Weekly Progress Reports
Project Log
Meeting Notes

Weekly Progress Reports

Weekly Progress Report, 5/30/09 - 6/5/09

Last Week

Layout, Layout, Layout
I changed all components in my circuit from 0805 to 0603 parts per Andrew's direction
I also adjusted the USB data lines according to the 2.0 spec using qucs for reference as to correct spacing and trace width
I still need to lay main power and ground layers to complete the circuit
There is no meeting this week as we have our poster presentation Friday, so hopefully what needs to be done will be discussed via e-mail, etc.

This Week

Had final project due in another class which took pretty musch all my time
Was able to update schematic per request of last meeting
We had poster presentation lasf Friday, went pretty well, but we didn't win any cash
Still have a lot of layout that is needed, not sure of this will get done or not. I guess we'll find out tomorrow at our last meeting

Next Week

Finals Week
We have final presentation next Wed. so that is probably what we'll spend remainder of our time on.
We need to know everything we need to have done by wed.

Weekly Progress Report, 5/23/09 - 5/29/09

Last Week

Updated specs for usb hub to add all components and explanations thereof
Spent the vast majority of time on board layout
At this point, I have a pretty good start but what I have will need review and I'm not sure how everyone else is doing their layouts. Since we will need to fit all of our stuff together, I have left several things unfinished until the meeting

This Week

Layout, Layout, Layout
I changed all components in my circuit from 0805 to 0603 parts per Andrew's direction
I also adjusted the USB data lines according to the 2.0 spec using qucs for reference as to correct spacing and trace width
I still need to lay main power and ground layers to complete the circuit
There is no meeting this week as we have our poster presentation Friday, so hopefully what needs to be done will be discussed via e-mail, etc.

Next Week

Essentially the last full week before our final presentation on Wednesday, June 10th
We need to put our main focus on finalizing what we have and getting everything put together
We also need to put a great deal of time into our final documentation and get our presentation prepared
Over the next few days, we will need to get together as a team and figure out exactly what needs to get done. We also need some feedback from sponsors and academic advisors as to what we need by the 10th

Weekly Progress Report, 5/16/09 - 5/22/09

Last Week

Wrote in depth specifications for switches, USBbhub, and umbilical
The USB spec still needs component selection section and description of signals that the ARM will need to provide for configuration options
Updated schematic slightly to reflect which off sheet signals go where, see rev 5 of switch schematic
Did some work on layout, but really achived nothing substantial as specs took significantly longer than expected

This Week

Updated specs for usb hub to add all components and explanations thereof
Spent the vast majority of time on board layout
At this point, I have a pretty good start but what I have will need review and I'm not sure how everyone else is doing their layouts. Since we will need to fit all of our stuff together, I have left several things unfinished until the meeting

Next Week

This depends on what happens at this week's meeting, if we get the layout done everything should be OK, but we need to get documentation done ASAP and we need to integrate all of our parts.
What will most liklely happen is board finalization, system integration (hopefully), and a lot of work on documentation.
I think we also need a definite date for our final presentation, which as I understand now, is the first...

Weekly Progress Report, 5/9/09 - 5/15/09

Last Week

Removed battery and shore power placeholders as those circuits were moved to Daves charger ship circuit
Capstone team got together to discuss the Capstone poster, due next Friday, and we developed a solid idea of what we are doing
Made minor changes to switches and hub schematic to make things easier as we get closer to integrating and finalizing the design
Looked into connectors for the battery, I think I found a good candidate however i think i need a little more info aboout size, etc.
Played around with board layout a bit more, have some questions about size limitation of EAGLE light.

This Week

Wrote in depth specifications for switches, USBbhub, and umbilical
The USB spec still needs component selection section and description of signals that the ARM will need to provide for configuration options
Updated schematic slightly to reflect which off sheet signals go where, see rev 5 of switch schematic
Did some work on layout, but really achived nothing substantial as specs took significantly longer than expected

Next Week

Focusing on layout, layout, layout
Andrew obtained the USB2517 eval board which should be fun to play around with and offers some reference for layout
Again... layout, layout, layout

Weekly Progress Report, 5/2/09 - 5/8/09

Last Week

We had our first design review with the PSAS. There were several minor changes and additions which need to be added to the schematic.
We decided to change the USB hub to the smsc USB 2517, which required creating a new part in EAGLE and researching how to connect the chip.
Added in a placeholder for the battery and shore power connection

This Week

Removed battery and shore power placeholders as those circuits were moved to Daves charger ship circuit
Capstone team got together to discuss the Capstone poster, due next Friday, and we developed a solid idea of what we are doing
Made minor changes to switches and hub schematic to make things easier as we get closer to integrating and finalizing the design
Looked into connectors for the battery, I think I found a good candidate however i think i need a little more info aboout size, etc.
Played around with board layout a bit more, have some questions about size limitation of EAGLE light.

Next Week

Poster is due Friday so that will no doubt require some time next week
Decide on a connector for the battery board
Continue with board layout and APS integration

Weekly Progress Report, 4/25/09 - 5/1/09

Last Week

Fixed the power switches per advice of Andrew and Tim
Also realized that the EAGLE parts I made were not on the grid so that needed to be fixed which in turn required redoing a good deal of the schematic
Began experimenting with board layout, but need practice
Named my components per psas conventions

This Week

We had our first design review with the PSAS. There are several minor changes and additions which need to be added to the schematic.
We decided to change the USB hub to the smsc USB 2517, which required creating a new part in EAGLE and researching how to connect the chip.
Added in a placeholder for the battery and shore power connection

Next Week

I think the plan is to be able to put my, Dave, Ai Ling and Ken's portions together to form the complete APS.
I need to add conncetions to the USB hub that will allow the ARM to essentiall control how the hub is configured.
We will also probably be starting serious board work on the APS.

Weekly Progress Report, 4/18/09 - 4/24/09

Last Week

Layed down the 'almost' finalized schematic of the power switches and USB hub.
At last weeks meeting, Ai Ling, Ken, Dave, and I put our schematics together for teh first time and saw how close we are to having an APS
Also at the meeting we were told what needs to change about each of our schematics, and what Andrew and Tim will be looking for in the final product.

This Week

Fixed the power switches per advice of Andrew and Tim
Also realized that the EAGLE parts I made were not on the grid so that needed to be fixed which in turn required redoing a good deal of the schematic
Began experimenting with board layout, but need practice
Named my components per psas conventions

Next Week

Continue board layout
Update wiki with the large amount of design and log notes in my notebook
Make whatever changes are needed to my schematic and begin adding necessary components to make integration of other parts happen

Questions

I need to get the umbilical interface finished and I'd like to spend a little time at tomorrow's meeting talking about what I need to do for things such as launch detect (pull up resistor, perhaps?), umbilical detect (Can we just use the AC adapter detect on charger chip?), etc.
I also would like to go over USB hub chip and see if anyone has any suggestions as to how to make the layout better as I feel it could be.

Weekly Progress Report, 4/11/09 - 4/17/09

Last Week

Researched USB HUB so that I could add it to my schematic
Updated switch schematics a bit. Found a TI excel tool to calculate values for external TPS2490 components. Used this tool to verify my design
Talked with rest of group about integration. IT was decided that this would wait and it was decided that each of our parts need to get finished before integration

This Week

Verified switch design and compared my calculated component values with those provided by excel tool I found. So far they were they agreed or were very close.
Added USB2507 chip to my schematic, and tried to get it connected as correctly as possible based on reference design of evaluation board.
Have a few more questions as to how this is hooked up
Before meeting, I plan to finish a design verification as well as a parts list of all chips and components used in design.

