User`s manual

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Meet the Eggtimer TRS
The Eggtimer TRS is a barometric altimeter-based flight computer with two deployment
channels and an integrated GPS RF tracker. It can record up to 32 flights, of varying length. It
can deploy two parachutes, a drogue chute that deploys near apogee to slow the rocket down
from high altitudes and a larger main chute that brings the rocket to a safe landing. While this is
happening, the Eggtimer TRS sends out NMEA-formatted tracking data that can be picked up by
an Eggfinder RX “dongle” or Eggfinder LCD handheld display receiver, and the coordinates can
be used to take you right to where your rocket landed. Up to 72 Eggtimer TRS units can be
operated simultaneously by simply changing the center frequency and ID code, and you can
“name” your device so you’re sure that it’s yours when you pair it with your Eggfinder LCD
receiver.
The Eggtimer TRS is designed to be used with FAA Class I, II, and III rockets The only
limitation is how high the rocket is expected to go… we recommend it for flights up to about
10,000’ with the included wire antenna, and about 20,000’ with external antennas. The Main
deployment channel is programmable so that it may be triggered at a fixed altitude from 100-
1200 feet. The Drogue output can be deployed just after apogee, or it can be used as a backup
channel so that it deploys two seconds after apogee. This allows the Eggfinder GPS to be used
as a backup deployment altimeter in projects that require redundant recovery systems.
The deployment channels are capable of triggering a medium-current Estes igniter or #36
nichrome wire using an appropriate battery (such as a small 7.4v LiPo pack). You can also use a
low-current igniter such as a Quest Q2G2 with a single 3.7v LiPo battery. Like the “classic”
Eggtimer, it features separate batteries for the computer and deployment circuits, which are
100% electrically isolated from each other through optoisolators. This absolutely prevents a
dead-short on the deployment side from causing the computer to stop working, resulting in a less
than optimal recovery deployment.
Programming and status can be done wirelessly with the Eggfinder LCD receiver, and you can
also use it to review the milestones of your saved flights (apogee, main deployment altitude,
etc.). You can also check the status prior to launch, and arm the deployment channels remotely;
other than the NAR/TRA required deployment power disconnect switch, you do not need to use
a separate power switch. If something is not right and a flight should not be attempted, you will
be alerted on the LCD display and by an audio alert, and the Eggtimer TRS will not arm.
Programming can also be done using a standard VT100/ANSI serial terminal program,
connected to your computer with a USB-serial cable. Since there is no special software
required, you can use just about any computer, running Windows, Mac, Linux, or just about
anything else you can come up with. Flights can be downloaded to a standard CSV-formatted
file, and can be imported into virtually any spreadsheet or data analysis program to produce
flight graphs.
The firmware on the processor chip performs real-time data analysis during flights to detect and
report significant flight events such as launch, apogee, deployments, and landing. A software
filter is used to ensure that “noise” doesn’t affect flight events, a velocity profile algorithm is
used to prevent deployments due to the pressure changes that occur during mach transition, with