User`s manual

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from the “-“ wire. You can also use solid wire, but solid wire is harder to work with and has a
tendency to break after being bent a few times. These breaks can be a pain to find, because they
are typically inside the insulator jacket where you can’t see them. To prevent them, we
recommend that you zip-tie the wires to the sled to strain-relieve them.
If you use stranded wire, you MUST TWIST AND TIN THE WIRES BEFORE SOLDERING
TO THE BOARD. This is to prevent stray “whiskers” of wire strands from coming loose and
bridging pads, or breaking off and landing on the board in some random place. We’ve seen the
results of this happening, it’s not pretty, and they can be very hard to find if they lodge
underneath the processor chip or in some other hidden spot on the board.
All that being said, you CAN install .150” (3.81mm) screw-terminal blocks, the holes are spaced
for two sets of 4-terminal blocks. We know that a lot of you out there really like the convenience
of terminal blocks, so we give you the option; the kit does not include the terminal blocks,
however. If you do use terminal blocks, make sure that you check the screws before every
flight so you can be sure that the wires don’t work loose.
Eggtimer TRS Battery Options
There are actually two battery connections for the Eggtimer TRS: One for the computer side,
and one for the deployment side. They are electrically isolated from each other via optoisolators,
they do not even share a common ground. This is different from most other flight controllers on
the market, which typically use a single battery for both the computer and the deployment side.
The reason that we do this is to provide 100% immunity from any power issues on the
deployment side from interfering with the processor’s operation. If you have a dead-short on the
deployment side, even if the current surge was enough to destroy an output transistor, it would
have no effect on the processor and GPS; you would still get a GPS feed and the processor would
continue to log flight data, and possibly continue with deployment of the other channel.
“Brownouts” are basically impossible.
It IS possible to operate the Eggtimer TRS with a single battery, but we recommend that you
only do that with very low current igniters such as a Quest Q2G2, or of course if you’re not
doing deployments. You’ll need to be a little careful with your battery choice, more on that
below. Of course, you give up the brownout protection if you do that, so be careful.
The computer side of the Eggtimer TRS will run on anything from 4.5V-30V. Current draw is
about 80 mA continuous, with a startup peak of about 200 mA as the GPS module searches for
satellites. Most of the power draw in the Eggtimer TRS is from the GPS/RF side; the processor
side only draws about 8 mA. Like a cell phone, you will get better battery life with a stronger
signal, so you may find that the battery life varies significantly from time to time, since the GPS
will draw more current if there are fewer satellites in view.
We recommend using a 2S 7.4V LiPo battery, at least 350 mAH. This will run the Eggtimer
TRS for at least 5 hours continuously. If you have a bigger rocket and have room for a bigger
battery, a 800 mAH or 1000 mAH battery will easily run your Eggtimer TRS for a whole day,