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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.
projects / fw / altos / blobdiff