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CAREER EPISODE -1

Introduction:

CE1.1

Designation : Hardware Design EngineerCompany : MindTree LtdProject Name : Bluetooth Voice Gateway – Car Email Manager - ILANELocation : Dallas, Texas, USAProject Duration: Sep 2008 – Aug 2009

The episode I narrate here is my experience, while designing and implementing hardware board for a product named ILANE which is a Bluetooth Voice Gateway/Car Email Manager.

b) Background

CE1.2 NATURE OF THE OVERALL ENGINEERING PROJECT

This Project involved design, development, testing and manufacturing of an embedded electronic product named the ILANE. The ILANE intelligent, portable device that lets the user control a smart-phone using simple voice commands when inside a vehicle without having to use hands which ensures undivided attention towards the road. The product lets the user access and control lots of other smart-phone applications including managing phone calls, SMS messages, and calendar.

CE1.3 OBJECTIVE OF THE PROJECT:

To design, develop, implement, and test a hardware platform board based on an IMX31 processor from Freescale Semiconductors that would meet the requirement specifications for a complete product.

To provide following functions:

A Hardware platform based on IMX31 processor that would host a Linux based Operating system for voice based applications to run on

Dual Bluetooth Radio Frequency interfaces with dedicated Antenna and Base Band Devices Multiple Input power sources – the device should be capable of being powered by

Automotive battery, USB OTG Expansion and On-the-go ports The multiple input power sources required an intelligent switching and selection system

which was one of the highlights Clear and Audible Audio design that required an in house speaker on the PCB within the

product casing Miniature form factor comparable to hand held smart-phones Mechanical design and thermal analysis of the product to meet agency compliance

requirements Efficient usage of input power – various modes of low power operation enabled by software Optimized design for Testing, Manufacturing, Cost, Assembly, Packaging thereby ensuring

ready to manufacture product Designed to meet compliance requirement of various safety agencies like UL, FCC and

qualified by Bluetooth Organization The firmware and application software to be provided by the customer

Regular customer reviews to report the progress and escalate outstanding issues if any for smooth progress of the project

Ensuring timely delivery of high quality deliverables and achieving project based milestones Supporting customer throughout the design life cycle, transition to production and post

production issues Build expertise and knowledge on next generation embedded engineering technologies

CE1.4 NATURE OF MY WORK AREA:

Design, development, Implementation and testing of Main PCB and debug board for software development

Involved in the design of power supply topology and circuit for the entire board Various power input sources and priority selection and switching Overview and guidance of the PCB layout design team during the PCB design. Involved in component selection and cost reduction activities. Involved in driving the

physical layout of the design in a highly integrated form factor PCB. Involved in board bring up and testing of the assembled boards Interacted extensively with the manufacturing team to ensure the PCB was Designed for

Test and Manufacturing Involved in interacting with the Mechanical design team, software team, component

engineering team, component and external vendors etc Played the role of onsite coordinator for the offshore team interacting with customer and

conveying specific requirements to offshore team and ensuring high quality deliverables Created and maintained design documentation – High & Low level design document,

Schematic Capture, Bill of Materials, Test Document, Requirements tracking Handling customer requirements, change requests and defect tracking, regular project

updates, customer reviews at critical junctures and ensuring smooth progress of project and achievement of milestones

CE1.5 ORGANIZATIONAL STRUCTURE CHART:

CE1.6 STATEMENT OF YOUR DUTIES:

I coordinated with customer to understand the requirements and the key deliverables to be considered in the project

I created a detailed Requirement tracking matrix from an extensive requirement document to ensure all the requirements were tracked to its logical closure

I interacted with various certifying and qualifying agencies to clearly understand their requirements for our product to be designed for certification and qualification

I suggested cheaper alternatives to some of the modules to be used on the product to replace expensive ones

I suggested for the Bluetooth module to be replaced by discrete circuit design to save a significant cost on the Bill of Materials

Designed the processor (IMX31) subsystem, memory subsystem, and key interfaces like USB 2.0 (host and OTG), UART, CSPI, PCM etc

I designed the power supply circuitry to meet automotive requirements including design of protection circuit against transients, Electro Magnetic Interference

I designed an intelligent power switching and priority-based selection for input power sources among the car’s battery, USB-OTG expansion and USB OTG inputs.

I created a dedicated document to list down special instructions for the layout and routing of PCB which was a significant phase to ensure first-time-right design

I worked on selecting the right components after detailed study of data sheets to meet the requirements and created comparison matrix of various choices available for a class of component

I designed a simple multiplexing system to work with either an 8GB or 16GB flash memory without manual intervention which meets the processor requirements

I designed the input ESD protection circuits for USB and Audio to ensure clean signal integrity I designed a standalone test fixture PCB for debugging and testing the Main board consisting of

serial interfaces like the RS232 and USB I coordinated the delegation of work from onsite to offshore and review of deliverable work

from offshore team before handing it over to the customer I supported the PCB fabrication and assembly teams for smooth progress of production and

assembly line testing I worked on tuning the dual Bluetooth Antennae for best performance by testing with a network

analyzer and dedicated tuning circuit on the board. I tested multiple boards with a test suite and software developed by the software team to bring

up the fresh PCBs for further testing at customer location I created various documentation for the different phases of the project – requirement

specification, high level design document, low lever design document, schematics, change feasibility document, impact analysis document, root cause of failures, reliability matrix as per process templates

c) Personal Workplace Activity

CE1.7 TECHNICAL DETAILS OF THE WORK

My technical responsibilities and the technical details of the project are explained in stages.

i. Requirements Collection and Discussion with Customer

Various requirements of the project and product were discussed over extensive meetings with different teams of customer. A high level requirements document was created to capture the meeting points and critical requirements along with important milestones and delivery dates. Planning with the customer and various design teams – mechanical, manufacturing, purchasing etc to come up with a viable plan for smooth execution of the project and meeting of goals.

ii. Power Supply Topology and Design

The power supply for the device consisted of DC-DC switching regulators to deliver clean 5V –LT3685- and 3.3V –TPS40222- power supplies to the different chipsets and analog portions. A power supply companion chip was also used to deliver power to the processor and memory. A standalone LDO was used to power up a low power micro controller that would be ON all the time.

