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