HIRES CCD Controller Electronics

This section contains descriptions of the overall electronics for the HIRES CCD controller.

Block Diagram, EL-3410

Schematic: schematics/Block.sch.pdf
Page last updated: August 2, 2004

The HIRES CCD upgrade block diagram is a road map to the interconnection of the overall system. The left side of the diagram shows the data taking computer (lehoula) and the VME crate (hccdvmep) and their 100MB/S ethernet connection. The high speed connection is made over a private connection and is used to transfer image data from the VME crate to the data taker. The data taking computer is also in the general observatory network. The VME crate is connected to the CCD Controller via a dedicated set of fiber optic cables. This provides the widest possible bandwidth for fast transfer of the CCD readout from the CCD controller to the VME crate. Note, in the original HIRES system, the VME crate lived in the HIRES electronics vault at the nasmyth deck. With this upgrade the VME crate will now live in the computer room with the data taking computer.
The dashed box in the middle of the diagram represents the new footlock that has been installed with this upgrade. The two major components inside the footlocker are the CCD controller and the FLIC (FootLocker Interface Chassis). The CCD controller runs the CCD dewar, provides power for the dewar preamps, and controls miscellaneous functions such as automatic dewar filling and footlocker cooling fan control. The FLIC interfaces the CCD controller to the outside environment and provides isolation for the CCD controller's circuitry. The other major function of the FLIC is to provide the same over temperature protection that the original footlocker had.

The dewar connections are illustrated on the right side of the sheet and consist of preamp power, CCD video outputs, and signal cables. A major part of the HIRES upgrade is a change from a single CCD device to a mosaic of three devices. With three devices the cabling has grown by nearly three times. Thus, there are three signal cables, six coax cables, but still only one dewar power cable. Due to problems with amplifier A on CCD 2, the mosaic is restricted to single amplifier readout. In as far as the diagram is affected, the coax cables for the three B amplifiers are not used. The three 51-pin signal cables contain the various clock and bias voltages for each of the three devices. The power and control cable contains the +/-15v power for the Analog Switch boards, the temperature sensor diode signals, the heater resistor signals, and the analog switch control signal. This control signal is used to turn the analog switches open or closed.

The FLIC chassis accepts and controls the AC power for the footlocker via the AC Control Module, EL-3419. The module contains the input AC connector and input fuse, the over temperature control relay, and the controlled AC outlet for the CCD controller. The Cooling Fans module consists of a general purpose opto-isolated solid state relay that controls an AC outlet on the back of the FLIC box. The control of the fans is done in software. The dewar fill interface allow the CCD dewar to be filled either automatically or manually from a 50L dewar that lives on the nasmyth deck. The system uses a level sensor in each of the dewars to determine, again by software, when the CCD dewar LN2 level is low and initiates a fill cycle. The software also monitor the LN2 level in the 50L dewar so that it can notify the observatory if dewar gets low. (See EL-3415) The last module in the FLIC chassis is an updated version of the original HIRES shutter controller. The updated board is functionally identical but the board was reworked to fit a 3U form factor.

On the right side of the diagram is a representation of the CCD dewar. The power and filter board received the analog supply voltages, provides filtering, and distributes them to the preamps and analog switch boards. The two channel preamp boards amplify and send the CCD output back to the CCD controller Video boards. There are three preamp boards, one for each CCD device. The Analog Switch boards isolate all of the clock and bias voltages from the controller. The analog switches are off until the software has set and checked the clocks and voltages. Once the controller comes up correctly and the clocks and voltages are correct the software will then turn on the switches. Again, there are three analog switch boards, one for each CCD device. Within the vacuum chamber of the CCD dewar, there are the CCD, flex cables, and interconnect boards for each device in the mosaic.

Above of the dewar is a representation of the Ilex shutter. This is the shutter from the original HIRES instrument.