TXLog - an Eggfinder accessory

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Worsaer

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The Eggfinder can be a very effective tool for locating your rocket - GPS coordinates transmitted to your handheld receiver works great. Some folks also have experience with capturing the GPS data via Bluetooth for post flight analysis. Cris @ Eggtimer Rocketry has thoughtfully designed the Eggfinder TX in such a way that it can also be interfaced with a data logging module like OpenLog, which writes data to an on-board micro SD memory card.

When I first started playing with the OpenLog module, it simply worked; no coding or special configuration was required. I was impressed with the small footprint. My first mock-ups included a piggy back board with some short leads connecting to the TX serial connectors. It then occurred to me that a custom PCB could be mounted on the TX doing away with the wires completely.

In a nutshell, through trial and error I came up with a simple adapter board that mounts an OpenLog module directly on an Eggfinder TX. I had some boards made, and they seem to work well. I have all that I need, and thought that other Eggfinder owners might also like an easy option to capture GPS data during the flight, while also transmitting the data to their receiver. (Important note: This only works with the current B6/B7 version of the Eggfinder TX. This isn’t designed for earlier versions.)

You can import the flight data into Google Earth, manually look at timestamps to correlate events, etc.

Sound Interesting?

Effective July 2017, these are now available from Eggtimer Rocketry.

See post #54 for additional details.
 
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Here is a photo if the commercially available OpenLog module:

OpenLog_Module_sm.jpg



And here's the module mounted on the custom board:

IMG_0325.JPG



And some photos of how it all comes together...

IMG_0326.JPG


IMG_0327.JPG
 
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That's a very neat solution, does it even increase the height of the board?

Price? Weight?
 
That's a very neat solution, does it even increase the height of the board?

Price? Weight?

As the photo shows, the tallest components on the Eggfinder TX are the header pins. This simply slides over the existing pins, and as built, is about the same height.

It does not require separate battery - it uses the power supplied by the Eggfinder pins.

Weight of the entire sub assembly (including a micro SD card): 0.16 oz


From the manufacturer of the OpenLog module:
VCC Input: 3.3V-12V (Recommended 3.3V-5V)
Log to low-cost microSD FAT16/32 cards up to 64GB
Two LEDs indicate writing status
2mA idle, 6mA at maximum recording rate


Price: TBD - I want have some people log some flight time on them before I make them generally available. Reliability and ease of use are really important.
 
Dude, I'm so down for one of these toys! Logging is the only thing that the eggfinder is missing, and could make the difference for me between staying eggfinder or going MW RTX.
 
Dude, I'm so down for one of these toys! Logging is the only thing that the eggfinder is missing, and could make the difference for me between staying eggfinder or going MW RTX.

Your choice should be based upon whether you need the 250mW Rf output from the Missileworks, can deal with the larger footprint of the MW product with the ability to record the
positions.
GPS Rocket Locator can save a log but one has to manually deal with it so it's not that easy with the EF. The expressed purpose of the EF was to find rockets. It shouldn't be
considered a telemetry system by any stretch of the imagination. The EF does the job of finding most rockets nicely though.
One is best served if they can weigh their needs to each device in question and base their decision on that. Kurt
 
This is datalogging, not telemetry. A lot of people like to see the GPS trace... I wish I had it from my Double Shot flight that drifted 5 miles downrange and over a hill. It's very easy to get this data out of an OpenLog, since it's just an NMEA data file. Put your uSD card into an adapter and stick it in your laptop, open the file up with Google Maps, and there you go.

Technically, any data that you send out via radio is telemetry: GPS data, altitude, deployment channel status, etc. (Gee, that sounds a lot like the TRS. :) ) It could be argued that a beacon locator is telemetry too, it's sending out a "I'm alive" beep which can be used to find the rocket by inference (I see you're alive and your signal is coming from "there" and it's "this" strong so you must be "that" far away).
 