The power supply needed to be protected against various transients that are present on a typical automotive power source. A protection circuit was designed that consisted of high voltage capacitors, ESD diodes, EMI filters to filter out the noise and unwanted signals from the power supply input to the circuit.

iii. Design of Intelligent Power Switching Routine

The possible power supply inputs to the ILANE device were 12V from Automobile, 5V from USB OTG expansion port and 5V from USB-OTG port. The device needed to be powered by any of the above sources according to the following priority:

12V input Expansion USB-OTG port USB-OTG Port

Using transistor switches controlled by two least priority power sources and analog power switches a circuit was designed to select the power source with the highest priority according to the table above to power the device. The circuit was also made robust against changes in the input power sources when the device was powered.

iv. Guiding the PCB Layout Design

The ILANE PCB design was challenging due to the following requirements:

Small form factor – comparable to a hand held smart-phone High density of components – close to 650 components were on the PCB High speed, Critical Audio, RF signals – USB, High quality audio, Bluetooth signals all in the close

vicinity of one another Requirement for 100% test coverage – needed almost 300 test points on the board to give the

board complete test coverage on the assembly line to bring down the production time

I created an extensive document listing down specific instructions for PCB layout and routing of critical signals, power supply rails, high speed signals, audio signals, Bluetooth RF area etc. Designed the PCB stack-up consisting of 10 layers of signal, power and ground areas.

v. Tuning the Bluetooth (BT) Antenna for Best PerformanceThe ILANE device consisted of two BT circuits dedicated for interface with the smart phone. The tuning circuit for each BT antenna consisted of four critical elements – PCB layout, matching element, coarse tuning element and fine tuning element. Board and antenna tuning was performed using a Vector Network Analyzer (VNA). The RF circuit on the PCB from the balun to the antenna is 50 Ohms real and single ended. The balun was removed. A 50 Ohm coaxial cable was soldered directly to the RF+ pad. The circuit needed to be tuned to attain a resonance of better than -10dB peak (S11 measurement), with better than 200MHz bandwidth between the two -4.5dB points on the S11 response. We need 100MHz bandwidth for basic Bluetooth operation.

CE1.8 APPLICATION OF MY ENGINEERING KNOWLEDGE AND SKILLS

I used my engineering knowledge and experience to study and understand the various design requirements on the ILANE project.

I used my knowledge and skills in power supply design to come up with the topology for entire device.

I used my knowledge of automotive transients as specified by the ISO standard ISO7637 to design the input protection circuit of the device.

I applied by skills in schematic capture and bill of material generation to produce error-less, clear schematics to capture the detailed design and MS excel skills to generate bill of materials.

I used my knowledge and experience to define the PCB layout stack-up and specific routing instructions for the ILANE PCB.

I used my knowledge and skills to bring up the ILANE PCB by powering up the device and testing individual interfaces and handing it over to the software team for further testing

I used my knowledge and experience in RF design to design the layout for Bluetooth PCB and tune the same to get best performance from the antenna.

CE1.9 TASKS DELEGATED TO ME AND THEIR ACCOMPLISHMENTS

I was assigned to meet with the customer to completely understand the requirements and expectations

o I achieved the same by clearly capturing all the requirements and expectations in a track-able requirement matrix that was used to bring all the requirements to its logical closure.

I was assigned to understand and design the power supply topology for the entire deviceo I achieved the same by designing a robust and efficient power supply topology with

minimal losses and excellent immunity against input transients. I was assigned to understand the problem of multiple power input sources and come up with a

solution for the same.o I accomplished the task by coming up with a unique solution based on priority selection

of input power sources that involved intelligent sensing and analog switching. I was assigned the task of designing the Processor and sub-systems of the device

o I achieved the same by designing the power supply for IMX31 processor, selection of DDR SDRAM for memory, Flash for storage memory, USB physical device interfaces and Bluetooth Baseband interfaces.

I was assigned the task of selecting and designing the Bluetooth RF interface

o I accomplished the task by selecting a Bluetooth chipset from CSR and corresponding RF circuit using Murata’s Balun and Antenna along with the tuning circuit. The layout of the PCB was designed carefully to meet Bluetooth quality standards

I was assigned the task of handling the Bill of Materials and procurement.o I accomplished this task by maintaining a clear and detailed bill of materials of all the

components of the system and PCB. Critical components were identified and 2-3 alternative components were selected as backup for these components.

I was assigned the task of designing a Debug board for testing the PCBs that would be manufactured.

o I accomplished this task by designing a simple but effective debug board along with a mating connector on the main PCB to help bring up the board during initial testing and loading of software.

I was assigned the task of documentation for the entire project.o I accomplished the task by maintaining clear and precise documentation from the

requirements phase to the manufacturing phase. Some of the key documents I generated were Requirements Traceability matrix, high level design document, low level design document, schematics, layout instruction document, and impact analysis documents.

I was assigned the task of interacting with the customer, various vendors and in house teams.o I accomplished this task by organizing regular meetings with customer to review and

update on the progress of the project, escalate outstanding issues and seek approval, conduct reviews of the design and other artifacts at critical junctures of project.

CE1.10 TECHNICAL DIFFICULTIES/PROBLEMS AND ITS SOLUTION

Multiple Power Input Selection and Sequencing

Problem Definition: The possible power supply inputs to the ILANE device were 12V from Automobile, 5V from USB OTG expansion port and 5V from USB-OTG port. The device needed to be powered by any of the above sources according to the following priority:

o 12V inputo Expansion USB-OTG porto USB-OTG Port

Solution: Upon power-up the source currently powering the device needed to be maintained even if other sources were available no matter what priority. After power-up, power switch state must be sensed before changing

o Sense 5V Exp out using voltage divider leading to an IMX31 GPIOo Sense 5V on USB using ISP1507 VBUS lines, using analog switch to check each port

Current limited analog switches are used to control the power input from the two USB OTG ports. The switches are default in ON position. The control to the two switches sense 12V presence and if present it disables both the switches thereby powering the circuit from 12V. IF the 12V rail is not present then the first switch remains ON letting USB_EXP rail and the second switch is disabled sensing USB_EXP presence. If USB_EXP and 12V both are not present then the second switch turns ON thereby powering the device from USB_OTG rail.

