Communications Interoperability



Communications Interoperability

Device

Power Detailed Design Document

Version 1.8

Senior Design II 2006

Lafayette College

Table of Contents

1 Definitions 4

2 Power Team Members 4

3 Overview 5

4 Requirements 7

5 POWER 8

5.1 Inputs 8

5.2 Outputs 8

5.3 User Interface Signals 8

5.4 Functionality 9

6 Functional Blocks 9

6.1 BACKUP BATTERY AND CHARGER 9

6.1.1 Inputs 10

6.1.2 Outputs 10

6.1.3 States 10

6.1.4 Functional Sub Blocks 10

6.1.4.1 12 VDC BACKUP BATTERY 10

6.1.4.2 BACKUP BATTERY CHARGER 12

6.2 PROTECTION SYSTEM 13

6.2.1 Inputs 13

6.2.2 Outputs 13

6.2.3 User Interface Signals 13

6.2.4 Design 14

6.2.5 Functional Sub Blocks 14

6.2.5.1 Fuse Protection 14

6.2.5.2 Circuit Breaker Protection 15

6.2.5.3 Low Voltage Alarm 15

6.3 Voltage Conversion 16

6.3.1 Inputs 17

6.3.2 Outputs 17

6.3.3 Design 17

7 Cable List 18

Table of Figures

Figure 1 – Communication Interoperability Device Top Level Architecture 5

Figure 2 – Requirements vs. POWER Functionality 7

Figure 3 – Power Top Level Diagram 8

Figure 4 – Battery Backup AND CHARGER Diagram 9

Figure 5 – Power Sonic Rechargeable Sealed Lead-Acid Battery 12 Volt 100 Amp. Hrs. 10

Figure 6 – Power Profile 11

Figure 7 – Power Requirement vs. Battery Size 12

Figure 8 – SRM-30M Front View 12

Figure 9 – SRM-30M Rear Panel View 12

Figure 10 – Protection System Diagram 13

Figure 11 - Example of a Protected PCB 14

Figure 12 – Low Voltage Alarm Circuitry 15

Figure 13 – Voltage Conversion Diagram 17

Figure 14 – Cable List: Source, Destination, Voltage, Gauge, and Color 18

Definitions

Ampacity Limit – The amount of current a line can carry without exceeding the wire’s thermal limit.

AWG – Measure of wire diameter. As AWG size decreases, ampacity increases.

CB – Circuit Breaker, an overcurrent protection device.

Protection Philosophy - Electrically isolate sections of the system to provide overcurrent protection. A technician will find which sub block lost power via visual indication (LED).

SPG – Single Point Ground. The system will not have floating grounds.

Power Team Members

Laura Fredley

Tricia Indoe

Marc London

Overview

This document contains the detailed design of the POWER block of the system. The POWER block distributes power to each block of the system as shown in Figure 1. The POWER block has 4 LRUs, the BATTERY CHARGER, the BACKUP BATTERY, the VOLTAGE CONVERSION board, and the PROTECTION SYSTEM. This is shown in Figure 2. The Communications Interoperability Device plugs into a 120 VAC outlet. The BATTERY CHARGER charges the backup battery while the system is receiving 120 VAC. If the 120 VAC should fail, the battery backup powers the system for approximately 7 hours. The PROTECTION SYSTEM contains an alarm that will be set if the battery voltage falls below 11.5V. Also, the PROTECTION SYSTEM contains circuit breakers and fuse that protects the system from overcurrent. The VOLTAGE CONVERSION board provides the system with the appropriate voltage levels for the INTERFACE LRU and HUB/SANITY LRU.

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Figure 1 – Communication Interoperability Device Top Level Architecture

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Figure 2 – Communication Interoperability Device LRU Diagram

Requirements

This section lists the Project Requirements that are relevant to the POWER system.

R002 - “Suitable technology interfaces (CSE) shall be supported providing appropriate signal levels, control, and equipment protection.” Power is distributed at various voltage levels meeting the system power needs. The system equipment is protected via fuses and circuit breakers. Also, a single point ground exists.

R006 - “A single battery backed external voltage source shall power each system.” External 120 VAC normally powers the system. In the event of an outage, a backup power in parallel with the external source will power the system.

R007 - “The target operational environment shall be an equipment rack in a telephony equipment shelter.” The battery charger fits the industry standard of a 19” rack. Other power system parts (excluding battery) are encased within equipment shelter.

R008 - “Each system shall support fault localization to the LRU level.” Power LRU detects low voltage of the backup battery. Power supply to a faulted LRU will be isolated.

