Spring 2018 AT-ST Fritzing Diagram

May 17, 2018/in 3Dot AT-ST/by Intiser Kabir

By: Shweta Hebbalkar (Electronics and Controls – Hardware)

Verified By: Intiser Kabir (Project Manager)

Approved By: Miguel Garcia (Quality Assurance)

Introduction

Fritzing is a tool for the student to create clean and professional images of electronics projects. Building a virtual circuit in breadboard view, using Fritzing, gives a better representation of circuit connection close to the real circuit. Fritzing introduces a user-friendly interface for a quick and easy workflow. A user can build and edit virtual electronic circuits, schematics, or PCBs. The concept is drag and drop; the user can drag and drop components from the part library to the project window. Parts are connected using the breadboard and wires. Wires are created instantly by clicking and dragging a part’s connector. Fritzing software made our life so easy because we can change the color of the wires and make the wires curve or bend them. If I click and hold on the connector, Fritzing will highlight all equipotential connectors. I can also select the schematic and PCB tabs to watch or edit my circuit.

Body

I found all components from the default library; if I could see any parts in the library, I can look in Fritzing official website or Google. Some of the parts I could not find, but lucky in Fritzing, we can make our custom parts, by opening the inspector then selecting the component whose properties that we want to change. Then we complete the circuit by connecting all the connection.

Figure 1: Fritzing Diagram

In this figure, I have the 3-DoT board, gyroscope, I2Cexpander, two UV sensor, two IR LEDs, Servo, Ultrasonic, two motors, actually, we are using the micrometer with shaft encoder and 3 volts.

Conclusion

This is a sophisticated tool to use to create a virtual breadboard, and it will help us build it physically. If we miss a connection, then we can always look back and fix any problem.

Spring 2018 3DoT Hexy: Lessons Learned

May 17, 2018/in 3Dot Spiderbot Generation #2, Spiderbot/by Eduardo De La Cruz

By: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Raymundo Lopez-Santiago (Mission, System, and Testing Engineer)

Kris Osuna (Electronics and Control Engineer)

Approved By: Miguel Garcia (Quality Assurance)

Introduction

The purpose of this post is to provide helpful tips for the next generation of spiderbot based on our experience taking 400D. This post will be broken down into lessons learned by each division: Management, MST, E&C, and Manufacturing.

Project Manager Remarks

By: Eduardo De La Cruz

The goal of the project manager is to make sure the team finishes all tasks on the task matrix. The team will regularly depend on the project manager to get tasks published for feedback by the professor. If the project manager slacks off in posting a blog post, he/she will delay the teams progress. Making sure the professor is aware of all the things the team is doing is an important task of the project manager so make sure you know what each team member is regularly doing. If you are expecting not to meet project requirements make sure to let the professor know, as he will guide you to a solution, or just make you fill out a waiver for the requirement.

Mission, System, and Testing Engineer Remarks

By: Raymundo Lopez-Santiago

One issue identified in the system integration and assembly was the wire management and routing. As mentioned by the customer, the project should be designed from the cabling. Additional time should be spent on this section from the MST. As for testing peripherals, this should be done as soon as possible. One mistake on my part was starting late to do any testing on peripheral devices with the rest of team. For the verification document, I learned the hard way to not separate every requirement and make too many test cases. After meeting with the customer on a frequent basis, I went from 15 test cases to 8 test cases. One recommendation for future MSTs is to verify all requirements as soon as you can. Even if you do not have the 3DoT board in time, prototype with a sparkfun pro micro board. A heads up, order extra parts in case they stop working when testing is begun. Level 1 and Level 2 requirements were defined by the customer, but I recommend to meet with the customer to make sure the wording makes sense and that all system/subsystem requirements have a path back to high-level requirements. This will save you a lot of time when you are writing test cases. In my experience, all verification should be done at the Level 1 requirements. This is allowed since all system requirements lead back to Level 1 requirements.

Electronics & Control Engineer Remarks

By: Kris Osuna

Getting familiar with Fritzing and EAGLE software is very important. Fritzing gives a visual for the end product. It shows you the pins you need and if the project is possible. I recommend working on the schematic and PCB as soon as possible. When making the schematic do not pick the first part you find in the EAGLE library. I highly suggest researching the part you are thinking about using. A mistake I made was not checking the availability of the integrated circuits I used in my schematic. The gyroscope I chose was three generations back and was unavailable in most places. The unavailability meant I could not purchase the item with the other components increasing the shipping costs and the overall cost of the project. I learned that when I finish the PCB the PCB is not done. The PCB goes through multiple levels of quality checks. If you turn in the PCB design on Monday you will get feedback and changes that need to be done, which will make your finished date Friday. Take into account corrections you might need and give yourself extra time for it. I suggest planning for redesigns and things that need to be fixed. Purchase extra pieces because things can go wrong.

Take pictures all the time. When doing blog posts I found that I was not taking enough photos to show the work being done. It is easier to show something than it is to describe something. Stay on top of your blog posts. Start your blog posts as you go along even if you do not finish because the event you are posting about just happened and it is harder to remember.

Manufacturing Engineer Remarks

By: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Purchase a digital caliper if you do not have one already you will find it very useful throughout the semester. Learning SolidWorks as soon as possible is critical to getting things done in time. The Manufacturing Engineer should become competent in designing simple parts by the end of the first month and should be able to make more complex parts by the end of the second month. Review during every class meeting with the professor, a.k.a the customer, design changes or ideas as you will come to learn that sometimes the customer does not agree or like what you are making and will send you back to the drawing board. Sometimes groups would go weeks working on something only for the customer to dislike it and making them start over. Therefore, COMMUNICATION with the customer is critical to finishing things on schedule.

Getting acquainted with more than one 3D printing source will play to your advantage. The professor recommends his own 3D printing guy (Ridwan), however, far too often 3D prints would get delayed for days due to everyone reaching him around the same time. The manufacturing engineer should consider other 3D printing sources such as CSULB Makers group (located in VEC 518) or other off-campus printing shops.

