4 image::easytimer.jpg[width=400]
6 EasyTimer is built on a 0.8 inch by 1½ inch circuit board. It's
7 designed to fit in a 24mm coupler tube.
9 EasyTimer is designed to control events during ascent. It has
10 an accelerometer and gyroscope that can measure acceleration
11 and rotation and compute speed and tilt angle. EasyTimer has
12 two pyro channels which can be configured to fire at various
13 points during flight. Because EasyTimer has no barometric
14 sensor, it cannot be used to fire recovery charges at apogee
15 or during descent. EasyTimer is configured using the AltosUI
16 application which is available for Linux, Mac OS X and Windows.
18 === EasyTimer Screw Terminals
20 EasyTimer has two sets of four screw terminals near
21 one end of the board. Using the picture above, the top
22 four have connections for pyro channel B and an
23 external battery and the bottom four have connections
24 for pyro circuit A and the power switch. Counting from
25 the left, the connections are as follows:
27 .EasyTimer Screw Terminals
28 [options="header",grid="all",cols="2,3,10"]
30 |Terminal #|Terminal Name|Description
33 |Pyro channel B connection to pyro circuit
37 |Pyro channel B common connection to battery +++
41 |Positive external battery terminal
45 |Negative external battery terminal
49 |Pyro channel A connection to pyro circuit
53 |Pyro channel A common connection to battery +++
57 |Switch connection to flight computer
61 |Switch connection to positive battery terminal
64 === Connecting A Battery To EasyTimer
66 There are two possible battery connections on
67 EasyTimer. You can use either method; both feed
68 through the power switch terminals.
70 One battery connection is the standard Altus Metrum
71 white JST plug. This mates with single-cell Lithium
72 Polymer batteries sold by Altus Metrum.
74 The other is a pair of screw terminals marked 'Battery
75 +' and 'Battery -'. Connect a battery from 4 to 12
76 volts to these terminals, being careful to match polarity.
78 === Charging Lithium Batteries
80 Because EasyTimer allows for batteries other than the
81 standard Altus Metrum Lithium Polymer cells, it cannot
82 incorporate a battery charger circuit. Therefore, when
83 using a Litium Polymer cell, you'll need an external
84 charger. These are available from Altus Metrum, or
87 === Using a Separate Pyro Battery with EasyTimer
89 As described above, using an external pyro battery involves
90 connecting the negative battery terminal to the flight
91 computer ground, connecting the positive battery terminal to
92 one of the igniter leads and connecting the other igniter
93 lead to the per-channel pyro circuit connection.
95 To connect the negative pyro battery terminal to EasyTimer
96 ground, connect it to the negative external battery
97 connection, top terminal 4.
99 Connecting the switched positive battery terminal to the pyro
100 charges must be done separate from EasyTimer, by soldering
101 them together or using some other connector. Note that for
102 safety, you must put a switch between the pyro battery and
103 the rest of the circuit!
105 The other lead from each pyro charge is then inserted into
106 the appropriate per-pyro channel screw terminal (top
107 terminal 1 for pyro channel A charge, bottom terminal 1 for
108 pyro channel B charge).
110 === Using an Active Switch with EasyTimer
112 As explained above, an external active switch requires three
113 connections, one to the positive battery terminal, one to
114 the flight computer positive input and one to ground. Use
115 the negative external battery connection, top terminal 4 for
118 The positive battery terminal is available on bottom
119 terminal 4, the positive flight computer input is on the