Eggtimer Rocketry Eggtimer TRS Assembly Manual page 5

The Eggfinder LCD handheld receiver will give you the coordinates and real-time altitude
during your flight, and will also allow you to program the flight settings remotely without
having to use a cable. You can also add a Bluetooth module (not included) to stream real-tiem
NMEA data wirelessly to your laptop, just like the RX "dongle" receiver. Whichever receiver
you choose, we recommend that you build the Eggtimer TRS first, because it's easier to tell if
it's working, and when you have the RX or LCD kit completed it will be easy to tell if that one
is working too since it will be easy to see if they are transmitting/receiving data.
About Soldering Your Eggtimer TRS Kit...
Assembling your Eggtimer TRS isn't that hard, but we recommend that you don't choose it as
your first kit project. You must be able to solder small components using fine solder and get
nice shiny solder joints. If you have never soldered before, you need to learn anyway, because
if you are going to do rocketry electronics you're going to be doing some soldering. If you
want to get into advanced projects like telemetry, you're probably going to be doing a lot of
soldering. We recommend that you get a few small kits from Ramsey or SparkFun, put them
together, and hone your skills on them first. There's a lot of fun stuff out there, so go for it!
The Eggtimer TRS uses quite a few Surface Mount Technology (SMT) parts, they are large by
SMT standards, and are within the realm of being hand-solderable. In our case, there are two
"modules", the GPS module and the RF module, that could potentially be damaged by the heat
of surface-mounting them in an oven; that's why we chose to have you hand-solder them. In
order to help make your assembly successful, we have included about 36" of very fine (.020"),
very low temperature (about 180°C), no-residue solder. This is not the stuff that you get at
Radio Shack... it's designed for soldering small temperature-sensitive parts without
transferring much heat to the part itself.
Important note about using extra flux with this board: The solder that comes with the kit is
Kester 245, it uses a water-based "no-clean" flux. If you wish to use extra flux with the board,
it MUST be compatible. You want a liquid (not paste) water-based no-clean flux. Kester 951
is ideal, if you can get it. Chip-Quik sells little 2ml tubes for about $2 each (unfortunately they
sell them in 6-packs, you can't just get one) which works very well. If you decide to add flux,
you must use only a tiny amount. One drop will suffice for the entire GPS module. DO NOT
use Rosin Core flux, or you will make a mess of the board and possibly damage components.
We have built many kits without using any additional flux without any issues, the board is pre-
tinned to make solder adhesion easier so in general you should not need to use additional flux.
For soldering components on a board like the Eggtimer TRS, we recommend a small pencil
soldering iron, about 15W. If you are only going to use it occasionally, Weller makes a decent
cheap 12W iron, it's about $15. There is also a similar iron that's sold by ECG. We like those,
but the copper tips seem to oxidize and corrode rather quickly compared to some more
expensive irons; fortunately, the tips are replaceable and cheap. Better would be a fancier
soldering pencil with iron tips; those run about $30, but they'll last forever. The best iron
would be a temperature-controlled solder station, they typically start at about $50 for a cheap
one and can go to a few hundred dollars if you want to get really fancy. Weller makes a good
one for about $50, if you make the investment that will probably be the last soldering iron you