with a maximum dissipation of 2.5 W at 60 Degrees Celsius (140
degrees Fahrenheit), and a thermal dissipation of 8.53 BTU/hr. The
maximum off-state leakage current of this module is 1 mA per point
and during an on-state, it has a maximum voltage drop of 1.2V DC at
2 A. It also has a maximum current of 2 A per point at 60 Degrees
Celsius and a maximum current of 8 A at 60 Degrees Celsius per
module. Its surge current per point is 4 A for 10 ms each that is
repeatable every 1 s at 60 Degrees Celsius and its minimum load
current is 2 mA per point. The module's isolation voltage is
continuous at 250V. This module also allows you to modify states in
Fault Mode per point and states in Program Mode per point. The
choices for both are Hold Last State, On, or Off, with 'Off' set as
default. Temperature ranges for the 1756-OB8 module are 0 to 60
Degrees Celsius when in operation and -40 to 85 Degrees Celsius
when not in operation. It also has a maximum surrounding air
temperature of 60 Degrees Celsius and a non-condensing relative
humidity of 5% to 95%.
FAQ for 1756-OB8
How many output channels does the 1756-OB8 have?
The 1756-OB8 has Eight (8) Output channels that delivers a nominal
output voltage of 24VDC.
Does the module come with an internal fusing?
No. Internal fusing is not built-in to this module.
How many chassis slots does the 1756-OB8 occupy?
The 1756-OB8 only occupies a single slot of the chassis.
Technical Description of 1756-OB8
Allen Bradley ControlLogix DC Output Module with 8-Point Outputs
Technical Specifications for 1756-OB8
| Manufacturer | Rockwell Automation |
| Brand | Allen-Bradley |
| Signal Delay, OFF Transition | 2 ms max |
| Signal Delay, ON transition | 1 ms max |
| Current per module, max | 8 A @ 60 °C (140 °F) |
| Current per point | 2 A @ 60 °C (140 °F) |
| No. of channels per group: | Four (2) |
| No. of output groups: | Two (2) |
| Output Voltage range | 10-30VDC |
| Output Voltage | 24VDC |
| No. of Outputs | Eight (8) |
| Backplane Current, 5.1VDC | 165 mA |
| Backplane Current, 24VDC | 2 mA |
| Total Backplane power | 0.89 W |
| Part Number/Catalog No. | 1756-OB8 |
| Series | ControlLogix |
| Module Type | Digital DC output module |
| Removable Terminal Block (RTB) | 1756-TBNH 1756-TBSH |
| Outputs | 8-Point |
| Voltage | 12-24 Volts DC Source |
| Operating Voltage Range | 10-30 Volts DC |
| Maximum Output Current Rating-Point | 2 Amps at 60 degrees Celsius |
| Maximum Output Current Rating-Module | 8 Amps at 60 degrees Celsius |
| Power Dissipation (Max) | 2.5 Watts at 60 Celsius |
| Removeable Terminal Block(s) | 1756-TBNH, 1756-TBSH |
| Isolation Voltage | 50 Volts Continuous |
| Enclosure | None |
| UPC | 10612598171412 |
| UPC | 10662468702994 |
