<chapter>
<title>Introduction and Overview</title>
<para>
- Placeholder.
+ Welcome to the Altus Metrum community! Our circuits and software reflect
+ our passion for both hobby rocketry and Free Software. We hope their
+ capabilities and performance will delight you in every way, but by
+ releasing all of our hardware and software designs under open licenses,
+ we also hope to empower you to take as active a role in our collective
+ future as you wish!
+ </para>
+ <para>
+ The focal point of our community is TeleMetrum, a dual deploy altimeter
+ with fully integrated GPS and radio telemetry as standard features, and
+ a "companion interface" that will support optional capabilities in the
+ future.
+ </para>
+ <para>
+ Complementing TeleMetrum is TeleDongle, a USB to RF interface for
+ communicating with TeleMetrum. Combined with your choice of antenna and
+ notebook computer, TeleDongle and our associated user interface software
+ form a complete ground station capable of logging and displaying in-flight
+ telemetry, aiding rocket recovery, then processing and archiving flight
+ data for analysis and review.
</para>
</chapter>
<chapter>
<title>Specifications</title>
- <para>
- Placeholder.
- </para>
+ <itemizedlist>
+ <listitem>
+ <para>
+ Recording altimeter for model rocketry.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Supports dual deployment (can fire 2 ejection charges).
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ 70cm ham-band transceiver for telemetry downlink.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Barometric pressure sensor good to 45k feet MSL.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ 1-axis high-g accelerometer for motor characterization, capable of
+ +/- 50g using default part.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ On-board, integrated GPS receiver with 5hz update rate capability.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ On-board 1 megabyte non-volatile memory for flight data storage.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ USB interface for battery charging, configuration, and data recovery.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Fully integrated support for LiPo rechargeable batteries.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Uses LiPo to fire e-matches, support for optional separate pyro
+ battery if needed.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ 2.75 x 1 inch board designed to fit inside 29mm airframe coupler tube.
+ </para>
+ </listitem>
+ </itemizedlist>
</chapter>
<chapter>
<title>Handling Precautions</title>
<para>
- Placeholder.
+ TeleMetrum is a sophisticated electronic device. When handled gently and
+ properly installed in an airframe, it will deliver extraordinary results.
+ However, like all electronic devices, there are some precautions you
+ must take.
+ </para>
+ <para>
+ The Lithium Polymer rechargeable batteries used with TeleMetrum have an
+ extraordinary power density. This is great because we can fly with
+ much less battery mass than if we used alkaline batteries or previous
+ generation rechargeable batteries... but if they are punctured
+ or their leads are allowed to short, they can and will release their
+ energy very rapidly!
+ Thus we recommend that you take some care when handling our batteries
+ and consider giving them some extra protection in your airframe. We
+ often wrap them in suitable scraps of closed-cell packing foam before
+ strapping them down, for example.
+ </para>
+ <para>
+ The TeleMetrum barometric sensor is sensitive to sunlight. In normal
+ mounting situations, it and all of the other surface mount components
+ are "down" towards whatever the underlying mounting surface is, so
+ this is not normally a problem. Please consider this, though, when
+ designing an installation, for example, in a 29mm airframe's see-through
+ plastic payload bay.
+ </para>
+ <para>
+ The TeleMetrum barometric sensor sampling port must be able to "breathe",
+ both by not being covered by foam or tape or other materials that might
+ directly block the hole on the top of the sensor, but also by having a
+ suitable static vent to outside air.
+ </para>
+ <para>
+ As with all other rocketry electronics, TeleMetrum must be protected
+ from exposure to corrosive motor exhaust and ejection charge gasses.
</para>
</chapter>
<chapter>
<title>Hardware Overview</title>
<para>
- Placeholder.
+ TeleMetrum is a 1 inch by 2.75 inch circuit board. It was designed to
+ fit inside coupler for 29mm airframe tubing, but using it in a tube that
+ small in diameter may require some creativity in mounting and wiring
+ to succeed! The default 1/4
+ wave UHF wire antenna attached to the center of the nose-cone end of
+ the board is about 7 inches long, and wiring for a power switch and
+ the e-matches for apogee and main ejection charges depart from the
+ fin can end of the board. Given all this, an ideal "simple" avionics
+ bay for TeleMetrum should have at least 10 inches of interior length.
+ </para>
+ <para>
+ A typical TeleMetrum installation using the on-board GPS antenna and
+ default wire UHF antenna involves attaching only a suitable
+ Lithium Polymer battery, a single pole switch for power on/off, and
+ two pairs of wires connecting e-matches for the apogee and main ejection
+ charges.
