Programming instructions

10
Unpowered Extension Blocks
The second way to expand the I/O of the FX3U system is through
the use of unpowered extension blocks. These do not have a
power supply, so they draw upon the power supply of the main
unit or powered extension unit. As such, there is a limit (short of
the I/O allocation limit for FX3Us) to the number of extension
blocks that can be added. How to calculate this number will be
covered later.
Unpowered extension blocks for the FX3U provide 16 I/O points.
These points are either inputs or outputs, but not both. Inputs are
24 VDC, and all three output types are available. If the available
models don’t meet the needs of the system, units from the FX0N
PLC line can be used, as well as from the FX PLC line (through the use of the
FX2N-CNV-IF converter).
Note: Be aware of the terminology used. An extension unit
is powered, while an extension block is unpowered.
2.4 Inputs
Input devices are the interface between PLC and machine. The base unit of an
FX PLC has a number of integrated inputs available. If more are needed, input
extension blocks and units are available to be connected.
There are 2 different input types …
• DC Inputs
o Fast response
o 90% of new designs use this type of input
o mostly 24VDC, but FX1N has 12VDC option
o sink or source logic
• AC Inputs
o Slow response
o Easy to interface AC devices
o All AC inputs are 120VAC
Integrated Inputs