Design Project - Purdue University



Homework 4: Packaging Specifications and Design

Due: Friday, February 10, at NOON

Team Code Name: _____H. E.A.D. GEAR_______________ Group No. _12_

Team Member Completing This Homework: ___Atandra Nath Burman____

Evaluation:

|Component/Criterion |Score |Multiplier |Points |

|Introduction |0 1 2 3 4 5 6 7 8 9 10 |X 1 | |

|Commercial Product Packaging |0 1 2 3 4 5 6 7 8 9 10 |X 3 | |

|Project Packaging Specifications |0 1 2 3 4 5 6 7 8 9 10 |X 2 | |

|PCB Footprint Layout |0 1 2 3 4 5 6 7 8 9 10 |X 2 | |

|List of References |0 1 2 3 4 5 6 7 8 9 10 |X 1 | |

|Technical Writing Style |0 1 2 3 4 5 6 7 8 9 10 |X 1 | |

| |TOTAL | |

Comments:

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

1. Introduction

A maximum power point tracker (MPPT) is a special DC to DC converter that converts the input voltage from a solar cell array to the output voltage of a battery pack. For a given solar array, there is an optimum “power point” along the current versus voltage curve that produces the most power. Special logic on the group’s board will provide control of the DC to DC converter in order to achieve this power point. [source: PSR’s papers].

We are looking at having approximately 8 maximum power point trackers to fit within the solar car. Hence, there packaging must be compact and rugged all weather, water proof and light weight.

2. Commercial Product Packaging

Considering our packaging specification and design we would analyze two commercial products: the BRUSA power trackers and the Biel boost MPPTs that have both been commercially designed for the market and have certain similarities to our design model.

1. BRUSA:

The BRUSA power trackers have been designed towards providing optimal utilization of solar panels and have two applications – Maximum Power Tracker and Mains Battery Charger. The Maximum Power Tracker unit maintains maximum power by continuously measuring of the solar panels power output. This process takes place as long as the battery is not full charged, as the loading characteristic gets the higher priority. This unit is designed as a step-up DC-DC converter which means the input voltage (solar panels) has to be at least 5% lower than the output voltage (battery). The BRUSA power trackers achieve a remarkable 99% efficiency or more which is one of their positive aspects given that they have a proven design over the years.

Also the unit is designed to work unattended and has the following key features:

• Auto power maximizing

• Full-automatic operation

• Independent night-switch-off

• Very short optimizing time

• Minimal own-consumption

[pic]

Figure1. BRUSA Maximum Power Trackers

BRUSA has some negative aspects: the major one with respect to our model is that it does not have CAN. It also weighs considerably heavy at around 1kg and with 8 of such units 8kg is a big consideration factor. Also the cheapest of these devices is priced at $704.00 per unit. The BRUSA custom made packaging on the right as shown in the Figure1 gives us an idea of a compact box shaped packaging that we plan to implement in our packaging model.

2. BIEL boost MPPTs:

The BIEL boost MPPTs are a high efficiency stand alone performance voltage converter that’s designed to get maximum power from a time-variant source, and converts it to the desired output voltage level. Its key features are:

• High Conversion Efficiency up to 99%

• Seeks and Tracks MPP

• Wide I/O Range

• High Reliability and Durability due to Low Thermal Stressing

• Separate Control and Power Part

• Output Capacitor Precharge Circuit

• Data Transmission via CAN Bus (optional)

• Input and Output Protection

[pic]

Figure2. BIEL boost MPPT

Given that the BIEL boost MPPTs are a high efficiency model and relatively light weight (0.650kg) and have the CAN features, it is yet very expensive at $780.00. Further, it does not come with a custom made packaging. Another key design aspect where our design is going to differ would be the fact that the BIEL runs off a 110V nominal battery pack, while our MPPT version would be running off a 65V battery pack.

Keeping these key similarities in mind we are going to design a compact and rugged all weather, water proof and light weight packaging enclosure that would be relatively inexpensive. It would look somewhat on the lines of the BRUSA MPPT but much refined to our requirements.

The key aspects of our project’s packaging that are unique as compared to the BRUSA and the BIEL MPPTs would be the inclusion of a fan ventilation system for cooling the MPPT unit for better performance as well as the packaging material used for the enclosure would be 1/8” foam core fiberglass.

3. Project Packaging Specifications

After careful analysis of project packaging details of the two commercial power point trackers available, and the dimensions of our proposed PCB we determine the following packaging details of the enclosure for the maximum power point trackers:

• Detailed CAD drawing illustrating size and shape of the Maximum Power Point Tracker may be found in Appendix B.

• Materials List – Microcontroller (PIC18F2680), CAN Transceiver, Step-down DC-DC converter (12V-5V), Inductors, Capacitors, Resistors, 3Op-AMP chips, 6 converters (2 CAN connectors, 1RS-232, Microcontroller programming header, temperature sensors and heat sink)

Tooling Requirements – PIC demo boards, CAN application software, soldering tools in 477lab, and miscellaneous tools available in lab.

