Contemporary-control-systems BAScontrol20 Installation Guide Manual do Utilizador descarregar pdf (Página 11)

TD100700-0IA

Binary Inputs BI1–BI4

To sense the action of a push-button or relay, the

contacts must have no applied energy, and be rated

for low-voltage, low-current switching. The

BASC20 provides the energy to be sensed.

Configuration is only required to set the BACnet

properties. As shown in Figure 10, connect the

contacts between points A and C. For common

mechanical contacts, polarity is not an issue. The

open-circuit voltage is 12 VDC and the short-circuit current is 1.2 mA.

For solid-state switch sensing, we recommend that an attached solid-state

device have an opto-isolated open-collector NPN transistor output stage

with a collector-emitter output voltage (Vce) of at least 30 V. Output

sinking current should be greater than 5 mA. The collector-emitter

saturation voltage should be less than 0.2 V when sinking 2 mA. The

emitter must be connected to point C and the collector to point A (the

more positive point). The BASC20 sets the low-threshold to 3 V and the

high-threshold to 7 V. When a contact is made or the solid-state switch

is on (resulting in a saturated output), the voltage at point A is close to

zero volts. The corresponding LED for that channel will be on. If the

contact is opened or the solid-state switch is turned off, the voltage at

point C quickly rises towards 12 V. Once the voltage passes the 7 V

high-threshold, the “off” state is sensed. To return to the “on” state, this

voltage must fall below 3 V. The four-volt difference is called hysteresis.

There is no need to add an external pull-up resistor when using a contact

closure input.

Contact closure inputs are sampled every 10 ms and for a change of state

to be recognized, the input state must be stable for two consecutive

samples. Therefore, contact closure response is 20 ms.

Figure 10 — Binary

Input Connection

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Contemporary-control-systems BAScontrol20 Installation Guide Manual do Utilizador Página 11