Rocket Track - Open Source GPS Tracker for Smartphones

[dosmithii]

Congrats on the successful flight! I'd like to see how you mounted the tracker in your ventris. I'd like to use it in mine.

Thanks, I'm looking forward to having some fun with this.

As far as mounting the tracker in my Ventris, I simply cut out a piece of plywood sized to fit the payload bay for the sled. I then of course drilled the proper holes and used four 1/4" pieces of 1/8" nylon spacers (just like 1/8 Estes launch lugs, but made from nylon instead), and used very small (I can't remember the size) stainless steel nuts with matching bolts. I hope you can see the pics ok.

I have some different batteries coming, and I plan to do a little more to secure the batteries than the tape shown here, but this one was just a test.

 

[Derek]

Hi Darrell,

So you cut into the transition and/or nose cone to get that sled to fit? There is only about 1" of height if you don't.

 

[rbelknap]

Hi Darrell,

So you cut into the transition and/or nose cone to get that sled to fit? There is only about 1" of height if you don't.

I'm interested in seeing this as well. I have a Ventris which is pretty much done, but I'm still trying to decide if I want to make the "payload" section actually serviceable as an altimeter bay or just glue the thing together and be done with it. (I did cut into the transition so I could add an eybolt - I don't trust those plastic cut-outs for mounting recovery gear anymore - so I'm already 1/2way there...)

 

[cerving]

This is what I did with my Ventris. I cut off the bottom of the nose cone and the top of the transition, put a 1/4" ply bulkhead in the middle of the payload section, and built a slide-in sled to fit into the nose cone. Lots of room for the sled, and enough room for the main chute in the bottom payload section/transition section.

I'm interested in seeing this as well. I have a Ventris which is pretty much done, but I'm still trying to decide if I want to make the "payload" section actually serviceable as an altimeter bay or just glue the thing together and be done with it. (I did cut into the transition so I could add an eybolt - I don't trust those plastic cut-outs for mounting recovery gear anymore - so I'm already 1/2way there...)

 

[dosmithii]

Hi Darrell,

So you cut into the transition and/or nose cone to get that sled to fit? There is only about 1" of height if you don't.

Yep. I cut off the base of the nose cone and the top of the transition, then used motherboard screws to hold it all together. Which by the way, I would really like to use with computer standoffs to mount the transmitter, but the holes in the transmitter board are too small to accommodate them. Just sayin'

This works pretty well because you can use the inside edges of the nose cone and transition base to hold the sled in place.

 

[dosmithii]

I'm interested in seeing this as well. I have a Ventris which is pretty much done, but I'm still trying to decide if I want to make the "payload" section actually serviceable as an altimeter bay or just glue the thing together and be done with it. (I did cut into the transition so I could add an eybolt - I don't trust those plastic cut-outs for mounting recovery gear anymore - so I'm already 1/2way there...)

Not trusting the plastic cut out and retro fitting with an eyebolt is a very good idea... I learned that the hard way on this model. I was lucky though, the payload section sort of glided down and did not sustain any damage.

 

[cerving]

The shock cord on mine is 12' of 3mm braided Kevlar, it goes from the motor mount, ties around the loop in the transition, goes through the hole, and up to the bulkhead in the middle of the bay. Essentially the stress on the parachute goes in a straight path without really stressing the transition or the AV Bay. This saves weight too, there's no metal hardware. The one time that I tried a traditional AV bay with metal hardware was on an Executioner with an F39... it only got to 500'. Weight in MPR is the enemy...

Not trusting the plastic cut out and retro fitting with an eyebolt is a very good idea... I learned that the hard way on this model. I was lucky though, the payload section sort of glided down and did not sustain any damage.

 

[Derek]

...but the holes in the transmitter board are too small to accommodate them. Just sayin'

thanks for the pics. nice setup. I may just copy it...

yeah, #2 holes aren't very big, but that is about all that I could fit without making the board bigger. other altimeters I have use #2 holes as well so I felt ok with using them.

 

[Tetrahedron]

View attachment 127108

Assembly Tips

All of the components were chosen with an eye towards relatively easy assembly. The board can be assembled with just a fine tip soldering iron, some tweezers, a magnifing glass and a little patience in about 30 minutes.

Solder the voltage regulator and supervisor on the board first followed by the passive components (resistors, capacitors and LEDs). At this point, use a multimeter to check for shorts on the battery connections and between pins 1 and 10 on the XBee socket.

If you don't have any shorts, then power up the board and measure the voltage at pins 1 and 10 on the XBee socket. Even if you had a short, the voltage regulator's output is protected against shorts and won't destroy it. However the battery input is not protected against shorts.

You should read 3.2 V and the green power LED should be on. At this point it is safe to finish the assembly with the XBee and GPS modules. If you ever plan on removing the XBee module, then only solder pins 1 - 3, 10 and 15. If you solder all 20 pins, you will have an extremely difficult time removing the module, even with the right tools.

