Eggtimer Rocketry Eggtimer User Manual page 41

5) 12v "A23" batteries work well for firing low-current igniters (i.e. Quest Q2G2's), but they
don't have a lot of capacity so they're not going to be able to fire very many times before they
will need to be replaced. 9v batteries are heavy (almost 50 grams) but they will fire a Q2G2
igniter several dozen times before you need to worry about replacing them. That being said,
batteries are a lot cheaper than motors and rockets, so if there is any doubt whatsoever about the
capacity of your ignition battery, replace it. When in doubt, TEST THEM FIRST before you try
to fly them, and replace them if they read under 80% of their rated voltage.
A lot of people replace their deployment battery after EVERY flight regardless of the voltage or
the current draw being used. With a 9v Alkaline battery and a Quest Q2G2 igniter this may be
overkill, but for smaller batteries such as an A23 12v battery it may be a really good idea.
Compared to the cost of the rocket, motor, Eggtimer, and last but not least, your time, a few
dollars per launch to ensure that you get a good deployment is cheap.
6) The default ON-Time parameter is 2 seconds; that is long enough for just about any type of
electric match or igniter that you're likely to use. Most igniters will go electrically "open" after
they fire, so they're not going to draw any more current from your battery after they fire even if
you set this value higher. If you have any doubt at all about how long it takes your igniter to heat
up, increase the On-Time value; chances are that it won't drain the ignition battery more than it
needs to. If you are using a relatively high-current igniter like #32 gauge nichrome wire and a
9v battery, you may want to increase this time by a second or so to give the nichrome extra time
to heat up.. If the igniter fires and does not melt through, however, it's going to keep drawing
current from the battery while it's on, so don't make this parameter any longer than you really
need it to be or you may unnecessarily drain your battery. Of course, if you're replacing the
battery after every flight it probably doesn't matter.
7) If you are using a non-pyro deployment (i.e. a small motor or a solenoid), you may need to
set the ON-Time to "continuous" (zero). That setting will keep it on until you reset the
Eggtimer, or press the button at the end of the flight to beep out the maximum altitude. If you
have a high-current load, like a solenoid, it WILL drain your deployment battery. Keep that in
mind before you set this to zero!
8) If your rocket is going to be approaching or exceeding mach transition, we strongly
recommend that you make sure that your ascent samples are set appropriately. In general, it's
going to be over 20 for a mach-capable rocket because it's virtually by definition a high-power
rocket.
9) If you are using a pyro ejection charge, you MUST have an external power and/or reset
switch to disarm the Eggtimer until shortly before launch. This is a Tripoli and NAR safety
requirement, and is just good common sense too. Additionally, you may want to put an external
shunt across the igniter terminals, pulling it out right before you remove the Reset shunt. This
will prevent the pyro from firing when you are setting it up on the pad. We recommend that you
use a large gauge wire, at least 16 awg, for the shunt, because some of the very low current
igniters such as a Quest Q2G2 will fire at under 200 milliamps of current.
10) If you are using servos, you MUST connect the "control" lead of the servo to the "+" output
of the deployment channel, and you MUST connect a 39 ohm 1/4W resistor between the "+" and
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