Next Week

What happens next week depends on what everyone gets done this week. Hopefully we'll be able to move on to board layout

Questions

Do we need to use the overcurrent sense (OCS) pins of USB hub? If so, how? If not, do we need the amber LEDs since they pretty much deal with ocs issues?
I think I need to go over how to push stuff on git

Weekly Progress Report, 4/4/09 - 4/10/09

Last Week

Updated (corrected my eagle parts)
created the USB hub chip (smsc usb2507) device in eagle
Created the new connectors in the psas library

This Week

Researched the usb hub chip described above. (USB hub is now my responsibility)
Updated my schematics a bit, added new connectors, added most resistor values, added hub chip and bus from connectors to hub
I did seem to loose access to the psas eagle library, so I will probably now have to re-make that part
This week Dave, Ken and I met to discuss integration. After discussion we realized it would be a good idea to try and get the entire group together as we are behind, running ouot of time, and need to be on the same page at this point.
I also re-visited the switch design, and realized that I'm not entirely sure how to implement the soft-start function. Need to discuss this at this week's meeting.

Next Week

After this week's meeting I hope to have a much better understanding of the USB hub interface, I can then finish this part of the schematic
Hopefully, the group will have met as a whole to discuss overall integration as this is whcat we need to start focusing on ASAP
Work on board layout and BOM

Key Questions

I need to discuss soft-start with other group members and figure out how it should be implemented with the TPS2490
Also wondering if we plan to get the usb2507 evaluation board or not. If so, need to know what I need to do to get it.
I think it would be a good idea to go over USB interface at meeting as well.

Weekly Progress Report, 3/28/09 - 4/3/09

Last Week

Spring break week. Due to the fact that i was out of town, progress was limited. I did make the spring break meeting and was able to get the psas GIT set up so I now have access to psas EAGLE libraries. I also was able to complete the overall schematic for the power switches.

This Week

As I was working on EAGLE schematics, I realized that the parts I had created were incorrect for various reasons, and so spent a good deal of time making sure the problems were corrected.
At last meeting, I was assigned the task of handling the USB hub chip in EAGLE, and so I was able to create that part in EAGLE and it is now ready to be integrated into the system. At this point I am wondering if this has become my task or not. Should I be studying the USB hub chip in detail?
I was also given the task of updating the connectors which will be used to connect the various nodes to the APS. Detail of these connectors will be added to the specs page soon. Hopefully, I will get the connectors updated by tomorrows meeting as it is essentially adding 8 pin ports to the existing connector.

Next Week

Hopefully I will be able to make significant progress on the actual board layout.
I am also thinking that we as a group should begin thinking about how we will integrate our sections of the APS, and other components of the rocket.

Questions

As stated above, my main question right now is geared towards the rest of the group and pertains to how we will begin to integrate our project portions into final product
I also had a question about the smd function in EAGLE part creation (which I e-mailed to psas list) having to do with the ability to manipulate the shapes that can be created with the smd.
Also, as I re-examine the power switch design, I think I have had an incorrect understanding of the required soft start function. Perhaps at this weeks meeting we will be able to address this issue, which as I understand is a matter of adding a capacitor. The problem is choosing that capacitor value.

Weekly Progress Report, 3/20/09 - 3/27/09

Last Week

Finals week so not much accomplished for the capstone. Did a little work in Eagle but nothing substantial due to other obligations.

This Week

Out of town for most of the week
Almost finished with APS power switch schematics, however final component values are not official as I still have some things to figure out.
Still need to get GIT set up, so that my schematics can be shared with rest of group

Next Week

Spring term starts.
Finalize APS schematics and board layout and, if everyone else's progress allows, begin combining into complete system
Possibly get working on Pyro node?

Weekly Progress Report, 3/7/09 - 3/13/09

Last Week

Met with Dave, Tim and Andrew and made the final decision regarding the battery charger IC (see specs for details).
Dave was put in charge of designing the charger circuit
My mission was to focus on the ideal diode, for which I chose an IC (LTC4357: See umbilical specs). We also decided that the transistor used for the ideal diode circuit would be the same as that used in the power switches.

This Week

I focusede on getting my circuits created in EAGLE
Created my own library (still need GIT?) and created packages and symbols for all parts so far (TPS2490, Si4122DY and LTC4375)
Started schematics for the power switch network and ideal diode

Next Week

finals week... Not sure if too much will get done
I would like to, and will try, to get the EAGLE schematics done, at least for power switches.
Need more information on the rest of the umbilical interface so that I can get to work on that aspect of the APS

Questions

I have some questions about how dimensions work when creating schematics. Specifically, what constitutes worst case design with respect to dimensions?
For the LTC4357 which package is better? DCB (smaller with exposed GND pad) or MSOP-8?
A lot of questions about schematic design such as types of resistors/capacitors/diodes to choose out of the huge amount available on EAGLE. Also, I would like to discuss what components can be removed from previous APS with current design.

Weekly Progress Report, 2/28/09 - 3/6/09

Last Week

Dave and I searched for a battery charger chip to no real avail.
We found several that are new and have I2C CMBus interface capabilities, but we wondered if any of these do anything more than complicate the design with no significant improvement.
Came to the tentative conclusion that the LTC4007 (Chip already in use) will still do what we need and since we already have it,as well as a working reference design, this would be ok to use in new APS.

This Week

Andrew, Tim, Dave and I met on Tuesday evening to discuss and research more charger chips, in the hopes of finding the perfect chip which charges at the ideal current, and also offers I2C interface capabilities which are actually helpful, and benificial to the design
After some discussion and research, we decided on the LTC4007-1 (refer to battery charger spec page), this is the same as the chip we have now without the "auto-restart" feature which we decided we wouldn't need anyway.
Also at the meeting, we decided that Dave would handle designing the charger circuit and I would move on to ideal diode, as well as continue with umbilical interface circuits.

Next Week

I must make significant progress on the EAGLE schematic for my circuits. This should not be too dificult, but it really needs to happen.
Hopefully I will be able to finish up the umbilical interface, but I will need to know more about how the launch detect, APS-wake functions work, i.e. options as to how to implement these functions.

Weekly Progress Report, 2/21/09 - 2/27/09

Last Week

Used the TPS2490 datasheet so derive external component values for pwr. switch circuit
Derived all but the variable which will probably not become available until overall design is further along such as load capacitance

This Week

Met with Dave and we searched for new charger IC's
Dave and I looked over a fairly decent amount of chips (datasheets posted on design spec page)
From what I saw, I think we can find a charger that performs the umbilical interface we need

Next week

If indeed we find a charger which performs all the umbilical interface functions such as umb. detect, etc. we should be able to get going on schematic for this portion of APS
I mainly plan on spending this week getting the schematic put together for the power switch circuit

Questions

My main questions this week have to do with chargers. Will AC detect work sufficiently for an umbilical detection, and can this also somehow be used for a launch detect signal?
Is the "automatic power source selection" feature sufficient to meet the spec to switch seemlessly between battery and umbilical?

