Note The Power Requirements; Understand The Low-True Format - Allen-Bradley ControlLogix 1756-IG16 Installation Instructions Manual

Note the Power Requirements

This module receives power from the 1756 chassis power supply and
requires 2 sources of power from the ControlLogix backplane:
• 110mA @ 5.1V dc
• 2mA @ 24V dc
Add this current/power value (0.61W) to the requirements of all other
modules in the chassis to prevent overloading the power supply.
This module requires power from a user-provided +5V
IMPORTANT
dc power supply in addition to requiring power from
the ControlLogix backplane. The user-provided power
supply is used for the transmission of TTL signals.

Understand the Low-True Format

This module requires both (+) and (-) connections from a 5V dc
power supply to function. The module also operates in a low-true
format. Inputs may be in the ON or OFF state depending on the
voltage applied to the input.
• -0.2V to 0.8V dc = Input guaranteed to be in ON state
• 0.8 to 2.0V dc = Input state not Guaranteed
• 2.0 to 5.5V dc = Input guaranteed to be in OFF state
The graphic below shows the input state in each voltage range.
IN
-0.2V dc
COM
(Measure voltage from common
terminal to input terminal.)
0.8V dc
On state Input state not guaranteed
TTL inputs are inverted (-0.2V to +0.8V dc = low voltage = True = On
ControlLogix TTL Input Module 7
Publication
1756-IN584B-EN-P - August 2003
2.0V dc 5.5V dc
Off state