When printing parts it is very important to consider how the part will be placed for printing. Like wood, 3D prints will have either vertical layers or horizontal layers based on the printing position. Sometimes moving parts will require you to pick a specific printing position in order to prevent layer splitting, or if you are considering inserting threaded screws into the material. If the layering is perpendicular to the angle at which the screw is being inserted you will most likely split the printing material as you insert the screw. Click here to read more about layering and print positioning.

Print positioning is also very important when it comes to parts that will be elevated off the ground at an angle greater than 45 degrees. Areas that will be off the ground will require print support in order to prevent sagging. Adding support decreases the print quality, as well as increases 3D print times. Click here to read more about this.

Finally, when talking to your 3D printing supplier, it is important to understand the role layer height plays in determining the quality and cost of the print. The thickness of each layer determines the resolution of the print. The smaller the layer height the smoother the print. However, as layer height decreases the longer the print and the higher the cost. Usually for prototyping, since time is critical to meet the 2-2-2 print requirement, layer height might be set around .3 mm for quicker production, whereas for final prints layer height could be less than .1mm since time is not an issue. Click here to read about layer heights.

References

Spring 2018 3DoT Hexy: Custom PCB Assembly

May 17, 2018/in 3Dot Spiderbot Generation #2, Spiderbot/by Eduardo De La Cruz

By: Kris Osuna (Electronics & Control Engineer)

Verified by: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Approved by: Miguel Garcia (Quality Assurance)

Introduction

The custom PCB only has two IC chips. On the PCB we have the I²C expander that will read the three calibrated light sensor values and the gyroscope. The gyroscope will also be incorporated on the custom PCB and will be used to make turns. The reason only two IC chips are on the PCB is due to the location of the 3DoT in relation to where the IC chips need to be. We use headers and cables to connect from the PCB to the IC chips, specifically the three calibrated light sensors, the ultrasonic sensor, and five LEDs. The sensor shield will connect to the J3 header of the 3DoT board.

Related Requirements

Level 1 Requirements

The robot will need to navigate remotely through a custom-built maze (built by AoSa image), memorize the path it took, start over, and autonomously travel through the path it took.
The robot shall avoid collisions if it encounters other robots while navigating through the maze. This involves detecting the robot, retracing steps back, and moving to a room that allows the other robot to have a safe passage.
The robot shall use a v6.43 3DoT board.
The robot shall demonstrate the capabilities of the 3DoT micro-controller for DIY hobbyists.

Level 2 Requirements

The robot shall use a single RCR123A 3.7 V, 650mA rechargeable Li-ion battery to power the 3DoT board, which will power the drivetrain and all attached peripherals.
The robot shall use three calibrated light sensors connected to a custom PCB.
The robot shall use a HC-SR04 ultrasonic sensor to handle robot avoidance.
Ultrasonic sensor shall have a range of 0.5-meter radius to detect and respond accordingly to other robots.

PCB Assembly

Figure 1: Sensor shield fabricated from the EAGLE schematic.

Figure 2: SMD 603 package resistor size compared to penny

Figure 3: Solder paste is spread on all SMD components

Figure 4: Placing PCB in the reflow oven. A gif can be found here.

Figure 5: Solder flowing in the reflow oven. A gif can be found here.

Figure 6: Pin headers will have to be manually soldered on

Figure 7: Finished PCB

Figure 8: Back of the PCB with all connections

Conclusion

The sensor shield could have gone on J1 and J2 and placed on top of the 3DoT but the sensor shield was designed for J3. Originally, we were going to have a booster shield on J1 and J2 so sensor shield had to go to the J3 header. Testing on the finished soldered PCB showed that only channel two on the I²C expander is getting data. I tried cleaning up the soldering on the I²C but it did not fix the problem. If we cannot get all 4 channels working a breakout board might be used. When the Gyroscope arrives we will solder the gyroscope on.

References

Spring 2018 3DoT Hexy: Electronic Component BOM and Order

May 17, 2018/in 3Dot Spiderbot Generation #2, Spiderbot/by Eduardo De La Cruz

By: Kris Osuna (Electronics and Control Engineer)

Verified by: Eduardo De La Cruz (Project Manager and Manufacturing Engineer)

Approved by: Miguel Garcia (Quality Assurance)

Introduction

The 3DoT Hexy project will be using the following electronic components.

05/08/2018

The complete cost will be $123.72 which includes shipping and handling. We will not be using the booster shield so none of the components for the booster shield were ordered. Below you can see the cost of the parts. A price of $0.00 means the parts were obtained from the resource cabinets and did not have to be purchased.

Figure 1: Purchase parts

04/19/2018

We will be making two custom PCBs, one for the sensor and one for the booster shield to power our motors. A team member has an ultrasonic sensor so one does not need to be purchased.

Figure 2: Hexy Sensor Shield BOM

Figure 3: Booster Shield BOM

Figure 4: Electronics that will not go on the PCB but will still be needed

Conclusion

Electronic components will cost $108.81. This price does not include shipping and handling. When the purchase is made we will update the total. We will be ordering more parts than we need in case there is a problem soldering the components.

References

EAGLE BOM Extraction

Spring 2018: BiPed Custom PCB Layout/Design & Modify Micro FOBO for 3DoT

May 16, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Jorge Hernandez (Electronics & Control Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved By: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

The PCB layout for Micro FOBO was modified to fit the 3DoT which will be provided by Professor Gary Hill. The way we modify Micro FOBO for a 3DoT board is by having the blank 3DoT layout template, which was kindly provided to us, and implement the pinouts in our board layout design. Once we have our template where the pins are ready to mount to the 3 DoT directly, we can start routing and building the PCB for Micro FOBO.

Given

Fig.1 3DoT 6.41 Shield

This is the blank pin headers for the 3DoT which was created by Gary Hill and Fabian Suske for the Spring 2018 semester.

Fig.2 3DoT Shield Pins

Board layout for 3 DoT pin header above with the correct dimensions, will be used as a foundation to build the PCB for Micro FOBO. This board layout was also provided by Gary Hill and Fabian Suske.

