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FMT 3000 Hardware Reference Guide - Option Installation and Operation
Digital I/O Option
The digital I/O option, if originally ordered with the unit, is implemented on the power board
of the unit.
Note: If this option was not ordered the power board will not have any of
the optional components (opto-isolators, relay, or screw terminators)
mounted or soldered in.
Six optically isolated digital inputs and two digital relay outputs for applications like machine
monitoring and access control are provided. Also provided is a removable terminal strip with
screw-down type terminal connections which allow external wires to interface with the
digital inputs and outputs. The terminal block’s connections accept up to 18 AWG wire
(0.823 mm
2
).
The unit’s keyboard controller (a 81C51SL chip) controls the digital inputs and outputs. The
INT2F interrupt simplifies reading and setting the digital I/O channels. Refer to Chapter 9,
Custom Function Reference, of the FMT 3000 Software Manual for information on
programming digital I/O functions.
shows a schematic diagram of the digital I/O option.
Isolated Digital Inputs
These six inputs have opto-isolators to isolate the electronics from noisy or high voltage
factory signals. The inputs may be used either as high or low level voltage inputs or as contact
inputs with the addition of a wetting current source (which may come from the DC power
out lines on the board, see below).
The input voltage range for turning an input “On” is from 4 VDC to 28 VDC. The inputs
can withstand 35 VDC without damage.
Relay Outputs
The two relay outputs use low profile, 2 amp, form C relays. A transistor drive converts the
TTL signals from the controller chip to the relay control voltage.
The relay’s contacts have a 2 Amp maximum current rating for switching 30 VDC, and a
maximum 0.5 Amp current rating for switching 125 VAC.