I stand corrected but both units do telemeter the data strings. The issue is capturing the strings through the vagaries of Rf propagation, transmitted power and antenna polarity.
Data logging overcomes this except that one must find the rocket to have at the on board data. True, with GPS the chance of recovery is much higher than without but bottomline
is one has to get the rocket back for that.

If one can plot the telemetered strings reliably, that goes a long way to establish a trend line to assist with a recovery that goes out of radio tracking range. True, most sport flights don't go to that extreme so plotting is not really necessary for a reliable recovery. Sure helps with a main at apogee and one has to go on a chase scenario. Kurt
 
From my perspective, more data is always a good thing. Having data from multiple altimeters, GPS, etc, can present an interesting perspective of the flight. Yes, this assumes you have found the rocket.

Thinking of Matt's now infamous L3 flight as an example, after locating the rocket he would have had data to tell if the eggfinder shut down ( perhaps due to the battery dropping below an acceptable range) and when that occurred. I also hear of flights 'losing lock' on the ascent. The data would be interesting to look at to better understand what the GPS saw during the flight. The NMEA sentences contain a wealth of data. I don't think I would rely on altitude readings, but 'speed over ground' could tell you a lot about less than vertical flights, winds aloft, etc.

Did I say I like data? <grin>
 
I like the the memory card, stick it in a laptop after your flight. Personally, I would use it a lot with the ability to have all that data in one spot. I never remember how to use the putty terminal program.

Will it work with the TRS and the Mini?
 
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From my perspective, more data is always a good thing. Having data from multiple altimeters, GPS, etc, can present an interesting perspective of the flight. Yes, this assumes you have found the rocket.

Thinking of Matt's now infamous L3 flight as an example, after locating the rocket he would have had data to tell if the eggfinder shut down ( perhaps due to the battery dropping below an acceptable range) and when that occurred. I also hear of flights 'losing lock' on the ascent. The data would be interesting to look at to better understand what the GPS saw during the flight. The NMEA sentences contain a wealth of data. I don't think I would rely on altitude readings, but 'speed over ground' could tell you a lot about less than vertical flights, winds aloft, etc.

Did I say I like data? <grin>

In Matt's case, the strings would have just stopped and one might be able to know when that happened. It's moot because it's known that happened by using
a single 1S battery. Kurt
 
In Matt's case, the strings would have just stopped and one might be able to know when that happened. It's moot because it's known that happened by using
a single 1S battery. Kurt

Is it truly known, or just assumed? Certainly it's likely.


Steve Shannon
 
I like the the memory card, stick it in a laptop after your flight. Personally, I would use it a lot with the ability to have all that data in one spot. I never remember how to use the putty terminal program.

Will it work with the TRS and the Mini?

This particular board is sized for the TX B6/B7 versions, but you can connect an Openlog to any of the Eggfinders and the TRS; you just need to solder 3 wires. I'm working on a document for that...
 
This particular board is sized for the TX B6/B7 versions, but you can connect an Openlog to any of the Eggfinders and the TRS; you just need to solder 3 wires. I'm working on a document for that...

The big question unasked , 'Will this void the warranty ??'

Kenny
 
The big question unasked , 'Will this void the warranty ??'

Kenny

LOL, of course not. However, there are six ways to connect 3 wires to 3 pads, and only one of them is going to work...

Just in case you can't wait, here's how you hook one up, for any Eggfinder or TRS version. On the RF module pads from left to right, solder wires to the OpenLog as follows:

First pad - +3.3V (VCC) on the OpenLog
Third pad - GND on the OpenLog
Fourth pad - RXD on the OpenLog
 
Got a bunch of those lying around already. 4gb enough for a flight or two? Kurt

At about 150 bytes/sec, a 4 GB card is good for about 7400 hours of recording. That's about 44 weeks of continuous recording. Yeah, it's long enough...
 
Talking with Chris now about getting set up. Would love to incorporate this.
 
If you are interested in obtaining one, more information is available here.


5/20/17 Update: I have a few units available, with more to follow. Please use the email address in the above link for questions or to place an order.
 
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