Non approved layouts

Fig.3 First Custom Shield V1

When I first started routing, it was a total mess to be honest. I had all the addresses for the servo expander & Multiplexer on the board layout which just took up a lot of space. I was also using the wrong Multiplexer as it was an 8 Channel Multiplexer which was just a huge waste of space as I only needed a 2-channel multiplexer. Another mistake I had was having everything connected to my external battery source ‘VBATT’ which is not necessary because everything but the Servo Expander operates at 3.3V just like the 3DoT. As one can see I was using the 4 pin header for the Ultrasonic(HC-SR04) which only operates at 5 V. Now using a SEEED ultrasonic, which operates at 3.3V and only has 3 pins, eliminates a need for a booster shield. I also learned about DRC, which is “Design rule checking or check(s) (DRC). This is the area of electronic design automation that determines whether the physical layout of a particular chip layout satisfies a series of recommended parameters called “design rules” and my first board layout had many errors as seen below.

Fig.4 DRC Errors

Second draft

Fig.5 Custom Shield V2

Having 90-degree bends are not allowed and is a reason this board layout did not get approved. Another reason is how some wires were not routed to its simplest form, therefore the routing needed to be more direct. Since the plan was to mount our PCB on top of the 3DoT, everything below the orange line will interfere with the battery which will need to be moved to accommodate this issue. Also, the size of this vias needs to be increased as they are too tiny. The power routing width needs to be increased to satisfy the current running through the power routings.

Final approved Layout

Fig.6 Custom Shield Final Version

The reason this board is approved

No 90-degree routes
Direct/clean wiring
Larger vias
No battery interference
Power wiring widths are larger
Ratsnest and DRC were satisfied

Fig.7 DRC-All Clear

Finished routed board

Fig.8 Custom PCB Eagle

Custom Parts

The PCA9540BDPN 2-channel multiplexer default part from Digikey gave us overlapping pinouts which didn’t go through OSHParks DRC. Therefore I had to go directly to its library and move the pins apart in order to use this part.

Before the modified PCA9540BDPN chip

Fig.9 Before-PCA9540BDPN Chip

It is obvious changes needed to be done to prevent overlapping

After the modified PCA9540BDPN chip

Fig.10 After-PCA9540BDPN Chip

Modified pins and DRC approved.

Conclusion

My Micro FOBO board layout consists of 2 UV headers, a Servo Expander, 8 micro servo pin headers, a coupling capacitor, resistors, LED pin headers, ultrasonic pin headers, and a 2 channel multiplexer. The exact specifications of these components can be found at Micro FOBO Electronics Component BOM blog post. The final PCB board layout is 39.958 x 27.941 mm which fits perfectly on top of the 3 DoT which is 60×74 mm which overall fits within Micro FOBO’s head which measures 60×74 mm.

References

Spring 2018: BiPed (Micro FOBO) System Block Diagram

May 16, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Jorge Hernandez (Electronics & Control Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved By: Miguel Garcia (Quality Assurance)

System Block Diagram

New and improved System Block Diagram for Micro Fobo, which shows in a general diagram, how many pins will be needed for each component and how they connect to each other. As seen, we are using a total of 5 sensors, a custom PCB, Bluetooth module, external battery and of course a Pro Micro. This helps a lot for our E&C engineer when it comes to PCB designing as they need to plan accordingly.

Fig.1 Micro FOBO System Block Diagram

The sensors subsystem (custom PCB) will be in charge of telling Micro FOBO’s next action. When the IR sensor on the UV breakout board sense a change in IR reading, this will alert the Pro Micro which ultimately leads to the Actuators subsystem (Micro Servos) to adapt accordingly based on our code. The same process will occur when the Ultrasonic sensor senses an object or a wall ahead of Micro Fobo. Bluetooth is considered a sensor because it collects inputs from a source, in this case, an Android phone then sends that data to the Pro Micro thus telling Micro FOBO what to do based on our code. The communication subsystem (Bluetooth module) is connected to the Pro Micro because through Bluetooth the Arduino will obtain information on the action it will take. The Power subsystem consists of the battery which has been tested for our overall system and a regulator to ensure the safety of the system and the user(s). Our Actuator subsystem is our output, Micro FOBO’s desired movement, based on our sensors and code

References

https://www.arxterra.com/spring-2016-rofi-preliminary-design-documentation/#System_Block_Diagram

Spring 2018: BiPed System Schematics (EagleCAD)

May 16, 2018/in Biped Generation #5/by Miguel Gonzalez

By: Jorge Hernandez (Electronics & Control Engineer)

Verified By: Miguel Gonzalez (Project Manager)

Approved By: Miguel Garcia (Quality Assurance)

Introduction

After the Fritzing design was completed, an EagleCAD schematic has to be designed to create a PCB in order to move the project forward. EagleCAD is a software program that allows the user to place components on the board, and wire all the connections properly. Pins such as I2C pins can be connected across the network

Here I explain the mistakes I have made and my final schematic for Micro FOBO which has been approved by Gary Hill and Fabian Suske.

Requirements

Level 1:

L1-18: Micro FOBO shall utilize a printable Circuit Board (PCB)

L1-7: Micro FOBO will utilize a 3DoT board (PCB will be mounted on 3DoT board)

Previous Schematics

Fig.1 Previous Schematics

For my first rough draft at Micro FOBO’s Eagle schematic, I did not implement the 3 DoT shield pin header which was a huge mistake. The reason this is a mistake is that if I did order this board, it would become a floating board which will require extra wires to connect my custom PCB to the 3DoT. As one can see, I also included the 12C TCA9548A Multiplexer, as the Micro FOBO will use 2 UV sensors which require different addresses to read values from each UV sensor. Using the TCA9548A was a mistake because it takes too much space, as it has the ability for 8 different I2C sensors and all we needed was 2. Another mistake which was making pinouts for the HC-SR04 ultrasonic, as that specific ultrasonic required 5V to operate which would have required a booster shield. A trade study for ultrasonics was done and found that the SEN136B5B ultrasonic sensor operates at 3.3V which eliminates a need for a booster shield as all the other components (UV, LED’s, Multiplexer, PCA Servo Expander) run at 3.3V or less(limiter resistor required).

