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Read June 01, 2010, 11:10:18 AM #0
Rian

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10km Project 2010 Electronic Payload discussion
Anyone who would like to join this work group is welcome to do so. Please add your name here.
Rian Venter rianventer@ananzi.co.za 0836272792
We need to decide what we need to control, record and transmit.
I suggest the following systems
Parachute deployment
Flight recording
Tracking and recovery system.
•   I am testing a Skytraker this weekend. It is an APRS system used by HAMs. The system uses a GPS and transmit the coordinates via a 7W (WOW) transmitter on a HAM licensed frequency. The signal is received by a small handheld receiver and decoded by a TinyTrak decoder before the coordinates are displayed on the laptop screen.  This is an independent system from any network. I am a licensed HAM operator. The flight can be recorded and tracked in real-time on the ground on decent.
•   David has posted previously information about a new product of his which looks stunning.

I will keep you posted on my test this weekend.
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Read June 01, 2010, 02:22:30 PM #1
johanngr

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Re: 10km Project 2010 Electronic Payload discussion
Any information on the limits of the tinytrak2?  The rocket will reach speeds of more than Mach 2.2 and acceleration of 17Gs.

If the limits are a problem, could we use an accelerometer to determine when to switch on the GPS?

I remember someone mentioning something about 1800km/h or 500m/s for the speed limit.  The rocket should decellerate to below that after about 12s from take-off.

I was very happy to see your email on the sponsorship of the tracking system.  Thanks for your effort!


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Read June 01, 2010, 07:09:09 PM #2
Rian

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Re: 10km Project 2010 Electronic Payload discussion
Here is some more info on the GPs technology. All GPS receivers capable of functioning above 18 km (60,000 ft) altitude and 515 m/s (1,000 knots 1854 km/h) are classified as munitions (weapons) for which U.S. State Department export licenses are required. These parameters are clearly chosen to prevent use of a receiver in a ballistic missile. It would not prevent use in a cruise missile since their altitudes and speeds are similar to those of ordinary aircraft.
Spesification of the GPS in my tracker:
Start-up Times Hot_start_ <3.5_sec_
Warm_start_ 33_sec_
Cold_start_ 34_sec_
Aided_start_ 5_sec_
Reacquisition_ <_1_s_
Sensitivity Acquisition_ -140_dBm_
Tracking_ -150_dBm_
Timing Accuracy RMS_ 50_ns_
99%_ <100_ns_
Operational
Limits
Velocity_ 515_m/s_(1000_knots)_
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Read June 06, 2010, 07:16:21 PM #3
Rian

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Re: 10km Project 2010 Electronic Payload discussion
A quick update on the progress on the tracking system.
I got the decoder from RFdesign on Friday.  Unfortunately no cables came with it and I spend yesterday and today soldering interface cables. Not a big job but finding the connectors in your scrap box is.
The decoder is now talking to the serial box. The serial box is talking to the PC. Only to find Hyperterminal is not included in Win 7. Found IVT and it is talking to everything. Only need to get the radio receiver to talk to the decoder. So far so good. I have hoped to have received a coordinate by now.
By Wednesday this should work. I will keep you posted.
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Read June 06, 2010, 07:54:25 PM #4
johanngr

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Re: 10km Project 2010 Electronic Payload discussion
Thanks, Rian!


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Read June 07, 2010, 10:17:53 PM #5
entacore

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Re: 10km Project 2010 Electronic Payload discussion
Hey guys!

Ok, so Im back in South Africa, ready to get things going!

I have been working hard to get my GPS system ready before the 10km Challenge this year, but things are looking good so far...

I have managed to get a position fix with very good accuracy (<3m) from indoors, which I think is great.

The chip im working with is the AMY5M from Ublox. Here are some specs:

4 updates / second
-160 dBm tracking

So, once its got a lock, its not going to lose it easily.

I did a spin test amongst some houses and it didnt seem to affect the lock, which is important as the rocket might rotate as it climbs.

Now, the transmitter on the unit is a lot less powerful than the TinyTrack. Its only 100mW, but I have tested it and it achieves about 2.5km NON LINE OF SIGHT. Considering that we will have direct line of sight, I dont see any range issues.
The frequency is on the ISM band of 433.92 Mhz, facilitating a very small helical antenna of about 50mm.

The receiver connects via USB to your PC, giving flight information in real-time.

The next issue is power consumption.
The current configuration I have draws 170mA from a 9 volt battery.
If you use a 250mA hour 9 volt battery, it should be good for at least an hour at full transmit power.

The 7 watt transmitter will draw at least 14 watts im guessing which is about 1500 mA. So, that will drain a 250mA hour 9 volt in less than 10 mins, so we will have to think about a larger power source.

The big advantage that the TinyTracker has is that it is probably going to be ready sooner and that it is a dedicated tracking device.

We can discuss the merits of both setups and see what happens in the next few weeks before making a final choice.

If the AIM XTRA doesnt get used for telemetry, it can still give other data such as triple axis acceleration measurements and pressure, as well as triggering ejections.