There was a similar switch system designed to deal with the other signals of the USB interface and the physical device for the same.

Reducing Noise in the 3.3V Power Supply Rail

Problem Definition: The 3.3V power supply rail powers the Processor companion chip which generates all the necessary power rails for the processor. 3.3V also powers the Audio circuitry and other critical components on the board. Hence it was necessary for the 3.3V rail to be clean with noise levels at less than 40mV ripple voltage. However when the first version of the board was tested the measured noise level was 140mV which was not acceptable.

Solution: The solution to this problem consisted of analyzing the circuit and the PCB layout for the same. Some of the observations made were:

o The switching frequency was at 2MHz which higho The capacitance on the output rail was lesso Bulk capacitor on the output rail was not placed close to the pino The switching loop on the layout was bigger than necessary

To reduce the noise of the power supply rail the following actions were taken:

o The switching frequency was reduced to 1.2MHz by changing the corresponding resistoro Another bulk cap of 10uF was added to the circuito The bulk capacitor placed on the output rail was brought closer to the pino The switching loop was reduced by bringing the components closer on the PCBo A Snubber circuit consisting of resistor and a capacitor was added to reduce the noise

Enhancements to the USB Powering Scheme

The Device PCB consists of one USB OTG controller and physical transceiver shared by two USB OTG ports – one through µAB connector and another through expansion connector. The device can be powered through the VBUS power source – 5V – of the USB OTG connections.

However since there could be conditions where more than one of the three available power sources – 12V, 5V Exp, 5V µAB – are connected to the board, there is a power sequencing circuit that handles the priorities of power supply as below:

1) 12V input2) Expansion Connector USB VBUS3) USB-OTG microAB Connector VBUS

Problem Definition:

The device entered unstable states in three conditions from the table above:

When being switched from being powered from 12V to USB OTG µABThe initial condition for this test is when the board is being powered off of the 12V DC input power supply with the USB OTG µAB plugged in. The 12V power supply is switched off and the device is expected to reboot and come up being powered off of USB OTG µAB power source. However the device enters an unstable state and does not boot up as expected.

When being switched from being powered from USB OTG EXP to USB OTG µABThe initial condition for this test is when the board is being powered off of the USB OTG Expansion connector bus with the USB OTG µAB plugged in. The USB OTG Expansion is disconnected or powered off and the device is expected to reboot and come up being

powered off of USB OTG µAB power source. However the device enters an unstable state and does not boot up as expected.

When being switched from being powered from USB OTG µAB to USB OTG EXPThe initial condition for this test is when the board is being powered off of the USB OTG µAB connector bus as the lone power source. The USB OTG Expansion bus is now plugged in to the device. The USB OTG Expansion bus power source is expected to take over the priority and reboot the device to be powered off of the USB OTG EXP power source. However, the device enters an unstable state and does not boot up as expected.

Solution: The following changes to the ILANE Board makes the device boot up without any failures during hot plugging and hot swapping of the available power supplies.

Addition of Boost Diode to the 3.3V Switching regulatorThe addition of a boost diode between the PVIN (pin 4) and BOOST (pin 6) of the TPS40222 provides the required boost for the 3.3V switcher to kick start the regulation and bring the 3.3V rail to a steady state. This was implemented in Rev 1.01 of device. However, during testing it was observed that the addition of the diode did not have any major impact – negative or positive – on the performance of the power supply and hence removed from Rev 2.0.

Addition of 40K Ohm Pull Down resistors to the ON pins (pin 6) of analog switches that handle the USB power input.

The addition of one each 40K Ohm Pull Down resistor to the ON Pins (pin 6) of U44 and U45 respectively brings the Analog switches to a definite OFF state when they change from ON state. This helps to keep the other switch in a definite ON state since the two switches are exclusive of one another during switching between the two USB sources – USB OTG µAB & USB OTG EXP.The device did not enter in to the unstable conditions on Hot Plug/Swap of multiple power supplies as experienced before the enhancements.

CE1.11 STRATEGIES DEVISED BY ME

I developed & implemented the Power Supply architecture and selection of components along with the detailed design of the same.

I strategized the design and development of the USB power scheme which was used to power the device through the various input sources according to a pre-determined priority

I co-ordinated with various teams like mechanical design team, industrial design team, and the software team to ensure smooth progress of the design to meet all the requirements

I strategized the design to make it suitable for Test, Manufacturing and Assembly. I interacted with the Bluetooth RF antenna vendor providing necessary requirements and design

details to ensure a robust performance of the Bluetooth circuit. I also fine tuned the RF circuit with the help of network analyzer to tune the antenna to maximum performance.

I developed and maintained the requirements matrix capturing all the requirements of the customer and ensured all of them were met or exceeded in the design and implementation.

I designed a test fixture to test, simulate and validate the board bring up of the Main PCB for the device and also made it easier for other team members to follow a simple routine to test a large number of boards as required by the customer.

CE1.12 W ORKING WITH OTHER TEAM MEMBERS

Working with the offshore engineers (PCB Layout & Schematic team) helped me in executing the project ahead of time and to customer’s satisfaction.

The project success was the result of team effort of our firm and client engineers. Embedded hardware, mechanical and software team worked together to develop a first-time-right design of the intended automobile installed device.

Working with the Bluetooth qualification experts helped me understand the various aspects of Bluetooth standards and qualification by continuous engagement, technical reviews and meetings.

Summary

CE1.13 MY VIEW OF THE OVERALL PROJECT

Exposure to high end automobile embedded system design, complex power supply circuitry and complex layout of multi-layer PCB were highlights of the Project.

Enhancements made to the USB powering scheme for the device, Tuning the antenna circuitry for Bluetooth were significant challenges and opportunities for learning.

CE1.14 HOW THE PROJECT FARED IN MEETING THE GOALS

All the customer requirements were either met or exceeded and a number of unique and efficient circuits were designed for the device.

USB powering scheme, RF Antenna circuit design to handle 2 Bluetooth circuits, Design for Test, Manufacturing and Assembly, Four button remote control circuits were proposed to and accepted by the customer to meet functional requirements a reality.

