Carbon Doors

Four of the five doors operate remotely, the fifth needing further testing before it is certified reliable. The doors use the EPICS control system to activate and read back the various components.

Each layer of carbon doors has one relay board. Each board is identical in operation and there is one spare in the event one of them should fail. The global purpose of the relay board is as follows:

1. Turn on the 12V to power to rest of circuit board.

2. Set the polarity on the 90V used to power the motors.

3. Turn the 90V on.

4. Cut off the 90V to a motor if the appropriate limit switch is hit.

5. Read back the status of the limit switches.

The 12V used to power the circuit board runs through this relay and it is activated via an EPICS relay in VME crate 4 (hallasc4). Relay #1 turns on the 90V and it too is activated by an EPICS relay in VME crate 4. Relay #2 switches the polarity of the 90V being fed to the driving motors. When activated it reverses the polarity to the motors and it is controlled by a relay in VME crate 4. Relays #3 and #5 are activated by the inner limit switches of the carbon doors. When these switches are depressed the relay activates and the 90V is cut off. Relays #4 and #6 are activated by the outer limit switches of the carbon doors and like relays #3 and #5 cut off the 90V when activated. Relays #4 and #6 activate when opened rather than when depressed. It would be nice in the future to have relays #3 and #5 also activated by an open limit switch condition and deactivated when the switch is closed. This way the 12V could be off to one of the switches and the doors would stop moving. As it is now, a broken wire/short while the doors are closing could cause the doors to continue moving risking possible damage.

The status of the limit switches is readout via an ADC in VME crate 4. If the switches are closed a -4V is seen at the ADC input. This is effected via a voltage splitter of 3 k$\Omega$ - 6 k$\Omega$ resistors. The readouts are plugged in via telephone jacks (PJ4, PJ5, PJ6, and PJ7). A temporary fix has been put in place which sends the signals through a capacitor first to block voltage spikes going into the ADC. These voltage spikes caused the ADC to trip off-line which can only be fixed by resetting the VME crate.

Figure 5.23: EPICS GUI for the carbon doors.

1.

The operation of the carbon doors is done via a GUI style control panel . This panel is located under the detector screen of the hadron arm (FPP Carbon Doors). The 3/4" carbon door has been disconnected at the 90V power supply and is not implemented in the software GUI. This door had what may have been some sliding problems. Since it may take a great deal of force to remove this door if it should jam, it will need to be tested so it can be removed easily if it should jam. The normal operating procedure with the GUI is to first make sure all the 90V power is off to each door (Blue switches), then to turn on the 12V power to each door to see where it is located in the stack (in vs. out). If you wish to change the status of a door (in/out) then simply toggle the IN/OUT switch appropriately and turn on the 90V. It takes some time for the doors to move the entire range, so be patient. When the limit switches have been reached the appropriate indicators will light up. You should then turn the 90V off. The important aspect of this procedure is to make sure that you do not change the polarity of the 90V while the doors are moving. This place undue stress on the motors and the power supply as well.