psas/launch-tower

CAD files and software for the launch tower computer (LTC)

PSAS Launch Tower Computer (LTC)

PSAS has had three generations of launch tower computers:

• LTC v1 (2005-2012)
  • PC-104+ 486 running Linux 2.4 talking CAN to PIC18F-based boards with relays and analog
  • Lucent "Wavelan" PCMCIA WiFi card
  • 12V SLA battery powered with 30W solar panel
  • Metal IP66 case on independent
• LTC v2 (2012 - 2014)
  • Beagle board talking USB to Phidget relay and analog boards
  • Alpha WiFi board
  • Ethernet umbilical cord
  • 12V SLA battery powered with 30W solar panel
  • Medium sized plastic IP67 enclosure
• LTC v3
  • BeagleBone Black using GPIO and analog mounted on a single custom carrier PCB
  • 14.7V LiPo pack with solar charger.
  • Smaller case

This repo contains everything related to the launch tower computer (LTC), with the exception of the userspace software, which is contained in the launch-tower-comm repo.

Contents

• doc

  • Documentation, what there is of it.

• eagle

  • Schematics and PCB layouts, made with Eagle.

• laser_cut_drawings

  • Line art of the power and ignition boards' mounting panels, suitable for use with a laser cutter.

• ltc3

  • Everything related to the design and manufacture of the third generation launch tower computer, LTC3.

• os

  • Everything needed to bring up a fresh, bootable Debian GNU/Linux system, just the way we like it.

launch-tower's Issues

Create "UI" sketches for LTC3

Using the included whiteboard snapshots, create simple sketches of LTC3 front and side panels. We want to explore ideas for the placement of switches, connectors, and gauges.

select LTC3 12-to-19 V DC-to-DC converter

This converter will supply the rocket's shore power connection; 19 VDC @ ~ 4 A.

See Requirements doc for details. If you discover additional requirements that are not already in the doc, please update it.

Start off by coming up with a list of promising candidates. At this point, we will consider both board- and chassis-mount styles.

Make BQ77PL900 footprint and schematic symbol in KiCAD

Create LTC hardware issues

-Migrate Launch Tower Comm hardware-specific issues
-Create other hardware-specific issues

Create functional spec for LTC3

A document that describes what we want out of LTC3 (as opposed to how it works, which is covered by the design doc).

select LTC3 ignition battery charger

12 VDC input, direct from PV panels. Not integral to the LTC main board; chassis-mount only.

See Requirements doc for details. If you discover additional requirements that are not already in the doc, please update it.

Create schematic sheet for LTC3 5 V DC-DC converter

A placeholder sheet ("DC-DC Converter, 5V") already exists. Drawing up the schematic should be reasonably straightforward.

We're using a Cincon EC4BU-12S05. Refer to the design spec and data sheet for the particulars. A custom component will likely need to be drawn to represent the converter. The data sheet contains a table of pin assignments.

Please do not commit your work to the repo's "master" branch. Create a new branch. We can merge to "master" when you're finished.

Create design spec for LTC III

Work has begun in launch-tower-comm/ltc3/doc/design/.

Investigate BeagleBone Black power options

Can the BBB be powered through its GPIO pin headers, or only through the micro-USB port?

Design Beaglebone Black Cape Interface

LTC Power architecture overview - Review switching from 4s to 8s batteries, plus part choices

Cross-posted to Avionics list.

I wanted to send out an update about some design decisions the LTC made recently and solicit feedback.

Based on internal discussions and conversations with Andrew and Kenny, we've decided to swtich from a 14.4V nominal, 4s lipo battery to a 28.8V nominal, 8s lipo configuration.

The primary advantage of this is that it lets us use buck converters down to our power rails at 19V and 5V; configurable buck converters are cheap and easy to find, and have higher efficiencies at a low price point than the boost converters.

The downside of this is that we need to do a custom charging circuit because we're moving away from standard 12V nominal MPPT and 4s battery setups.

But, upon further investigation, we found the LT8490, which is a combination charger/voltage regulator/solar MPPT, and is discussed below. It will be difficult to implement but is a big win as far as cost and system flexibility.