Second revision of the device PCB were manufactured in large numbers and tested with various wireless carriers and were found to perform exceptionally well.

The device today is a commercial success across North America waiting to be deployed in other parts of the world.

CE1.15 MY PERSONAL CONTRIBUTION TO THE PROJECT I carried out client interactions for technical requirement understanding, field report analysis

and technical reviews. I designed & developed concept for Power Supply Circuit Design, USB Powering Schemes, and

Bluetooth RF Antenna Tuning. I created and maintained the requirements matrix capturing all the requirements of the

customer and ensured they were all met or exceeded at the end of the project. I conceptualized and designed the system for easy Testing, Manufacturing and Assembly in the

production lines.

CAREER EPISODE -2

Introduction:

CE2.1

Designation : Hardware Design EngineerCompany : MindTree LtdProject Name : Demonstrate Electricity Generation & Storage using a Bio-Mechanical Energy Generator SystemLocation : Bangalore, IndiaProject Duration: Aug 2010 – Mar 2011

The episode I narrate here is my experience, while conceptualizing, designing and demonstrating a Proof of Concept for generating electricity from a Bio-Mechanical Energy System.

b) Background


This Project involved conceptualization, design, development, testing and demonstration of the Bio-Mechanical Energy generator system. The system consisted of a legacy bi-cycle, a mechanical stand to support the bicycle, a permanent magnet DC generator/motor, a charge controller circuit PCB and a battery to store the energy.


The objective of the project was to demonstrate the working of a bio-mechanical energy generator system. Also to conceptualize, design, develop and test a successful method to charge a lead acid battery using a legacy bicycle and a mechanical stand.

The PoC would ideally have the following features:

A system where a human being could pedal a bicycle to run the DC generator and produce electricity which would be used to charge a lead acid battery

A charge controller circuit PCB that would accept the various voltages and different currents being generated from the DC generator and smoothen it charge the battery in a controlled manner

A mechanical stand that would hold the bicycle so as to allow the user to pedal the bicycle and also provide a mounting option for the charge circuit PCB and enclosure

Employ the prototype in a rural school or home for pilot run of the system and gather feedback for the same regarding the usability and ease of use vectors.

The system would be made very low-cost so as to be available for a broader spectrum of people from emerging economies like India, Brazil, China and some of the countries from Africa where there is a scarcity of electricity which limits certain areas of growth.

To produce research papers which would capture the features, ideas, areas for improvement, efficiency studies etc and published on internationally acclaimed journals.

Another important objective of the project was to pursue the motivation vector of the pedal-for-power system. This involved converting the bicycle into a joystick which would be used to play a computer based video game when pedaling.


Conceptualize, Design, development, Implementation, and testing of Charge Controller Circuit used for charging the Lead Acid battery

I was involved in the rigorous procedure of various component evaluation, literature research, component selection, testing of components across various use conditions and procurement.

Literature research of various alternative technologies presently being researched and developed.

Exploration of under the hood of various designs, systems involved in alternative energy generation

Cost analysis of various alternative energy solutions and other systems. Characterization study of Solar power systems, wind power systems etc. Design, development and testing of power supply control board to handle various input

supply sources. Design, develop and test intelligent battery monitor circuit to indicate battery level and

signal low battery conditions Simulation of analog and power circuitry using PSPICE tool set from Linear Tech, Texas

Instruments etc. Evaluation, testing and selection of components suited for the circuit to handle high power

and transients The activity generated unique ideas to motivate energy generation which uses an analog

sensing circuit and data acquisition Responsible for entirely setting up the infrastructure required for complex data acquisition

with respect to the system efficiencies as well as human energy expenditure profile. This was used to collect data intended for use in publication of research papers.

Worked with Labview software and data acquisition devices from National Instruments.



I coordinated with the customer to understand the requirements for the concept of the project and also visualize a solution

I created a requirements matrix to capture all the requirements of the customer to track and take it to closure

I conducted extensive research on present systems that were similar to what we wanted to achieve

I shortlisted various systems that were similar to what we wanted to achieve with different limitations and features

I put in all the effort required to identify, get the information required and order a few systems that were similar and procured them to study them in the lab

I conducted extensive research on the systems that were procured to list down their way of working, their features, short comings and areas that we could improve upon.

I extensively visited manufacturing units and factories to identify various components of our system – mechanical stand, DC Generator/motor, bicycle etc – that would be low-cost, dependable and met our requirements

I studied and researched various Solar energy based chargers, wind power based charges to list down similarities and differences between those and our system to aid the design

I designed various circuits and simulated them using PSPICE software from different vendors like Linear Tech, Texas Instruments etc.

I procured various components and different samples of components from various vendors to test them in the lab and list down their parameters that would aid the selection of the best component for the final design. This process was important since the power to be handled by the components was in the range of 150-200 watts and hence the heating and eventual break down of components was expected. We needed components that could withstand high currents and power offering least lossy performance.

I hand soldered the components on general purpose PCBs to test out the circuits that were designed and simulated in the lab.

I conducted extensive testing on each of the components of the charge controller circuit to identify the right one from each component group – which were current sense resistor, power MOSFET, high current diodes, high voltage operational amplifiers etc.

I put together the final charge controller circuit with the least number of individual components that was low cost but still effective and could handle various power ranges from 10-200 watts.

I also designed a battery monitor circuit that would intelligently indicate the amount of charge left in the battery and when to charge the same.

I designed a circuit that would intelligently indicate to the user to pedal the bicycle at an optimum speed which would generate the highest usable electrical energy from the generator without putting too much of human effort. This circuit also let out a beep from a buzzer if the user put in too much of effort to pedal the bicycle which would waste human/electrical energy.

I designed a sensor based circuit that would calculate the rotations per minute of the bicycle wheel which could be used for various purposes.



My technical responsibilities and the technical details of the project are explained in stages.i. Requirements Collection and Discussion with Customer

Various requirements of the project and product were discussed over extensive meetings with different teams of customer. A high level requirements document was created to capture the meeting points and critical requirements along with important milestones and delivery dates. Planning for the concept of the system, various blocks of the same, different teams to be involved, necessary tools and components were discussed.

ii. Conceptualization of Bio-Mechanical Energy System

The system was to be designed for emerging markets and hence needed to be as low cost as possible to appeal to the bigger group of low income people who faced acute shortage of electricity.

