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== EasyTimer
.EasyTimer Board
image::easytimer.jpg[width=400]
EasyTimer is built on a 0.8 inch by 1½ inch circuit board. It's
designed to fit in a 24mm coupler tube.
EasyTimer is designed to control events during ascent. It has
an accelerometer and gyroscope that can measure acceleration
and rotation and compute speed and tilt angle. EasyTimer has
two pyro channels which can be configured to fire at various
points during flight. Because EasyTimer has no barometric
sensor, it cannot be used to fire recovery charges at apogee
or during descent. EasyTimer is configured using the AltosUI
application which is available for Linux, Mac OS X and Windows.
=== EasyTimer Screw Terminals
EasyTimer has two sets of four screw terminals near
one end of the board. Using the picture above, the top
four have connections for pyro channel B and an
external battery and the bottom four have connections
for pyro circuit A and the power switch. Counting from
the left, the connections are as follows:
.EasyTimer Screw Terminals
[options="header",grid="all",cols="2,3,10"]
|====
|Terminal #|Terminal Name|Description
|Top 1
|B -
|Pyro channel B connection to pyro circuit
|Top 2
|B +++
|Pyro channel B common connection to battery +++
|Top 3
|Battery +++
|Positive external battery terminal
|Top 4
|Battery -
|Negative external battery terminal
|Bottom 1
|A -
|Pyro channel A connection to pyro circuit
|Bottom 2
|A +++
|Pyro channel A common connection to battery +++
|Bottom 3
|Switch Output
|Switch connection to flight computer
|Bottom 4
|Switch Input
|Switch connection to positive battery terminal
|====
=== Connecting A Battery To EasyTimer
There are two possible battery connections on
EasyTimer. You can use either method; both feed
through the power switch terminals.
One battery connection is the standard Altus Metrum
white JST plug. This mates with single-cell Lithium
Polymer batteries sold by Altus Metrum.
The other is a pair of screw terminals marked 'Battery
+' and 'Battery -'. Connect a battery from 4 to 12
volts to these terminals, being careful to match polarity.
=== Charging Lithium Batteries
Because EasyTimer allows for batteries other than the
standard Altus Metrum Lithium Polymer cells, it cannot
incorporate a battery charger circuit. Therefore, when
using a Litium Polymer cell, you'll need an external
charger. These are available from Altus Metrum, or
from Spark Fun.
=== Using a Separate Pyro Battery with EasyTimer
As described above, using an external pyro battery involves
connecting the negative battery terminal to the flight
computer ground, connecting the positive battery terminal to
one of the igniter leads and connecting the other igniter
lead to the per-channel pyro circuit connection.
To connect the negative pyro battery terminal to EasyTimer
ground, connect it to the negative external battery
connection, top terminal 4.
Connecting the switched positive battery terminal to the pyro
charges must be done separate from EasyTimer, by soldering
them together or using some other connector. Note that for
safety, you must put a switch between the pyro battery and
the rest of the circuit!
The other lead from each pyro charge is then inserted into
the appropriate per-pyro channel screw terminal (top
terminal 1 for pyro channel A charge, bottom terminal 1 for
pyro channel B charge).
=== Using an Active Switch with EasyTimer
As explained above, an external active switch requires three
connections, one to the positive battery terminal, one to
the flight computer positive input and one to ground. Use
the negative external battery connection, top terminal 4 for
ground.
The positive battery terminal is available on bottom
terminal 4, the positive flight computer input is on the
bottom terminal 3.
|
