Group C interlock board

Functions

FEB protection

FEBs must not be powered without cooling: MPOD trips and does not start if FEB flow switch is below setpoint (bypass switch)

SVT protection

SVT must not be cooled without dry air: SVT chiller trips and does not start unless dry air dewpoint is below setpoint (unplug serial cable/disable remote control to bypass)

SVT must not be powered without cooling: MPOD trips and does not start if SVT chiller doesn't respond to RS-232 or is not running (bypass switch)

Monitoring

Report system status every 10 minutes, and failures as they happen

Inputs:

• HTM2500LF temperature+humidity sensor inside SVT box
• Flow switch in FEB chiller return line
• RS-232 connection to FEB chiller - status, set T, measured pressure/flow/T
• RS-232 connection to SVT chiller - status, set T, measured pressure/flow/T

Thresholds:

• Ambient T inside SVT box < 25 C (set in Arduino script)
• Ambient RH inside SVT box < 5 % (set in Arduino script)
• Cooling system flow > 20 GPH (adjustment screw on flow switch)

Logic:

• Check inputs every 1 s; if any input is abnormal, trip and stay tripped (must reset Arduino board to clear)

Outputs:

• RS-232 to FEB chiller: if tripped, send "stop" command every 1 s
• RS-232 to SVT chiller:
• Enable to MPOD crate (5V) - always on if interlock board is powered
• Interlock to MPOD crate (0V normal, 5V tripped) - trip turns off all outputs immediately
• Prints status to USB serial connection every second (if plugged in)

Normal startup

Check dry air is flowing, and all interlock inputs are plugged in. Both chillers and MPOD should be powered but not running. Interlock board should be off.

Start EPICS controls. Verify that MPOD channels cannot be turned on with the interlock board off.

Set SVT chiller setpoints using its touchscreen. When done, switch to remote RS-232 control.

Start FEB chiller and adjust setpoint, then stop the chiller.

Turn on the interlock board. Green LED should turn on immediately; MPOD trip LED should clear as chillers start. The other LEDs should stay off.

Turn on MPOD channels through EPICS.

Start the Arduino monitor script on hpstracker. It should send an initial status tweet.

Special startup (interlock disabled, no unattended running allowed)

Flip the switch on the interlock board to the "BYP" position to bypass the MPOD interlock.

Unplug the RS-232 cables for any chillers you don't want to run.

Turn on the interlock board. The top three LEDs (green, yellow, red) on the interlock board should be on.

Turn on MPOD channels through EPICS.

Shutdown

Turn off the interlock board and chillers, in any order. This should trip the MPOD.

Stop the Arduino monitor script on hpstracker.

LED indicators

Top (green): power on/MPOD enable - should always be on

#2 (yellow): MPOD interlock bypassed (controlled by switch on interlock board)

#3 (red): MPOD trip signal (OR of flow switch trip and Arduino output) - this trips the MPOD unless the interlock is bypassed

#4 (red): chiller trip (this is an Arduino output)