1756-IB32 ControlLogix Input Module


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Dear Control community,

I am studying about ControlLogix IO modules 1756-IB32, with the respective link to the picture below.


Page 142 1756-IB32

In the IB32: Voltage from IN-0 (10-30V) passes through the Current Limiter, the LED, and finally through the GND-0 Ground.

The LED will emit light to the Optical transistor's gate terminal, and it will pass the current from the to the collector terminal (+5V) to the ControlLogix Backplane Interface and into the Display.

This is what I don't understand, how come when IN-0 is ON, the IO module (IB32) will be powered on, do it's function (sending information to Processor, sending data to display...etc...), and if IN-0 is OFF, the Module will be off.

I always thought that, there is a power supply that provides a signal and another power to the IO modules.

Kindly help me on this matter.

Thank you in advance.
The module will be powered from the backplane regardless of the voltage/logic state of IN-0. Which is what the simplified schematic is showing, so the transistor side of the opt-isolator is always active.