Isolated Digital I/O Connections; Dry/Wet Contact Support For Digital Input; Isolated Digital Output Connections - Advantech USB-4750 User Manual

3.3

Isolated Digital I/O Connections

3.3.1

Dry/Wet Contact Support for Digital Input

Each digital input channel accepts either dry contact or 0 ~ 60 V
inputs. Dry contact capability allows the channel to respond to changes in external
circuitry (e.g., the closing of a switch in the external circuitry) when no voltage is pres-
ent in the external circuit. Figure 3.2 shows external circuitry with both wet and dry
contact components, connected as an input source to one of the card's digital input
channels.
Note! External 5kΩ resistor is suggested to be added in wet contact context, to
maintain the voltage level while the external signal source is set to OFF
state.
3.3.2

Isolated Digital Output Connections

Each of the 8 isolated digital output channels comes equipped with a Darlington tran-
sistor. Every 8 output channels share common collectors and integral suppression
diodes for inductive loads. Channels 0 ~ 7 use COM0, and channels 8 ~ 15 use
COM1 as a common pin. If an external voltage (5 ~ 40 V) is applied to an isolated
output channel (IDO 0 ~ IDO 15) while it is being used as an output channel, the cur-
rent will flow from the external voltage source to the card. Please take care that the
current through each GND pin not exceed 200 mA.
Figure 3.3 shows how to connect an external output load to the card's isolated out-
puts.
USB-4750 User Manual
Figure 3.2 Isolated Digital Input Connections
12
wet contact
DC