By the way, the GPS limits are OR, not AND. So, either we can exceed 18km, or 515m/s. Im guessing we wont exceed 18km just yet, so the speed isnt an issue.
What is an issue is the acceleration, as the GPS filtering system which calculates position cant handle high accelerations. But, the GPS will re-acquire lock as soon as the acceleration falls below about 4gs (thats for the AMY5M).

Ok, so thats me rambling on late at night...
I will keep everyone updated...
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Read June 07, 2010, 10:36:07 PM #6
johanngr

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Re: 10km Project 2010 Electronic Payload discussion
Thanks David!

I would like both units and Phlip's unit as well.  Which unit is ultimately going to be responsible for parachute recovery will be another story!


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Read June 08, 2010, 08:40:39 AM #7
twostage

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Re: 10km Project 2010 Electronic Payload discussion
Hi David

Cant you configure the transmitter to run of one of those lithium polymer batteries which they use on the remote control cars and planes
I think its a 7200mah if im not mistaken

Thats just my thoughts


We all strive for perfection...but we fly for fun
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Read June 08, 2010, 10:27:13 AM #8
entacore

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Re: 10km Project 2010 Electronic Payload discussion
The larger battery is definitely an option. But, the voltage is important.
I'm not saying its going to be a problem, but we should look into weight requirements carefully.

In the end, a lithium battery pack will be the best option as the power/weight is highest with lithium technology.

Johann:

It would be great to stick in as much electronics as possible.
I can program the AIM XTRA to control ejections using its pressure sensor and accelerometers.
It would be great to use the telemetry features as the GPS is working well.

We have to wait for a payload allowance in terms of weight and size.
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Read June 08, 2010, 02:49:18 PM #9
johanngr

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Re: 10km Project 2010 Electronic Payload discussion
As for payload allowance.  I think each electronics package supplier should come up with numbers and we'll fit it in.  Unless the unit is huge as in shoebox size, it should easily fit.

One thing which has come up - The airframe is aluminium.  Will this make things difficult or impossible?


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Read June 08, 2010, 09:19:24 PM #10
Rian

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Re: 10km Project 2010 Electronic Payload discussion
Welcome back David.
I am looking forward to see your new system. I had a look at the GPS chip in your system. It looks impressive. Please give me more info about the 433Mhz USB receiver. I still need to connect a receiver successfully to the TinyTrack decoder. About the power consumption. The APRS SkyTracker can be set to transmit at predetermind intervals, this will help to conserve battery
I suggest that we use both systems for redundancy. If your system will be broadcasting all the time we could use it to calculate speed and height by using Doppler effect. We can also use it to track the signal with directional receiver.
It is good news that we could exceed either speed or height.
Thanks for the hard work.
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Read June 08, 2010, 10:35:55 PM #11
johanngr

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Re: 10km Project 2010 Electronic Payload discussion
Thanks guys!  This is really good to see!


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Read June 09, 2010, 10:42:08 AM #12
twostage

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Re: 10km Project 2010 Electronic Payload discussion
Hi Guys

Well this is good to see that every one is coming together to make this project a success.
I personaly think that the south african teams are going to make history in october

DAVID
How much will one of your units cost me ,me and my brother wil be entering our own rocket (Aurora) for the 10k and we need a tracking system.


We all strive for perfection...but we fly for fun
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Read June 10, 2010, 05:08:33 PM #13
Rian

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Re: 10km Project 2010 Electronic Payload discussion
I have just managed to decode a position transmitted from my Skytracker. The transmitter and receiver is now independent from any other network.
I receive the following from the TinyTrak4 on my pc:
ZS6RXY-9>APERXQ,WIDE1-1,WIDE2-1:!2452.60S/02809.38E>339/000/A=004831
ZS6RXY-9>APERXQ,WIDE1-1,WIDE2-2:!2452.59S/02809.38E>185/000/A=004864
ZS6RXY-9>APERXQ:!2452.60S/02809.38E>137/000/A=004854
ZS6RXY-9>APERXQ,WIDE1-1:!2452.59S/02809.38E>059/000/A=004628
ZS6RXY-9>APERXQ,WIDE1-1,WIDE2-1:!2452.60S/02809.38E>071/000/A=004864
ZS6RXY-9>APERXQ,WIDE1-1,WIDE2-2:!2452.60S/02809.38E>303/000/A=004864
ZS6RXY-9>APERXQ:!2452.60S/02809.38E>000/000/A=004874
ZS6RXY-9>APERXQ,WIDE1-1:!2452.60S/02809.38E>056/000/A=004864
ZS6RXY-9>APERXQ,WIDE1-1,WIDE2-1:!2452.60S/02809.38E>061/000/A=004860
ZS6RXY-9>APERXQ,WIDE1-1,WIDE2-2:!2452.60S/02809.38E>000/000/A=004870
The A= 004870 is altitude information
It might be possible to connect the TinyTrak directly to a handheld GPS and see the Skytraker as a waypoint on the handheld’s screen.
I will keep you posted.
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Read June 10, 2010, 06:00:23 PM #14
johanngr

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Re: 10km Project 2010 Electronic Payload discussion
Whoa!

That is want we want to hear!!

Great work Riaan!

Michele and I just returned from Potch after booking the 9th of October with SM van Heerden of the SANDF.


Johann - The Rocket Guy!
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