1 == Using Altus Metrum Hardware
3 Here are general instructions for hooking up an Altus Metrum
4 flight computer. Instructions specific to each model will be
5 found in the section devoted to that model below.
7 === Wiring and Electrical Interference
9 To prevent electrical interference from affecting the
10 operation of the flight computer, it's important to always
11 twist pairs of wires connected to the board. Twist the switch
12 leads, the pyro leads and the battery leads. This reduces
13 interference through a mechanism called common mode rejection.
15 === Hooking Up Lithium Polymer Batteries
17 All Altus Metrum flight computers have a two pin JST PH
18 series connector to connect up a single-cell Lithium Polymer
19 cell (3.7V nominal). You can purchase matching batteries
20 from the Altus Metrum store, or other vendors, or you can
21 make your own. Pin 1 of the connector is positive, pin 2 is
22 negative. Spark Fun sells a cable with the connector
23 attached, which they call a
24 link:https://www.sparkfun.com/products/9914[JST Jumper 2 Wire Assembly]
26 Many RC vendors also sell lithium polymer batteries with
27 this same connector. All that we have found use the opposite
28 polarity, and if you use them that way, you will damage or
29 destroy the flight computer.
31 === Hooking Up Pyro Charges
33 Altus Metrum flight computers always have two screws for
34 each pyro charge. This means you shouldn't need to put two
35 wires into a screw terminal or connect leads from pyro
36 charges together externally.
38 On the flight computer, one lead from each charge is hooked
39 to the positive battery terminal through the power switch.
40 The other lead is connected through the pyro circuit, which
41 is connected to the negative battery terminal when the pyro
44 === Hooking Up a Power Switch
46 Altus Metrum flight computers need an external power switch
47 to turn them on. This disconnects both the computer and the
48 pyro charges from the battery, preventing the charges from
49 firing when in the Off position. The switch is in-line with
50 the positive battery terminal.
52 === Using an External Active Switch Circuit
54 You can use an active switch circuit, such as the
55 Featherweight Magnetic Switch, with any Altus Metrum
56 flight computer. These require three connections, one to
57 the battery, one to the positive power input on the flight
58 computer and one to ground. Find instructions on how to
59 hook these up for each flight computer below. The follow
60 the instructions that come with your active switch to
63 === Using a Separate Pyro Battery
65 As mentioned above in the section on hooking up pyro
66 charges, one lead for each of the pyro charges is connected
67 through the power switch directly to the positive battery
68 terminal. The other lead is connected to the pyro circuit,
69 which connects it to the negative battery terminal when the
70 pyro circuit is fired. The pyro circuit on all of the flight
71 computers is designed to handle up to 16V.
73 To use a separate pyro battery, connect the negative pyro
74 battery terminal to the flight computer ground terminal,
75 the positive battery terminal to the igniter and the other
76 igniter lead to the negative pyro terminal on the flight
77 computer. When the pyro channel fires, it will complete the
78 circuit between the negative pyro terminal and the ground
79 terminal, firing the igniter. Specific instructions on how
80 to hook this up will be found in each section below.
82 === Using a Different Kind of Battery
84 EasyMini and TeleMini v2 are designed to use either a
85 lithium polymer battery or any other battery producing
86 between 4 and 12 volts, such as a rectangular 9V
87 battery. TeleMega, EasyMega and TeleMetrum are not designed for this,
88 and must only be powered by a lithium polymer battery. Find
89 instructions on how to use other batteries in the EasyMini
90 and TeleMini sections below.