The challenge was to design a bio-mechanical energy generation system using widely available off-the-shelf components and with very less customized parts to bring down the cost.

iii. Research of existing systems and comparison to Solar and Wind power systemsThere are quite a few pedal powered generator based systems available in the market mostly in the US. Another challenging aspect was to study, understand the existing systems and identify areas where our system could be designed to improve and also achieve the lowest cost comparable to existing systems. The other area of research was to compare our system to more widely accepted Solar Energy based systems and Wind Power based systems. The research activity threw up some very interesting results which helped us to conceptualize and design of bio-mechanical energy generator system.

iv. Design and Implementation of Charge Controller CircuitThe charge controller circuit for Bio-mechanical energy generator system was to be designed to meet following requirements: Lowest cost of components & PCB. Ability to handle high range of power Ability to handle voltage transients from the DC GeneratorMy responsibilities involved design of the charge controller circuit, identification of the various components, and evaluation of the components to select the most suitable one available from various vendors. I was also responsible for design and simulation of the circuits before being built in the lab for testing.

v. Converting the Bicycle as a JoystickAnother important objective of the project was to pursue the motivation vector of the pedal-for-power system. This involved converting the bicycle as a joystick which would be used to play a computer based video game when charging the battery. The important factor was the computer would be powered off the battery which would encourage users to pedal the bicycle as long as they could to actively participate in the game and win it. This involved re-engineering of an existing off-the-shelf joystick like Logitech Rumblepad.


I used my engineering knowledge and experience to study and understand the various design requirements on the project.

I used my knowledge and skills in conceptualization of the project and the various components of the same.

I used my knowledge of analog electronics and power electronics to design, simulate, build and test the charge controller circuit and the sub modules of the same.

I applied by skills in schematic capture and bill of material generation to produce error-less, clear schematics to capture the detailed design and MS excel skills to generate bill of materials.

I used my knowledge and experience to successfully test out the prototype in the lab integrating the various sub-systems of the system.

I used my knowledge and skills to convert the bicycle into a Joystick for using it to play a game as and when the user was charging the battery.

I used my experience and knowledge of various low cost systems to come up with the lowest system cost to set up the bio-mechanical energy generator.




I was assigned to understand the concept requirements and come up with a system design ideao I achieved the same by coming up with a concept to generate energy using a legacy

bicycle and a simple charge controller circuit and battery. I was assigned to come up with an idea to pursue the motivation vector for the system.

o I accomplished the task by coming up with a unique solution converting the bicycle in to a joystick that could be used to play a computer based video game.

I was assigned the task of designing a low cost charge controller circuit o I achieved the same by designing a low cost charge controller circuit from the scratch

after researching various systems, existing methodologies and careful selection of components.

I was assigned the task of putting together a setup to take continuous readings from the systemo I accomplished the task by setting up a National Instruments’ Data Acquisition device

based set up to capture various parameters of the system to aid continuous data acquisition from the system when being used. I also created a generic MS Excel based template to receive data from data acquisition system and project graphs and plots relevant to the measurement criteria.



I was assigned the task of maintaining documentation for the entire project.o I accomplished this task by maintaining all the documents related to the project in an

organized folder structure that was easy to follow and locate the necessary documents. I created clear and precise schematics needed to capture the design through various phases of change and updation.




Designing a low cost charge controller circuit

Problem Definition: The system needed a charge controller circuit to charge the battery with the energy generated from the DC generator. This charge controller needed to be a very low cost solution keeping with the objective of the project.

Solution: The battery chosen for the system was a Sealed Lead Acid battery with a capacity of 26AH. There are various methods to charge a lead acid battery and the most effective one is to use an off-the-shelf charge controller IC from leading IC manufacturer’s like Texas Instruments. Though a few of them were studied from an understanding perspective, the cost of actually using one on our system would have been very high.

Hence we wanted to use a simple circuit that would do the job of effectively charging the circuit without damaging the battery or its life. After a lot of research, study and simulations, we agreed

upon a simple constant current based charging circuit that would set the current at which the battery would be charged by a current sense resistor. The components that were part of this circuit were very less. The prominent ones being, a large capacitor functioning as a low pass filter, power MOSFET, current sense resistor, reverse charge limiting diode and high voltage operational amplifiers. This circuit was demonstrated to withstand high voltages and current and effectively charge the battery by limiting the current to a maximum set point.

Setting up the infrastructure to acquire data on a continuous mode

Problem Definition: One of the objectives of the project was to acquire test data on a continuous basis for analysis and characterization of the system. There was a data acquisition device from National Instruments available in the lab. However the limitation of this device was that it could measure and log data within a voltage range of -10V to +10V. Since our system was characterized by voltages as high as +35 volts, this device would not be useful. However, the time and cost on the project was limited and hence a simple yet effective solution was needed to achieve the objective.

Solution: The solution to this problem consisted of designing a sub-circuit system that would bring down the voltages of the signals needed to be acquired to within the -10V to +10V range. I designed such a circuit sub-system using the already available components and a general purpose PCB and tapped the different locations of the charge controller circuit to acquire data on various signals indicating generator voltages, current, battery voltages and rotations per minute of the DC Generator shaft.Another challenge was to calculate the current through the circuit at which the battery was being charged with. The current sense resistor was used for the same purpose along with a differential amplifier and the current was calculated from the output of the differential amplifier. This gave an exact instantaneous value of current at which the battery was being charged.

Calculation of RPM of the DC generator shaft was another challenging parameter to be acquired. For this purpose a flywheel with a round shaped black and white screen was attached to the shaft of the generator. A circuit sub-system was designed with an optical sensor that would sense one rotation of the flywheel with one pulse and send out that pulse. This was sent to an instrumentation amplifier to amplify the signal to be large enough to be sensed by the data acquisition device. This was captured in an excel sheet and using MS Excel formulas, the instantaneous RPM of the flywheel which in turn was the RPM of the DC Generator shaft was calculated. This input was used for various analysis and graphs to measure the efficiency of the system.


I developed the concept of the bio-mechanical energy generator using a legacy bicycle and a simple setup.

