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]
27 Many RC vendors also sell lithium polymer batteries with
28 this same connector. All that we have found use the opposite
29 polarity, and if you use them that way, you will damage or
30 destroy the flight computer.
32 === Hooking Up Pyro Charges
34 Altus Metrum flight computers always have two screws for
35 each pyro charge. This means you shouldn't need to put two
36 wires into a screw terminal or connect leads from pyro
37 charges together externally.
39 On the flight computer, one lead from each charge is hooked
40 to the positive battery terminal through the power switch.
41 The other lead is connected through the pyro circuit, which
42 is connected to the negative battery terminal when the pyro
45 === Hooking Up a Power Switch
47 Altus Metrum flight computers need an external power switch
48 to turn them on. This disconnects both the computer and the
49 pyro charges from the battery, preventing the charges from
50 firing when in the Off position. The switch is in-line with
51 the positive battery terminal.
53 === Understanding Beeps
55 Altus Metrum flight computers include a beeper to
56 provide information about the state of the system.
57 TeleMini doesn't have room for a beeper, so instead it
58 uses an LED, which works the same, except for every
59 beep is replaced with the flash of the LED.
61 Here's a short summary of all of the modes and the beeping (or
62 flashing, in the case of TeleMini v1) that accompanies each
63 mode. In the description of the beeping pattern, “dit” means a
64 short beep while "dah" means a long beep (three times as
65 long). “Brap” means a long dissonant tone.
68 [options="border",cols="1,1,2,2"]
77 |battery voltage in decivolts
78 |Calibrating sensors, detecting orientation.
83 |Ready to accept commands over USB or radio link.
88 |Waiting for launch. Not listening for commands.
93 |Accelerating upwards.
98 |Decelerating, but moving faster than 200m/s.
103 |Decelerating, moving slower than 200m/s
108 |Descending after apogee. Above main height.
113 |Descending. Below main height.
118 |Stable altitude for at least ten seconds.
124 |Error detected during sensor calibration.
127 === Turning On the Power
129 Connect a battery and power switch and turn the switch
130 to "on". The flight computer will signal power on by
131 reporting the battery voltage and then perform an internal self
132 test and sensor calibration.
134 Once the self test and calibration are complete, there
135 are two modes that an Altus Metrum flight computer can
139 The flight computer is waiting to detect
140 launch and then fly the rocket. In this mode, the USB
141 link is disabled, and the radio goes into
142 transmit-only mode. The only way to get out of this
143 mode is to power the flight computer down.
146 The flight computer is ready to communicate over USB
147 and in packet mode over the radio. You can configure
148 the flight computer, download data or display
151 For flight computers with accelerometers (TeleMetrum,
152 EasyMega and TeleMega), the mode is selected by the
153 orientation of the board during the self test
154 interval. If the board is pointing upwards as if ready
155 to fly, it will enter Flight/Pad mode. Otherwise, it will
158 For EasyMini, if the USB cable is connected to a
159 computer, it will enter Idle mode. Otherwise, it will
160 enter Flight/Pad mode.
162 For TeleMini v1.0, if a packet link is waiting to
163 connect when the device is powered on, it will enter
164 Idle mode, otherwise it will enter Flight/Pad mode.
166 You can see in <<_understanding_beeps>>
167 how to tell which mode the flight computer is in.
169 === Using an External Active Switch Circuit
171 You can use an active switch circuit, such as the
172 Featherweight Magnetic Switch, with any Altus Metrum
173 flight computer. These require three connections, one to
174 the battery, one to the positive power input on the flight
175 computer and one to ground. Find instructions on how to
176 hook these up for each flight computer below. The follow
177 the instructions that come with your active switch to
180 === Using a Separate Pyro Battery
182 As mentioned above in <<_hooking_up_pyro_charges>>, one
183 lead for each of the pyro charges is connected through
184 the power switch directly to the positive battery
185 terminal. The other lead is connected to the pyro
186 circuit, which connects it to the negative battery
187 terminal when the pyro circuit is fired. The pyro
188 circuit on all of the flight computers is designed to
191 To use a separate pyro battery, connect the negative pyro
192 battery terminal to the flight computer ground terminal,
193 the positive battery terminal to the igniter and the other
194 igniter lead to the negative pyro terminal on the flight
195 computer. When the pyro channel fires, it will complete the
196 circuit between the negative pyro terminal and the ground
197 terminal, firing the igniter. Specific instructions on how
198 to hook this up for each flight computer will be found
199 in the section below for that flight computer.
201 === Using a Different Kind of Battery
203 EasyMini and TeleMini v2 are designed to use either a
204 lithium polymer battery or any other battery producing
205 between 4 and 12 volts, such as a rectangular 9V
209 TeleMega, EasyMega and TeleMetrum are only designed to
210 operate off a single-cell Lithium Polymer battery and
211 cannot be used with any other kind. Connecting a
212 different kind of battery to any of these will destroy