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.

Bit 17 (not used)

Bay C & D fans on: I/O bit 18 is wired to turn off and on the fan/heat exchanger located between bays C and D. The rotation PC controls the fans. It uses ambient temperature sensors in each of the bays to close the cooling loop. (More info)

Bay A & B fans on: I/O bit 19 is wired to turn off and on the fan/heat exchanger located between bays A and B. The rotation PC controls the fans. It uses ambient temperature sensor in the bay to close the cooling loop. (More info)

Bit 20 (not used)

Bit 21 (not used)

Movement Warning: Bit 22 is wired to the AC socket labeled AC3. It is used to turn an audible buzzer to tell people near the instrument that the instrument is about to rotate. (More info)

Motion Alarm: Bit 23 is is wired to the AC socket labeled AC4. It is used to turn on a flashing light to tell people near the instrument that the instrument is moving. Obviously, this was implemented during the building of the instrument and the lamp removed. However, the AC socket is still powered via software and available. (More info)

Bit 24 (not used)

Over Temperature Shutdown: Bit 25 controls the AC power connection to the locker. The instrument computer can cut the AC power if the temperature rises above 85 degrees F. in the locker. If this path fails there is a 85º F mechanical thermostat that can also shut down the locker. (More info)

Bit 26 through Bit 32 (not used)

Rotation Disabled - Toggle LED 3: Bit 33 is wired to the Toggle LED 3 in the manual rotation paddle. The LED is labeled Hatch Open and tells the rotation computer that one or more of the man hatches is opened. (More info)

Rotation Bypassed - Toggle LED 4: Bit 34 is wired to the Toggle LED 4 in the manual rotation paddle. The LED is labeled Rotation Bypassed and tells the rotation computer that . (More info)

E-STOP Signal - Toggle LED 5: Bit 35 is wired to the Toggle LED 5 in the manual rotation paddle. The LED is labeled E-STOP Active and tells the rotation computer that the observatory wide STOP has been issued. (More info)

Band Brake Engaged - Toggle LED 1: Bit 36 is wired to the Toggle LED 1 in the manual rotation paddle. The LED is labeled Band Brake On and tells the rotation computer that the band brake is engaged and the instrument can not be rotated. (More info)

Rotation Locked Out - Toggle LED 2: Bit 37 is wired to the Toggle LED 2 in the manual rotation paddle. The LED is labeled Panic Button Pushed and tells the rotation computer that one or more of the red Emergency stop buttons have been pushed. (More info)

Manual Paddle Forward Limit LED: Bit 38 is wired to the red forward limit LED. When activated, the instrument can only be rotated in the reverse direction. (More info)

Manual Paddle Reverse Limit LED: Bit 39 is wired to the red reverse limit LED. When activated, the instrument can only be rotated in the forward direction (More info)

Manual Paddle Stage is Moving LED: Bit 40 is wired to the yellow In Motion LED and is an indicator that the stage is rotating. Note that the barrel can rotate slowly enough that motion is not percept able.(More info)