WYFFOS - Wide Field Fibre Optic Spectograph


The WYFFOS intrument control electronics consists four sub-racks which are housed in a 19 inch rack enclosure in the GHRIL control room. The four sub-racks are: The control electronics connects to the instrument via a number of cables to each of the assemblies that have electronic controls or monitoring which are Each of the assemblies has a number of connectors that group the signals accoring to their functions.

All the signals from the sub-assemblies connect to the Lemo interface unit, here they are re-distributed to the relevant VME port or to the LIMPIT. The Lemo Interface unit also contains a power supply and the signal conditioning amplifiers for the LVDT position encoders.

VME Controller

The VME controller is a 7U 19 inch sub-rack with a full 84HP wide 6U VME backplane and power supply. The extra 1U is taken up by a fixed fax tray. The proccesor card used is a Motorola MV147S-1 with an MVME712M transition module providing four RS232 ports an Ethernet connection, a printer port and a SCSI interface. The VME also includes 5 I/O boards An EPICS Database Index can be found here.

OMS8 Stepper Motor Controller

This provides 8 axis each independantly controllerable. Each axis has a step and direction output to drive the motor and has positive and negative limit inputs to provide hareware limits of movement. A datum input is also provided which can be used to move the motor to a known position to check calibration of the encoder. All connections are made via the P2 connector on the VME backplane.

XVME 240 Digital Input/Output (DIO)

Each card provides 8 ports of TTL level digital input/output. Each port,consisting of 8 bits can be configured to either input or output but in our application ports 0 to 3 (Connector JK1 on the front panel) are used for inputs and ports 4 to 7 (Connector JK2 on the front panel) are used for outputs.

XVME 220 Digital Output (DOUT)

This card provides 32 channels of opto-coupled digital output. Each channel has a positive and negative connection so all channels are completely isolated. Channels 0 to 15 a via JK1 on the front panel and channels 16 to 31 are via JK2.

XVME 566 Fast Analogue Input (FAIN)

This card is capable of providing 16 channels of single ended 12-bit analogue to digital converstion or as in the WYFFOS application 11 channels of double ended 12-bit analogue to digital converstion.

Comparison Lamp Controller

The unit currently fitted The Alternative Comparison Lamp Controller is a 2U high 19 inch mains distribution panel providing three standard mains sockets which can be turned on and off and a status returned via a digital interface. Each socket is controlled via a solid-state relay and provides 240V 50Hz ??amps. The control interface is via a 25 way D connector on the backpanel and is designed to be equivalent the interface on the comparison lamp controllers used on ISIS and UES with the exception of and extra +5V supply required on pin 12 of the connector which is unused on the ISIS/UES interface which means the alternative controller will not work in place on the standard controller (without the addition of the extra 5V supply) but the ISIS/UES controller will work in place of the Alternative Controller.

A full description of the contrller can be found in the Alternative Comparison Lamp Controller Technical Manual


The back panel of the limpit provides an interface to the VME8 stepper motor controller via a 64 way DIN41612 connector and provides a motor (15 way D) and a limit (9 way D) connector for each of the 5 motor axes used. There are also connections for the fibre back illumination (9 way D) and a serial (9 way D) and a parallel (25 way D) connection for the grating encoder. The limpit contains five single eurocard circuits and three power supplies in a 3U 19 inch sub-rack. The three power supplies are Vero types supplying +5V +12V and +24V. The five eurocards are:

D225 5 Phase Stepper Motor Drive Card

This is a commerically available drive card designed specifically to drive the Begher Lahr 5 phase stepper motors. It is the same drive card as used in the Prime Focus Instrument Platform (PFIP) Limpit. The card has 4 inputs Step, Direction, Half/Full and an Enable and produces the drive currents required to move the stepper motor.

SMD4 3 axis 4 Phase Stepper Motor Drive Card

This card is an RGO designed and built card and provides three independant drives for 4 phase stepper motors. It has the same inputs as the 5 phase stepper motor drive card for each of the three axis (Step, Direction, Half/Full and Enable).

A full description of the circuit can be found in the SMD4 3 Axis 4 Phase Stepper Motor Drive Card Technical Manual

DC Motor Drive Card

This is an RGO designed and built card. It has a similar interface as the other drive cards (Step, Direction, and Enable) but drives a DC motor using a commercial four quadrant linear output motor driver (RS 715-005). A monostable is retriggered on each rising edge of the step input and the output is used as the drive request for the DC motor driver. Therefor the motor is driven all the time the step input is clocking fast enough to stop the monostable from timing out. However varying the step rate above this frequency does not affect the speed of the motor, this is set by a pot on the driver module.

A full description of the circuit can be found in the Slit Translation DC Motor Driver Technical Manual

Fibre Back Illumination Driver

This is an RGO designed and built card. The circuit is specifically designed to drive the fourteen high output infra-red emmiters used to back illuminate the WYFFOS fibres. Two 15V DC to DC converters are used to supply the 30V required to drive the emmiters and cooling fan. A status is also returned to verify that current is flowing through the array.

SPEC - Serial to Parallel Encoder Converter

This is an RGO designed and built Card. The device used to encode the angle of the grating (ROC417) produces a serial output. To avoid the problems of ensuring the VME controller could poll the encoder at the required rate to read the serial data and convert it into a parallel word a separate card was designed and built. The card has one input to request a new word to be read from the encoder. When this request is set the seventeen position bits and the parity bit are read from the encoder and put through a shift register to produce a parallel word that can be read by the VME controller. A conversion complete bit is set to indicate that the new word is ready to be read.

Lemo Interface Unit

The main function of this unit is re-distribute the signals from the instrument to the correct VME I/O or to the limpit.