I strategized the design and development of the charge controller circuit and evaluation and selection of major components of the same.

I designed and setup the infrastructure for continuous data acquisition with the existing equipments in the lab

I came up with the re-engineering of the off-the-shelf joystick idea to convert the bicycle in to a joystick that could be used to play a computer based video game as a motivation vector of the project.

CE2.12 W ORKING WITH OTHER TEAM MEMBERS

Working with the system engineers gave me the perspective of the entire system since I am a Electronics engineer.

The project success was the result of team effort of our company and client engineers. The electronics and mechanical design teams worked together to make the concept a working demonstration.

Summary


Exposure to fundamental research based conceptualization and exhibiting the demonstrable proof of concept were the highlights for me personally.

Literature research, component selection, evaluation, comparison of existing systems, their efficiencies and effort to better them along with lower cost were significant challenges and opportunities for learning.

CE2.14 HOW THE PROJECT FARED IN MEETING THE GOALS All the customer requirements were either met or exceeded and a number of unique and

efficient yet simple low cost circuits were designed. The concept was brought to a practicable form and demonstrated to various stakeholders of the

project and received acclaim about the use cases, simplicity, efficiency and low-cost. A Number of research papers were published and patents were filed for various system ideas

and circuits.


and technical reviews. I designed & developed concept for charge controller circuit, bike as a joystick conceptualization

and design. I created and maintained the requirements matrix capturing all the requirements of the

customer and ensured they were all met or exceeded at the end of the project. I conceptualized and designed the system for continuous data acquisition of the critical

parameters of the system for future analysis and calculations.

CAREER EPISODE -3

Introduction:

CE3.1

Designation : Hardware Design EngineerCompany : MindTree LtdProject Name : Automotive Telematics SystemLocation : Bangalore, IndiaProject Duration: Jan 2007 – Oct 2007

The episode I narrate here is my experience, while designing and implementing hardware printed circuit boards for a product named DZLIVE which was an automotive Telematics system used for Fleet management and communication.

b) Background


This Project involved design, development, and testing of an embedded electronic product named the DZLIVE. DZLIVE is an automotive Telematics product which will also have the diagnostics capability along with navigation, wireless capabilities like 802.11g, Bluetooth, Satellite modem. The product is intended for use in automotive fleet management and asset tracking. DZLIVE is the derivative of earlier version product Prism 3 with new features included such as touch panel LCD module, 802.11g, Bluetooth, GSM/GPRS and Satellite modem.


To design, develop, implement, and test a hardware platform board based on an IMX31 processor from Freescale Semiconductors that would meet the requirement specifications for a complete product.

To provide following functions:

A Hardware platform based on IMX31 processor that would host a Windows CE based Operating system for different communication applications to run on

ST92F150JDV1 acts as a vehicle I/O controller in the system .It has J1850 VPW controller and 2 CAN controllers integrated into it. An external PWM controller and transceivers for CAN, J1708, J1850 VPW, J1850 PWM and ISO-K complete the vehicle interface circuit. ST9 sends data pertaining to all of these interfaces through SPI, on request by main processor iMX31.

CDMA/GSM Muxed interface for Wireless voice communication Bluetooth interface for communication within the different compartments of the

automobile, typically a truck, for controlling and monitoring different parameters. Global Positioning System device and interface for the same to help the fleet manager locate

the trucks across North America for various purposes. USB On-the-GO interface for connection of various USB based slave devices. A TFT-LCD for displaying different parameters of the automobile and its compartments that

would enable the driver to keep track of status.

An Ethernet interface on the device for debugging the same in case required during maintenance and software upgrades.

To efficiently and safely handle the various high voltage transients present on the automotive battery environment of a typical truck. The DZLIVE device would be powered off the vehicle battery.


Design, development, Implementation and testing of Main PCB and daughter board for further software deployment and integration

Involved in the design of power supply topology and circuit for the entire board including the daughter board.

Strategizing and designing the power input circuitry that would handle the high voltage transients present at power input (battery)

Overview and guidance of the PCB layout design team during the PCB design. Involved in component selection and cost reduction activities. Involved in driving the

physical layout of the design in a highly integrated form factor PCB. Involved in board bring up and testing of the assembled boards Interacted extensively with the manufacturing team to ensure the PCB was Designed for

Test and Manufacturing Involved in interacting with the Mechanical design team, software team, component

engineering team, component and external vendors etc Created and maintained design documentation – High & Low level design document,

Schematic Capture, Bill of Materials, Test Document, Requirements tracking Handling customer requirements, change requests and defect tracking, regular project

updates, customer reviews at critical junctures and ensuring smooth progress of project and achievement of milestones



I coordinated with customer to understand the requirements and the key deliverables to be considered in the project

I created a detailed Requirement tracking matrix from an extensive requirement document to ensure all the requirements were tracked to its logical closure

I interacted with various certifying and qualifying agencies to clearly understand their requirements for our product to be designed for certification and qualification

I suggested cheaper alternatives to some of the modules to be used on the product to replace expensive ones for GSM module, GPS module, Bluetooth module etc.

Designed the processor (IMX31) subsystem, memory subsystem, and key interfaces like USB 2.0 (host and OTG), UART, CSPI, PCM etc

I designed the power supply circuitry to meet automotive requirements including design of protection circuit against transients, Electro Magnetic Interference

I created a dedicated document to list down special instructions for the layout and routing of PCB which was a significant phase to ensure first-time-right design

I designed the input ESD protection circuits for USB and Audio to ensure clean signal integrity I coordinated the delegation of work to junior team members and review of deliverable work

from them before handing it over to the customer I supported the PCB fabrication and assembly teams for smooth progress of production and

assembly line testing I worked on bringing up the boards from the initial assembly, sub-system by sub-system and

finally integrated the firmware and board support package on the main PCB with the support of firmware engineers.