Weekly Progress Report, 2/14/09 - 2/20/09

Last Week

Researched the TPS2490
Tim and I discussed som of the important design considerations
Also researched the Di4212DY MOSFET, which was the main candidate for use in switches

This Week

Used TPS2490 datasheet reference design and design guide to calculate component values for use in the circuit
I think I have all but a couple of the components calculated, those that are not require more information which I will hopefully get at Friday's meeting such as load capacitances and desired power dissipation in the MOSFET
Have begun shopping for power path controllers and ideal diode transistors for use in the umbilical interface. I also need to find overvoltage protection to follow this "ideal diode" circuit.

Next Week

I will start making the switch circuit schematic in EAGLE
Dave and I will start searching for a battery charger IC, or at least start trying to decide whether to use the chip already in use.
Continue work on umbilical interface design

Questions

Do we know the load capacitances of the loads controlled by the power switches? Do we know desired on times?
Are there any other specific design constraints for the ideal diode circuit besides those in design criteria?
What is my status as far as the Pyro node is concerned? Where should I be on this part of the project?

Weekly Progress Report, 2/6/09 - 2/13/09

Last week

Researched power switch controllers
Also researched transistors
At this point we have decided on the TPS249X hot swap controller, and Si4122DY N-Channel MOSFET

This week

Researched the TPS249X and its functionality
Should be able to come up with a preliminary design in the near future (early next week)
Have a couple of questions as to certain parameters needed for component values, see below.

Next Week

Will hopefully have a power switch circuit which everyone agrees will work
Will attend the eagle workshop next Tues.
After workshop, will hopefully be able to implement the switch design in eagle by end of next week.

Questions:

My key questions pertain to calculating component values for the switch circuits

1. Is I-max as defined in datasheets, the the load current limit, or the max current the MOSFET can handle?
2. Is there another name for Ts(max) - max case temp. prior to start or restart?  Not sure where this value is in MOSFET datasheet
3. Do we know load capacitances of the different nodes?
4. What do we know about on-times for the loads for soft start?
5. How are the switches going to interface with the microcontroller?  What are the design considerations pertaining to the microcontroller?

Weekly Progress Report, 1/30/09 - 2/5/09

Last week

Did an in depth study of the APS design notes. All parts of the circuit were researched.
Main focus of the study was of course the power switch circuits and components

This Week

Searched IC manufacturers for a new power switch controller
Found many, but there are two that might be very good candidates
Need to discuss a little more what should be guiding my decision for new IC. Sent e-mail out earlier this week to PSAS list about what to look for but recieved no reply. Will discuss at the meeting

Next Week

Hopefully I will be able to choose an IC at end of meeting on Fri the 6th or soon thereafter
Once chosen, it should not take long to design a new switch circuit and move on to umbilical connection which is my goal
Also need to find out more about the Pyro node power swithc criteria. Hopefully, experience gained with APS power switches will prove helpful in pyro switch design

Weekly Progress Report, January 26 - January 30 2009

Last Week

Researched the functionality of the current power switch design. From last meeting, I now have a pretty good understanding as to what purpose the switches serve in the APS, and the reason for redesign. Essentially the switches are power switches with circuit breaker capability. 4 more switches need to be added to the current APS and the design of each switch should be simplified.

This Week

Studied the LV2b APS component design in depth, on the level of each component. I now have a very solid understanding of the fundamentals of what is going on in the circuit, namely the power switches. Searched the internet for potential alternative ICs to use. Was a bit overloaded since I had a midterm this week so I still need to transfer my log entry from logbook to wiki.

Next Week

With a pretty good understanding of how the switches work, along with the newly posted requirements, I will look for IC's which can perform the same functionality reliably, meeting the specs, and perhaps be implemented in a simpler way. Will produce a decision matrix, and hopefully be able to begin redesign of the switch network.

Questions/Problems

Aside from the newly posted requirements, I still do not know the specifics of what the specs of a new IC need to be. From the documentation I have gathered the following:

Problems with the LTC1154
- SO8 package not desireable (Is it too big?); Desired package at time of documentation SOT-23 (is this still true?)
- Too many input pins (3) for a single FET driver
- Draws too much off current (20uA)
Good things about LTC1154:
- Does current limiting w/ "somewhat reasonable" 100mV +/- 25% shunt (desired 50mV)
- Can run at 20V
Assumptions/questions based on this info
- IC needs to be rated to handle >20V supply voltage
- Low off current < 20uA. how much less? What is desireable?
- needs to limit current at 4A? min? max?
- Low Rdson. Range?
- What other important considerations need to be made?

Weekly Progress Report, 1/19/09-1/23/09

Last Week

Studied LV2b recovery node schematics and component design thinking that the pyro node would be where my focus began
Attended capstone meeting 2 (see meeting recap for details)
Was directed to change my focus to redesigning power switches for APS

This Week

Researched current design of the power switch bank on APS node
finally downloaded EAGLE on new laptop

Next Week

Continue research on power switch design
hopefully after meeting on 23rd, some questions as to how the switch circuits work will allow me to move forward to simplifying the existing design
possibly build a decision matrix for new high side driver ICs
definitely research possible alternative ICs to LTC1154

Key questions and discussion topics

My main design questions at this point pertain to specific functionality of the switch circuits on component level.
hopefully we will be able to discuss more specifics as to what needs redesign
Logistics questions
- What are our documentation requirements/expectations?
- Are we each doing seperate documentation or compiling all work into one doc? (I assume one doc but would like to clarify)
- Should we prepare PDSs for each portion of the project we are working on?

Weekly Progress Report, 1/12/09-1/16/09

Last Week

Conducted our first oficial capstone meeting 1/9/09. Topics discussed included:
- logistics; i.e. obtaining appropriate tools for project, getting everyone on the psas mailing list, changes in meeting times
- Project Specifics; i.e. recap of assignments, a brief discussion of what needs to be done for the pyro and APS nodes, discussed what should be accomplished over the following week, which essentially was research.

This Week

Focused my research attention on the Recovery node. My main goal of the week was to research the history of the recovery node, i.e. what led to its current design. The key questions I have at this point regarding the recovery node are:
- What specific aspects of the recovery node (on the circuit level) need redesign?
- How does the existing recovery node measure up to the new requirements? i.e. What needs to be changed/added/removed/modified with respect to the existing system?
- How up to date are the current recovery node schematics found on the Wiki? How up to date are the Engineering Design Notes?
- I would like to discuss a little more about the functionality of the circuits on the component level. Specifically, the pyro actuator ignition circuit, the SPS, the current HAP

As for the LTC communications link, with the implementation of the Universal Rocket Bus, how is this portion of the project affected?

Hopefully we'll have time to address each of these questions at the next meeting.

Next Week

The research will continue. Hopefully after the next meeting I will have at least partially narrowed down my objectives so that my research will be more focused on the important topics.
Other goals for next week will no doubt be given at the next meeting.