R009 - “An error reporting mechanism shall be implemented.” A low voltage alarm occurs when the backup battery voltage falls to the threshold of 11.5 V.

R010 - “The design of the system shall be manufacturable.” The voltage conversion board layout can be sent to an external vendor to print.

R011 - “The design and deployment shall be such that the system safely interacts with its environment, users, and equipment installers/maintainers.” The protection system protects the entire system and the user.

R012 - “The system shall be sustainable to the extent of new voice technology insertion at the system level.” Power (12 VDC) will be available for a new technology to plug into.

Figure 3 shows the Requirements vs. POWER Functionality Matrix. This figure shows that the functionality of the POWER system fulfills the requirements of the projects.

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Figure 3 – Requirements vs. POWER Functionality

POWER

This section describes the POWER system subblock shown in Figure 4. It contains VOLTAGE CONVERSION LRU, PROTECTION SYSTEM LRU and POWER SUPPLY LRU. A listing of the inputs, outputs, user interface signals, and functionality are provided below.

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Figure 4 – Power Top Level Diagram

1 Inputs

• 120 VAC

2 Outputs

• 12 VDC @ 35 Amps max

• 5 VDC @ 3 Amps max

• 5 VDC @ 2 Amps max

• 3.3 VDC @ 1 Amps max

• Digital Low Voltage Alarm 3.8 VDC

3 User Interface Signals

• Audible Low Voltage Tone

• LED

o After Every Fuse on Voltage Conversion Board

o After Every Fuse on System Printed Circuit Boards (PCB) – Not in Power Block

4 Functionality

• Convert external 120 VAC to 12 VDC. (R006)

• Convert 12 VDC to 5 VDC and 3.3 VDC. (R002, R010)

• Charge the backup battery. (R006, R007)

• Crossover to backup power in the event of an external power outage. (R002,R006)

• Provide power to all functional blocks. (R002, R006, R010, R011, R012)

• Create an SPG. NO floating grounds or loops. (R002, R011)

• Detect dangerous operation conditions (overcurrent) and trip off the system. (R002, R011)

• Detect a low voltage operation condition and send warning. (R002, R008, R009, R011)

• Isolate power supply to different system functional blocks. (R002, R008, R010, R011)

A mapping of this functionality to the requirements is shown in Figure 3.

Functional Blocks

The power system is subdivided into three smaller functional blocks: BACKUP BATTERY AND CHARGER, PROTECTION SYSTEM, and VOLTAGE CONVERSION. A description of the design considerations for each of these blocks follows.

1 BACKUP BATTERY AND CHARGER

The BACKUP BATTERY and CHARGER are shown in Figure 5. The CHARGER plugs into a 120VAC source and charges the BACKUP BATTERY. A listing of the inputs, outputs, states and functional sub-blocks follow.

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Figure 5 – Battery Backup AND CHARGER Diagram

1 Inputs

• 120 VAC

• Ground – Single Point Ground

• Neutral

2 Outputs

• 12 VDC

• Ground SPG

3 States

• Normal Power on:

1. External 120 VAC charging the backup battery

2. System taps 12 VDC from battery leads

• External Power outage:

1. Zero crossover time upon power failure to backup battery – battery begins to drain and not be recharged.

4 Functional Sub Blocks

1 12 VDC BACKUP BATTERY

A 12 Volt 100 AmpHr battery shown in Figure 6 was purchased as the backup battery.

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Figure 6 – Power Sonic Rechargeable Sealed Lead-Acid Battery 12 Volt 100 Amp. Hrs.



2 Inputs

• none

3 Outputs

• 12 VDC Terminal

• Ground Terminal - SPG

4 Design and Purchase

For safety reasons, the battery terminals should be covered or the battery encased. A low voltage alarm will be set if the BACKUP BATTERY voltage drops below a threshold value of 11 VDC. However, the DC to DC converters work until a battery voltage of 9 VDC.

Power requirements are estimated, based upon specifications of the system parts. For example, the FPGA can pull a maximum of 3 Amps if the entire chip is utilized. There are buffers, analog to digital converters, LEDs, and opamps in the system that all require some amount of power. In the following table, each part and total current needed is tabulated.

