Eggtimer Rocketry Eggtimer User Manual page 8

Channel A (Main) Battery (BCHA) - Two solder pads, marked "+" and "-", for connecting an
external battery for the deployment device (if used). Typically, these batteries are 3.7v LiPo
cells for low-current igniters such as a Quest G2Q2, or 9-12v alkaline batteries for #36 nichrome
wire or other igniters. The Eggtimer is capable of handling up to 60V/8A up to 65W, so you can
ignite even an Aerotech Copperhead igniter with it, assuming you have a strong enough battery
(i.e. 14.4v LiPo battery).
Channel B Deployment (CHB) - Two solder pads, marked "+" and "-" for connecting an
electric match or other low-to-medium current device. This channel may be used for a "drogue"
chute, airstarting second stage or booster motors, or a chute triggered at a certain time in the
flight. Maximum 8A current, 60 VDC, 65 W. You can also connect the input for a standard
analog hobby servo to the "+" terminal (along with a 39 ohm ¼ W resistor in parallel) for non-
pyro drogue deployment at nose-over (one second after apogee).
Channel B Battery (BCHB) – Separate battery terminals for the Channel B deployment. This is
provided in case you want to use two different batteries for Main and Channel B; this allows you
to mix pyro outputs and servos, since servos generally use 6v or less. If you are using both
Channel A (Main) and Channel B, and they are OK on the same battery (i.e. they're both either
servos or both igniters), then you can jumper the BCHA and BCHB terminals together: + to +,
and – to - .
AUX1 Output – The AUX1 output turns ON (+V) for two seconds, at nose-over detect. It can
be used to provide redundancy for the CHB channel in drogue (nose-over) mode, or it can be
used to trigger a drogue parachute if CHB is being used in airstart or timed modes. This is an
unbuffered (logic-level) output, a high-current driver circuit will be required to trigger a load of
over 20 mA or over +V (typically 3V-4V). See the Eggtimer web site (www.EggtimerRocketry)
for suggested high-current driver circuits.
AUX2 Output – The AUX2 output "shadows" the function of the CHA (MAIN) deployment
output. It can be used to provide redundancy for the CHA output. Note that if CHA is disabled
(set to "0"), the AUX2 channel will also be disabled. This is an unbuffered circuit, see the
description of AUX1 for details.
AUX3 Output – The AUX3 output turns ON (+V) when a landing has been detected (AGL of
less than 30 ft for at least 5 seconds after nose-over), and stays on until the Eggtimer is reset.
This is an unbuffered output, see the description of AUX1 for details. NOTE: This output is
designed to be used with an "always on" device such as a loud buzzer or telemetry device.
Because of a quirk in the processor chip, it flashes on briefly a few times when you first start the
Eggtimer. Therefore, DO NOT USE THIS OUTPUT WITH A PYROTECHIC LOAD, or it may
fire as soon as you turn on the Eggtimer!
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