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GPS Tracking of Deer Fawns Directly to Your Laptop! (Locosys LS20031)
L6E
Last month I signed up here in order to ask the forum a technical question about GPS output formats:
http://www.laptopgpsworld.com/3535-nmea-data-interpretation-issue

I was greeted enthusiastically with prompt and helpful advice. It’s my pleasure to return the favor by posting a thread describing in detail the construction of the project which led me to this excellent community. The project happens to have strong relevance here and I also believe that this post may contain welcome solutions for applications which some of you may encounter.

For those of you who are interested in tinkering with your own GPS receiver, included in this post will be a detailed DIY describing how to hook up, configure and use the excellent and tiny Locosys LS20031 GPS Module so that it can be run into any serial port, USB port, microcontroller, Stamp or whatever (Today I had it running Microsoft Streets & Trips). I’ve done the running around and researching of protocols, hookups, configuration software etc., and I’m posting what I’ve learned here so you don’t have to reinvent the wheel.

As For The Project:
A wildlife rehabilitation facility in my area handles about 1100 animal patients a year. Many of these are deer fawns which the facility eventually fosters out to wild herds. It’s really something to see a release. Deer are extremely protective and as soon as one sees the fawn among humans it will approach and fake charge until it acquires the fawn and hustles it away.

Here is the catch though. Zoologists are telling the facility that the deer herd will not adopt the fawn which is certain to perish. The facility however is telling the zoologists that they are watching the deer nurse the fawns as soon as they are released.

In order to solve this debate the facility wants to track the released fawns to monitor their progress. If the fawns are alive three weeks after release then it is obvious that the herd is feeding them. The facility has a limited budget so I am building the tracking devices for them.

The tracking collars will be GPS based so that the facility staff will not require advanced radio signal tracking skills.

The area is remote and there is no cell service and satellite service is expensive so the collars will communicate directly with the receiver.

The collars have to carry a release mechanism so that it drops off in three weeks.

The collars have to be very compact and light (the fawns can weigh as little as 8 pounds).

Once a day the collar will acquire its position, communicate it to the receiver and the receiver will in turn output it to a laptop which will use Microsoft Streets & Trips to display the collars position on a map.

That’s the idea anyway. Most of the collar is now designed and all the final parts have arrived. There is some firmware left to write and some assembly yet to do.

I will continue to post here as the project progresses. I’m not certain which details will be of interest here so questions are welcome.

Now for some snazzy pictures:


The GPS module I’ve chosen for the prototype collar is the Locosys LS20031. Highlights include. 32 channel, 5hz update rate, 3.3 volt, 41 milliamp, ttl outputs, just over an inch across. Hookup requires only 3 connections: power, ground, data out. More on this little beauty later.




For the transceiver module set I have chosen the Laird AC4790LR-1000. 915Mhz unlicensed band, spread spectrum, full duplex, built in DES encryption, 40 km range, built in masterless networking, etc, etc, etc.




Here is the front and back of the prototype PCB for the collars control section before populating. They are the exact same area as the transceiver modules. Not very fancy looking without a solder mask but they’ll do the job. There is a company near by that has a service for etching these overnight. The cost for the pair was just over thirty dollars and they did a great job.



Here is the board populated with components. Its entire goal is to conserve the collar’s batteries so that they last a month. Any transmitter system can transmit a GPS coordinate but without some smarts it will kill the batteries in hours. This board will power up the regulator and GPS once a day, grab and store the first valid fix that comes along and shut the GPS off. It will then wake up the communication receiver every ten seconds for a couple of hours and listen for a request to send the fix information, wait for a conformation that the data was received correctly, check for any other commands and then put the collar to sleep until the next day.




Here is an early layout of the main components showing the battery pack which consists of 4, AAA Energizer lithium Ultra cells. Believe it or not these came out on top for performance, at least without getting into batteries that cost thousands of dollars. 4 AAA cells is quite a bit of overkill for this application and I’ll probably go a little smaller once I am confident with the consistency of the cells and that my math is confirmed by a few runs of the tracker in the field. The oddities on the end of the battery pack are a 3.3volt 2.5 amp switching regulator and its filter capacitors that will be used for supplying power to the transceivers power amp.



Here is an image of how the parts will stack up.



The electronics will be encapsulated in resin and carried in a nylon pouch which will be sewn to the collar. Here is the collar itself. It is made out of 1 inch tubular climbing webbing. The webbing is supple and it is hollow in the center providing a protective envelope to run wiring through. The release mechanism is a waterproof R/C servo that has been modified to turn continuously (most servos only turn a few degrees in each direction.). It is attached to a course thread screw which unthreads to detach the collar. As a backup to the release mechanism the collar has a cat collar style safety release so that the deer cannot hang up on something or outgrow the collar if the electronic release fails. The electronic release will be programmed to release in 21 days, or if remotely signaled to do so, or if the battery pack reaches a critical low level.