Project Log

Log Entry, 3/12/09

Log Entry, 3/3/2009

Today DaVe, Andrew, Tim and i met to further discuss charger chips
If we do decide to use the LTC4007, we will need to rework the circuit (ext. components)to facilitate new APS design
Andrew mentioned Analogic Tech, they turned out to have nothing of interest

Mission agenda for the evening

* Look over alternatives to the LTC4007
* If we can't find any alternatives, we'll talk about how to redesign the LTC4007
* Also talk a littl e more about system "glue"

ISL9518 (charger): has I2C interface but doesn't seem to offer much
LTC4007-1: Newer version of the LTC4007. Essentially the same but with no Auto-restart.
- This will be our charger chip
Dave will handle the charger circuitry design
I will move my focus to the ideal-diode

Ideal Diode stuff

Picking the transistor is key since it is in the main power path
- very low Rds_on
- High switching frequency capability
For the controller
- 50mV shunt vs. 25mV shunt
- kind that relies on resistance
- 25mV shunt better, if it can be found
Needs to handle around 10A
Must have acceptable Rds_on based on PWR dissipation capabilities of transistor
Becomes a thermal design question:
- P = I^2R
- Are there going to ba a lot of things running at once?
- Is there going to be a time when charging the battery when the system is pulling 8A
Si4422DY Should work, but will need to think about layout that would optimize heat dissipation
Controller needs to handle all stresses, want it to be able to run at 30V, with a turn on/off time of 10-20us (up to a few ms OK)
Currently using the LTC4412
- Has the right voltage capabilities, but typical current capability only 5A (not enough)
- LTC4412HV is more rugged version of above, but still has the same current constraint
LTC4375 a bit better
LTC4435:
- Vin range 9-80V
- Typical operating current capability 20A
- DFN package
- t_off 200-500ns

See Umbilical Spec Page at this link for details: Umbilical Specs

Log Entry, 2/24/2009

Dave and I met at 2:00pm today to research battery charger chips
First step, discuss what we need based on specs and desired functionality
Ideally, we want to charge at 8.5A (1C), it is acceptable to charge at 4.25A (C/2)
LTC4007 would be acceptable since it's charge current ">4A"

Other Chips

National Semi: nothing of intrest
Maxim: Several chips which could work, we will look more into these
Linear: Have the LTC4007, and a few newer chips which could work
Micrel: nothing of interest
STM: nothing of interest
Intersil: Several possible candidates, we need to know more about how useful some of these features will be for our purposes
After looking over several chips (see battery charger spec page) our tentative choice is to stay with LTC4007 for now
Ideally, I'd like to find a chip that might contain all the funtions I need for the umbilical interface such as launch-detect, power-good, etc.
See battery charger spec page for list of chips we researched: Charger Specs

Log Entry, 2/18/2009

At this point I have chosen the TPS2490 hotswap controller, and the Si4122DY transistor for the power switches.
The next step is to carry out calculations using reference designs in the datasheets to derive component values. See the link below to the power switch spec page for the datasheets and details of these calculations and this circuit.
I also need to look into the ideal diode, also know as power path controllers, for use in the umbilical interface. Dave and I need to begin searching battery charger ICs, or decide to continue using the one we already have.

Follow this link to the switch spec page:

Switch Specs

Log entry, 2/4/2009

This week was spent searching for a new switch controller IC for use in the my redesign. This search has been all internet based. Below is a list of the manufacturers searched, and if applicable, products those coompanies offer.
If the company had any ICs of interest, they will be added to an excel spread sheet to aid in decision.
Ideally at this point I am looking for a wider operating voltage range than the current LTC1154, a smaller package, and a simpler circuit (i.e. less external components). The new IC still needs to meet all of the newly specified specs as well.

Manufacturers searched and relevant products

Texas Instruments
- TPS2490/TPS2491
- Datasheet: http://focus.ti.com/lit/ds/symlink/tps2490.pdf
  - Programmable power limiting and current limiting
  - latch off/auto retry
  - Operating range of 9V - 80V
  - small 10-pin MSOP package (3.1mm x 3.1mm)
- TPS2400
- Datasheet: http://focus.ti.com/lit/ds/symlink/tps2400.pdf
  - Simple 5 pin SOT-23 package
  - Recommended operating voltage way too low (3.1V tp 6.8V)
MAXIM
- MAX4838A - MAX4842A
- Datasheet: http://datasheets.maxim-ic.com/en/ds/MAX4838A-MAX4842A.pdf
  - Wide operating voltage
  - "Overvoltage" protection
  - doesn't seem to have as many programmable options as above
  - Small simple 6-pin package design (2.2mm x 1.35mm)
- MAX4867
- Datasheet: http://datasheets.maxim-ic.com/en/ds/MAX4864L-MAX4867.pdf
  - Same operation voltage as above
  - reverse polarity protection
  - same small package option
- MAX6397
- Datasheet: http://datasheets.maxim-ic.com/en/ds/MAX6397-MAX6398.pdf
  - Operating voltage 5.5 - 72V
  - weird pin config, seems like something i don't want
National Semi
- LM5069
- Datasheet: http://www.national.com/ds/LM/LM5096.pdf
  - V range 9 - 80V
  - latch off/auto retry options
  - pwr. good output
  - inrush current limiter
  - active current limit
  - 10 pin SOIC package (3mm x 3mm)
  - programmable UVLO and OVLO
  - 55mV shunt
Also checked Infineon, On-Semi, Analog Devices, Vishay, Micrel, and others with not much luck
The LM5069 and TPS2490 are my top choices at this point. I will provide data sheets soon about both of these (some datasheets added 2/6/09-SS). Need to discuss design criterion a little more in depth at next meeting.

Log Entry, 1/29/09

This week I did an in depth study of the APS documentation provided on the wiki. Though not all of the information is relevent to my work, I thought it would be benificial to try and understand tha APS as a whole. In doing so, I feel I understand the APS board better, but as the project progresses I'll need to know a lot more about the different parts of the circuit. For now, I'll focus on the power switch circuits. Below is a summary of the components used in the APS power switches and their function.

Notes from APS Component Design Spec

ICs conbsidered other than LTC1154:
- LTC1910
  - not chosen since off current of 2.5mA way too high
- LTC1161
  - again, off current too high in this IC
- LTC1981
  - Does have desired small package (SOT-23)
  - does not provide current limiting
  - Max Vin of 7.5V is too low
- IPS511/512
  - 5A current limit considered "semi-convenient"
  - Rdson of 0.15 Ohm, too high
  - min current limit 3A (too high? too low?)
- IPS5451
  - Max current limit 50A (HIGH)
  - Continuous output current rating = 4A
Also noted that the following IC manufacturers were considered (this was at least 5 yrs ago)
TI, Vishay, Maxim, Toshiba, SGS, On-Semi (NIS5102 noted as "interesting"), Micrel, National, Infineon, and internet
LTC1154 was best choice, but far from ideal:
- Problems:
  - SO8 package too big
  - Too many input pins (3) for single FET driver
  - Draws too much (20uA) off current
- Pros:
  - Does current limiting with "somewhat reasonable" 100mV +/- 25% shunt (desired = 50mV)
  - runs (barely) @ 20V
LTC1153 almost identical but has auto reset after delay programmed by external cap.
Noted that since Vgs of the external FET switch amy approach 25V so logic level FET probably won't work. Instead a 25V rated power transistor probably better.
Also a 15V zener diode could be used.
Supply filter recommended to power the switch during short circuit condiditions
Refer to figure below to see these parts in the circuit:

Transistors used in switches (Q2006-Q2009)
- TPC8013-8, SO8
  - Rdson = 5mOhm
  - Vgs_max = 20V (rated >= 25V would be better)
  - Rdson_max @ 10V @ 25C = 6.5mOhm
  - Rdson_max @ 100C = 8.5475mOhm
  - 1/3 Watt pwr. dissipation
  - Idc_max = 6.24482A
Diodes used
- D2002-D2005: 1N4148WCT-ND, SOD-123
  - Short circuit protection speedup
  - Activates when V on current sensing shunt exceeds 700mV (x7 overload)
- D2006-D2009: 1N4148WCT-ND, SOD-123
  - Gate turn off diodes
  - If soft-on delay circuit used, diode must be included to bypass network resistanceand accelerate discharge of transistor gate
- Z2000-Z2003: Diodes Inc. BZT52C155DICT
  - Gate protection Diodes
  - Since modern circuits designed for low voltages, working above 12V can be problematic
  - Charge pump on LTC1154 does not regulate voltages, so at higher supply voltages (like the 20V used here), possibility that gate may suffer voltage breakdown
  - Dioides limit Vgs to 15V
  - 15V units sold in SOD-323 pkg. already in inventory
Capacitors used:
- C2012-C2015: 0.01uF??
  - OVerload response delay caps
  - Value depends on nature of loads that are powered.
  - 1ms delay suggests 0.01uF
- C2016-C2019
  - Soft-on delay caps
  - Provide energy storing element for RC turn on delay circuits provided for each power switch
  - Convenient to keep resistors fixed and control turn on time by changing the caps
Resistors Used
- R2022-R2025
  - paranoia resistors for high side driver inputs
  - necessity questionable
  - If Vs reversed, might limit current into PIC uController
  - Possibly limit current flow in the event of voltage breakdown in high-side drivers
- R2026-R2029
  - Paranoia resistors for high-side driver status outputs
  - Less convenient than R2022-R2025: force high values for pullup resistors R2050-R2053
  - necessity questionable
- R2030
  - "No blow up/No stay on" resistor
  - acts as LPF to eliminate powe glitches which could damage LTC1154. These are needed because the 1154 is running at Vmax so power glitches could cause overvoltage condidions
  - Also, if short circuit conditions brings bus voltage below LTC1154 min operating voltage (3.5V), 1154 will not function and thus will not turn off to interrupt the short
- R2032-R2035
  - Output current measuring shunts
  - APS outputs protected against overcurrents by monitoring voltage accross the shunts
  - If this voltage reaches 100mV +- 25%for some duration set by other components, output is shut down
  - 50mV would be better
  - Max DC current for each output 6A: R = 0.1V/6A = 16.667mOhm
  - max poer dissipation = 1W
- R2036-R2039
  - Along with caps. C2012-C2015, these form the delay network for each LTC1154
  - Allow brief overloads w/o shutting down load
  - 3 considerations in sizing:
    1. Power source (LiPo battery)
    2. Switch is N-channel MOSFET subject to safe operating area constraints
    3. Actual load sets most stringent overload requirements
  - Delay function of RC delay and magnitude found on datasheet
  - Values require knowledge of load characteristics
  - 1ms delay reasonable: 100kOhm resistor with 0.01uF cap.
- R2042-R2045
  - Turn on delay resistors
  - Control time allowed for inruch overvoltages on startup
  - soft-Start control
- R2046-R2049
  - Gate damping resistors

Log Entry, January 27, 2009

New Design Requirements Added to Wiki: For my power switches, requirements are as follows:

Power Switches

MUST have (8,,) independent resettable electronic circuit breakers with adjustable current trip and trip delay. Setting can be via resistor strap, EEPROM, etc.
Current trip should be latch-off or selectable.
MUST have Soft on feature (SHOULD have soft off).
MUST have no mechanical switches in main power path.
MUST indicate power switch on/off state
MAY indicate power switch fault state

With these requirements, the redesign becomes much easier since I now have a good idea of what I'm doing here. This week I will research power switch IC options: Available products, their features, etc. the next step will be a decision matrix which we as a group will probably need to evaluate.

Log Entry, January 22, 2009

My mission this week has been to study the existing power switches on the APS. The main questions driving my research are:

Overall functionality
- What purpose the switches serve with respect to the APS
- Is this purpose the same on other nodes; i.e. the recovery node
In depth functionality
- How do the switches work on a low level scale (circuit component level)
What were the deciding factors in choosing the LTC1154 IC
What alternative IC's were available and explored during the design of the first power switch circuit network
- Why were those ICs not chosen
- Should any of those alternatives be re-examined
What alternative ICs are available now
- comparison with current LTC1154
- availability
- Cost
what can be done to current design to simplify and provide the same functionality
If there is not a better alternative IC, is there a better design to simplify the external circuitry of the switching network

Overall Functionality

Figure 1 below is a copy of the power switch section of the current APS. Figure 2 shows a closeup of one of the power switches and external circuitry.

Figure 1: Power Switch Section of APS

Figure 2: Power switch close up

Figures 1 and 2 are both taken from the EAGLE schematic for the actual LV2b APS. In the APS component design spec. these circuits are explained as power switches for system loads. My first question becomes: What are the system loads here?

The external circuitry in the design shown in fig.1 is for the most part to control how the switch behaves during fault conditions such as overcurrent, i.e. the ability for the switches to act as breakers. The datasheet for the 1154 contains this exact circuit so that is where I will find more in depth info. as to the functionality of each part of this circuit.

I also am curious as to how the power switches here on the APS differ from those on the recovery node. Figure 3 shows one of the power switch circuits from the component design spec of the APS.

Figure 3: Power Switch from recovery node

The above figure, while rather unclear, shows that recovery switches are not at all the same as those for the APS. The switches on the pyro node are critical in the functionality of the igniter circuits, which I assume have very different power needs, etc. These switches, which utilize IR2118 ICs are also on the agenda for redesign and so I will be exploring them later.

In Depth functionality

The LTC1154 datasheet will no doubt provide much useful information about how these switch circuits function. The data sheet can be viewed by clicking the following link: http://psas.pdx.edu/AvionicsPowerSystemLv2/lt1154.pdf

As stated, the circuit shown above in figure 2 was taken directly from the datasheet. To understand how this circuit works, studying this datasheet will most likely prove useful. Parts of this datasheet will be repeated here to aid in my understanding of these circuits. Figure 4 shows a pin diagram for the ltc1154.

Fig 4: LTC1154 pin diagram

A brief description of each pin and my understanding in the APS follows:

INput pin
- Takes input from microcontroller (PIC18LF458)
- active high
- activates protection/charge pump circuitry when on
Shutdown (SD) pin
- Grounded on APS
- Immediately disables switch under secondary fault condition such as overtemp.
Enable# pin
- Grounded on APS
- active low
- allows switches to be used in banks such as in APS application
- Provides another means of control over switch
Gate Drive Pin
- Outputs to gate of Q2006-9 through network of resistors capacitors and diodes
- drives the gate of the N-channel MOSFET
- driven to grnd when switch off
- driven above supply rail when switch on
Supply pin
- Connected to supply voltage (5V from battery?)
- provides power to input, gate drive, regulation and protection circuitry
- provides a Kelvin connection (what is this?) to the top of the drain sense resistor for internal 100mV refference
Drain Sense pin
- Connects to Q2006-9 MOSFET drain accross parallel resistor and diode. Also connected to supply accross capacitor to introduce time delay in fault shutdown
- compared against supply pin voltage. If more than 100mV below supply pin voltage, the INput latch is reset and the gate of the MOSFET is discharged. RC circuit can be used between drain sense resistor and drain sense pin to introduce a time constant and control duration of discharge. This is employed in APS.
Status pin
- Output to PIC18LF458 micro-controller
- Open drain output
- driven low when a fault condition is detected
- recommended 51k pullup resistor used between this pin and logic supply

Log Entry, January 16th, 2009

As is stated in the meeting recap below, the week following the first meeting was dedicated to researching the history of the LV2 rocket and its design over the years. Specifically, since I'm going to be doing what I am imagining as a good deal of work on the recovery node, understanding this system is where I focused most of my attention over the last week.