Version 1.1 of the transmitter adds a 6-pin header that allows a FTDI USB to serial cable to be used to configure the XBee radio. In normal operation, there are two solder jumpers that need to be closed so that the serial data lines between the GPS and the radio are connected. In order to use the USB serial cable, you will need to remove the solder from the jumpers and insert the header. The black ground wire (pin 1) on the USB serial cable is identified by the "BLK" silk screen on the board. The USB serial cable will not power the board - you will need to connect the battery to power the board. You must make sure that you only use the 3.3 V version of the USB serial cable otherwise you may damage the XBee radio.

I covered the transmitter with some clear 1" heat shrink tubing to protect the tracker. It is probably a good idea to wrap it with something to prevent accidental shorts.

Update 1 (6-5-13): Added version 1.1 info

By the way, in your new post thread about this you mention in the assmbly tips about other components
like resistors, capacitors, LED, voltage regulators etc. Could you give a list of these components also needed to build
transmitter and receiver?

THX, John

 

[Derek]

Hi John,

Almost all of the components you need to buy to build the boards are the two zip files in post #5. Open up the BOM file in each zip.

The remaining items not on the BOM are: Lipo batteries, antennas and mating battery connectors. There are links to the batteries and antennas I use in the first two posts. You'll need to buy mating connectors for the battery leads. If you buy batteries with JST connectors, you can find mating battery connectors at hobby stores or online at places like hobby king, etc.

https://hobbyking.com/hobbyking/store/__9683__Female_JST_battery_pigtail_12cm_length_10pcs_bag_.html

Please let me know if I'm missing anything else.

Derek

 

[dosmithii]

You must have done a great job assembling it for it to survive that fall. Nice work!

There are two new apps that work with the tracker. The first is the Rocket Track app that Kevin is writing. This one is written for our tracker and he tweaks some parameters in the GPS to increase the battery life and accuracy. He hasn't released this app in the play store yet so you'll need to build it yourself.

The other app is called Rocket Locator in the play store and works with our tracker. There is a thread in this forum about it.

How do I go about getting the custom software, and what exactly do you mean by "build" the software? Do you mean compile? How can I "build" the software?

Thanks,

 

[Derek]

yes, you will need to compile Kevin's software yourself. The git repo is in post #4.You'll need the android sdk (I'd suggest using the adt bundle) and the google play services library.

 

[dosmithii]

yes, you will need to compile Kevin's software yourself. The git repo is in post #4.You'll need the android sdk (I'd suggest using the adt bundle) and the google play services library.

Is there a specific sdk app that you use? It appears that there are lots of choices unless I'm missing something. I'm new to the android world,

 

[kruland]

Darrell,

Pop me a PM with your email address and I'll send you the compiled code. Since there seems to be a bunch of interest in this (and some recurring interest in the OpenRocket Android application), I'll be trying to put it on G-Play in the next month.

Kevin

Is there a specific sdk app that you use? It appears that there are lots of choices unless I'm missing something. I'm new to the android world,

 

[mlinny]

Here is my take on Derek's tracker using through hole components. Now just need to build the receiver.

View attachment 145003

 

[Derek]

Here is my take on Derek's tracker using through hole components. Now just need to build the receiver.

View attachment 145003

Way to go! That looks great!

Derek

 

[mlinny]

I breadboarded my receiver last night to test and it seems to work as it picked up 10 satellites while in my living room. The voltage regulator on the TX got a little warm after being on for 30 minutes and was thinking about adding a heatsink, but I double checked the data sheet and with a single cell lipo it should be okay without one with an ambient temperature of over 100°C. What is the purpose of the LED on the RSSI pin on the XBee as it always just blinks and somewhat randomly at that?

View attachment 145332

 

[Derek]

the rssi pin indicates the received signal strength. I don't use it as it causes problems with some xbee pro modules. The flashing rate should change depending on the strength of the received signal.

 

[mlinny]

Yeah, it is not the RSSI pin, but rather Pin 15, the same pin you used.

 

[Derek]

Yeah, it is not the RSSI pin, but rather Pin 15, the same pin you used.

that is the associate pin. It should be on solid when it is connected to the other radio and blink when it transmits or receives data. both leds should flash at about the same time.

I think it flashes a little faster when it isn't connected to another radio. you can test this by turning off the transmitter. the problem with this setup is the gps is always sending data so it is always flashing as a result.

 

[mlinny]

I could cut my jumpers to the GPS, but I know data is being sent and received, so I won't worry about it. Hopefully I'll get to test it out next weekend.

 

[Derek]

I wouldn't worry about it. It sounds like it is work correctly.

 

[WoShuGui]

Has anyone tested this GPS up to or above 10,000 feet yet?