Ok, enough for today. Next I’ll post details on configuring and running the Locosys LS20031 GPS module that I used for this project.
Cheers,
L6E
tcassidy
Will Streets & Trips work with just a single GPS block of sentences or do you have to store a certain length of information to get it to wake up?

Terry
L6E
I haven't tested exactly how many strings it needs to consistently update a new fix. I presume that sometimes it will be more than one depending on what Streets & Trips and the rest of the PC is doing at the time strings start coming in. With my system the collar transmits just one string a day to save power so I have the receiver unit continuously repeat output of the latest string about every second. Because the string is stored and repeated as is the "valid fix" data within it doesn't change so Streets & Trips displays it as a current fix.
glennw
L6E,
Keep up the reports. I find this fascinating.
Marvin Hlavac
L6E, thanks for sharing with us the information about this project. That's what this forum is all about: sharing of information.

What will happen if the GPS unit is in an environment where it cannot acquire GPS fix for extended time period (several minutes, or more). Will that be a problem, or will the system patiently wait till a valid fix is acquired?
L6E
If the GPS cannot acquire a fix within about 5 minutes then position information for that day will be lost. The energy budget is not available for a lot of extended GPS operation. If field testing shows that there is considerable surplus power at the end of runs however, it is as simple as changing a few dozen lines of firmware to add another fix attempt into the schedule. It will come down to what features we want to add and how much more weight we want to trim off of the battery pack.

I had considered grabbing fixes a few time a day and then transmitting the latest valid one but the energy consumption began to sky rocket.

Given the terrain in the area I think we wont see many "no fix" occurances. Again, field testing will tell.
tcassidy
Quote:
Originally Posted by L6E
I haven't tested exactly how many strings it needs to consistently update a new fix. I presume that sometimes it will be more than one depending on what Streets & Trips and the rest of the PC is doing at the time strings start coming in. With my system the collar transmits just one string a day to save power so I have the receiver unit continuously repeat output of the latest string about every second. Because the string is stored and repeated as is the "valid fix" data within it doesn't change so Streets & Trips displays it as a current fix.
Do you have to update the time in each string or does S&T not care?

Terry
L6E
It doesn't care. I presume this is on purpose because the software cannot assume that the GPS will send updated time with every string or even that the time it sends will be consistent. For example, the GPS module that I'm using can be set to provide different information at different intervals (though I'm not sure if the time stamp is included in the options). If it becomes a problem for this project because we decide to move to another software that requires a progressive time stamp then it won't really be a problem to replace the time data in firmware each time the received string is sent to the computer.
Ken in Regina
It looks like you have made considerable progress since we last spoke here. That's a really fascinating project. I see you're using a Toonie for scale in the pictures. What area of the planet are the fawns going to be running around in? Canadian Prairies? Ontari-ari-ari-oooh? The left side of the Rockies?

...ken...
L6E
Alberta, lots of rolling land with bush, creeks, lakes and agriculture such as hay and cattle.
Ken in Regina
Reception won't be an issue. I drove across a big chunk of Alberta last night on the way from Kindersley to Calgary (can't get from Regina to Calgary directly because the TransCanada is washed out a few miles from the Alberta border). There was no place where you would expect less than perfect conditions except in heavy rain.

Alberta sure has some great secondary highways. We dropped a bit south of Oyen to highway 570. It's a beautiful two-lane in perfect condition with no traffic and runs through some of the prettiest rolling terrain you could ask for. I think we saw maybe half a dozen vehicles as we traversed over half of the province.

Tomorrow I'll be at Gleniffer Lake (just west of Innisfail) to play some golf with my brother. Some more very lovely country but with a little more tree cover than the east part of the province.

Are you primarily a technologist or are you involved professionally in wildlife in some way?

...ken...
L6E
Your going to be passing within ten minutes of me.
I design instrumentation for a living. Just an extreme nature enthusiast.
Supposed to be near perfect weather tommorrow. High of 25, mix of sun and cloud. Its a nice area. Should be a good golf day for you.
ki4nai
The project sounds great!!! I can see many other uses also, but animal tracking is first.. I may have missed it, how is the signal transmitted to the laptop
L6E
A radio transceiver identical to the one onboard the collar (AC4790LR-1000) recieves the data which is then stored in a microcontroller (PIC16F876). The microcontroller then repeats it once a second to a chip (MAX232CPE) that converts the signal to levels that the RS232 serial port on a computer can use. From there its easy to convert the signal with a serial to USB adapter (or leave it as serial if you have an old enough laptop) and Bobs your Uncle.
Ken in Regina
Quote:
Originally Posted by L6E
Should be a good golf day for you.
It was!

...ken...
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