Digital Input - Sierra Wireless AirLink LS300 Hardware User's Manual

AirLink LS300 Hardware User Guide
AirLink LS300 device
I/O Circuit
Pin 4 is normally at 3.3 V,
but is pulled low
when activated.
24

Digital Input

As a digital input, it monitors a switch, using its opening or closing to record
events or monitoring external voltages of up to 30VDC. For example, you could
use it to measure the voltage on a 24VDC light bulb and have the device react
when it turns on.
When the switch, or input voltage is:
• Open (3.3 VDC to 30 VDC) – It is read as a digital input=1
• Closed (0 to 1.2 VDC) – It is read as a digital input=0
AirLink LS300 device
51 k
internal
pull up
I/O Circuit
Examples: Door opening/closing, valve opening/closing, ignition on/off, tow bar up/down,
empty/full container.
Figure 3-5: Digital Input Operation
Digital Output/Relay Output
As a digital output/relay output, it can trigger an alarm, siren, door lock or opens a
valve or a switch. Pin 4 is an open collector transistor output normally at 3.3 VDC.
When triggered, it is pulled to low.
3.3 V
Voltage supply
51 k
internal
pull up
Figure 3-6: Digital Output Operation
3.3 V
Contact
CL+
Flyback diode
CL-
External Solenoid/Relay Circuit
(Exact voltages and configuration
depend on the actual system design.)
Contact closed
Digital 0
0 VDC to 1.2 VDC
Contact open
Digital 1
3.3 VDC to 30 VDC
Ground
COM
NC
NO
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