Flew one to about 13k and lost track over the launch pad. Same tracker worked fine on 4k flight the day before so I'm thinking 13k might be too far for the XBeePro even with full antenna. Did not recover the rocket so it may have been a different problem. Normally I'd expect the signal to be re-aquired as the rocket descends, but the wind may have kept it out of range throughout.

 

[cerving]

Hard to say when you lose it early on. I did some testing at ROC last weekend with the $29.99 3DR clone that Hobby King is selling, connected to the telemetry output of an Eggtimer, got to 5,000' and Mach 1.3, kept lock pretty much throughout except for the near-mach phase of the flight. I would expect the XBee PRO 900HP to get at least twice that given it's 250 mW rated output.

The thing with GPS transmitters is that you really can't expect both the GPS and the radio to keep lock throughout the flight, but once it slows down you should be able to get a signal and figure out where it is, and you should be able to track it coming down until it gets low to the ground. All you really need is the coordinates of the launch site and the last known coordinate, if the last one was within a hundred feet of altitude AGL then it's going to lead you right to your rocket.

Flew one to about 13k and lost track over the launch pad. Same tracker worked fine on 4k flight the day before so I'm thinking 13k might be too far for the XBeePro even with full antenna. Did not recover the rocket so it may have been a different problem. Normally I'd expect the signal to be re-aquired as the rocket descends, but the wind may have kept it out of range throughout.

 

[WoShuGui]

Hard to say when you lose it early on. I under some testing at ROC last weekend with the $29.99 3DR clknown thacoordinates King is selling, connected to the telemetry output of an Eggtimer, got to 5,000' and Mach 1.3, kept lock pretty much throughout except for the near-mach phase of the flight. I would expect the XBee PRO 900HP to get at least twice that given it's 250 mW rated output.

The thing with GPS transmitters is that you really can't expect both the GPS and the radio to keep lock throughout the flight, but once it slows down you should be able to get a signal and figure out where it is, and you should be able to track it coming down until it gets low to the ground. All you really need is the coordinates of the launch site and the last known coordinate, if the last one was within a hundred feet of altitude AGL then it's going to lead you right to your rocket.

Agree. Maybe you saw this flight at ROC Sunday morning. In every previous flight I had lock during descent and have been able to pretty much walk to the rocket from last recieved coordinates. In this case something went wrong. May never know.

 

[Derek]

That's a bummer. I wonder if the battery somehow came disconnected as I'd expect it to regain the signal during descent.

Hopefully someone will find it.

What was the altitude for the successful flight?

 

[mauinate]

So, I've read through this thread and the original, nice work! What I'd like to end up with is this: A singular base station (laptop or phone/tablet) that would be able to display the locations of multiple rockets at the field. So my ?'s are: 1. Is there a way in the radio settings to take advantage of the mesh network and still identify every different transmitter with a unique id that is sent to the base station? 2. Will any of the available apps be able to handle multiple rockets on screen? 3. Is there a way to publish the data in real time(ish) to a website so that others not at the field can see who is doing what, as identified by their specific transmitter id?.
It would be so cool to be able to go to the clubs laptop and see what is where, and for the guys at home to be able to see stuff to. Is any of this possible/probable? Thanks for everything
-Total Noob

 

[WoShuGui]

That's a bummer. I wonder if the battery somehow came disconnected as I'd expect it to regain the signal during descent.

Hopefully someone will find it.

What was the altitude for the successful flight?

The wind was kicking up a lot more than you'd like for a flight this high, so the tracker may never have gotten back into range. Tracker was in the nose cone.
View attachment 149485

Simulated altitude was 13K. Here is a video link of the flight and booster view of sustainer air start.

https://youtu.be/QYsjYbjz9Ck

 

[Derek]

So, I've read through this thread and the original, nice work! What I'd like to end up with is this: A singular base station (laptop or phone/tablet) that would be able to display the locations of multiple rockets at the field. So my ?'s are: 1. Is there a way in the radio settings to take advantage of the mesh network and still identify every different transmitter with a unique id that is sent to the base station? 2. Will any of the available apps be able to handle multiple rockets on screen? 3. Is there a way to publish the data in real time(ish) to a website so that others not at the field can see who is doing what, as identified by their specific transmitter id?.
It would be so cool to be able to go to the clubs laptop and see what is where, and for the guys at home to be able to see stuff to. Is any of this possible/probable? Thanks for everything
-Total Noob

The answers to your questions are:

1. Yes
2. No, but should be possible
3. Yes

2 and 3 will you require to write some code to implement.

 

[Derek]

The wind was kicking up a lot more than you'd like for a flight this high, so the tracker may never have gotten back into range. Tracker was in the nose cone.
View attachment 149485

Simulated altitude was 13K. Here is a video link of the flight and booster view of sustainer air start.

https://youtu.be/QYsjYbjz9Ck

That looks like a nice setup! Too bad you didn't recover it.

Is there any padding between the battery and the tx pcb? I'd worry that vibrations and/or shocks could cause the leads on the bottom of the pcb to puncture the battery.