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MAXIM Periscope Module. Electrical Design Estimates C. Paul Earle 25 April 2003. Design Assumptions. Design Notes & Assumptions Unregulated + 28V Supply from the S/C 1 pps timing signal + S/C time from the S/C MIL-STD-1553 Command & Data Handling Interface Requirements

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MAXIM Periscope Module

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Maxim periscope module

MAXIM Periscope Module

Electrical Design Estimates

C. Paul Earle

25 April 2003


Maxim periscope module

Design Assumptions

  • Design Notes & Assumptions

  • Unregulated + 28V Supply from the S/C

  • 1 pps timing signal + S/C time from the S/C

  • MIL-STD-1553 Command & Data Handling Interface

  • Requirements

  • Provide regulated power to Sensors, Actuators, & Circuit Boards

  • Time-Tag Sensor Data (ie. tip/tilt/piston) based on 1pps signal from S/C

  • Implement Thermal Control & Monitoring

  • Collect Housekeeping Data – Temperatures, Voltages, Currents


Maxim periscope module

Functional Block Diagram

Instrument

Spacecraft

Periscope

(1 of 4)

Instrument Electronics

1pps (1Hz)

Aperture

Motor (1)

Actuators (4)

InstrumentCPU

Mechanism

Drive

&

Control

S/C C&DH

1553 I/F

Sensors:

Encoders (3)

Tip/tilt (2)

RAM

H/K & Thermal

Control

DC/DC

Converter

Heaters

& Temp

Sensors

+28V Supply

+28V Survival

Power

Figure 1.


Instrument architecture

Instrument Architecture

Address & Data Bus

1pps

CPU

Board

(+RAM)

Mech

Drive

Board

Actuators

1553 I/F

BUS

H/K

& Therm

Board

Position

Sensors

Sensor

Board

Regulated

Power

Power

Board

+28V

(Unregulated)

Figure 2.


Sensor readout board

Sensor Readout Board

8:1

MUX

(Analog)

Pre-Amps

(8)

Tip/Tilt

Sensors

(8)

A/D

(1)

8

Buffer

(FIFO)

13:1

MUX

(digital)

To RAM

12:1

MUX

(digital)

Linear

Encoders

(12)

12

A/D, MUXs, FIFO Control

Readout

Control

FPGA

To/From CPU

(1 Sensor Readout Board per Free Flyer)

Figure 3.


Maxim periscope module

Power Board Load

Calculations:

CPU Board = 6 Watts

H/K & Thermal Board = 4 Watts

Sensor Board = 4 Watts

Mech Drive Board = 4 Watts

Aperture Motors = 1 Watts each (no simultaneous operation)

Actuators = 1 Watts each (no simultaneous operation)

Total Conditioned Power = 20 Watts

Assume Converter Efficiency of ~ 70%

=> Power Board Dissipation = (20/0.7) – 20 = 8.6 Watts


Maxim periscope module

Electronics Box Power Summary


Maxim periscope module

Main Electronics Box Summary

Main Electronics Box

Mech Drive Board (4W)

Sensor Board (4W)

H/K & Thermal (4W)

Power Board (8.6W)

6 in

(15 cm)

CPU Board (6W)

6 in

(15 cm)

7 in

(17.5 cm)

8 in

(20 cm)

10 in

(25 cm)

Total: ~ 26.6 Watts (avg.)

Estimated Mass ~ 7 Kg

Estimated Power ~ 26.6 Watts (Avg.) Estimated Size ~ (25 x 15 x 17.5) cm.

Figure 4.


Maxim periscope module

Instrument Power Summary

Spacecraft Power Bus Requirement


Maxim periscope module

Cost Estimate

  • Main Electronics Box ~ $4.3M

  • (Includes Design, Parts, Fabrication, Test, & ETU)


Maxim periscope module

Conclusion

  • Low risk design. Essentially design re-use for each of the

  • circuit boards. No science data on the Free-Flyers and the

  • Hub spacecraft. All Sensor Data and Housekeeping Data

  • is passed to the spacecraft via the 1553 bus.

  • Design could possibly be further optimized by moving

  • CPU functions to the spacecraft side of the bus and

  • utilize the FPGA for the instrument control functions.

  • Packaging could possibly be reduced by combining the

  • actuator drive board with the sensor readout board at the

  • expense of drive circuitry redundancy.

  • Example: A single drive circuit (with one backup) could

  • be multiplexed to each of the actuators given non-

  • simultaneous operation.


Maxim periscope module

Backup Slides

(Electrical Design Estimates)


Processor board

Processor Board

Startup ROM

1553 I/F

CPU

(RAD 6000)

1553 I/F

RAM

EEPROM Memory

(Thermal control logic)

S/W Dev.

Time Stamp

Function

S/C 1pps

Ethernet I/F

Figure 5.


Maxim periscope module

-

-

+

+

Driver

Amp

I+

Mechanism Drive Circuit

Aperture door

Drive Cmd

From

Processor

motor

HK

Mux

Open/close

detection

Actuator Current

+

To H/K

Board

Actuator Voltage

-

Figure 6.


Maxim periscope module

-

-

+

+

+

+

-

-

-

-

+

+

I+

I+

Thermal Control circuit

DAC

From

Processor

V+

Heater

Tsensor

HK

Mux

Heater Current

From

Processor

Heater Voltage

+

To

Central HK

-

Tsensor Voltage

Tsensor Current

VRef

ISource

(1 of n circuits shown)

Figure 7.


Maxim periscope module

HouseKeeping Circuits

Mux

16-ch

AD506

A/D

Conv.

AD 1672

H/K

FIFO

Power

Temp

...

To Controller Board

.

.

.

Mux

V-

Tsensor Voltage

-

+

V+

Tsensor Current

-

+

Mux

I+

VRef

ISource

(1 of n temp sensors)

Figure 8.


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