Fig.2 Another Schematic (not approved)

Final Schematic Ordered

Fig.3 Final Schematic

Instead of individual resistors that protect the PWM of the Servo Expander, Hill suggested a resistor package for routing simplicity and a cleaner look (SO16 package). Another major change was to simply ground all address (A0-A5) on the Servo Expander to use the default address on that chip. 3DoT pin headers were introduced which will make this PCB sit on the 3Dot and not have loose wiring connections between these two boards. Voltage declarations were updated as everything operates at 3.3V other than the 8 Micro Servos, which will operate together, require an outside power source and therefore are connected to VBATT. Changing our multiplexer to the PCA9540BDPN was critical, as it is a 2 channel multiplexer which will save space on the PCB, compared to the 8 channel multiplexer from the previous schematics.

Conclusion

The completed Fritzing diagram and the Eagle schematic move our project closer to mission success. We now have a concrete version of our schematic and how each component is connected to each other. This is then sent to the Manufacturing Engineer and Project Manager to be approved. Once approved, the board layout (routing) will be completed.

References

Spring 2018: Biped Lessons Learned

May 16, 2018/in Biped Generation #5/by Miguel Gonzalez

Written By: Miguel Gonzalez (PM and Manufacturing)

Approved By: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

EE 400D is a very fast pace class in which students are expected to learn new material on their own to succeed with their group project. At first, everything may become stressful with all the new information given to you about how the class structure is set up. Hopefully, you were instructed to look at previous student blog posts to get an understanding of what is expected of you. It is important you take the researching phase of the semester seriously. The success of your project is highly dependent on you and your team in understanding how to setup your semester schedule base on the work you need to do.

This blog post covers all the struggles my team and I had throughout the semester and provide advice on how to prevent your team from encountering issues with your own project. I urge the reader to look at other groups “lessons learned” blog post as some problems students encounter are not robot dependent and some may have other solutions/strategies on how they solved them or prevent them.

Hardships that faced the Micro FOBO group

Our group was small. Since the start of the semester, it became evident that our class had fewer students than other semesters. For this reason, our class had only two group projects each of which had three students working on them. With only three members on the team, the PM had to do the Design and Manufactures job which doubled the workload.
We struggled to find the right project to work on. I suggest choosing something that you are passionate about. It wasn’t until I designed the Micro FOBO to emulate 1950s tin toys that I got passionate about the project. What I’m trying to say is that you need to make the project related to you and your teammates add some personal touches. Only then you will find yourself doing work on the project without thinking of it as work
3DoT Board was never given to use to use. Professor Hill worked hard on version 6 of the board but unfortunately, the board encountered problems that delayed the manufacturing of the board.

Things I wish I did not do

Spend to much time on the PCB board that did not work
Start team meetings without having an agenda/plan made beforehand
Do not spend all semester without a single visit you the customer’s office hours. I recommend updating the customer on your project at least twice a month.
Do not miss any days of class and try to be on time. Pop quizzes often occur the days you are absent

Things I wish I did do

Talked to my teammates about their individual roles and make sure they know what tasks they are responsible for.
Set strict timelines for the group
Read the class lectures a week in advance and ask questions about any concerns I may have had about the lecture the professor as soon I saw him.
I wish I emailed the TA and the Professor more about questions I had. They typically respond quickly to your emails.
Update the Customer with your process as much as you can. The customer will always try to help you out with any issues or struggles your team may be having. It will also prevent your team from doing things that the customer does not want and can save you a lot of time in the future.
Become acquainted with the QA engineer and make sure he/she knows about any changes or updates your team has on the process of your project.

Things I wish I learned/knew

Task Matrix was initially hard to understand and its benefits were overlooked
Download and learn SolidWorks early in the semester
You can always get waivers/approval of things that violate the requirements if you ask the customer. The customer can be understanding of special situations if valid reasonings are provided.
Take a deep dive in the resources available in professor Hill’s class website. There are many hidden outlines and resources that provide great value to the success of your project. But be cautious of any outdated material as Professor Hill tends to change things from semester to semester. If you are not sure the material is relevant, just ask.

Advice for future generations

Choose your job positions wisely an understand what the job entails. Software engineers typically have a large workload, I advise them to start work early and to ask for help.
Make sure the team reads past blogs as they are very useful. You should do heavy research on Arxterra, Professor Hill’s class website, and other sites early in the semester but I suggest you constantly look back on past project blogs whenever you need clarification on task or need examples. Tip: look at the score the blog posts received to differentiate the good post from the bad.
Get a prototype working ASAP. You and your team need to be able to visualize the tasks needed to make your robot work by the end of the semester. You can simply try to get the pass semester’s robot to work and begin revisions from there.
Plan to make many versions of your robot. You will never be able to design your robot perfectly at the start. That’s okay, just try to 3D print the model and assemble it together. Then you can begin to understand what things you need to revise to make it work. Our group made 3 full 3D printed iterations of the Micro FOBO with some parts having 6 different versions.
Make the meeting minutes as soon as you finish having a team meeting. I highly suggest spending 20 minutes after each meeting writing down what your team did for that day. Make a spot on the meeting minutes for “Homework/Things to do before the next meeting section” and assign group members with the task that they should work on in their own time and before the next meeting. Make a Google Drive Folder with all meeting minutes and share them with all your group members and the customer so they can remain updated with any progress your team is making. Look at our group’s meeting minutes folder as an example of how you can make your own.
When doing your Preliminary Design Presentations make sure you follow the Outline provided on the class website. Memorize your sections in your presentation. Do not read from the slides and be prepared to answer questions from the customer.

References

Spring 2018 AT-ST Assembly of Custom PCB

May 16, 2018/in 3Dot AT-ST/by Intiser Kabir

By: Shweta Hebalkar (Electronics and Controls – Hardware)

Verified By: Intiser Kabir (Project Manager)

Approved By: Miguel Garcia (Quality Assurance)

Introduction

A custom PCB is used for less wires, clean look, and being neat as possible. This is a example of the small custom PCB made and manufactured by oshpark. This PCB has 13 surface mount components and seven through-hole parts for integration and testing of it. Customer wants us to build the PCB, implement, and integrate it into the three-dot board, which is another custom PCB (microcontroller). From that, create the design in eagle software and have him review it for approval.

