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Tracker Tech Notes

Here is where all the technical notes go about building a tracker system. This would be used in the live map display that is outlined here: ProjectDetails19#Live_Map_Asset_Tracking_System

Feature Lists:

Trackers:

  • Sturdy waterproof box that is easy to mount on power carts and gators.
    • Possibly 3D printed, with drywall screw mounting tabs, or day pack / zip tie strap slots.
    • Ideally be slim like a cell phone with the connectors on the top or bottom edges.
  • Runs off a wide range of input voltages as some of our power carts are 12V and others are 24V.
    • Uses a low cost and efficient DC-DC converter for this.
    • Has an Anderson connector charging port.
  • Self contained battery.
    • This allows it to run for a while even if the unit is accidentally disconnected.
    • Simple charge circuit so it is not overcharged.
  • Should work in the hot sun or in an engine compartment in the summer.
  • Robust non-breakable antennas.
    • Use a popular connector so we have access to many low cost antennas.
    • Option to screw the antennas to the box, or mount them up to 6 feet away.
  • At least one watt RF output, optionally more.
  • Possibly have a modem chip / firmware that can do multiple speeds. We might need them someday.
  • Serial port to receive data from the power carts battery monitor.
    • This is how we'll get SOC, current use, battery temperature, etc...
  • Ability to receive and act on commands, such as small tuning updates.
    • Firmware Over-The-Air (FOTA) would be nice but optional.
  • Non volatile storage for tuning parameters.
    • Prefer a small flash partition, but NV-Ram could work.
  • GPS features:
    • Consider GPS / GLONASS + Dual band GPS devices. eg. L1, G1, and L2, L5, G3.
      • "It will help with tree cover and nearby tall buildings."
    • WAAS would be good too, or National Differential GPS (DGPS) service.
    • Consider Assisted GPS A-GPS, A-GLONASS, perhaps send updates to trackers via internet.
    • Phantom powered antenna 5V?
      • This helps with GPS lock under trees.
      • Asset Tracker project below uses Max2674 for Active antenna switching.
    • Others: China's: BeiDou (BDS), Europe's: Galileo 2020ish
  • Very low power sleep mode with fast wake up, (think GPS lock) for all components.
    • You can use this to turn it "off" in software.
    • No actual power switch, except perhaps inside the box next to the internal battery connector.
  • USB data and charging port.
  • A push button to request status, or ask for a transmit.
  • A Green / Red LED to show status.
  • Lay out the Circuit board with marked areas for optional sub assemblies that are not necessarily populated.
    • So the GPS may be optional.
    • Have an optional Bluetooth link so it can work with cell phones like the Mobilinkd.
    • Optional display and keypad for simple standalone use.
    • Optional mike and speaker for emergency communications or PA type announcements to folks that don't have radios.
  • SW selectable power setting
  • Siri type smart phone app that tells you where the unit is.
  • Low cost! smile
  • It could just be a Cell phone App that sends location date to the database to be displayed.
    • GPS Logger for Android.

Mobilink downloads: http://www.mobilinkd.com/downloads/

Map Server:

  • Can serve a web page for cell phone use.
    • Should be able to center the map on a given call sign.
  • Ability to filter APRS stations by type.
  • Ability to show telemetry by clicking on an icon.
  • A pop up window with a list of power carts sorted by charge state.
    • Show weather it's charging or not.
  • Perhaps a way to get a station to temporary send many packets at a higher rate.
  • Have dead reckoning or speed estimation based on last packet.
  • Can we have animated icons in YAAC?

APRS:

1200 Baud:

This is the most popular mode for general packet radio, and APRS in particular. It is based on the Bell 202 modulation standard, which uses two distinct tones. The tones are 1,200 Hz for Mark and 2,200 Hz for space (1,000 Hz shift). The data is differentially encoded with a NRZI pattern, where a data zero bit is encoded by a change in tones and a data one bit is encoded by no change in tones.

2400 Baud:

Initially we could probably run our tracking network just fine using 1200 baud, which is the most popular speed for APRS around the world. Though there are other speeds used, such as 9600 baud, which is eight times faster, but requires fancier radios. 2400 baud is the next step up from 1200 and requires almost no extra work to get. Since we get to set the standard for our own network, it doesn't matter that this speed is not that popular in most other APRS systems. Of course, we will have to test it to see if it is just as reliable as 1200 baud, and ideally we should use a modem chip, and or firmware that can do both so we can switch back and forth under software control.

Some products and specs for other 2400 baud APRS systems:

Direwolf is an app for decoding many modulation modes using SDR hardware. Here is a page for 2400 baud: https://github.com/wb2osz/direwolf/blob/master/doc/2400-4800-PSK-for-APRS-Packet-Radio.pdf

9600 Baud modulation (Not for us):

Schematics to cut and paste from:

Power Cart Battery Monitoring:

Some of the power carts are pretty old now, and have broken battery monitoring units (Fuel Gauges). What we have been using for these is some version of a Xantrex Link 10, because way back then, that was the only product on the market. Nowadays, there are many more choices. One of the least expensive ones that has most of the features we would like is the Victron BMV-700 series. It's important to standardize on one, to make them easy to hook up to the trackers. Note some of our carts have been updated to TM-2025-A monitors which should work fine.
Manufacture Model Serial? CostSorted descending
Xantrex LinkLITE No $206.25
Xantrex LinkPRO Yes $195.08
Bogart Engineering TM-2025-A Yes $169.16
Victron BMV-702 Yes $156.39
Bogart Engineering TM-2030-A Yes $147.81
Victron BMV-700 Yes $127.59
NASA Marine BM-1 Compact No $127.11
NASA Marine BM-1 No $126.20
Protocol specs: VE.Direct-Protocol-3.25.pdf

Interesting Parts:

Interesting Projects:

Software:

Here are links to the various software projects that we might draw on.

DMR Decoders:

The fair is moving to digital radios, which will have built in GPS. Possible decoding chains are:

APRS Map Servers (Clients):

Papers:

-- ClifCox - 26 Jan 2019
I Attachment Action Size Date Who Comment
Datasheet-BMV-700-series-EN.pdfpdf Datasheet-BMV-700-series-EN.pdf manage 208 K 2019 Jan 28 - 11:52 Main.clif  
TQP7M9105_Data_Sheet-1.pdfpdf TQP7M9105_Data_Sheet-1.pdf manage 637 K 2019 Feb 04 - 22:49 Main.clif  
VE.Direct-Protocol-3.25.pdfpdf VE.Direct-Protocol-3.25.pdf manage 2 MB 2019 Jan 24 - 11:35 Main.clif  
aprs_tracker_pdr.pptxpptx aprs_tracker_pdr.pptx manage 3 MB 2019 Jan 27 - 09:20 Main.clif APRS design power point
ot1plus-smt-1_5-schematic.pngpng ot1plus-smt-1_5-schematic.png manage 52 K 2019 Jan 27 - 08:34 Main.clif Auto-attached by ImagePlugin
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Topic revision: r32 - 2022 Jun 13, clif
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