PRELIMINARY COMPONENT CHOICES FOR LTC POWER SYSTEMS:
Voltage regulators:
This is a 7-pin drop-in converter. It's about $30 per, but it will just work, and give us the current, power, and temperature specs we need.
TI PTN78020H (19V rail)
TI PTN78020W (5V rail)

Battery front-end:
LT8490
This is a switching buck/boost regulator with a wide input/output range + charging (LiPO compatible) + solar MPPT. It's very robust and costs about $15. This will be the most complicated circuit and largest time investment of our design, but the work will largely transfer over to the CubeSat power systems.

Battery protection:
TI BQ77PL900
This is a cell protector/balancer that normally runs on I2C with an analog front-end, but can be configured for stand-alone operation. It is cheap, relatively simple to use, and will do cell balancing for us in the field.

Battery:
Because we need at least a 2V overhead to provide 19V for shore power in order to use a down-regulator, we will likely use an 8s configuration. 6s is too close (21.6V) to the output, and 7s is available but is a very non-standard battery configuration.
Based on assumptions: 90% efficiency, calc. 96W of power (a conservative estimate), 4 hours pure battery, we need a capacity of:

13.2Ah at 28.8V nominal (8s)
15.2Ah at 25.2V nominal (7s)
17.8Ah at 21.6V nominal (6s)

We can get two 8s packs at 5.8Ah or four 4s packs at 5.8Ah for around $160.
Here's a good option:
http://www.hobbyking.com/hobbyking/store/__21385__ZIPPY_Compact_5800mAh_8S_25C_Lipo_Pack.html

Here's a higher energy-density, lower-discharge (but more than high enough for our purposes) option for the same price:
It's a 4p2s pack with 16Ah of storage.
http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=66309&aff=3019
However, it seems to be perpetually out of stock. We'll keep an eye on it; this would be bulkier but a ton of storage.

Create schematic sheet for LTC3 19 V DC-DC converter

A placeholder sheet ("DC-DC Converter, 19V") already exists. Drawing up the schematic should be reasonably straightforward.

We're using a nameless switching converter shipped direct From China, With Love. Datasheet? Ha! Ha! The eBay auction page makes the following claims:

• Input voltage: 12V (10V-15V)
• Output voltage: 19V
• Output Current: 4A
• Output power: 76W
• Soft start time: 500mS
• Over-current protection
• Overheat protection
• Short-circuit protection and automatic recovery
• Full waterproof potting
• Conversion efficiency: >85%
• Load regulation: ± 2%
• Voltage regulation: ±1%
• Dynamic response speed: 5% 200uS
• Module Properties: Non-isolated
• working temperature: industrial grade(-20° C to 85° C)
• Distance between mounting 2 holes:55mm
• Diameter of mounting hole: 7mm
• Size:68_58_25(mm)
• Weight:160g

A custom component will likely need to be drawn to represent the converter. From the photos on the auction page, it appears to be a four-terminal device (Vin, 2x ground, Vout).

Please do not commit your work to the repo's "master" branch. Create a new branch. We can merge to "master" when you're finished.

Investigate BeagleBone Black WiFi options

It would be nice to not have a USB-based WiFi dongle strapped to the inside of the LTC enclosure. Find out what WiFi adapter options are currently available for the BeagleBone Black. If there are no existing WiFi capes, perhaps we could integrate a WiFi adapter into our new board. Will the GPIOs support this?

Document LTC II high-level components, connections

Existing docs do not make it easy for new engineers to gain a high-level understanding of how LTC II works. Create a functional diagram of LTC II, based on info gleaned from existing connection schematic, etc.

Preferably update ./launch-tower/LTC\ Whole\ System\ Schematic

Select enclosure for LTC3

Shop for a new enclosure for LTC3. The redesign should allow us to use a significantly smaller enclosure than the one used by LTC2.

The requirements doc does not include many specific details about the enclosure.