Estimated Weight – The final MPPT unit would weigh in the range: 0.250kg - 0.300kg with the packaging weighing nearly 0.050kg

Estimated Unit Cost – Packaging costs could be estimated at around $5.00 for each of the MPPT unit which includes $2.00 - $3.00 for the foam core fiberglass sheets and $2.00 for the screws.

Based on the dimensions for the finished PCB in section 4.0, we decided a 0.125 mm thick Foam Core Fiberglass packaging with nearly 0.250 mm spacing on both sides leading to the following dimensions:

• Width = 5.210

• Length = 5.300

• Height = 2.750

The packaging would also include a 80mm x 80mm x 10 mm ventilation enclosure for the cooling fan on the top part of the package that would provide necessary cooling in the MPPT unit.

4. PCB Footprint Layout

The major components for the Maximum Power Point Tracker are:

• Microcontroller

• CAN Transceiver

• Op Amp

• Power Supply

Microcontroller: Based on smaller footprint and less pins, a 10-bit A/D converter vs. 8-bit, higher clock frequency, CAN interface availability and lower price our team decided to go for the PIC18F family of microcontrollers. Amongst the PIC18F2XXX series, the microcontroller for the maximum power point tracker chosen by our team was the PIC18F2680 which has the maximum memory available.

The PIC18F2680 is a 28-Lead Plastic Small Outline (SO)–Wide, 300 mil (SOIC). Keeping pin count in mind and he overall width and length, the 2 closest footprints would be the SOG.050/28/WB.420/L.700 and the SOG.050/28/WB.420/L.725. The chosen footprint of this from the Layout Footprints Library is the SOG.050/28/WB.420/L.700. [Find footprints in Appendix C]

[pic]

Figure3. SOG.050/28/WB.420/L.700

Power Supply: The chosen Power Supply is the MAX1684/MAX1685 which is a low noise, 14V input, 1A, PWM Step-Down converter. The closest footprint for this is the SOG.025/WG.244/L.200. [Find footprints in Appendix C]

CAN Transceiver: The chosen CAN Transceiver is MCP2551 which is a 8-Lead Plastic Small Outline (SN)–Narrow, 150 mil (SOIC). The closest footprint for this is the SOG.050/14/WB.244/L.200. [Find footprints in Appendix C]

Op Amp: The chosen Op Amp is MCP6001/2/4 which is a 14-Lead Plastic Small Outline (SL)–Narrow, 150 mil (SOIC). The closest footprint for this is the SOG.050/14/WB.224/L.350. [Find footprints in Appendix C]

Upon carefully analyzing the footprints for the parts, the following are the estimated dimensions required for the finished PCB:

• Width = 4.25

• Length = 4.75

• Height = 2.00

5. Summary

This report carefully analyzes two commercial products similar to our Maximum Power Point Tracker. Based upon the closest footprints that match our chosen components, we came up with our initial finished PCB footprint layout. Based upon these dimensions and weight and cost considerations, the packaging specifications were determined and implemented.

List of References

[1] Biel School of Engineering and Architecture, “MPPT New Generation MMPTs”:

[2] BRUSA boost MPPTs

[3] “MAX6225-MAX6250 Datasheet,” Maxim Integrated Products, 2001,

[4] “PIC18FXX8 Datasheet,” Microchip Technology Inc., 2004, 28-pin/CAN interfaced microcontroller.

[5] proE tutorial

[6] “MAXIM Low-Noise, 14V Input, 1A, PWM Step-Down Converters,” Maxim Integrated Products, 2001,

[7] “MCP6001/2/4 Datasheet,” Microchip Technology Inc., 2005,

Appendix A: Project Packaging Illustrations

[pic]

Figure4. Front view of MPPT packaged unit showing slots for

[pic]

Figure5. Back view of MPPT packaged unit showing vent for heat dissipation

[pic]

Figure6. MPPT packaged unit without front panel to show finished MPPT unit

Appendix B: Project Packaging Specifications

Screenshot of proposed packaging:

[pic]

Figure7. Layout of MPPT packaging

Specification Details:

Estimated Weight – 0.250kg - 0.300kg (packaging weight ~0.050kg)

Estimated Unit Cost – $5.00

Dimensions: 0.125 mm thick Foam Core Fiberglass packaging with nearly 0.250 mm spacing on both sides resulting in Width = 5.210, Length = 5.300, Height = 2.750

Ventilation Enclosure: 80mm x 80mm x 10 mm

Appendix C: PCB Footprint Layout

[pic]

Figure8. Finished PCB layout

-----------------------

IMPORTANT: Use standard IEEE format for references, and CITE ALL REFERENCES listed in the body of your report.

NOTE: This is the first in a series of four “design component” homework assignments, each of which is to be completed by one team member. The completed homework will count for 10% of the team member’s individual grade. It should be a minimum of five printed pages.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download