Liebert iCOM Microprocessor TM-10098 Manuale Utente Scaricare il pdf (Pagina 121)

iCOM

Controls Training and Service Manual

120

Troubleshooting the Input Opto-Isolator

The opto-isolator IC chips used in these circuits are the H11AA (input) devices. The

pin location for component checks on the input opto. The indented circle in the

upper left hand corner of this chip indicates the location of Pin 1. Note that the

number sequence is in a "U" format: down 1 and 2 on the left and up 3 and 4 on

the right.

Input Opto-Isolator Pin Location

INPUT VOLTAGE CHECK

Pin 1

Receives the AC source voltage (This voltage is 24 VAC prior to the Opto

and is about 1.2 VAC at the opto).

Pin 2 Completes the AC source to the neutral and or safety ground.

Pin 3 Completes the DC source to the digital ground.

Pin 4

Receives the DC voltage source from the microprocessor (This voltage

level is 3.3 VDC when not activated and is 0 VDC when activated.)

Note that all AC source checks are referenced to the associated transformer

neutral and/or the safety ground, and that the DC source reference is to -V or

digital ground.

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Liebert iCOM Microprocessor TM-10098 Manuale Utente Pagina 121