Figure 2-10. Open-Collector (NPN) Connection To Digital Input
Figure 2-10 shows typical connections. Rground is typically 0-100 Ω, Rseries is typically 0 Ω, and Rpullup, the external pull-up
resistor, is generally not required. If there is some uncertainty about whether the signal is really open-collector or could drive a
voltage beyond 5.8 volts, use an Rseries of 22 kΩ as discussed in Section 2.9.1.1, and the input should be compatible with an
open-collector signal or a driven signal up to at least 48 volts.
Without the optional resistors, the figure simplifies to:
Figure 2-10b. Simplified Open-Collector (NPN) Connection To Digital Input Without Optional Resistors
Note that an individual ground connection is often not needed for every signal. Any signals powered by the same external supply,
or otherwise referred to the same external ground, should share a single ground connection to the UE9 if possible.
2.9.1.3 - Input: Mechanical Switch Closure
To detect whether a mechanical switch (dry contact) is open or closed, connect one side of the switch to UE9 ground and the other
side to a digital input. The behavior is very similar to the open-collector described above.
Figure 2-11. Basic Mechanical Switch Connection To Digital Input
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Summary of Contents for UE9
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