I tested multiple boards with a test suite and software developed by the software team to bring up the fresh PCBs for further testing at customer location

I created various documentation for the different phases of the project – requirement specification, high level design document, low lever design document, schematics, change feasibility document, impact analysis document, root cause of failures, reliability matrix as per process templates



My technical responsibilities and the technical details of the project are explained in stages.i. Requirements Collection and Discussion with Customer

Various requirements of the project and product were discussed over extensive meetings with different teams of customer. A high level requirements document was created to capture the meeting points and critical requirements along with important milestones and delivery dates. Planning with the customer and various design teams – mechanical, manufacturing, purchasing etc to come up with a viable plan for smooth execution of the project and meeting of goals.

ii. Power Input Protection Circuit Strategy and DesignThe requirements and constraints of the input power protection circuit were very stringent as can be seen from below.

The operating temperature range shall be -40C to 125C The operating voltage range shall be +4V to +18V The maximum continuous load current can be 3A The maximum inrush current can be 5A The voltage regulator design should survive typical automotive requirements and

standards listed below.o ISO 7637 Automotive Transientso ISO 10605 ESD Requirementso ISO 11452 EMI/RFI Requirements

All inputs and outputs, excluding grounds, shall be capable of direct connection to system voltage (defined as battery voltage or any derivative of battery voltage) for a minimum of 12 hours without damage

The power input protection circuit was designed with utmost care and diligence to meet the stringent requirements and constraints of various ISO Standards.

iii. Creation of Power Supply Hardware Verification Test PlanSince the power supply circuit was complex and built to withstand high voltage transients of various kinds, the customer requested for a detailed hardware verification test plan for the same. I created the test plan filled with details about the functional requirements, compliance requirements of different standards, and constraints of the circuit. The document also contained detailed explanation

about the impact of the requirement, how the designed circuit met or exceeded the requirement with circuit description and simulation results wherever applicable.

iv. Guiding the PCB Layout DesignThe DZLIVE PCB design was challenging due to the following requirements: Small form factor – 5 in X 3 in High density of components High speed, Critical Audio, RF signals – USB, High quality audio, GSM, GPS, Bluetooth signals all in

the close vicinity of one another on the daughter board. IMX31 being a high speed processor with BGA packaging and power supply requirements being

demanding, high speed RAM and large density Flash memories used and the number of interfaces along with a co-processor from ST micro, the main PCB consisted of 12 PCB layers. Hence the stack-up definition, routing guidelines, component placement etc assumed greater importance.

I created an extensive document listing down specific instructions for PCB layout and routing of critical signals, power supply rails, high speed signals, audio signals, Bluetooth RF area etc. Designed the PCB stack-up consisting of 12 layers of signal, power and ground areas.

v. Creation of an Intelligent Bill of MaterialThe customer required different flavors of the DZLIVE system which he wanted to offer as different products consisting of different features. This requirement necessitated us to come up with different bills of material for different flavored product offering along with price information and listing down of features.

To satisfy the above requirement, I created an intelligent MS Excel based Bill of Material that consisted of various sheets for differently flavored product offering. The main sheet would prompt the user to enter the different features of the product that they required and at the end of selection, a new sheet would offer them the complete Bill of Material, cost for different volumes – 10, 100, 10000, etc – and features for their product. This application received acclaim from customer for the ease of use and innovative yet simple techniques used to solve the problem.


I used my engineering knowledge and experience to study and understand the various design requirements on the DZLIVE project.

I used my knowledge and skills in power supply design to come up with the power supply distribution topology for entire device.

I used my knowledge of automotive transients as specified by the ISO standard ISO7637, 10605 for ESD and 11452 for EMI/EMC to design the input protection circuit of the device.

I applied by skills in schematic capture and bill of material generation to produce error-less, clear schematics to capture the detailed design and MS excel skills to generate an intelligent feature-rich bill of materials.

I used my knowledge and experience to define the PCB layout stack-up and specific routing instructions for the DZLIVE Main and Daughter PCBs.

I used my knowledge and skills to bring up the Main PCB by powering up the device and testing individual interfaces and handing it over to the software team for further testing

I used my knowledge and experience in RF design to design the layout for Bluetooth, GSM, GPS and tune the same to get best performance from the antenna.




I was assigned to understand and design the power supply topology for the entire deviceo I achieved the same by designing a robust and efficient power supply topology with

minimal losses and excellent immunity against input transients that met the compliance requirements of various ISO standards like ISO 7637, ISO 10605, ISO 11452.

I was assigned to understand the problem of multiple RF modules and interfacing them to the IMX31 processor and come up with a solution for the same.

o I accomplished the task by coming up with a unique solution by logically isolating the various RF modules to be placed on a daughter PCB and the processor and sub-systems to be built on the main PCB.

I was assigned the task of designing the Processor and sub-systems of the deviceo I achieved the same by designing the power supply for IMX31 processor, selection of

DDR SDRAM for memory, Flash for storage memory, USB physical device interfaces and Bluetooth Baseband interfaces.

I was assigned the task of selecting and designing the different RF interfaceso I accomplished the task by selecting RF modules dedicated for GSM/CDMA, Bluetooth,

GPS and Satellite Modem by conducting extensive research and compiling comparison reports of various modules offered by different manufacturers.



I was assigned the task of documentation for the entire project.o I accomplished the task by maintaining clear and precise documentation from the

requirements phase to the manufacturing phase. Some of the key documents I generated were Requirements Traceability matrix, high level design document, low level design document, schematics, layout instruction document, and impact analysis documents.



I was assigned the task of handling and mentoring 2 junior members on my team and also to delegate work to share the burden

o I accomplished the task by effectively delegating schematic capture, draft documentation and datasheet comparison work to efficiently manage my time as well as mentor the junior members.


Building a robust input protection circuit for the device.

Problem Definition: The power supply input to the DZLIVE device would be the automotive battery on the truck which is usually characterized with high voltage transients, harmful radiation and Electro Static Discharge which damage the Electronic Circuits on the device. The

requirement was to build a robust input protection circuit that would withstand all the harmful high voltage transient signals as well as be most efficient in terms of power dissipation and cost.

Solution: The protection from automotive transients described in ISO 7637 is provided at the power supply point. The protection circuit protects the electronic circuits from Load dump pulse, Battery reversal and over-voltages. We used RBO40 which is an application specific discrete IC from ST Microelectronics.

The circuit has following features:-

40A Diode to guard against battery reversal

Breakdown Voltage: 24 V min.

Clamping Voltage: ± 40 V max.