+ </para>
+ <para>
+ By default, we use the unregulated output of the LiPo battery directly
+ to fire ejection charges. This works marvelously with standard e-matches
+ from companies like [insert company and product names for e-matches we've
+ tried and like] and with Quest Q2G2 igniters. However, if you
+ want or need to use a separate pyro battery, you can do so by adding
+ a second 2mm connector to position B2 on the board and cutting the
+ thick pcb trace connecting the LiPo battery to the pyro circuit between
+ the two silk screen marks on the surface mount side of the board shown
+ here [insert photo]
+ </para>
+ <para>
+ We offer two choices of pyro and power switch connector, or you can
+ choose neither and solder wires directly to the board. All three choices
+ are reasonable depending on the constraints of your airframe. Our
+ favorite option when there is sufficient room above the board is to use
+ the Tyco pin header with polarization and locking. If you choose this
+ option, you crimp individual wires for the power switch and e-matches
+ into a mating connector, and installing and removing the TeleMetrum
+ board from an airframe is as easy as plugging or unplugging two
+ connectors. If the airframe will not support this much height or if
+ you want to be able to directly attach e-match leads to the board, we
+ offer a screw terminal block. This is very similar to what most other
+ altimeter vendors provide by default and so may be the most familiar
+ option. You'll need a very small straight blade screwdriver to connect
+ and disconnect the board in this case, such as you might find in a
+ jeweler's screwdriver set. Finally, you can forego both options and
+ solder wires directly to the board, which may be the best choice for
+ minimum diameter and/or minimum mass designs.
+ </para>
+ <para>
+ For most airframes, the integrated GPS antenna and wire UHF antenna are
+ a great combination. However, if you are installing in a carbon-fiber
+ electronics bay which is opaque to RF signals, you may need to use
+ off-board external antennas instead. In this case, you can order
+ TeleMetrum with an SMA connector for the UHF antenna connection, and
+ you can unplug the integrated GPS antenna and select an appropriate
+ off-board GPS antenna with cable terminating in a U.FL connector.
</para>
</chapter>
<chapter>
<title>Operation</title>
- <para>
- Placeholder.
- </para>
+ <section>
+ <title>Radio Link </title>
+ <para>
+ The chip our boards are based on incorporates an RF transceiver, but
+ it's not a full duplex system... each end can only be transmitting or
+ receiving at any given moment. So we have to decide how to manage the
+ link...
+ </para>
+ <para>
+ By design, TeleMetrum firmware listens for an RF connection when
+ it's in "idle mode" (turned on while the rocket is horizontal), which
+ allows us to use the RF link to configure the rocket, do things like
+ ejection tests, and extract data after a flight without having to
+ crack open the airframe. However, when the board is in "flight
+ mode" (turned on when the rocket is vertical) the TeleMetrum only
+ transmits and doesn't listen at all. That's because we want to put
+ ultimate priority on event detection and getting telemetry out of
+ the rocket and out over
+ the RF link in case the rocket crashes and we aren't able to extract
+ data later...
+ </para>
+ <para>
+ We don't use a 'normal packet radio' mode because they're just too
+ inefficient. GFSK is just FSK with the baseband pulses passed through a
+ Gaussian filter before they go into the modulator to limit the
+ transmitted bandwidth. When combined with the hardware forward error
+ correction support in the cc1111 chip, this allows us to have a very
+ robust 38.4 kilobit data link with only 10 milliwatts of transmit power,
+ a whip antenna in the rocket, and a hand-held Yagi on the ground. We've
+ had a test flight above 12k AGL with good reception, and my calculations
+ say we should be good to 40k AGL or more with just a 5-element yagi on
+ the ground. I expect to push 30k with a 54mm minimum airframe I'm
+ working on now, so we'll hopefully have further practical confirmation
+ of our link margin in a few months.
+ </para>
+ <para>
+ Placeholder.
+ </para>
+ </section>
</chapter>
<chapter>
<title>Using Altus Metrum Products</title>
if the rocket is hiding in sage brush or a tree, or if the last GPS position
doesn't get you close enough because the rocket dropped into a canyon, or
the wind is blowing it across a dry lake bed, or something like that... Keith
- and Bdale both currently own and use the
- <ulink url="http://yaesu.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=111&encProdID=4C6F204F6FEBB5BAFA58BCC1C131EAC0&DivisionID=65&isArchived=0">
- Yaesu VX-6R
- </ulink>
- at launches.
+ and Bdale both currently own and use the Yaesu VX-7R at launches.
</para>
<para>
So, to recap, on the ground the hardware you'll need includes:
<para>
The best hand-held commercial directional antennas we've found for radio
direction finding rockets are from
- <ulink url="http://www.arrowantennas.com/" >
- Arrow Antennas.
- </ulink>
-The 440-3 and 440-5 are both good choices for finding a
-TeleMetrum-equipped rocket when used with a suitable 70cm HT.
+
<ulink url="http://www.arrowantennas.com/" >
+ Arrow Antennas.
+ </ulink>
+ The 440-3 and 440-5 are both good choices for finding a
+ TeleMetrum-equipped rocket when used with a suitable 70cm HT.
</para>
</section>
<section>
projects / fw / altos / blobdiff