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Sea/Spece Buoy Project

May 30th 2012, 19:08

WA8SME

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Hi all,

After taking the buoy on a road trip for show and tell, I got it back in the water for some more R&D for a while. I will be putting something on the Forum page about it and probably post some things are the education web page and time permits. You can see the location and data via findU at this location, the call sign of the buoy is WA8SME-9. It is deployed in the brackish water in Long Cove, that connects to Long Island Sound via the Thames River.

http://www.findu.com/cgi-bin/find.cgi?call=WA8SME-9

Here is some of the data:

WA8SME-9>APTT4,WA8SME*,WIDE2-1,qAR,KA1CQR:/122507z4124.66N\07205.10WN/1022,0358,0203,0191,0605,0242,0538,0434,0891
WA8SME-9>APTT4,WA8SME*,WIDE2-1,qAR,KA1CQR:/132502z4124.66N\07205.10WN/1023,0342,0202,0179,0576,0239,0545,0450,0906
WA8SME-9>APTT4,WA8SME*,WIDE2-1,qAR,KA1CQR:/132502z4124.66N\07205.10WN/1023,0342,0202,0179,0576,0239,0545,0450,0906

There will be repeats of the data, as indicated by the date-time-group. The data is being sent every hour. I send the current hour’s data and the previous hour’s data for redundancy. There may be more hits on the data depending on what nodes happen to pick up the pings. The primary node is WA8SME at my home. APRS data link reliability is one thing that I want to do more work on.

After the time/lat/long, the data fields are as follows:

Barometric pressure in mBar
Pressure sensor internal temperature in C (0342 = 34.2), used to do the pressure calculations and a rough indicator of the internal temperature of the buoy
Air temp ADC
Sea Surface temp ADC
Salinity ADC
Accelerometer X axis ADC
Accelerometer Y axis ADC
Accelerometer X axis ADC all used to test a concept of measuring sea state with accelerometers
Battery voltage ADC

I have a spread sheet that the data can be cut and pasted into to convert the ADC values into temps. The salinity and accelerometer data has not been calibrated yet so the values are relative and not absolute. If you want the spread sheet or the algorithms for converting ADC to temp or battery voltage, let me know.

I expect this deployment to be around 2 weeks or until the next sinking of the buoy whichever comes first.

Mark
Jun 4th 2012, 02:31

AD6QF

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Mark,

How feasible do you suppose it would be to use the APRS one-line message capability to send a command string back to the device to change its status in some way. For example to command your buoy (or whatever device is sending telemetry) to change the sampling rate or to switch a particular transducer on or off or to command it into a power-saving mode,. I have a friend at JPL who is trying to help me design a project for my physics students and he thinks the ability to add command and control functions would be a powerful teaching opportunity. I immediately thought of using DTMF tones, but since the APRS network allows the data to be received remotely, it would be cool to use the same network to talk to the device. Your thoughts?
Jun 4th 2012, 13:18

WA8SME

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Before I give my thoughts, I tried to upload to this page some graphs of data collected to date but the system will only accept text and not graphics. That is too bad because there are a lot of teachable moments that are immediately obvious once you see the data displayed graphically.

On the command issue, the first issue to consider is the power budget. The buoy and other remoted systems using APRS to my exerience are transmit only without a transceiver. If you include a transceiver then you increase the demand for power and also increase the cost of the datalink by an order of magnitude.

That being said, there is no reason why you couldn't program the controller to monitor the output of the TNC watching for command sets for control. This also will increase power consumtion because the system would need to be active to receive commands and not be in low current sleep modes between collections.

Related, I have not been happy with the reliability of using APRS for the buoy system (I am running about 100 mW). Here on the east coast, the APRS channel is very congested and it is almost impossible to get a packet out of the buoy into the system directly from the buoy...too much competition for bandwidth. My work around is to have a shore side Node that the buoy can get into, and then the Node gets it into the system (the Node is WA8SME). This is certainly not optimal and even with this set up I miss a few data sets and the work around for that is the repeat transmitting the data sets. This also increased power consumption.

I am working on a little UHF transceiver system (which is the relation to your C&C question) that seems pretty capable as an alternative to using the APRS channel to get info out of the buoy. The transeiver module is the RFM22, it is frequency agile, has some DSP, GFSK, and packet handeling capability. It runs 100 mW and consumes around 64 mA at 3.3V when in full transmit, a much smaller number (don't remember at the moment) when in receive. When I get some time I am going to explore putting the RFM22 in the buoy and have the link to the shore on a quiet UHF frequency. On the shore, have a RFM22 connected to the input of the Node, the output connected to the 2 meter APRS equipment (somehow I want to have the squelch of the 2 meter receiver connected to the TNC to prevent collissions) to get the datasets into the APRS system.

You might consider a similar arrangement for C&C, send command packets over the same channel that is used to report out data.

The RFM22 is about the size of your thumb nail, and cost around $25. The problem is that there is a very steep learning curve on how to program the system and get it running (you have to control it with a microcontroller) so this is not a trival effort. One of my goals is to make the interfacing programming with the system a little more intuitive to get it out to the teachers, but it will never be a full plug and play system without some major, major effort. And I don't have the time or proclivity to do that.

(BTW, the real reason why I am working with the RFM22 is that I want to develop a standarized data link system for use in PocketQub satellites, it just also seemed a good fit for remote sensor applications.)
Jun 4th 2012, 19:04

KE6BAQ

Joined: Sep 22nd 1998, 00:00
Total Topics: 0
Total Posts: 0
Hi All,

Chris, KE6BAQ, I am a physics teacher at Sunny Hills High School in Fullerton, CA and I thought I'd Chime in.

First, Mark I love this idea for this project! Being near the ocean and also a 'sailor' I am thinking of some great ideas on how to use such a buoy system/network to help my kids sail better when they race their Naples sabots in Long Beach.

Second, I am working on a similar system for use in my school's solar powered boat engineering project. We are developing, albeit very slowly, an APRS telemetry system to continuously monitor boat performance while its on the water. We want to measure the following: Battery System Voltage, the Photovoltaic System Supply Current and the Total System Current supplied to the motor and the control. We are basing our system on equipment we purchased from Argent Data Systems, using the OpenTracker1+-SMT for the TNC, a SRB MX146 transmitter (like the one in figure 2 of p.34 of the artilce in teh May QST), and a Unitraq GT-525 GPS. So far, we have bought all the parts using a grant from the Orange County . Engineering Council. Now we are scratching our heads trying to figure out how to assemble the parts.... I need some (more likely a lot) of Elmering for this part....

Anything we develop at here at SHHS we'll gladly share with the group and TI-2!

73,

Chris Peoples
Jun 5th 2012, 02:44

AD6QF

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Chris,

Small world. I live just over the fence from SHHS (about 500 feet northeast of home plate). I, too, teach IB Physics.We may have to meet up (on the air or in person).
Jun 6th 2012, 11:33

WA8SME

Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Chris,

Sounds like an excellent project. I believe you will need a microcontroller to collate the data and send it to the TNC. Have you decided on a microcontroller platform?

Mark

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