|HUB/SANITY |Voltage |Max. Current |% Operating Time |# of |TOTAL (amps) |

| | | | |Parts | |

|FPGA |4.5-5.5V |3 |100% |1 |3 |

|Buffers |3.3 |0.0108008 |100% |5 |0.054004 |

|EEPROM |3.3 |0.015 |100% |1 |0.015 |

|LEDs |5 |0.015 |100% |4 |0.06 |

|Sanity Chip |3.3 |0.000023 |100% |1 |0.000023 |

| | | | | | |

|INTERFACE LRU | | | | | |

|A/D |5 |0.015 |100% |8 |0.12 |

|D/A |5 |0.0013 |100% |8 |0.0104 |

|OpAmp-LM741 |5 |0.0028 |100% |64 |0.1792 |

|Tone Generator | | | |8 |0 |

|LEDs |5 |0.015 |100% |40 |0.6 |

| | | | | |0.3096 |

|RADIOS | | | | | |

|M120 | | | | | |

|transmit 12A |12 |12 |5% |8 |4.8 |

|receive 1.5A |12 |1.5 |5% |8 |0.6 |

|standby .35A |12 |0.35 |90% |8 |2.52 |

| | | | | |0 |

|POWER | | | | |0 |

|LEDs |5 |0.015 |100% |6 |0.09 |

| | |Total Current Per Hour: |12.36A |

Figure 7 – Power Profile

The table in Figure 7 lists all the system parts and the estimated maximum current consumption. We assume all parts are operating at full current with the exception of the radios. This assumption will allot the power requirements with a high factor of safety. To calculate the power requirements due to the radios, we assumed a radio would be transmitting 5%, receiving 5%, and in standby 90% of the time. A transmitting radio pulls 12 amps. Assuming we have 8 radios connected to the system, we need 4.8 amps an hour to power radios talking 5% of the time. After summing all system power requirements, the power group needs to supply 12.36 amps per hour.

|Power per hour |Battery Life |Battery Size |

| |(hrs) |(amphour) |

|12.36 |5 |61.79 |

|12.36 |10 |123.58 |

|12.36 |15 |185.37 |

|12.36 |20 |247.16 |

Figure 8 – Power Requirement vs. Battery Size

Batteries are rated with an amphour rating. For example, a 100 amphour battery can supply 25 amps for 4 hours or 20 amps for 5 hours. For this system, a 250 AH battery should be placed as the backup if 20 hours of backup supply are necessary as shown in Figure 8. For the prototype system, the power requirement is scaled back to two radios transmitting as a maximum. We chose a 100 amphour PowerSonic battery PS-121000 to back up the system. This provides the prototype system with a back up supply for approximately 14 hours.

2 BACKUP BATTERY CHARGER

The BACKUP BATTERY CHARGER recharges the system battery. In the event of an external power outage, the system power will transfer immediately and solely to the backup battery. There is zero crossover time.

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Figure 9 – SRM-30M Front View

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Figure 10 – SRM-30M Rear Panel View



1 Inputs

• 120 VAC Terminal

• Ground Terminal

• Neutral

2 Outputs

• 12 VDC

• Ground Terminal

3 Purchase

The decision was made to purchase a BACKUP BATTERY CHARGER rather than design one. The SRM-30M model was chosen based on price and its specifications. The SRM-30M from Astron shown in Figure 10 charges the 12 VDC battery with 25 Amps of continuous current. This is enough to recharge and keep the battery charged with two radios talking. Two radios talking pulls 24 Amps (12 Amps x 2 radios). If more than two radios are talking, the battery will begin to drain. The SRM-30M is 19-inch rack-mountable.

2 PROTECTION SYSTEM

The protection philosophy was to electrically isolate sections of the system in the event of an overcurrent fault as shown in Figure 11. A technician will find which sub block lost power via visual indication (LEDs) and a low voltage alarm signal is sent to the HUB. This signal would allow a technician to view the error in the error log from the CONFIGURATION USER INTERFACE.

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Figure 11 – Protection System Diagram

1 Inputs

• 12 VDC

• Ground – Single Point Ground

2 Outputs

• 12 VDC on Communication Interface Bus

• Ground on Communication Interface Bus

• Digital Low Voltage Alarm

3 User Interface Signals

• Audible Low Voltage Tone

• LED

o After Every Fuse on Voltage Conversion Board

o After Every Fuse on System Printed Circuit Boards (PCB)

o Battery Voltage Indication

4 Design

The PROTECTION SYSTEM monitors for low voltage and overcurrent. An overcurrent alarm is only set for a large fault event. High enough overcurrent will trip all power to the system (35 Amps). An alarm is set for a low voltage condition (audio tone) when the battery voltage drops to 11.5 VDC. This provides a sensory warning to any surrounding operators. The PROTECTION SYSTEM includes three sub blocks: Fuse Protection, Circuit Breaker Protection, and Low Voltage Alarm.

For safety, the chassis must be grounded. If not grounded, the chassis might be at some potential voltage. We are using an SPG to avoid floating grounds.

