MR380-1 Series Instruction Manual
Page 24 of 35
7.
Theory of Operation
A functional block diagram is shown in
, showing the Switch Sensor, Optical Link
and Controller Module. The switch is connected by a duplex fiber optic cable of readily
available 50/125µm, 62.5/125µm multi-mode fiber and 9/125 µm single mode fiber. The
transmit fiber guides steady optical power from a near-IR light source to the optical switch.
A second receive fiber returns the light relaying if the switch is closed or open.
Controller
The light source power is held constant under normal operating conditions allowing for a
known system loss budget when designing a system. The optics within the switch itself are
designed to couple maximum light back into the receive fiber allowing for long distance
and chaining multiple switches.
The optical power is then detected by the Photodetector and translated into a logic signal
depending on the power level. The photodetector operates with an active low signal
scheme allowing for a known failure state. If a fiber were to break, poor connection, high
loss, or depressed switch the controller would interpret those events as a failure or
‘EMERGENCY ON.’
The photo detector outputs a logic signal to the remaining logic circuitry which then
interprets high or low levels for the +24V and +5V digital outputs.
Switch
Digital Out
Logic
Circuitry
Relay
Contacts
Light
Source
Photodetector
1300nm
1310nm
Figure 15 Block Diagram of Basic Theory of Operation for MR387 Fiber Optic E-STOP