I spent a good deal of time pouring over the Avionics Team page on this Wiki which proved relatively informative. The major problem I encountered during my research is that it is not entirely obvious what documents are out of date. Thus, it is sort of unclear whether the version of the node I am attempting to understand is the most recent version.

Below is a list of helpful documents and wiki pages I encountered over the week as well as links to those pages/documents:

AvionicsIntro, An introduction to the history, developement and goals of the PSAS avionics team
PSAS Avionics System Design Project (http://psas.pdx.edu/ProjectLV2/lv2_avionics_design.pdf), this document, dated 1999, I found provided a detailed history of design of the avionics systems of the original LV2 rocket. While obviously out of date, it was helpful to see the design choices made then, as well as the goals for the future, and then compare to the state of the LV2 project of the present. From what I saw, there have been a great deal of changes over the last 10 years, as should be expected. The history of the CANbus and why it was chosen was very informative, though now out of date.
recovery node lv2c: This Wiki page provides a very brief explanation of blocks that make up the recovery node, and the requirements for the new system. There is also space for design specs which I imagine I will be contributing to at some point
- My key question here is, how does the existing recovery node measure up to these new requirements? i.e. What needs to be changed/added/removed/modified with respect to the existing system?
CapstoneLV2b: The 2006 capstone page. This page contains a huge amount of useful links and pages pertaining to their project.
RecoveryNodeLV2: This page provides huge amounts of detail about the recovery node, along with schematics and engineering notes about the design of the node.
- In particular these pdf circuit schematics seem like they will be helpful: http://psas.pdx.edu/RecoveryNodeLV2/LV2-Recovery_pdfs.zip. Again the key question here is whether these schematics are up to date. If so, more study is required to fully understand functinality
- In accompaniment to the above schematics the following engineering notes helped to explain functionality and design choices: http://psas.pdx.edu/RecoveryNodeLV2/ComponentDesign.pdf. At this point I do not have enough of an understanding of the systems to effectively follow the component design notes. Major questions: How do these components work? What about them has changed? What needs redesign?
- The component design document also provides a vast multitude of equations used to justify circuit component selection. However there is little or no derivation of these equations (which may not be necessary for engineers experienced in this field) so I will need to do some more study into these justifications.

The above list of documents and wiki pages is a small sample of all the material available on this topic, so obviously more research is necessary. At this point I think it's a matter of finding out exactly what my goals in this project will be, and then the necessary research will be greatly narrowed down.

Recap of important questions for next meeting

What specific aspects of the recovery node (on the circuit level) need redesign?
How does the existing recovery node measure up to the new requirements? i.e. What needs to be changed/added/removed/modified with respect to the existing system?
How up to date are the current recovery node schematics found on the Wiki? How up to date are the Engineering Design Notes?
I would like to discuss a little more about the functionality of the circuits on the component level. Specifically, the pyro actuator ignition circuit, the SPS, the current HAP
With regards to the LTC communications link, how does the recent change to USB affect this part of the project? It would seem to me that with this change, the communications problem over this line is essentially solved. If this is not the case, where is a good place to start in designing this system? Does anyone have any suggested reading?

Meeting Notes

Meeting 13 Notes: April 3, 2009

At this point, Andrew feels we're getting too far behind. Firmware needs to get things happening so we can begin overall system integration

Pyro status unknown at this point
If we can we'll crank through the APS design from here and move on to PYRO
Ken, Dave and I need to begin integrating our sections of APS
Someone needs to take over LPC2368 (Probably Ken)
Andrew/Tim will be expecting re-done version of previous capstone schematic
Would like to see this done in the next week/week and a half
After that point we'll move to pyro
It was decided that we will be updating PSAS EAGLE library as we go instead of making our parts and merging later
Will be using DIFF in cygwin for library sharing/updating
- Need to download and install notepad++
- Add compare plugin
Diff compares files
- the eagle libraries are binary files w/ symbols, packages, and devices
- library can be exported as script
- export libraries to ASCII files
- export PSAS library to ASCII file
- diff the 2 files and replace changes line by line
- this is now an updated library which needs to be pushed back to git repository
We also need to start pushing our schematics

Meeting 12 Notes: March 27, 2009

Spring break meeting, only 3 team members showed up
Set up account to access psas git repositories. This will allow sharing of libraries and parts
- using cygwin bash shell as linux environment in which we will work with the git repositories
- Inportant files found in C://cygwin/home/Scott
I need to create a new connector for each of the 7 power switches (note here: spec was changed to 7 switches instead of 8 since on 7-port USB HUB chips could be found)
- The old connectors (not in schematic I've been using) have 8-connections (each one below is doubled up in actual connector:
  - Vbatt
  - CAN+
  - CAN-
  - GND
- Need 4 more pins for USB interface, USB+ and USB-, again doubled up
- Since these connectors only come in 8, 16, and 24 pin-port packages, will use the 16
- The remaining 4 pin ports will be used for direct board to board connections
- Call new connector CONN_NODE5
- Part name (actual connector) JST-16PS-JED
I have now been assigned the USB HUB chip design in EAGLE
We're using SMSC USB2507 chip, get datasheet
Try and have done by next week

Meeting 11 Notes: March 20, 2009

Was unable to attend this meeting due to the fact that I had a final project in one of my classes to finish. Will be checking other team members' blogs for meeting info

Meeting 10 Notes: March 13, 2009

Andrew brought up the fact that we're a little behind as a group as far as getting EAGLE schematics and board layouts finished. May have to edit the project timeline accordingly.

SPI Interface

Turning out to be more difficult for Firmware people than expected
- Manufacturer documentation on sensor and LPC not up to par
- Pre-lab research on interface not done well by firmware team
- At this point there is no code for SPI
SPI will become the fouondation of everything so this must become more of a focus fpr the team

Jeremy

* At the point where he can program the LPC
* Also able to do some work with freeRTOS

Dave

Found a few candidates for HAP batteries
Still working on EAGLE schematics for the LTC4007 battery controller chip

Dave's Goals * Needs to have the EAGLE schematic of battery system (shore power to batteries)

Ai Ling

Working with Tim/Andrew on sensor stuff today

Me(Scott)

Familiarize myself with the Rocket Names wiki page which explains the naming conventions for ICs and otyher circuit components.
GIT; set up on wiki (called E-cad or Avionics-cad). Now ned to set up psas account to access git suppositories.
In response to my question about package to use for LTC4357 FET controller, I was told to use the DCB (DFN) package
By next week, need to have initial schematic for powewr switches completed

Ken

Working on feedback/controll equations for SPS, feels a little lost
Has initial schematics for SPS essentially layed out (no board)

Other Topics Discussed

Still planning to meet as a group next week (finals week for winter term) to go over our schematics on a projector
4pm today, pressure sensor testing taking place (I need to study for finals and get term project done so will be unable to attend)
We all need to start looking into BOM for our sections and keep track of Digikey part numbers for our ICs used.

