Eggtimer Rocketry TX Board Rev B4d, RX Board Rev B4d User Manual

Eggfinder GPS Tracker

Users Manual

TX Board Rev B4d

RX Board Rev B4d

© 2014 Eggtimer Rocketry
All Rights Reserved

California Proposition 65 Warning

WARNING: This product contains chemicals (lead) known to the State of

California to cause cancer and birth defects or reproductive harm.

This kit includes a special low-temperature ultra-fine leaded solder wire.
Including the solder with the kit ensures that you will have solder that can be
used to mount the surface-mount parts in the kit. Leaded solders have been used
for over a century in electronic assembly, but you should take the following
precautions when using it (or just about any chemical, for that matter):

• Do not eat or drink while using it

• Wash your hands after handling it

• Keep it in the protective bag when you’re not using it

The MSDS can be found at

http://www.kester.com/download/245%20FluxCored%20Wire%20Lead%20Allo
y%20SDS.pdf

The European Union RoHS (Restriction on Hazardous Substances) regulations
exempt kits such as the Eggfinder from its regulations, because they are not for
resale and since it is well known that hand soldering with non-leaded solder is
much more difficult and more damaging to heat-sensitive components.
Nevertheless, we do not certify the Eggfinder as RoHS, and we cannot ship them
to EU countries. Since the Eggfinder’s RF module runs on the 902-928 MHz
band which is not an unlicensed band in the EU, we couldn’t sell there anyway.

Important Regulatory Information

This device complies with Part 15 of the FCC Rules. Operation
is subject to the following two conditions: (1) this device may
not cause harmful interference, and (2) this device must
accept any interference received, including interference that
may cause undesired operation.

It is intended to be used ONLY for educational and
experimental use in Class II/III amateur High Power Rockets
which are classified as aircraft by the Federal Aircraft
Administration (CFR 14 §101.25), and which must by FAA and
NFPA regulations be operated at least 1,500’ away from any
populated buildings. Although unlikely, this device may cause
interference with consumer devices that run on the
unlicensed 902-928 MHz band, and therefore must not be
used in residential areas.

The Eggfinder uses RF modules in the 902-928 MHz ISM band manufactured by Hope RF,
model HM-TRP-915. They are intended to be used only in the United States. These modules
have been tested by Hope RF to be compliant with the FCC Part 15 regulations for non­licensed intentional emitters, and as such have been permitted to be imported into the US.
However, Hope RF (at the time of this document) has not obtained formal certification with the
FCC. As a hobby kit, designed for educational and experimental purposes, the Eggfinder is
considered by the FCC to be “generally exempt” from authorization requirements.
Nonethless, we have made a good faith attempt to comply with all technical regulations, and
you should too by building it exactly as per the instructions, and by using only the antenna on
the transmitter module that we recommend in the instructions, or a suitable replacement as
outlined in the Appendix.

Because the Eggfinder runs on an unlicensed band, there is no protection against interference
from other sources; basically, you get what you get. We’ve done substantial testing and are
confident that your Eggfinder system is unlikely to be significantly affected by outside radio
sources, but there’s no guarantee.

If your Eggfinder causes interference in a residential setting, or with licensed radio systems
(such as TV or ham radio), you must stop using it until you correct the problem. This is
extremely unlikely given the small amount of power and the “tightness” of the transmitter’s
output, and in particular the distance from any population that HPR rockets must be flown.
Nevertheless, you need to be aware of this, and be willing to abide by the rules. These are the
same rules that govern other non-licensed transmitters, such as cordless phones, WiFi and
Bluetooth® devices, and garage door openers.

Important Links:

FCC Part 15 (governing unlicensed intentional emitters)

http://www.ecfr.gov/cgi-bin/text­idx?SID=adb12f74b498e43ec453f7899d9df0fd&node=47:1.0.1.1.16&rgn=div5

Hope RF HM-TRP Documentation (FCC test documentation)

http://www.hoperf.com/upload/rf/HM-TRP-915(20dBm)-FCC.pdf

FAA Regulations for Amateur Rocketry (Part 101)

http://www.ecfr.gov/cgi-bin/text­idx?c=ecfr&rgn=div5&view=text&node=14:2.0.1.3.15&idno=14

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Before You Start…

• If you bought a Starter Set (both Eggfinder TX and RX kits), make sure that both of them are
on the same frequency (it’s marked on the package label). If they are not, do not open the kits;
contact us immediately so we can send you a replacement kit and a no-charge return label.

• Go to our web site at www.Eggtimerrocketry.com and download the latest Release Notes.

• Go to our web site at www.Eggtimerrocketry.com and download the latest Assembly/Users
Guide..

• Read them thoroughly before starting… it will save you some grief later, we promise!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thanks for buying an Eggfinder GPS Tracker! The Eggfinder is a hobby rocketry GPS tracker
that uses a GPS module and a 900 MHz license-free transmitter module to broadcast your
rocket’s location in real-time to a computer or tablet. With appropriate GPS tracking software,
which is available for free on the Internet, you can actually track your rocket in flight, and
ultimately find out exactly where it landed.

