WHT-ISIS-8    WHT ISIS Polarisation

Hardware Design Document

V.E. Austin

Issue 1.1; 08/05/96

Contents:

1. Introduction

2. Description

3. VME

4. Lemo Interface

5. Polarisation Module

6. Wiring Schedules

7. Cable Schedules

APPENDIX A.

DOCUMENT HISTORY

1. Introduction

1.1 Purpose

This document describes the electronic and computer hardware used in the ISIS polarisation module control system.

The intended readership of this document is those who wish to understand the ISIS polarisation module hardware design. Those users involved in the maintenance of the ISIS polarisation module at the hardware level will also benefit from reading this document.

1.2 Definitions, acronyms and abbreviations


ISIS Intermediate-dispersion Spectrograph and Imaging System

ISISP ISIS Polarisation

2. Description

The ISIS Polarisation module consists of two mechanisms. These mechanisms are the half-wave polarisation plate which is generally used for linear polarisation; and the quarter-wave plate, generally used for circular polarisation. To use either of these mechanisms the waveplate must be inserted into the beam where it can either be set to a specified angle or rotated continuously.

When the polarisation module is required for circular polarisation the positions of the two waveplates must be physically swapped (i.e. the half waveplate is placed in the top mounting and vice-versa). In order for the software to maintain the mount positions of the waveplates, the waveplate mechanisms are referred to as the top and bottom waveplates, which is the convention followed in all the hardware design and documentation.

The ISISP control electronics consists of two sub-racks which are mounted on ISIS. The two sub-racks are the VME crate and the Lemo interface unit. The VME crate controls and monitors the status of the ISISP mechanisms via interface boards accommodated in the VME crate. The Lemo interface unit redistributes signals from the mechanisms to the relevant VME port. The Lemo interface unit also contains two power supplies and the stepper motor drive cards for the waveplate motors.

2.1 System Schematic

 

 


3. VME

3.1 Physical Description

The ISISP VME is a 4U high 550 mm deep 19 inch sub-rack. It has a 7 slot horizontal VME backplane and power supply. Three interface cards are fitted along with a transition module. The transition module provides the connection to the network and system console via the P2 connector on the backplane. The interface cards comprise a stepper motor controller, a digital input/output module and a digital output module. The stepper motor controller card connects to the rear connector panel via the P2 connector on the backplane whilst the remaining two interface cards connect to the rear connector panel via connectors on the front panel of each card. The VME crate also contains a 40 _C thermal switch mounted on the top panel and a fan fail monitor and output module located between the backplane and power supply. The fan filter medium is accessible from behind the front panel. The mains switch is also behind the front panel, mounted on the left-hand side. This switch controls the mains to the VME power supply and also switches the mains to the IEC outlet on the rear of the VME.

3.2 Electrical Description

The processor card used is a Motorola MV147-011 with an TM1x7 transition module providing four RS232 ports, an Ethernet connection, a printer port and a SCSI interface. The three I/O cards used are:-

1 off OMS VME44-4E Stepper Motor Controller

1 off XVME 240 Digital Input/Output (DIO)

1 off XVME 220 Digital Output (DOUT)

3.2.1 MVME 147-011 Microcomputer

This card is a 32-bit microcomputer system containing a MC68030 MPU with a clock speed of 25MHz, a MC68882 floating-point coprocessor and 4MB of memory. It connects to both P1 and P2 on the VME backplane using the latter to connect to a transition module. The ethernet address is 08003E22AF09.

3.2.1.1 Setup

ROM Configuration

The ROM is configured in two banks, U22 and U30 form bank 1, U1 and U15 form bank 2. Only bank 1 is used which is configured by J2. This is set for 64K x 8 PROM by linking the following pairs of pins on J2

Link Pins 2 & 4

Link Pins 5 & 7

Link Pins 14 & 16

Link Pins 13 & 15

System Controller

The MVME147-011 is selected as the system controller. Link J3

Serial Port 4

Receives RTXC4 J8 Pins 2 & 3 linked

Receives TRXC4 J9 Pins 1 & 2 linked

3.2.2 TM1x7 Transition Module

The transition module provides the interface between the MVME147-011 processor card and the external peripherals. It provides 4 serial ports, a printer port, a SCSI interface and an ethernet connection.