Meeting 9 Notes: March 6, 2009

Short meeting this week as Andrew's presence was required at an ECE Undergraduate fair.
At this point I have been and will continue to work on EAGLE schematics for the APS power switches.

Meeting 8 Notes: February 27, 2009

Pressure test possibly next Friday in place of usual 2:00 meeting

Mike and Jeremy

Jeremy looking for multichannel ADC stuff for firmware
Experimenting with something called JCREN(sp?)
Meeting Tues to discuss firmware so far
Team members all need to get GIT to be able to share EAGLE libraries

Some EAGLE notes

T-Cream restrict: a command to be used to restrict the solder cream on exposed pad IC's
This will be critical for our designs

Dave and I

Meeting with Andrew and Tim on Tues at 4 to discuss more charger chips
Dave and I met earlier in the week and looked at several chips and came to the conclusion that none were really any better than the LTC4007. At this point that is what we're using for the design
If we can find one, an I2C compatible chip (SMBus) would be cool for our design
MAX 1909 which we looked at, has this, but it seems to just complicate things
We don't really want multi-chemistry battery chargers.
Dave and I looked at a few more chips at this meeting, but we will finalize our decision at Tuesday's meeting

Meeting 7 Notes: February 20, 2009

Dave

chose a battery!!
See last link before "power calculations" on battery spec. page
Need 8: 4-series, 4-parallel
A little less than stellar: loses 2/3 capacity after 300 charge/discharge cycles
Looked at 6 charger chips (also my job). We need to focus on:
- 8A charging current
- no real, hard spec on charging rate
- will need to charge at a rate > C/2 or > around 4A
We should be looking into eval boards for our chips
Dave and I are meeting Tues. 2/24 @ 3:00pm to discuss charger chips

I asked where i should be on the pyro node, was told to focus on getting APS done first.
Since I have pretty much chosen my power switch and the design is close to completion, I will be focusing my attention on the battery charger with Dave at this point.

Ai Ling

Still working omn sensor stuff
She will be given responsiblity of finding sensors related to the battery such as gas guage, etc.

Mike and Jeremy

good to go for now
Andrew wants to see sensors working and communicating with the ARM enough to run pressure tests in 1 week ideally. 2 weeks is the absolute deadline

Ken

Looking at 3 chips
Still hopes to find the "perfect chip" that does everything needed by the SPS/HAP
Top choices at the moment are LT8023 and LT8032 (see Ken's pages)

Meeting 6 notes: February 13, 2009

Battery

* <www.all-battery.com/37volt-4000mah15cli-polycell.aspx> 
* At this point this looks like the top choice, if so will buy
* need datasheet
* no cahrger-chips found yet
    *  This is a key part of design so Dave and i need to get to work on this

Add table of contents to blogs

Umbilical

I am responsible for designing the circuitry for interface between the rocket and shore power. This interface will most likely consist of some kind of detection of when shore power is plugged in, which will allow for launch detect when pulled out. Also need and "ideal diode" (FET with controller) to controll power path when shore power is plugged/unplugged. See diagram below:

Shore power diagram

Will look more into power path controllers over next week
keep umbilical at forefront of goals

Firmware

* Need to discuss what it should do
* Andrew, Mike and Jeremy will be getting together
* Free RTOS running
* Also need to look into test harness for Ai Ling

Sensors

* HUB chip chosen by Sarah
* High speed stuff irrelevant at this point because using PWR PC, but spped will matter in the future
* Will look into developement board for HUB
* check out ALCOR
* 80XL02 accelerometer chosen (good to 70g)

Power Switch stuff

* Tim and I did a little calculating and discussed thermal characteristics of transistors
* With what we talked about, i should be able to do calculate component values
* We also went over the "constant power engine"

* Also look for developement boards for our chips*

Meeting 5 notes: February 6, 2009

Important Topics

EAGLE workshop, Feb 17 (Tues.) 7-10pm
More axbout this will be posted on the Wiki

Project Updates

Ai Ling
- Looked for pressure sensor
- found high temp accuracy sensor
  - We don't really need high temp. sensitivity, in fact we don't really want it
  - More interested in low temp. low pressure associated w/ high altitudes
  - ideal p-range 0-115 kPa
  - Low end of p-range is important
  - Need absolute range
- Andrew and Ai Ling will sit down later to to look at more options
Dave
- Narrowed battery choices to 2
- 2 choices can get roughly 8.5A-10.7A, respectively
- Polyquest 1600 is top candidate as of now
- Dave is to find the battery by next week since this is crucial to project moving forward
Ken
- Did not find the "magic chip" he's been looking for
- having problems similar to mine where he's not really sure how to choose among the vast set of chips out there
- Needs more detailed info about criteria for choosing the chip
Mike and Jeremy
- Still working on firmware and producing flowcharts

Some notes on IC packages:

BGA is a problem since they are so sma
DFN = small Dual Flat No-lead. These have good thermal performance.
TQFP is OK
SOT is just right for our purposes if possible
try to stay with a size somwhere between SOIC and XFN

Power switch discussion

tim and I discussed the TPS249X in some detail, as well as some of the less intuitive aspcts of data sheets and design considerations.
We also looked at some potential transistors:
- We want Vds good for 30V+, with Rds_on <= 10 mOhm
- SO-8 or smaller package OK, good because they are popular and easy to find in various types of FETs
- Large V range
- low charge capacitance OK (this determines how fast the gate dischsrges when FET turned off
- looked at: D-pak, super SO-8, exposed SO-8 and others
- SO-8 looks like it might be the right choice
We want to make sure the chosen controller gets to the min. Vgs threshold voltage to turn the transistor off
also need to look into leakage currents, make sure they are not enough to actually power devices that are supposed to be off
For next week work on a sketch of the circuit including the transistor
Continue researching the TI controller (TPS2490)

Meeting 4 notes: January 30, 2009

For Power Switch:

9-20V operating range ideal
check LTC4256-1
Maxim, Micrel
Analog Devices
TI
On-Semi
Smaller than SO8 package good
More Questions Encouraged

Meeting Minutes

Jeremy and Mike (Firmware) in high demand
- Need SPI & ADC knowledge to start talking to pressure sensor
Ai Ling
- Research analog output pressure sensor
- ideal single output, small
- Check oout absolute pressure sensor
We should be starting to get schematics put together
Note: At apogee the rocket is traveling relatively slow so even though SPI is relatively slow, it should not be a problem
Note: Input from shore power needs to match amperage of the battery, I'll need to stay in touch with Dave as this is a basis for the umbilical interface with the APS

Meeting 3 notes, January 23, 2009

Note: it was mentioned that RecoveryNodeLv2b wiki page contains most recent schematics (version 1.2) for revovery node

Documentation questions:

I had a general question as to expected documentation the group will need to produce for this project
As far as project proposals, since we don't necessarily have a specific problem that we're attempting to solve, we will not be expected to produce official proposals. However, product design specs will be expected on an "as we go" basis
We will need to put together a final document containing each of oour portions of this project which will need to be a cohesive, easy to understand, etc. with abstract, intro, etc.
Final Presentation:
- Will be presented to rocket group at the end of the project
- Should include a projector of some kind
- Should be added to wiki, but needs to be prepared, possiby power point, etc.
Our PDS will need to be produced as we go along since we will be working on different parts of the LV2 throughout the duration of the project
Team evaluations should be completed by next meeting (Jan, 30)

