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.
58 TeleMini doesn't have room for a beeper, so instead it
59 uses an LED, which works the same, except for every
60 beep is replaced with the flash of the LED.
63 Here's a short summary of all of the modes and the
65 ifdef::telemini[(or flashing, in the case of TeleMini v1)]
66 that accompanies each mode. In the description of the
67 beeping pattern, “dit” means a short beep while "dah"
68 means a long beep (three times as long). “Brap” means
69 a long dissonant tone.
72 [options="border",cols="1,1,2,2"]
81 |battery voltage in decivolts
82 |Calibrating sensors, detecting orientation.
87 |Ready to accept commands over USB
88 ifdef::radio[or radio link.]
93 |Waiting for launch. Not listening for commands.
98 |Accelerating upwards.
103 |Decelerating, but moving faster than 200m/s.
108 |Decelerating, moving slower than 200m/s
113 |Descending after apogee. Above main height.
118 |Descending. Below main height.
123 |Stable altitude for at least ten seconds.
129 |Error detected during sensor calibration.
132 Here's a summary of all of the Pad and Idle mode
133 indications. In Idle mode, you'll hear one of these
134 just once after the two short dits indicating idle
135 mode. In Pad mode, after the dit dah dah dit
136 indicating Pad mode, you'll hear these once every five
139 .Pad/Idle Indications
140 [options="header",cols="1,1,3"]
142 |Name |Beeps |Description
146 |No continuity detected on either apogee or main igniters.
150 |Continuity detected only on apogee igniter.
154 |Continuity detected only on main igniter.
159 |Continuity detected on both igniters.
164 |On-board data logging storage is full. This will
165 not prevent the flight computer from safely
166 controlling the flight or transmitting telemetry
167 signals, but no record of the flight will be
168 stored in on-board flash.
171 |four very short beeps
172 |Continuity indication for the four additional pyro
173 |channels on TeleMega and EasyMega. One high tone for
174 |no continuity, one low tone for continuity. These are
175 |produced after the continuity indicators for the two
176 |primary igniter channels.
181 For devices with a radio transmitter, in addition to
182 the digital and APRS telemetry signals, you can also
183 receive audio tones with a standard amateur
184 70cm FM receiver. While on the pad, you will hear
185 igniter status once every five seconds.
187 .Pad Radio Indications
188 [options="header",cols="1,1,3"]
190 |Name |Beeps |Description
194 |No continuity detected on either apogee or main igniters.
198 |Continuity detected only on apogee igniter.
202 |Continuity detected only on main igniter.
207 |Continuity detected on both igniters.
211 During ascent, the tones will be muted to allow the
212 telemetry data to consume the full radio bandwidth.
214 During descent and after landing, a ½ second tone will
215 be transmitted every five seconds. This can be used to
216 find the rocket using RDF techniques when the signal
217 is too weak to receive GPS information via telemetry
221 === Turning On the Power
223 Connect a battery and power switch and turn the switch
224 to "on". The flight computer will signal power on by
225 reporting the battery voltage and then perform an internal self
226 test and sensor calibration.
228 Once the self test and calibration are complete, there
229 are two modes that an Altus Metrum flight computer can
233 The flight computer is waiting to detect
234 launch and then fly the rocket. In this mode, the USB
236 ifdef::radio[disabled, and the radio goes into transmit-only mode.]
237 ifndef::radio[disabled.]
238 The only way to get out of this
239 mode is to power the flight computer down.
242 The flight computer is ready to communicate over USB
243 ifdef::radio[and in packet mode over the radio.]
245 the flight computer, download data or display
248 ifdef::telemetrum,easymega,telemega[]
249 For flight computers with accelerometers (TeleMetrum,
250 EasyMega and TeleMega), the mode is selected by the
251 orientation of the board during the self test
252 interval. If the board is pointing upwards as if ready
253 to fly, it will enter Flight/Pad mode. Otherwise, it will
255 endif::telemetrum,easymega,telemega[]
258 For EasyMini, if the USB cable is connected to a
259 computer, it will enter Idle mode. Otherwise, it will
260 enter Flight/Pad mode.
264 For TeleMini v1.0, if a packet link is waiting to
265 connect when the device is powered on, it will enter
266 Idle mode, otherwise it will enter Flight/Pad mode.
269 You can see in <<_understanding_beeps>>
270 how to tell which mode the flight computer is in.
272 === Using an External Active Switch Circuit
274 You can use an active switch circuit, such as the
275 Featherweight Magnetic Switch, with any Altus Metrum
276 flight computer. These require three connections, one to
277 the battery, one to the positive power input on the flight
278 computer and one to ground. Find instructions on how to
279 hook these up for each flight computer below. Then follow
280 the instructions that come with your active switch to
283 === Using a Separate Pyro Battery
285 As mentioned above in <<_hooking_up_pyro_charges>>, one
286 lead for each of the pyro charges is connected through
287 the power switch directly to the positive battery
288 terminal. The other lead is connected to the pyro
289 circuit, which connects it to the negative battery
290 terminal when the pyro circuit is fired. The pyro
291 circuit on all of the flight computers is designed to
294 To use a separate pyro battery, connect the negative pyro
295 battery terminal to the flight computer ground terminal,
296 the positive battery terminal to the igniter and the other
297 igniter lead to the negative pyro terminal on the flight
298 computer. When the pyro channel fires, it will complete the
299 circuit between the negative pyro terminal and the ground
300 terminal, firing the igniter. Specific instructions on how
301 to hook this up for each flight computer will be found
302 in the section below for that flight computer.
304 === Using a Different Kind of Battery
307 ifdef::telemini[and TeleMini v2 are]
309 designed to use either a
310 lithium polymer battery or any other battery producing
311 between 4 and 12 volts, such as a rectangular 9V
314 ifdef::telemega,easymega,telemetrum[]
316 TeleMega, EasyMega and TeleMetrum are only designed to
317 operate off a single-cell Lithium Polymer battery and
318 cannot be used with any other kind. Connecting a
319 different kind of battery to any of these will destroy
321 endif::telemega,easymega,telemetrum[]