Micronor MR380-1-3, Instruction Manual

Page: 20 / 29

MR380-1-3 Instruction Manual
Page 20 of 29
Functional Block Diagram
A functional block diagram is shown in Figure 10 , showing the switch sensor, optical link and
controller module. The switch is connected to the controller by a duplex fiber optic cable of readily
available 50/125µm or 62.5/125µm multimode fiber or 9/125µm single mode fiber. The controller’s
9/125µm single mode transmit fiber guides steady optical power from a near-IR light source to the
optical switch. Then, a 62.5/125µm multimode receive fiber returns the light relaying if the switch
is open or closed.
Controller
Figure 10. Block Diagram for a MR380-1-3 Controller System
The light source power is held constant under normal operating conditions allowing for a known
system loss budget when designing a system. Additionally, the optics within the switch are
designed to couple maximum light back into the receive fiber enabling the ability to create long
distance systems and chain multiple switches.
Next, the optical power is identified by the photodetector and translated into a logic signal
depending on the power level. The photodetector operates with an active low signal scheme
which provides a known failure state. The controller then interprets events such as broken fiber,
poor connection, high loss or a depressed switch as a failure or ‘EMERGENCY ON’.
The photodetector outputs a logic signal to the remaining logic circuitry which then interprets high
or low levels for the +24V and +5V digital outputs.