Like other Eggtimer Rocketry products, we sell it as a kit, to keep costs down and provide an
outstanding value. This means that you have to do a little work, of course, but considering that
most hobby rocketeers that would use our products have some degree of electronics expertise,
this should not be much of an impediment. If you do not have any experience soldering kits
such as the Eggfinder, we recommend that you ask around… chances are that somebody in
your rocketry club would be more than happy to assist you for a small bribe (beverages work
well!).

There are actually two separate Eggfinder boards, the Eggfinder TX that goes into your rocket,
and the Eggfinder RX board that receives the data from your Eggfinder TX board and displays
it on your computer or tablet. They are similar in that they both have a radio module and
power supply, but only the TX board has a GPS module. We recommend that you build the
TX board first, because it’s easier to tell if it’s working, and when you have the RX board
completed it will be easy to tell if that one is working too since both boards have LEDs that tell
you if they are transmitting/receiving data.

An Introduction to Rocket Tracking

Once upon a time it was a big deal for a model rocket to go out of sight, especially if it was a
relatively large one (say, the size of an Estes Big Bertha). Rockets like that would go out of
sight at maybe 1,000’, but unless your field was surrounded by trees or tall grass there was a
good chance that you would get it back because it’s not going to stray more than a few hundred
feet away from the launch pad.

With mid-power and high-power rockets, that’s a different story. To begin with, your field has
to be much larger, particularly with high-power (the rules call for a minimum size of 1500’ on
either side, or ½ the estimated altitude whichever is greater). If your rocket is flying to 6,000’,
you may have to walk at least 3,000’ to find your rocket. Even with multiple-deployment
using a flight computer (like the Eggtimer), you may find that once the rocket gets out of sight
you have no idea where it went, and the field is too large to simply walk around looking for it.
Trust us, we’ve all done this… for longer than we like to admit.

The need to be able to find “lost” rockets has created a number of electronic tracking methods.
The simplest rocket finding device is a simple “sounder”, that creates a loud audible tone. The
idea is that as you get close to the rocket, you will be able to hear it and hone in on the source
of the sound. The advantage of sounders is that they are simple and inexpensive; the primary
disadvantage is that you have to be close enough to the rocket to be able to hear the tone. If
you don’t know where the rocket landed, or if it drifted in a direction other than what you were
expecting, the sounder isn’t going to be of much help.

A more sophisticated approach is to use some sort of radio system. This is a two part system:
There must be some kind of transmitter in the rocket that sends out some kind of signal, and
there must also be some kind of receiver to pick up the signal and somehow help you find the
rocket. There are a few different ways of doing this.

The simplest radio tracking device is a “beacon”, which sends out a tone to a receiver that you
carry with you as you wander around looking for the rocket. You point the antenna of the
receiver in different directions noting the signal strength, and the direction of the greatest
signal strength is going to be where your rocket landed. These systems can be relatively
inexpensive (a few hundred dollars), or they can be very expensive (up to a thousand dollars),
depending on many factors; primarily, the range of the transmitter. Ranges for beacon systems
can be from a mile or two, up to tens of miles. Most of these beacon systems require a FCC
Technican class amateur radio license (a “ham” license), and using the signal strength to
determine position (also known as “DXing”) requires patience and practice.

In the past several years, the advent of affordable GPS location technology as made it possible
to create a rocket finding device that uses a GPS in conjunction with a radio telemetry data link
to send the location of you rocket to a ground receiver, so that it actually tells you where your
rocket landed. Early GPS-based rocketry transmitters were relatively large and heavy,
expensive, and required a FCC ham license. With recent advances in semiconductor
technology, the cost of GPS receiver chips has dropped enough so that they are now
commonplace in consumer device such as smartphones, tablets, and portable navigation
systems. Some of these same advances have also filtered down to radio-frequency devices,
such as FRS radio units and various consumer devices using the unlicensed 2.4 GHz and 900

MHz bands. These advances have made it possible to create GPS-based rocket tracking system
for a fraction of what they would have cost 10 years ago.

Meet the Eggfinder

The Eggfinder is a GPS-based rocket tracking system that transmits using the license-free 900
MHz band. The radio modules used in the Eggfinder use the maximum legally-permissible
output power for this band, 100 mW. There are actually two pieces to the Eggfinder system,
the TX (transmitter) module and the RX (receiver) module. The Eggfinder TX board is about
3” long x 1” wide (+ 3” for the antenna), and weighs about 20 grams without the battery. It is
mounted in your rocket, preferably in the nose cone or payload bay area, and sends out a data
stream with GPS location data once per second. The Eggfinder RX board has a USB data
cable that plugs into your laptop or tablet, and receives the signal from the TX board in your
rocket. Optionally, you can connect a Bluetooth®-Serial board and a battery to the Eggfinder
RX board, so you can wirelessly connect it to a tablet.

