X-320M™ User's Manual
Installation and Setup
2.2.2 Digital Input/Output Connections
The Digital I/O's can be individually programmed to function as either inputs or outputs. When
configured as inputs, pull-up or pull-down resistors can be programmed. For unconnected inputs, the
pull resistors will be read as ON when pulled up, or OFF when pulled down.
Input Connection
The inputs can be configured to count the tips of the bucket in a rain collector, the rate of spin on a wind
speed sensor, or detect switch closures on other connected devices, such as a lightning detector.
Pull-Up/Pull-Down Resistors
Weak pull resistors are used to control the state of the inputs when they are unconnected, such as when
connected to an open switch. Devices that use a switch contact, such as rain buckets, require the input
to be configured with a pull-up resistor. One side of the contact is connected to I/O 1 or I/O 2, and the
other side is connected to Gnd. When the bucket in a rain collector tips, the contact is momentarily
closed, causing the input to pulse
OFF.
This pulse increments the rain bucket counter.
Pull-down resistors are similar, but this configuration is typically not applicable for common weather
sensors.
Xytronix Research & Design, Inc.
Page 17
Figure 2.2a - Digital Input Connections
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