Body

In this image, the surface mount is through the hole as per our requirement. For the project, we are using two UV sensors and two shaft encoders. As well as the gyroscope and the I2C expander for the UV sensor. The journey of getting it printed was rather quick because we had to pay extra for the service and shipping so we could get it on time.

Figure 1: Blank PCB board before any short of soldering take place.

This image shows the surface mount placed on the board. It was my very first time having to surface mount components, but I got lucky and my division manager helped me. Although I could have first assembled all the parts, I was waiting for one to arrive, so I did that later on with a heat gun. I never used a heat gun before, but I looked at a few youtube videos to get a better picture. I then used a heat gun and attached my last surface mount which was the I2C expander.

Figure 2: PCB on the pick and place machine. Having all components needed on it.

This picture shows the complete version of the board where I soldered the rest of the male headers. After that, I used a multimeter’s continuity test to see if there is a short circuit. Afterward, I mounted this on the new version of the three dot board.

Figure 3: PCB with all components on.

Conclusion

Overall I learned a lot in this class, like time management, keep working till you get the answer, and communicate with others. The PCB works fine and all that is left is to integrate it to the AT-ST robot!

Spring 2018 AT-ST Final Blog

May 16, 2018/in 3Dot AT-ST/by Intiser Kabir

By: Intiser Kabir (Project Manager)

Approved By: Miguel Garcia (Quality Assurance)

Table of Contents

Introduction

By Intiser Kabir (Project Manager)

The purpose of this document is to provide a closure to the Spring 2018 AT-ST Project. This document will provide linkages to all aspects of the project for a future generation, including our recommendations, what we learned, and what we should have learned beforehand. We will also provide what went wrong with our project as well. It is recommended to use the table of contents to jump to sections if needed.

Project Members:

Intiser Kabir (Project Manager)

Danny Pham (Manufacturing and Design)

Shweta Hebbalkar (Electronics and Controls – Hardware)

Samuel Yoo (Electronics and Controls – Software)

Joseph Cho (Missions, System, and Testing)

Executive Summary

By: Intiser Kabir (Project Manager)

Mission Objective

The AT-ST Walker BiPed was inspired by Spring 2017 Velociraptor which uses the Theo Jansen’s leg design as the walking feature. We ended up having to choose this design from the negotiations made by both the customer and the Robot Company project teams. While our robot is a direct spin-off of the Velociraptor, we are incorporating a lot of their designs in order to not be mistaken as the BiPed team within the Robot Company. The AT-ST Walker BiPed should be able to go through both S’18 Project and Mission Objectives and EE400D S’18 Project and Mission Objectives documents.

Missions Objective: Source: https://docs.google.com/document/d/1kwObe9HkGBeCjMYAETA5GiChyxhY1o6bpcmhWKbNFv8/edit?ts=5aa836cb#heading=h.m8d2ovwute3k

Key Features

Shaft Encoders

As a way of controlling the motors moving at different speed as well as helping our AT-ST robot to walk and turn. The Shaft Encoder is used to help see our motor’s movement as our AT-ST walks forward.

Ultrasonic Sensor

As a way of avoidance control, the Ultrasonic Sensor is used to help the AT-ST avoid getting into any sort of collision when navigating through the maze.

UV Sensor

As a method for line following, the AT-ST use 2 UV Sensors and 2 UV lights to pick up UV color as it navigates through the maze.

Theo Jansen Leg

The method we are using for walking was inspired by the Dutch artist Theo Jansen. He made robots powered by wind as it walks around. We use his method to create our legs to get the same method.

Micro Motor

To control the leg movement we decided to use Micro Motors since it consumes less current and is compatible with the Shaft Encoders

Project Requirements

The Level 1 and Level 2 requirements follow both the S’18 Project and Mission Objectives and EE400D S’18 Project and Mission Objectives documents. Also what our team is hoping to accomplish by the deadline May 15. Level 1 is for general requirements that the AT-ST is hoping to achieve. Level 2 requirements go down to specific requirements for each member hoping to accomplish.

Level 1 Requirements

AT-ST shall walk on a level surface
AT-ST shall use Theo Jansen leg design
AT-ST shall look like an AT-ST Walker from Star Wars
AT-ST shall turn left, right or turn around
AT-ST shall support its own weight
AT-ST shall not exceed pass the size of 6’’x 6’’
AT-ST shall not walk through walls
AT-ST shall walk straight
AT-ST should walk backward
AT-ST should have a dynamic walk
AT-ST should jump.
AT-ST shall not exceed the budget of $250

Level 2 Sub – MST Requirements

AT-ST shall use Gyro to obtain information for calculating the center of gravity.
The 3DoT Board shall receive commands from the Arxterra app via Bluetooth Transceiver. It will decode and transmit data to servos, PCB and other components of the robot.
The power source shall be able to fit inside our robot and must be integrated into the AT-ST such that it doesn’t conflict with the functionality of the robot.

Level 2 Sub – Electronic Requirements

AT-ST shall use 2 DC Motor to move the legs (1 per leg).
AT-ST shall use a Servo Motor to adjust the center of gravity of the robot so it can turn
The Battery’s duration shall last up to an hour.
AT-ST shall use 2 shaft encoder to keep track of the leg motion
AT-ST shall utilize 2 Lithium Ion Battery – 2Ah for its power supply.
AT-ST shall use an ultrasonic sensor to sense other robots within a 0.5-meter radius
AT-ST shall use UV sensor to navigate through the maze.