* Grading Criteria*

The group concensus is that the posted criteria is OK

Side Note

Dan/Dave from the Rocket Group might want to change backchannel serial bus to CANbus * this shouldn't affect our current assignments * this could eliminate the 8:1 MUX on APS

Group Progress/Questions

Firmware (Jeremy & Mike)
- Andrew would like to see some working code: flow charts, blinking lights
- Should understand the 2148 chip
- Get some GPIO pins functioning/interfacing with Ai Ling
  - Ai Ling needs to understand pressure sensor enough to give Jeremy and Mike commands for firmware
Ai Ling
- Waiting on physics dept. about the pressure chamber for sensor testing
- Needs help from rocket group (Andrew/Tim) choosing the right spressure sensor
  - Possibly 3-axis SPY(sp?) accelerometer
Dave
- Needs to develop undrstanding of each part of the battery system
- Asked if there are any recommended companies
  - General search probably best
  - Andrew will provide a list of Li ion polymer batteries for Dave and Ken
  - Li batts. cheap in large quantities, but for oour purposes, probably find batteries at a hobby shop or something
  - Can probably get the battery donated
- Not a lot distinguishing Li polymer batteries
- Don't want limited cycle capability
- reasonable voltage curve
- Specific e-density (per unit mass)
- Volumetric e-density (both ways to measure quality)
- requirement spec. will be posted
Ken
- Needs to find out how much power needs to be stored
- the ARM controller may utilize power saving mode, if not it could draw a lot more power
- Will be looking for small (quarter size)
  - Check the wiki
  - 50-125 mA range
- Needs to research tradeoff between frequency and quiescent power load
- Possibly LT part high running rate
- Perhaps make system synchronous

Some SPS Notes:

the system essentially consists of power being switched on and off producing a square wave. This square wave is then filtered through an inductor which produces a "sawtooth" triangle wave. However if the power is switched off for too long the system enters what's known as "discontinuous mode" which introduces noise into the system, among other things.

Solution: make inductor bigger, which then increases saturation current * this takes up board realestate

Power Switch notes (for my current portion of project)

the power switches essentially act as circuit breakers for APS overcurrent conditions
1 switch per device. Was 4, now system calls for 8 with new configuration
Switches can also be used to turn nodes on/off
- "Soft Start"
this gives name: power switch with circuit breaker capability
Look into integrated low vltage solutions
Employ ceramic filter caps (ideal characteristics)
- Withstand large inruch currents
"Soft Start" trip delay
- results in lower di/dt (less inductive kick)
- doesn't load down bus as much
look into "Current Limited Power Controller" (Maxim/Micrel)
look into Power Over Ethernet (POE) 48V
need high voltage capability
Overall objective: redesign power switch circuitry for simpler, more robust system

Meeting 2 notes, January 16, 2009

Ideal Agenda

Discuss the desired architecture for the new APS and recovery nodes
Get everyone started
discuss the "Universal Rocket Bus"
Discuss WPRs

WPRs

In regards ti the WPRs, Andrew would like us to have them complete and posted by Thursday night before the friday meetings so that he has time to go over them before the meetings.

The URB

For more information, see Andrew's post on this Wiki
The change has been made since Tim and Andrew aren't fans of the USB, but the software team like it due to its ability for good data transfer
The desire is to have all or most of the nodes be able to communicate directly with each other
specifically, the APS and recovery nodes need to talk directly to each other and the outside world due to their critical nature within the system
- it is also desired that all nodes are able to be turned off/on independently
- To best achieve this, the APS has now become the HUB in the system and provides power/communications to the other nodes
- This is desireable since it eliminates mechanical connectors, which are unreliable, by employing a dual 8:1 MUX which allows the APS to talk to each node when the UART is in state 0, and enables communication with the outside world ove the shore power umbilical when UART is in the 1 state.
- The device to achieve this is the LPC2148
- The communication over the umbilical shore power has now become much less complicated since there are now conductors added to the line which are dedicated to communication. This essentially eliminates this portion of the capstone 2009 project, which was my responsibility
- The APS has now become the central node to the rocket.

Getting Started (Task List)

David

Study Li polymer batteries
- better to pack, better energy density
- Lighter than other options
Research power budget (page on wiki)
Study the PDF for design of the APS

ME (Scott)

De-prioritize the LTC comm link due to introduction of URB topology
Focus attention on APS power switches
- Study PDF for the APS design, along with EAGLE schematics and research existing power switches
GET EAGLE ASAP!!
For pyro node, research HVS, power switches (different than APS)

Ai Ling

Read up oon sensors
Study VTI SCP1000
Possibly test chip operation down to vaccuum conditions, since alt. of 80000ft close to vaccuum
Desire to produce calibration curve
Test agains fundamental limit for mechanical guage
reserch USB HUB chip
- small, low power, high speed (USB 2.0), availability
reseearch Lynx Technologies radio transiever module

Ken

research SPS fsor both boards (APS and recovery)
- These are critical path components
- Study the last capstone
Must decide how much battery power can be lost in the switcher
- affect on overall battery life

Mike and Jeremy

Work on firmware

Notes on protected switches

The switches act as electrical breakers which trip in an overcurrent situation.
the problem is that it is possible that in a high frequency environment such as that of the APS, brief periods of high current can occur which are not necessarily a threat to the system.
The switches used currently are LTC1154. with the implementation of these are external RC networks, which allow a time constant to be created. This introduces an adjustable time limit for which a fault condition can be tolerated befor the breaker trips
These switches also require a manual reset function for "stay off mode"
It is desired that I find something a little less complicated than the switches in use
Some specs to start with are:
- 4A_hr battery
- Disharge rate at C/1 - OK
- Assume typically not drawing < 100mA or >4A at any given time
- SO-8 package with external FET for dsign flexibility
- Current range (0.1,5,10)Amps
  - research measured power requirements
  - add a factor of 2 padding to specs

Meeting 1 notes, January 16th, 2009

This is my first official entry into my "electronic project notebook." We had our first official capstone meeting January 9, 2009 (last Friday) where we discussed the following:

Logistics

The weekly capstone meeting time changed from 4:00 to 2:00
Those who were not already on the PSAS e-mailing list were added. We were all encouraged to post any and all engineering questions we may have to this mailing address (psas-avionics@psas.pdx.edu)
We were all reminded to download EAGLE cad from cadsoft.de as soon as possible
Grading criteria would be added to the Wiki soon (and is there now) see: Grading criteria

Project Specifics

We were directed to see: requirements page on the 2009 capstone homepage to get an idea of what is expected overall for the Pyro Node redesign, and APS
Assignment review: For the recovery node, the main areas of focus are safety, SPS, switches, HAP, with my particular focus on the first three.
For the APS (Avionics Power System) main areas of focus for the group are the Li battery charger, power switches, charger for shore power, LTC communication over shore power line. My focus in particular is on Li battery charger, and LTC comm.

Before the next meeting

Search the Wiki for any and all documentation pertaining to our particular areas of focus on the project
Prepare a list of in depth questions for discussion
Complete first weekly progress report
Specifically for me: Search for a history of the design of the recovery node and attempt to understand how node functions, why certain design choices were made, areas for improvements, etc.
For LTC comm: this is a new concept for the LV2c and thus will require a good deal of research. The key question is how can you reliably send information over a DC power line that is subjected to very large amounts of noise?