3.2.2.1 Setup

Serial Ports 1,2,3 and 4

All ports are configured for DCE operation using headers X1, X2, X3 and X4. The correct link orientation is shown on the PCB silk screen. Headers X6, X7 and X8 have no links made.
 

3.2.3 XVME 240 Digital Input/Output - DIO

This card provides 8 ports of TTL level digital input and output, each port being 8 bits wide. Ports 0 to 3 (connector JK1 on the front panel) are allocated as inputs whilst ports 4 to 7 (connector JK2 on the front panel) are allocated as outputs.

3.2.3.1 Setup

Base Address

0xD000 1(A10), 2(A11) and 4(A13) of S2 closed.

3(A12), 5(A14) and 6(A15) of S2 open.

Address Space

Short I/O Access J2B linked, switch 8 of S2 closed.

Supervisor/non-privileged mode

Supervisory only mode

Switch 7 of S1 open.

Address Modifier

Short I/O used, DIO will respond to 2DH only

J2B linked, switches 7 open and 8 closed of S2.

Interrupt Level

No level selected Switches 1, 2 and 3 of S1 closed.

Interrupt Input Edge Detection

Not required as interrupts are not used

J3 to J10 all linked on B.

3.2.3.2 Channel Allocation

Inputs

Port 0



 

Port 1



 

Port 2



 
 

Port 3



 

Outputs

Port 4



 

Port 5



 

Port 6



 
 

Port 7



 
 

3.2.4 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 and any load up to 30V and 100mA can be controlled. Channels 0 to 15 are available via JK1 on the front panel and channels 16 to 31 via JK2.

3.2.4.1 Setup

Base Address

0xC800 1(A10), 3(A12) and 4(A13) of S1 closed.

2(A11), 5(A14) and 6(A15) of S1 open.

Address Space

Short I/O Access J2B linked, switch 8 of S1 closed.

Supervisor/non-privileged mode

Supervisory or non-privileged mode

Switch 7 of S1 closed.

Address Modifier

Short I/O used, DOUT will respond to 29H or 2DH

J2B linked, switch 7 and 8 of S1 closed.
 

3.2.4.2 Channel Allocation








 
 

3.2.5 VME 44-4E Stepper Motor Controller

This card provides 4 independently controllable axes each with encoder feedback. Each axis has a step and direction output to drive the motor and has positive and negative limit inputs to provide hardware safety limits. A datum input is also provided to move the motor to a known position. All connections are made via the P2 connector on the VME backplane.

3.2.5.1 Setup

Base Address

0xFC00 A4, A5, A6, A7, A8 and A9 linked on J25 and J26.

A10, A11, A12, A13, A14 and A15 not linked on J25.

Address Modifiers

Default setting AM1 and AM4 linked on J26.

AM0 and AM5 not linked on J26.

Interrupt Selection

IRQ5 IRQ5 linked on J15.

IRQ1, IRQ2, IRQ3, IRQ4, IRQ6 and IRQ7 not linked on J15.

J1 linked on J35.

J2, J0 and USER not linked on J35.

Limit Polarity Selection

Channel X, Y, Z and T active Lo

Linked on J24.

Encoder Bias Selection

Default setting T and Z encoder bias, no links on J11

X and Y encoder bias, no links on J14

I/O and Pull-up Select

User definable I/O disabled

All links removed on J32 and J34

I/O output driver I.C.s U31, U33 and U34 removed
 

3.2.5.2 Channel Allocation



 
 

3.3  Parts List






4. Lemo Interface

The Lemo Interface unit provides the wiring interface between the ISISP module and the VME controller. It also contains the power supplies and the stepper motor drive cards for the stepper motors used in the module.

4.1 Physical Description

The ISISP Lemo Interface Unit is a 3U high 386 mm deep 19 inch enclosed sub-rack. The hinged front panel allows internal access, while the front panel mounted Lemo connectors provide the interface to the ISISP module. The rear panel provides the interface to the VME controller via two D-type connectors and two Lemo connectors. Inside the sub-rack are two power supplies and two stepper motor drive cards. The sub-rack was constructed from a Schroff ratiopac kit with additional components allowing recessed mounting of the eurocards.