5 Functional Sub Blocks

1 Fuse Protection

A typical fusing arrangement is shown in Figure 12.

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Figure 12 - Example of a Protected PCB

1 Design

The fuse protection electrically isolates sections of the system. If one section has a fault, the current increases. A fuse has a time-current characteristic which shows the time required to melt the fuse to clear the circuit for any given level of overload current.

We have fuse protection in three locations:

1. Each Functional Printed Circuit Board

Each LRU of the system utilizes a PCB. A 1A picofuse and LED are on each of the boards. The picofuse will blow and isolate a single board in the event of a local failure. The LED will always be powered indicating that the board has power. If the picofuse blows, the LED will no longer be lit indicating that there is no power on that board.

2. Voltage Conversion Board

Two 5 V sources and one 3.3 V source are created on the conversion board. Each voltage bus is fused rated at 1A. An LED indicates power after the fuse. See Figure 14.

3. Positive BACKUP BATTERY Lead

A 30A fuse protects the cables running from the BATTERY CHARGER to the BACKUP BATTERY. The fuse was implemented as a safety precaution.

The 8 communication devices are fused independently.

2 Circuit Breaker Protection

Circuit breakers were placed in the system to protect the system from overcurrent.

1 Design

For safety reasons, a circuit breaker will trip if a fault occurs downstream. The picofuse isolates a fault condition before the CB needs to trip. When a CB isolates a fault, a much larger portion of the system will be powerless.

We have circuit breaker protection in three locations:

1. Before Communication Devices – Trips @ 35 Amps

2. Before Voltage Conversion Board – Trips @ 5 Amps

3. At Battery Terminals – Trips @ 35 Amps

As a safety precaution, the breakers are able to be switched on and off and can be used to turn off system power.

3 Low Voltage Alarm

The car battery alarm indicates the current battery voltage and a low voltage alarm condition.

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Figure 13 – Low Voltage Alarm Circuitry



1 Inputs

• 12 VDC Battery Terminal

• Ground Battery Terminal

2 Outputs

• Digital Low Voltage Alarm (3.8 V)

3 User Interface Signals

• Audible Low Voltage Tone

• Battery Voltage LEDs

o > 14 V

o 13.5 – 14 V

o 13 – 13.5 V

o 12.5 – 13 V

o 12 – 12.5 V

o 11.5 – 12 V

o < 11.5 V

4 Design and Purchase

The decision was made to purchase the circuitry instead of designing it. The purchased low voltage circuitry also functions as a visual BACKUP BATTERY voltage indicator. The LEDs indicating the battery voltage are placed into an LED harness and brought to the front panel of the LRU. The alarm monitors the 12 VDC at the positive battery terminal. The battery is considered to be at a low voltage level at 11.5 VDC. A digital low voltage alarm is an output at 3.8 V.

3 Voltage Conversion

The VOLTAGE CONVERSION board, also known as the power distribution board, converts the 12 V into various voltages needed by other system blocks: hub board and interface boards.

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Figure 14 – Voltage Conversion Diagram

1 Inputs

• 12 VDC

• Ground – Single Point Ground

2 Outputs

• 5 VDC @ 2 max Amps (to Conversion/Detection LRU)

• 5 VDC @ 3 max Amps (to FPGA)

• 3.3 VDC @ 1 max Amp (to Hub/Sanity LRU)

• Ground SPG

3 Design

The voltage conversion is on a unique PCB and steps down 12 VDC and distributes the required voltages to functional blocks of the system. The communication devices are not powered through the power distribution board but tapped directly off the backup battery. Voltage conversion is an LRU.

• Communication Devices (x8) 12 VDC (tapped directly off battery)

• INTERFACE 5 VDC

• Hub/Sanity 3.3, 5 VDC

Three DC to DC converters step down the 12 VDC supply to 5 V, 5 V, and 3.3 V. The first 5 V converter can supply 15 W of power. This supply is dedicated to the FPGA which theoretically can require 15 W of power. We do not anticipate coming close to this level of power consumption. The second 5 V converter can supply 10 W of power and is dedicated to the Interface LRUs. One Interface LRU board requires 0.2 W of power. If eight boards are connected 1.6 W of power are required. The 3.3 V converter supplies power to various circuitry on the Hub Intermediate board, which requires 0.5 W of power. The 3.3 V converter can supply 5 W of power.

Cable List

The table shown in Figure 15 is a list of where each cable was connected, the voltage on each cable and the gauge and color of the each cable.

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Figure 15 – Cable List: Source, Destination, Voltage, Gauge, and Color

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