Schematics EL-3113 and EL-3115 show the layout for one each of the Opto-22 relay racks used in the cradle instrument electronics. The sheets have a block in the upper left-hand area that associates a channel number and a bit number with a function. The channel number gives the location of the I/O module on the individual rack. The bit number gives the I/O bit that the software can read or write and the function tells what the bit toggles or reads.

In the lower left area is a pictorial representation of the actual I/O rack. The drawing shows where the relays are and what their function is. It also tells what relay should be plugged into each slot. Notice that between each relay and its screw terminal is noted what color relay should be installed. The other important piece of information shown here is the position of the various bus bars. These are sheet metal strips that are used to connect from two to eight terminals together.

On the right-hand side of the drawing is a table showing the destination or the output connections of the I/O relays. The first column gives the I/O bit for programming. The pin column refers to the screw terminals on the edges of the relay racks. The next three columns give the connector and pin numbers that the output is connected to. The sixth column tells what relay part number populates each position on the relay rack. The last column tells the function that the relay controls. On the right-hand side of the table are the channel numbers as labeled on the board.

Mode Select Bit 2: Input bit 49 is wired to the binary 2-Bit output of the Mode thumb wheel switch. Together with bits zero and one, the switch setting is interpreted by the software to determine the mode of operation that the Forward and Reverse pushbuttons will initiate. (More info)

Mode Select Bit 1: Input bit 50 is wired to the binary 1-Bit output of the Mode thumb wheel switch. Together with bits zero and two, the switch setting is interpreted by the software to determine the mode of operation that the Forward and Reverse pushbuttons will initiate. (More info)

Mode Select Bit 0: Input bit 51 is wired to the binary 0-Bit output of the Mode thumb wheel switch. Together with bits one and two, the switch setting is interpreted by the software to determine the mode of operation that the Forward and Reverse pushbuttons will initiate. (More info)

Stage Select Bit 2: Input bit 52 is wired to the binary 2-Bit output of the Stage thumb wheel switch. Together with bits zero and one, the switch setting is interpreted by the software to determine which stage will be operated when the Forward or Reverse pushbutton is pushed. (More info)

Stage Select Bit 1: Input bit 53 is wired to the binary 1-Bit output of the Stage thumb wheel switch. Together with bits zero and two, the switch setting is interpreted by the software to determine which stage will be operated when the Forward or Reverse pushbutton is pushed. (More info)

Stage Select Bit 0: Input bit 54 is wired to the binary 0-Bit output of the Stage thumb wheel switch. Together with bits one and two, the switch setting is interpreted by the software to determine which stage will be operated when the Forward or Reverse pushbutton is pushed. (More info)

Auto/Manual Switch Setting: Input bit 55 is wired to the Auto/Manual switch labeled Computer to the left side and Manual to the right side. This bit is read back by the controller software and when in the active low state, the controller locks out any movement commands from the control computer and instead, receives instructions from the hand paddle. (More info)

Stop Pushbutton: Input bit 56 is wired to the Stop pushbutton and when read back by the controller software causes any rotation commands to be terminated. Note that this is a software control - not - hardware. In an emergency, the operator should use the large red emergency stop pushbuttons mounted around the instrument cradle. (More info)

Forward Pushbutton: Input bit 57 is wired to the Forward pushbutton and when read back by the controller software causes the instrument to begin moving in the forward direction. (More info)

Reverse Pushbutton: Input bit 58 is wired to the Reverse pushbutton and when read back by the controller software causes the instrument to begin moving in the revese direction. (More info)

Toggle1 Pushbutton: Input bit 59 is unwired but the bit is reserved to allow the software to be compatable between various instruments.

Toggle2 Pushbutton: Input bit 60 is unwired but the bit is reserved to allow the software to be compatable between various instruments.

Locked out: Input bit 61 is wired to the locked out signal that is generated when any of the large red emergency pushbuttons is pushed. Once one of these switches is pushed, the only way to restore power to the rotation motor is to manually push the green Reset button on the interlock electronics box inside bay C of the cradle. (More info)

Band Clamp Brake: Input bit 62 is wired to the Band Clamp Brake. This signal is derived from a limit switch mounted on the crable and is actuated by the hand clamp of the band brake. (More info)

Bit 63 (not used)

Air Pressure: Input bit 64 is wired to the air pressure sensor. If pressure drops below about 60 PSI the switch will pull the input line low signaling the failure condition. (More info)

Coolant Flow OK: Input bit 65 is wired to the Proteus flow switch mounted where the coolant lines come into the instrument. If the flow (More info)

Remote Rotation Lockout: Input bit 66 is not wired. It is reserved for future use by Keck.

Bit 67 (not used)

Bit 68 (not used)

ESTOP: Input bit 69 is wired to a relay driven by the observatory E-STOP line. When active, the signal tells the software to stop and then disable motion until the E-STOP line has been reset. (More info)

Rotation Bypass/Normal Mode Switch: Input bit 70 is wired to the Bypass/Normal switch located inside the AC circuit breaker box. When activated, the bypass system remove the controller power from the motor and substitutes a 15 volt supply. The supply is wired such that the motor will have the correct polarity voltage applied when the forward or reverse limit override pushbutton is actuated. The bypass system also includes an ammeter on the 15V supply. (More info)

Rotation Disable Switch: Input bit 71 is wired to the relay labeled DISABLED on sheet 6 of EL-3120. The relay is dropped when ever any of the man hatches or stage access doors are opened. Unlike the Lock Out signal, once these doors or hatches are closed the signal is unasserted and the instrument can be rotated without having to press the reset button. (More info)

Band Clamp Brake: Input bit 72 is wired to the Band Clamp Brake and is the converse of bit 62. This signal is derived from a limit switch mounted on the crable and is actuated by the hand clamp of the band brake. Note that this is not an indication that the band clamp lever is in the fully unclamped position. Rather, it indicates that the brake is not clamped. (More info)