Level 2 Sub – Manufacturing Requirements

AT-ST shall have a total weight of 600 g and weight will be properly distributed to the body and legs to support its own weight while walking.
AT-ST shall not exceed dimensions of 6” x 6” in order to fit in the maze and walk and properly turn without hitting the walls in the maze.
AT-ST shall have its body 3D printed (ABS)
AT-ST shall have legs 3D printed (ABS)

Reference:

Verification Test Plan: https://www.arxterra.com/at-st-verification-test-plan/
Preliminary Blog: linked once Published
L1 & L2 Blog: https://www.arxterra.com/spring-2018-at-st-project-specific-requirements-and-objective-l1l2/
Spring 2017 Velociraptor: https://www.arxterra.com/spring-2017-velociraptor-final-project-summary/
https://www.arxterra.com/spring-2017-velociraptor-preliminary-design-documentation/
Missions Objective: Source: https://docs.google.com/document/d/1kwObe9HkGBeCjMYAETA5GiChyxhY1o6bpcmhWKbNFv8/edit?ts=5aa836cb#heading=h.m8d2ovwute3k

System Design

System Block Diagram

By: Joseph Cho (Mission Systems and Testing)

Figure 1: System Block Diagram

The System block diagram above for AT-ST help visualize the system of the AT-ST. The 3DoT board uses ATmega32U4 as the microcontroller. The 3DoT board consists of a microcontroller, Bluetooth transceiver, servo header and dual motor driver. The 3DoT board (v6) will also be connected to the servos, motors and main custom PCB. PCB1 will be the master PCB that routes all input and output for the sensors. PCB 2 and PCB 3 are used for UV sensors which will be connected to the I2C expander on PCB 1. Bluetooth transceiver will connect to a mobile device using the Arxterra app via Bluetooth.

To read about it,

Blog post: https://www.arxterra.com/at-st-system-block-diagram/

Interface Matrix

By: Joseph Cho

Figure 2: 3DoT Interface Matrix

Figure 3: PCB 1 Interface Matrix

Figure 4: Custom PCB #2

Figure 5: Custom PCB #3

The interface matrix above shows the allocations of the components to the 3DoT board. List of connections to PCB1: ultrasonic sensor, gyroscope, shaft encoder 1, shaft encoder 2, PCB2 and PCB3.

On PCB1, there will be an I2C expander for the two UV sensors that share the same I2C address (0x60). The gyroscope has I2C address of 0x68 or 0x69, so it will not conflict with the UV sensor. PCB2 and PCB3 will be connected to PCB1 to utilize the I2C expander.

List of connections that are not shown in the interface matrix: servo header connecting to two servos and the motor driver connecting to two motors. The figure below shows an older version of the 3DoT board that shows the I/O headers. The new version of the 3DoT board has the motor driver, Bluetooth, and servo headers integrated internally, so they are not listed on the interface matrix.

Resource Reports

By Joseph Cho (Missions, System and Testing)

The resource report contains three parts: Mass report, power report, and cost report). These reports will be covering the resources’ mass, power, and cost. An estimate of the total mass will be shown on the mass report. For power report, the current values were taken from previous projects’ blog posts as reference. Lastly, cost report will show that the AT-ST project is within the budget.

Power Budget

Figure 6, Power Report

To Read more about Power Report: https://www.arxterra.com/at-st-resource-reports-mass-power-and-cost/

Power Budget: https://www.arxterra.com/at-st-power-budget/

Mass Report

Figure 7: Mass Report

Cost Report

Figure 8: Cost Report

Figure 9: Extra Cost (included in the Cost Report)

Preliminary Blog to see old report: Link will be provided when Published

Manufacturing Design

By: Danny Pham (Manufacturing and Design)

Mechanical Drawing

For our robot to walk and turn successfully, we will be designing elements of the robot that will be able to balance itself and move smoothly. The AT-ST walker design will incorporate parts of the velociraptor and biped design from previous semesters. The AT-ST will also incorporate dc motors instead of servos, so we switched out from our previous Titrus III leg design. In our case, our robot designs will be using the Theo Jansen leg design and split leg function that the previous 2017 Spring velociraptor project used.

Initial Design – Mechanical Drawing

Figure 10, 1st preliminary concept drawing.

Figure 11, Theo Jansen leg design

Figure 12, Measurement Parts

Figure 13: Mechanical design of AT-ST

Preliminary Prototype

By: Danny Pham (Manufacturing and Design)

Figure 14: Preliminary Model of AT-ST

This is our first model that incorporated the Theo Jansen legs and split leg mechanism. I used a box for the body and implemented door hinges on the side that would act as the split leg mechanism that turns the legs. There are servos inside the box that are connected to these panels, and the servos would move the panel in and out to turn the legs. The DC motors are planted on the other side of the panels inside the box, and the motor is connected directly to the Theo Jansen leg. The motor rotates the leg and creates the walking motion for the robot.

Rapid Prototyping

Figure 15: These are the components we printed that will be put together to build the legs of the robot.

We printed the pieces with PLA so the printed components are brittle and easy to break. We had to replace these with new reprints and increased the number of layers and density so that the components weren’t as easy to break when putting the bot together.

Figure 16: Rotation Shaft

First print of the rotating shaft. It is a complex piece to print because of alternating circles and different sizes throughout the shaft. It was also very easy to snap because we printed it vertically.

Cable Tree Diagram

By: Danny Pham (Manufacturing and Design) and Samuel Yoo (Electronics and Control – Software)

The cabling of this diagram contains the servo, ultrasonic sensor, and the dc micro motors. All of the cable used to connect the components were ribbon cable. These cables would make the cabling look cleaner compared to lose wires.

Figure 17: Cable Tree

Final Prototype

Figure 18: Final Model

There are a few things I would fix for this model. Because there are gaps between components in the model, it would be nice to hide some of the wires with panels that covered these gaps. I would also fix some of the screw holes for the model. In Solidworks, it is easy to reach these holes to put screws in, but for the actual model, it can be impossible to reach. Finally, I would adjust some holes in the box. When you 3D print the part, the 3D printing can deform the part so that your dimensions for size and holes are off. We had to sand down the parts to fix that. The issue for this type of design is that these components were not meant to be 3D printed. The design worked as intended but could be improved on. A solution to this is to redesign each component so that it is held together by screws instead of the connections and edges already on the kit components. Redesigning the components to basic connector shapes and using more screws to hold each part together will allow for easier 3D printing but maintaining the function of this design.

3D Printing

Figure 18: Print times

The Actual print time without the laser printable parts was 5 hours and 56 minutes. This is within the 6 hour project allocation for the 3D printing time.