4.2 Electrical Description

The interface between the ISISP module and the control electronics is via a number of cables terminated with Lemo connectors at both ends and routed through ISIS. The signals are grouped depending upon which assembly they originate from and their function. The function of the Interface Unit is to re-distributed these signals to the required VME port or stepper motor drive.

4.2.1 VME Interface

The interface to the VME cards is via 50 way IDC connectors. This type of connector is unsuitable for a wiring loom such as the one in the Lemo Interface so the cables between the VME and the Lemo Interface are terminated with a standard 50 way IDC connector and a 50 way IDC D-type connector at each end respectively. The table below gives a cross-reference of pin numbers between the two types of connector.










 

4.2.2 EDM-453 Stepper Motor Drive Card

This is a commercially available bipolar chopper driver (3A per phase, 45V) designed specifically to drive the Portescap two phase stepper motors.

4.2.2.1 Card Setup

Switch 1 (Mode) - OFF Regenerative mode

Switch 2 (D0) - OFF Resolution 64 microsteps per full step

Switch 3 (D1) - OFF

Switch 4 (D2) - OFF

Switch 5 (INT/EXT) - ON Mode and resolution selected internally

Switch 6 (I0) - OFF Phase current 3A

Switch 7 (I1) - OFF

Switch 8 (I2) - OFF

Switch 9 (I3) - OFF

4.2.3 Power Supplies


The Lemo Interface Unit contains two single output power supplies, providing 5V 12A and 24V 10A respectively. The table below details where each of the supplies is used.


 

4.3  Parts List








5. Polarisation Module

5.1 Physical Description

The polarisation module consists of two identical mechanisms, the top and bottom waveplates, mounted on a baseplate. Connector brackets providing the interface to the Lemo Interface Unit are also mounted on the baseplate. Each waveplate consists of a stepper motor, encoder, datum switch, clamp mechanism and clamp sensor mounted on a slide. The slide can be pneumatically deployed into the beam with two sensors giving positional information. The encoder, motor and waveplate holder are all mounted on separate gears with the following gear ratios:-

motor:encoder = 35:16

encoder:waveplate = 2.4:1

These gear ratios result in one encoder pulse measuring 0.025_ at the waveplate and one motor microstep measuring 0.01143_, giving approximately two microsteps per encoder pulse.
 

5.2 Electrical Description

The stepper motors used to rotate the waveplates are Portescap two phase stepper motors constructed using disc magnet technology and having a holding torque of 140 mNm or 20 oz-in. The stepper motors have a step angle of 3.6_ and are operated in microstep mode with 64 microsteps per full step. The encoders are Heidenhain optical, incremental modular encoders with a resolution of 1500 pulses per revolution. The encoder resolution is increased by four times (i.e. 6000 p.p.r.) using quadrature decoding at the VME44-4E card. In order to calibrate the zero-point of the encoders, inductive proximity switches are used to define the datum position. Inductive proximity switches are also used to give status information for the solenoid-activated pneumatic valves driving the clamp and slide sub-mechanisms.
 

5.3 Parts List




 



6. Wiring Schedules

The wiring schedules for each of the polarisation waveplates, from the mechanism assembly through to the VME crate, are available. The colour convention followed in the wiring schedules is described below.

6.1 Mains Wiring

Brown - Live (240 VAC)

Blue - Neutral

Green/Yellow - Earth Chassis
 

6.2 Power Supply / Chassis Wiring

Red - +5V

Black - 0V

Yellow - +24V

Green/Yellow - Chassis Earth

Pink - General Chassis Wiring
 

6.3  Top Polarisation Waveplate (not with this document)

6.4  Bottom Polarisation Waveplate (not with this document)

7. Cable Schedules

All external cables are wired straight through using the following colour convention:-







 
 

External cables between VME crate and Lemo interface


 

External cables between Lemo interface and polarisation module


 

Document History

Issue 1.1 08/05/96  Vicky Austin (RGO)   First issue.