Complaint with ISO / DTR 7637

Maximum Diode Forward Voltage @ 1A : 1V

To protect the power supply circuit against the ISO 7637 Transient surges, ST Microelectronics’’ RBO40-40G-TR Reverse Battery and Overvoltage Protection device was employed. The monolithic device has three functions integrated on to the same chip.

The Forward Diode D1 protects against the reverse battery connections. The Transil T1 provides clamping against the Negative Overvoltage surges. The Transil T2 protects against the positive overvoltage surges like the “load dump”.

Protection against ESD – ISO 10605: To protect the power supply circuit against Electro Static Discharge transients specified by ISO 10605, SMCJ78CA-13-F diodes from Diodes Inc are used across the Battery Power supply line and ground plane.

The SMCJ78 Diode has a Maximum Standoff Voltage of 78V and a Maximum Breakdown Voltage of 95.8V. Hence the ESD pulses like the ±25 kV is clamped to an acceptable value.

Protection against EMI/RFI – ISO 11452: To protect against the EMI/RFI for the automotive power supply circuit, BNX012H01 Block EMI Filter from Murata was employed. The BNX EMI Filter exhibits significant noise suppression effects over a wide frequency band – Extending from 100 kHz to 1 GHz – which is the primary requirement of the ISO 11452 EMI/RFI Standard

Various Glue Logic and Digital Switching Requirements

Problem Definition: The PRISM4 Main board requires some glue logic for peripheral bus address decoding, board control and status signals, board revision registers, and other miscellaneous functions. This would have required innumerable number of Gate ICs and would have added to the complexity of the PCB, cost of the BoM and number of individual components that would needed to be assembled on board.

Solution: The solution to this problem consisted of implementing all the glue logic and digital switching requirements in a Complex Programmable Logic Device (CPLD). The CPLD used was Altera EPM570T144I5N.

The key functions provided by the CPLD include:

Provide a 16-bit slave interface to the CPU data bus

Provide address decode and control for Ethernet controller

Provide control and status registers for various board functions.

Provide control and Muxing for interrupt sources from various sources

I strategized the use of a CPLD, defined its architecture, size, type of device, selection of CPLD

from various manufacturers and created the programmable code required to implement the

functions in Verilog HDL. This saved a lot of effort on individual circuit design, saved cost and

brought down the number of line items in the Bill of material making the circuit simpler and

efficient.

Intelligent Sleep Modes on the Device

Problem Definition: The customer required the DZLIVE device to enter in to various sleep states

based on various conditions and circumstances. The primary reason for this requirement was that

the device would be powered off the automobile battery and hence it should not be in fully ON state

when it was not required.

Solution: I strategized the solution to above problem in the following way. The IMX31 processor offered various sleep modes programmable and controllable by software. I studied the various modes and their usage and presented my understanding and study to the software team. I converted the different modes and their usage in simple software requirements to the benefit of the software team who were then able to create software programs to monitor the device continuously and push the device and the processor into different sleep modes thereby ensuring efficient usage of input power.

For this purpose, I also created a detailed power consumption estimation document that listed down the various components of the PCB and their individual power consumption on different voltage rails to accurately predict system power consumption. The document also listed down which of those components offered sleep modes and the method to control the same. Some of components could be controlled by the main processor’s general purpose I/Os and this was listed down in the document too. The PCB design included these inputs to build a highly power efficient system that could be pushed in to and out of various sleep modes.


I developed & implemented the Power Supply architecture and selection of components along with the detailed design of the same.

I strategized the design and development of the input protection circuitry for the whole system capable of efficiently handling high voltage input transients.

I coordinated with various teams like mechanical design team, and the software team to ensure smooth progress of the design to meet all the requirements

I strategized the method to make the device suitable for Test, Manufacturing and Assembly by employing DFM, DFT, DFA methodologies.

I strategized the concept of having 2 different PCBs – main and daughter – to meet the requirement of multiple RF modules. I logically isolated the sub-systems that would be present on the main board and daughter boards.

I developed and maintained the requirements matrix capturing all the requirements of the customer and ensured all of them were met or exceeded in the design and implementation.

I strategized and created an intelligent Bill of Material that would offer complete cost information, component list and features for a particular flavor of product selected by its user.

CE3.12 W ORKING WITH OTHER TEAM MEMBERS Working with the engineers of other teams (PCB Layout, Schematic draft, software team) helped

me in executing the project ahead of time and to customer’s satisfaction. The project success was the result of team effort of our firm and client engineers. Embedded

hardware, mechanical and software team worked together to come up with a design that met or exceeded all the functional and standards compliance requirements of the customer.

Working with the different qualification experts helped me understand the various aspects of ISO standards and qualification by continuous engagement, technical reviews and meetings.

Summary


Exposure to high end automobile embedded system design, complex power supply circuitry and complex layout of multi-layer PCB were highlights of the Project.

Handling of multiple teams located across various geographies, interaction among the teams and successful tracking of all the requirements to a logical closure gave me an opportunity to learn to work with distributed teams – logically & physically.

CE3.14 HOW THE PROJECT FARED IN MEETING THE GOALS

All the customer requirements were either met or exceeded and a number of unique and efficient circuits were designed for the device.

Power input protection circuitry, strategy to isolate sections of the device to form 2 PCBs, intelligent Bill of material document were proposed to and accepted by the customer to meet functional requirements a reality.

Second revision of the device PCB were manufactured in large numbers and tested with various wireless carriers and were found to perform exceptionally well.

The device passed all the major standards conformance pre-qualification tests which validated the methods employed and circuits designed.


and technical reviews. I designed & developed concept for Power Supply Circuit Design, Processor and sub-systems, RF

modules etc. I created and maintained the requirements matrix capturing all the requirements of the

customer and ensured they were all met or exceeded at the end of the project. I conceptualized and designed the system for easy Testing, Manufacturing and Assembly in the

production lines. I strategized and created the unique intelligent Bill of Material application that helped the

customer offer various flavors of the same product at different costs with different features to his end customers. This brought in a lot of interest for the product.

CDR-

Documents

escalate outstanding

40k ohm pull

electro magnetic

hardware platform

suggested

iso standard

organizing

continuous