PCB Design

By Shweta Hebbalkar (Electronics and Control – Hardware)

Custom PCB

Figure 19: Eagle Schemtic

Figure 20: Finalized and approved board

For the AT-ST project, one of our goals is to create custom PCB using Eagle software. This software allows the user to generate PCB layouts, in order to use the Eagle software, I need to learn how to use the software. With lack of experience using the Eagle software previously, it took me a week to two weeks to learn the general concept. So the overview of the concepts is learning a PCB, also it is most common named “printed wiring board” or “printed wiring cards”. So it is a board that has lines and pads that connect various points together.

Final Assembly

The custom PCB is for us to use less wire and clean and neat as possible and this the example of the small custom PCB made and manufactured by osh park. In this PCB has 13 surface mount component and seven through-hole parts l integration and testing of it. Customer wants us to build the PCB and implemented and integrated into the three-dot board, which is another custom PCB (microcontroller). From that Created the design in eagle software and had him to review it for approval.

Figure 21, PCB with all components on.

Fritzing Diagram

Figure 22: Fritzing Diagram

In this Figure 22, we have the 3-dot board, gyroscope, i2cexpander, two UV sensors, two IR leds, Servo, Ultrasonic, two motors, but actual we are using the micrometer with shaft encoder and 3 volts.

Old Fritzing Diagram: Preliminary Blog will be linked when published

Software

By: Samuel Yoo (Electronics and Controls – Software)

Walk Code

During the creation of AT-ST, this is a program that allows AT-ST to walk. Note that this program is used for the current model and might need to be updated later on. The code is very straightforward as it only uses the motor and control the speed. There are commented code for the servo to make it shift the bots weight.

Whichway Code

In this code we are creating a which way sub routine. There are two methods of doing this code one which is the switch case decision. The other method is the index method which saves a huge amount of coding. The method used for the AT-ST is the index method.

Line Following

For the robot to follow a line there must be two sensors in front of the robot. These sensors must be left and right of the line. The first reading from the sensor should be white or zero because it does not touch the line. Once the sensor touches the line the robot should move away from the line.

Turning

The turning part of the code relies only on the motor speed and direction. One of the motor speed has to be lower for the bot to turn. The turn is a bit wide however it will turn in the direction of the leg that slow down. The direction could also allow a pivot turn which in that case the motor must go the same direction.

Servo Control

The servo is controlled is set on a delay to move back and forth. This delay need to be in sync with the leg moving forward to replicate the Theo Jansen biped. There also need to be a heavy enough weight to move the center mass, however it can’t be too heavy to lose the balance of the biped.

Ultrasonic Sensor code

This code is helps detect objects in front of the robot. Once there something in front of the robot the code changes the path in the maze to avoid the object.

UV Sensor Code

The code here is to detect the line. The sensor also need a UV light, or any led that would result in finding the line. This led and sensor must be tested before line coding.

Shaft Encoder Code

This code allows the user to know where the shaft is located as the motor spins. The location of the shaft is important this can determine how robot would move forwards. With enough testing the values from the shaft encoder can have precise movement with correct speeds.

Custom Command Code for Arxterra

This code aids in controlling the robot movement through the app. Once the code on the app goes to the 3 dot board it would be able move.

Final Code & Calibration

At the end of the day the robot should be able to walk through a maze without falling down. It should be able to turn and detect robots in front of it. The motors might need to be set on differents speed to move straight because they are different.

Verification Plan

By: Joseph Cho (Mission, Systems, and Testing)

Verification test plan is used to verify our L1 and L2 requirements through analysis, inspection, demonstration, and/or testing. The L1 and L2 requirements are listed in the spreadsheet below. The test plans will be generated from the spreadsheet. Few of L1 and L2 requirements have been reworded by MST.

Figure 23: Verification Test Matrix

Figure 24: Verification Test Matrix Continued

Figure 25: Verification Test Matrix Continued

AT-ST Verification Matrix and Test Plans: https://docs.google.com/spreadsheets/d/1HHaQliwvLYbqErqJi2AVOlqGEzNX7grKOYJ2CBUFQ7M/edit#gid=0

AT-ST L1 and L2 requirements:

https://docs.google.com/document/d/1xd6XmBhFJmCM-EjkpJS05NfXEHCaKcGz9SlAz1I7_4M/edit?usp=sharing

AT-ST Set and User Guide

By Intiser Kabir (Project Manager)

Assembly

The assembly of the robot take around an hour to physically build the kit. First part that need to be created are the two legs. Then the next step is to get the shaft for each legs. After finishing the legs connect the whole body together and connect the pieces from the leg to the shaft.The electronics connection on the other hand will take less than a few minutes, as they have ribbon cables.

Project Documentation

Project Manager Resources

Project Burndown: https://docs.google.com/spreadsheets/d/1BA9CalRxpTEMkaj8f5vmxWCxLu6S8eY3skgKfgoj3_0/edit?usp=sharing

Project Task Matrix: https://docs.google.com/spreadsheets/d/1tRwaMMoftwmn_mTPSmE4tkiAcbTXb15QuQ_Iaq3tRSA/edit?usp=sharing

Project Gnatt Chart: https://docs.google.com/spreadsheets/d/1qJi5Dn5vKa3LCvSwmjcABUZHhiHcZaAdZUwo20mh_dQ/edit?usp=sharing

Work Breakdown Structure: https://drive.google.com/file/d/1kZrGJFDMnC0kTgMegdcvJuCHic7w2qYE/view?usp=sharing

WBS Blog: https://www.arxterra.com/spring-2018-at-st-work-breakdown-structure-wbs/

Creative Solution: https://docs.google.com/presentation/d/15-R1zJiGFsAFutUOhRmU5uyTVYaGsuqz92BFf58_nCg/edit?usp=sharing

Project Preliminary Budget: https://docs.google.com/spreadsheets/d/1oxZsYJLEbIrbdFIPajqWeOOjfz4Kuyb-HZ5zrYufdqY/edit?usp=sharing

AT-ST PDR Presentation: https://docs.google.com/presentation/d/1-NQhuu86UMHXlMK_8aWX3uDd6Hr-O2HtnjHZ4MrP_hY/edit?usp=sharing

AT-ST PDR Blog: Linked when Published

Weekly Meetings: https://drive.google.com/drive/folders/1gVZSaHw7cnSAfjJnVRijB9rwGvk1QtHc?usp=sharing

