VDC HV control
Relay Box with 8 relays (channels) controlled by RPi board is used to limit trip current and prevent trips for VDC high voltage line during HV on/off operation.
Two of them have been installed in Left and Right HRS at the end of March, 2017.
Relay box consists of 8 relays and 8 resistors with 68Mohm nominal. Resistor is connected in series between output of hv channel and VDC hv line, or shortened by relay.
RPi board is used as TCP/IP server to control relays by commands from clients. RPi board in HV crate (rpi8(left), rpi7(right)) runs 'shim-server' to control modules in crate.
Shim-server will send commands to relay box server to switch relay ON (closed, shortened resistor) or OFF (open, resistor in).
Shim-server checks commands/responses from GUI to hv channel that connected to VDC. The next logic will be used by shim-server to control relays :
- commands: HVON, HVOFF, demand voltage (DV) set, enable/disable channel (EN), channels status (ST>1) ---> relay is OFF (open, resistor in) for this channel.
- channels status (ST==1) --> relay is ON (closed, resistor out) for this channel.
Command format for relay box server is the same as used by LeCroy HV system (examples):
- set relay channel #1 to ON (closed)
LD S0.1 RLY 1
- set relay channels #0,#2 to ON (closed) and channels #1,#3-#7 to OFF (open)
LD S0 RLY 1 0 1 0 0 0 0 0
- get status of all relays channel (1 - is ON, 0 - is OFF)
RC S0 RLY
In Java GUI hv module for VDC will have one more property column 'RLY_en' that shows status of relay box channels (0 - relay is OFF, 1 - relay is ON).