• Either heavy duty plastic (like LTC2) or metal would be acceptable.
• Dust and dirt protection would be a very good idea.
• Moisture-proof would be nice, but unlikely to ever be a problem in our launch environment.
• The enclosure-to-tower mounting scheme needs to be sturdy and straightforward (tool-free, preferably).

We'll need to have a good idea of the size of the LTC3 main board prior to making a final selection.

Make PTN708020 footprint and schematic symbol in KiCAD

Double check if there are any pinout differences between the low- and high-powers versions.

Investigate BBB display options

The LTC3 Requirements doc calls for a front panel display to convey various vital signs to the user. Research what the BeagleBone Black supports, and shop for promising candidates.

See Requirements doc for details. If you discover additional requirements that are not already in the doc, please update it.

Redo safety interlocks diagram

The diagram needs to be redone for clarity, probably in coordination with someone who has actually worked on them in the past and understands them.

Document LT8490 configuration options

Get demo boards for charger, battery protection chips

Update LTC2 System schematic to be current

Find/Create footprint for LTC2991

Create schematic sheet for LTC3 power in

A placeholder sheet ("Power In") already exists. This schematic should contain circuitry related to the solar cell and lab power inputs (connectors, conditioning, etc.). Refer to the design spec and LTC2 schematics for guidance.

Please do not commit your work to the repo's "master" branch. Create a new branch. We can merge to "master" when you're finished.

Investigate Intel Edison as a board

Initially: the Edison is a lot smaller than the BBB, has very low power requirements, and is an x86 rather than ARM. On the other hand, there's very little support and we would need a separate analog input.

One thing that would help with this project is generating a list of what makes for a good LTC.

create diagram of LTC3 power system

Not a schematic, just a simple, high-level diagram of how the LTC's power sources and supplies relate.

For the purposes of this discussion, "sources" are what provide the LTC3 with its juice; "supplies" are the converted/conditioned power it provides to its subsystems.

Select Relay Driver Technology for LTC3 External Triggers

The BeagleBone GPIO have a very limited current sourcing capability, not nearly enough to drive a typical 12V relay. We'll either need to use discrete driver transistors, one each connected to its own GPIO, or use a relay driver IC (connected to the BBB over I2C or SPI). Investigate amongst yourselves. Refer to the Requirements Spec for details, as necessary.

BEAGLEBONE BLACK WITH WL1835 CAPE RUNNING FREERTOS

Hi , i am a newbie with beaglebone black.I have installed freertos(V7.0.1) on beagle bone black using https://github.com/guileschool/BEAGLEBONE-tutorials .
Now i want to use wilink wl1835 cape with beagle bone black running freertos.
I am not getting any reference regarding this.
I want to know step by step procedure for this .
Can anyone provide any links or videos to integrate this cape on board and test whether sdio integration is working properly in this????
@vosechu @donpdonp @fitzgen @aperiodic @BartMassey @guileschool @BeagleBoneBlack @FreeRTOS @WL1835 @OutboundFlight @ti @nellump

select LTC3 main battery cells

Rechargeable LiPo cells. 14.4 VDC nominal; 4 AH.

See Requirements doc for details. If you discover additional requirements that are not already in the doc, please update it.

Same style as the existing ignition battery cells?

select LTC3 12-to-5 V DC-to-DC converter

This converter will supply the computer, ignition board, and any digital peripherals; 5 ±0.25 VDC @ 2 A max.

See Requirements doc for details. If you discover additional requirements that are not already in the doc, please update it.

Start off by coming up with a list of promising candidates. At this point, we will consider both board- and chassis-mount styles.

Beaglebone black UART0 pin details on p8 and p9 header

hi
I am using beaglebone black ,but due to some reasons i am not able to use 6 pin header for serial debug.May i know which pins in p8 and p9 headers corresponds to uart0_tx and uart0_rx.please help me,i know other uarts pin details ,but only uart0 i need.
@vosechu @donpdonp @fitzgen @aperiodic @BartMassey @BeagleBoneBlack @ti @uart @andrewgreenberg @guileschool

inv LTC3 front panel voltmeters

Need several small, low-power digital voltmeters to provide at-a-glance measurements of the LTC's power rails.