E&C Resources

PCB & Fritzing Diagrams: final PCB and Fritizing, link if broke: https://drive.google.com/file/d/1JSqOuvCCSRSwIWFCpZrfkfj4Ga_RjFsW/view?usp=sharing

AT-ST Arduino Codes: Code-20180517T100914Z-001, link if broke: https://drive.google.com/drive/folders/1DZBI-riP9-Pr2yBkuRpEFd-wREy2lyig?usp=sharing

MST Resources

System Block Diagram: https://drive.google.com/file/d/1j5_l9pjMIDLRvQ1kjKGN6JH-4fDHt6XK/view?usp=sharing

SBD Blog: https://www.arxterra.com/at-st-system-block-diagram/

Project Breakdown Structure: https://drive.google.com/file/d/1TlbJeORAzsJNmbRW44lwExin888p_u7W/view?usp=sharing

PBS Blog: https://www.arxterra.com/at-st-product-breakdown-structure-pbs/

Resource Report: https://drive.google.com/drive/folders/1zvRPpSIN7W8F0zzLFqQXKC7xtbaw7mvQ?usp=sharing

Power Budget: https://docs.google.com/spreadsheets/d/1OaWtFrqYVQsylEh2nXOvKjFT-g2KG72ej-pF6OJWQ54/edit?usp=sharing

Mass Report: https://docs.google.com/spreadsheets/d/1_q0K2hwcqDshcp3e7MT1azD3lbXh80qJeSJ1bALZQZ0/edit?usp=sharing

Interface Matrix: https://docs.google.com/spreadsheets/d/1BBBQAYeuzqONEjrJYas0pvlGR3igG8wluO_shYIF2mE/edit?usp=sharing

AT-ST Command and Telemetry (Mobile App.) Blog: https://www.arxterra.com/at-st-command-and-telemetry-mobile-app/

Verification Matrix: https://docs.google.com/spreadsheets/d/1HHaQliwvLYbqErqJi2AVOlqGEzNX7grKOYJ2CBUFQ7M/edit?usp=sharing

Manufacturing Resources

Final Solidworks Model: Solidworks files-20180517T101958Z-001, Link if Broken: https://drive.google.com/drive/folders/1NlfKwoVS82mzJICGQdZJKbr_0ODFaeZI?usp=sharing

Lessons Learned

By: Intiser Kabir (Project Manager)

From this class. The most important thing I learn is time management and trying to find different ways of communicating with the group to get everyone together. One of the most Critical things to do is Planning and Scheduling, even then a lot of things don’t go to plan as one may expect.

Things Don’t Always Go Into Plan! Whenever you are scheduling meetings with your group, make sure to have a back-up plan. Especially since there are members that aren’t available on certain days and sometimes you or someone in the group will get sick. Always have some to plan around those situation.

Communication. One of the biggest issues I have faced as my time as Project Manager is certain members not informing issues they have, I recommend finding a way with such member that like voice chat on Discord or calling them up. Is best to know when they are free so you can talk them individually to see what issues they are having and see what can you do to help out.

Research. At the very beginning, do a lot of research on previous projects see why they fail, and see their advice on how to improve it. Do research on the parts you may buy. For us we had to buy specific type of Male to Male pins and had to custom make our housing just to connect the Shaft Encoder. If we never knew this a long time ago, we wouldn’t have as much issues regarding the Shafts.

Always Get Customer’s Approval. I myself learned this the hard way. For our preliminary design our Customer didn’t like the fact we were using servos to move our leg and especially wanted us to use motors. We had to go back into the drawing board at a crucial point of our project. The customer was generous enough to help and advice us on how to improve our project or what we should look into while doing our project. Don’t be afraid to approach him when you are facing issues.

Get a Prototype working ASAP. The Customer made a huge point on it especially before Spring break to get a working model ready. The long you hold off on that the harder it will take to get your project up and ready. You will find out issues a lot faster the quicker you make your prototype. Especially since you don’t have much time to begin with in class to work on such a massive project.

Plan to iterate the 3D model at least 5 times and don’t rely heavily on the 3D printing for some parts, find alternatives and don’t rely on one company for your prints. There are many parts that need to consistently be changes there will always be issues regarding 3D printing such deformation or parts come out too fragile. Find alternative ways to make certain parts like model injects. Research on how to do that!

PCB is Not Easy to Make. It took my E&C any different iterations to finally get approved. Assembling is the hard part of making a PCB. Please remember the quicker you quicker you can make your PCB the more money you can save. Also try to Remind your Customer you have more than 1 custom PCB so he doesn’t just focus on 1 and never check the other ones.

Provide Weekly Goals. To keep your project on task, see what each person has to do per task so they can work independently. Planning isn’t easy but, but as Project Manager just form a general goal and see how everyone is doing.

DON’T RELY ON 1 PERSON TO DO ALL THE WORK. There are some points where my E&C Software had to build and test by himself. Please don’t let this happen, make sure everyone do their part because you can’t let someone do all the work.

This class went fast and you will realize how important time is. Is hard to take breaks at time for this class. Plan accordingly, help each other, learn from your mistakes, and most importantly get in your Customer’s good side. You want the Project succeed as much as you can. Don’t wait to the last minute to get everything ready always have back up, 1 of our motors failed in the last minute which ended up hindering us. So having multiple replacements isn’t a bad thing!

Future Improvements

Find alternative ways on making some of the parts and don’t rely heavily on 3D Printing. Somethings aren’t designed to be 3D Printed!
Research on how to code Shaft Encoders.
Look into current regulators to prevent your motors draining out.
Find a way to control the balance of the the AT-ST so it doesn’t wobbles as it walks.
Look into getting a boost converter to give more voltage out for the motors.
Redesign leg components into simple connector shapes that work with screws to make 3D printing easier and more accurate.
Create panels to cover gaps in the model to hide wires and to make the robot more stable. Also to make the robot look cooler.
Implement more holes in the design for screws so that the holes are in the correct exact locations of the model and so that the screw holes in the model are easy to access.

Project Video

–Linked When Made–