C4 User Manual
October 25, 2021 ©2021 Smartrise Engineering, Inc. All Rights Reserved Page 21
EB4 – The force guided relay that is controlled by the main processor. The status of the relay is
monitored by both the main processor and the safety processor. When the relay is active,
contacts that are in series with EB1 pass through voltage from the EBS terminal to the EB
terminal.
NOTE: EB3 and EB4 are only used during preflight operation to bypass EB1 and EB2 relays so
they can be toggled without dropping the emergency brake.
Figure 23: MR Board SR3032 Safety Relays
2.2 SRU Board SR3030
The LEDs on the SRU board are either red, yellow, or green dependent upon the terminal and
status. Each color represents the following:
• Red – Indicates a fault has been detected or the board is resetting.
• Yellow – Indicates an active output terminal and alarm on the processors.
• Green – Shows power on an input terminal, power to the board and as a “heartbeat” to
show the software is running on the processors.
Each LED on the SRU board has a reference designator.
The input terminals are labeled 501 through 5XX (508 on the MR board). 24 VDC is connected
to the input terminals to run the logic circuitry.
WARNING
DO NOT APPLY AC CURRENT TO THE INPUT TERMINALS. APPLYING AC CURRENT WILL DAMAGE
THE BOARD.
The output terminal is connected to the negative side of the load and provides a reference
(REF) signal. The positive side of the load is connected to a 24 VDC power source.
If the yellow LED is not lit, the output transistors have no output and there is no load actuation.
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