Using readily-available (and mostly free!) software on your laptop or tablet, you can “read” the
transmitted GPS location data from your rocket and use that data to plot its location in real­time. Once the rocket lands, you record the landing coordinates, and you can either draw a
track line (compass direction/distance) to the landing spot and follow that heading, or you can
plug the coordinates into a smartphone app and have your GPS-enabled smartphone draw a
track that takes you right to your rocket.

The Eggfinder is a no-frills system designed for one purpose: getting your rocket back. It does
not have any kind of built-in recording capability (although you can, and most likely will,
record the received data onto your laptop/tablet). The range is adequate for the vast majority
of sport rocketry flights; we have tested it to over 8,000’ range line-of-sight with good signal
strength. This does not necessarily mean that you will be able to maintain a GPS signal
throughout the entire flight; in fact, it’s fairly normal to lose the signal while the rocket is
under boost and through the initial coasting phase, because the GPS module isn’t going to be
able to keep a fix on the GPS satellites while it’s moving fast. Once the rocket starts slowing
down, you’ll see it pick up again, and you will probably keep a lock on it until it gets fairly
close to the ground (well under 100’). Even if you lose the GPS data at that altitude, it’s so
close to the ground by then that finding it is not going to be a problem.

If your rocket does go out of the range of the Eggfinder, once it starts to come down you will
most likely be able to pick up the signal again, unless your rocket has drifted about 2 miles
downrange. That’s not something that happens very often, because you’re already going to
know about how high your rocket is going to go before you launch, and you’re not going to fly
if there’s too much wind. Even with a tracking transmitter, it’s still possible to lose rockets…
if you try hard enough.

A few guidelines…:

• Fly sensibly: If you KNOW that you’re going to fly out of the Eggfinder’s range, use a
higher-gain receiver antenna, or position yourself so that you will be most likely to pick up the
signal as the rocket comes down.

• Follow NAR/TRA guidelines… if it’s too windy to fly, an Eggfinder isn’t going to help the
situation.

• Having a transmitter doesn’t mean that you don’t need to pay attention to your rocket, a
visual fix on your rocket is still the best way to help get it back.

Mounting Your Eggfinder TX in a Rocket

The Eggfinder TX board is about 3” long and .9” wide; with its “stick” antenna it’s about 6”
long and .9” wide. It will fit into just about any rocket with a BT-50 or larger payload bay,
although some of the batteries may not fit in a space that small. (9V batteries and 7.4V 2S
LiPo packs are about the same size, and require a BT-55 or larger body tube.).

The cardinal rule of tracking transmitter mounting is

KEEP METAL AWAY FROM THE ANTENNA.

This means that if you have an A/V bay with two allthreads running the length of the bay, this
is going to be a really bad place to mount your Eggfinder. Large metallic or conductive items,
including batteries, hardware, and other electronics will significantly reduce the range of your
Eggfinder TX. Note that this also applies to metallic paints, and metallic film trim as they can
also block out radio signals. So can carbon fiber nose cones and body tubes. If you have any
of these, your best bet would be to mount the antenna outside of the body tube/nose cone.

If you HAVE to mount it somewhere near metal, you should keep the metal at least 2” away
from the antenna, farther is better. You may be able to get away with this in a very large­diameter rocket, but if you’re putting it in a minimum-diameter mach-buster, you will be very
disappointed in the range that you get out of it.

The best place to mount a telemetry tracker is in the nose cone. There are many ways that you
can mount it, we have had good success with simply mounting it on a small piece of
basswood/plywood located in the nose cone, with either a bulkhead or a piece of BT-55-sized
tubing to hold it in. This works very well for plastic and fiberglass nose cones. (It will work
for wood nose cones too, if you can still find one…)

We’ve seen some people wrap them in bubble wrap and stuff them into the nose cone. If you
do this, be aware that bubble wrap can generate static electricity, so be warned. Better would
be the natural foam rubber that is used in RC airplanes to cushion receivers, it does not
generate static electricity. You will also need to make sure that it can’t slide out at ejection,
and that it’s sealed off from corrosive ejection charge gases. Masking tape works fine for that
purpose.

We’ve also seen them mounted inside coupler tubes attached to the nose cone or shock cord.
This works fine, as long as you seal up the coupler so no ejection gases can get in. Also we
strongly recommend that if you tape it to the shock cord, you do not use plastic electrical tape;
the heat of the ejection charge gases can melt it, and you may end up finding your Eggfinder
sans the rocket. A few layers of duct tape works fine.

Important points to note are:

• If you use the mounting holes, use a nylon or polycarbonate screw or a plastic rivet in the
hole next to the antenna. Do not use a metal screw. It’s OK to use a metal screw at the back
(near the RDY LED).