+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "/usr/share/xml/docbook/schema/dtd/4.5/docbookx.dtd">
+<book>
+ <title>MicroPeak Owner's Manual</title>
+ <subtitle>A peak-recording altimeter for hobby rocketry</subtitle>
+ <bookinfo>
+ <author>
+ <firstname>Keith</firstname>
+ <surname>Packard</surname>
+ </author>
+ <copyright>
+ <year>2012</year>
+ <holder>Bdale Garbee and Keith Packard</holder>
+ </copyright>
+ <legalnotice>
+ <para>
+ This document is released under the terms of the
+ <ulink url="http://creativecommons.org/licenses/by-sa/3.0/">
+ Creative Commons ShareAlike 3.0
+ </ulink>
+ license.
+ </para>
+ </legalnotice>
+ <revhistory>
+ <revision>
+ <revnumber>0.1</revnumber>
+ <date>29 October 2012</date>
+ <revremark>
+ Initial release with preliminary hardware.
+ </revremark>
+ </revision>
+ </revhistory>
+ </bookinfo>
+ <acknowledgements>
+ <para>
+ Thanks to John Lyngdal for suggesting that we build something like this.
+ </para>
+ <para>
+ Have fun using these products, and we hope to meet all of you
+ out on the rocket flight line somewhere.
+ <literallayout>
+Bdale Garbee, KB0G
+NAR #87103, TRA #12201
+
+Keith Packard, KD7SQG
+NAR #88757, TRA #12200
+ </literallayout>
+ </para>
+ </acknowledgements>
+ <chapter>
+ <title>Quick Start Guide</title>
+ <para>
+ MicroPeak is designed to be easy to use. Requiring no external
+ components, flying takes just a few steps
+ </para>
+ <itemizedlist>
+ <listitem>
+ <para>
+ Install the battery. Fit a CR1025 battery into the plastic
+ carrier. The positive (+) terminal should be towards the more
+ open side of the carrier. Slip the carrier into the battery
+ holder with the positive (+) terminal facing away from the
+ circuit board.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Install MicroPeak in your rocket. This can be as simple as
+ preparing a soft cushion of wadding inside a vented model payload
+ bay. Wherever you mount it, make sure you protect the
+ barometric sensor from corrosive ejection gasses as those
+ will damage the sensor.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Turn MicroPeak on. Slide the switch so that the actuator
+ covers the '1' printed on the board. MicroPeak will report
+ the maximum height of the last flight in decimeters using a
+ sequence of flashes on the LED. A sequence of short flashes
+ indicates one digit. A single long flash indicates zero. The
+ height is reported in decimeters, so the last digit will be
+ tenths of a meter. For example, if MicroPeak reports 5 4 4
+ 3, then the maximum height of the last flight was 544.3m, or
+ 1786 feet. After reporting the last flight, MicroPeak starts
+ waiting for launch. It will flash once every three seconds
+ in this mode.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Fly the rocket. Once the rocket passes about 4m in height
+ (13 feet), the micro-controller will record the ground
+ pressure and track the pressure seen during the flight. In
+ this mode, the LED flickers rapidly. When the rocket lands,
+ and the pressure stabilizes, the micro-controller will record
+ the minimum pressure pressure experienced during the flight,
+ compute the height represented by the difference in air
+ pressure and blink that value out on the LED. After that,
+ MicroPeak powers down to conserve battery power.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Recover the data. Turn MicroPeak off for a couple of seconds
+ (to discharge the capacitors) and then back on. MicroPeak
+ will blink out the maximum height for the last flight. Turn
+ MicroPeak back off to conserve battery power.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </chapter>
+ <chapter>
+ <title>Handling Precautions</title>
+ <para>
+ All Altus Metrum products are sophisticated electronic devices.
+ When handled gently and properly installed in an air-frame, they
+ will deliver impressive results. However, as with all electronic
+ devices, there are some precautions you must take.
+ </para>
+ <para>
+ The CR1025 Lithium batteries have an
+ extraordinary power density. This is great because we can fly with
+ much less battery mass... but if they are punctured
+ or their contacts are allowed to short, they can and will release their
+ energy very rapidly!
+ Thus we recommend that you take some care when handling MicroPeak
+ to keep conductive material from coming in contact with the exposed metal elements.
+ </para>
+ <para>
+ The barometric sensors used in MicroPeak is
+ sensitive to sunlight. Please consider this when
+ designing an installation, for example, in an air-frame with a
+ see-through plastic payload bay. Many model rockets with payload bays
+ use clear plastic for the payload bay. Replacing these with an opaque
+ cardboard tube, painting them, or wrapping them with a layer of masking
+ tape are all reasonable approaches to keep the sensor out of direct
+ sunlight.
+ </para>
+ <para>
+ The barometric sensor sampling ports 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, and also by having a
+ suitable static vent to outside air.
+ </para>
+ <para>
+ As with all other rocketry electronics, Altus Metrum altimeters must
+ be protected from exposure to corrosive motor exhaust and ejection
+ charge gasses.
+ </para>
+ </chapter>
+ <chapter>
+ <title>Technical Information</title>
+ <section>
+ <title>Barometric Sensor</title>
+ <para>
+ MicroPeak uses the Measurement Specialties MS5607 sensor. This
+ has a range of 120kPa to 1kPa with an absolute accuracy of
+ 150Pa and a resolution of 2.4Pa.
+ </para>
+ <para>
+ The pressure range corresponds roughly to an altitude range of
+ -1500m (-4900 feet) to 31000m (102000 feet), while the
+ resolution is approximately 20cm (8 inches) near sea level and
+ 60cm (24in) at 10000m (33000 feet).
+ </para>
+ <para>
+ Ground pressure is computed from an average of 16 samples,
+ taken while the altimeter is at rest. Flight pressure is
+ computed from an exponential IIR filter designed to smooth out
+ transients caused by mechanical stress on the barometer.
+ </para>
+ </section>
+ <section>
+ <title>Micro-controller</title>
+ <para>
+ MicroPeak uses an Atmel ATtiny85 micro-controller. This tiny
+ CPU contains 8kB of flash for the application, 512B of RAM for
+ temporary data storage and 512B of EEPROM for non-volatile
+ storage of previous flight data.
+ </para>
+ <para>
+ The ATtiny85 has a low-power mode which turns off all of the
+ clocks and powers down most of the internal components. In
+ this mode, the chip consumes only .1μA of power. MicroPeak
+ uses this mode once the flight has ended to preserve battery
+ power.
+ </para>
+ </section>
+ <section>
+ <title>Lithium Battery</title>
+ <para>
+ The CR1025 battery used by MicroPeak holes 30mAh of power,
+ which is sufficient to run for over 15 hours. Because
+ MicroPeak powers down on landing, run time includes only time
+ sitting on the launch pad or during flight.
+ </para>
+ <para>
+ The large positive terminal (+) is usually marked, while the
+ smaller negative terminal is not. Make sure you install the
+ battery with the positive terminal facing away from the
+ circuit board where it will be in contact with the metal
+ battery holder. A small pad on the circuit board makes contact
+ with the negative battery terminal.
+ </para>
+ <para>
+ Shipping restrictions prevent us from including a CR1025
+ battery with MicroPeak. Many stores carry CR1025 batteries as
+ they are commonly used in small electronic devices such as
+ flash lights.
+ </para>
+ </section>
+ <section>
+ <title>Atmospheric Model</title>
+ <para>
+ MicroPeak contains a fixed atmospheric model which is used to
+ convert barometric pressure into altitude. The model was
+ converted into a 469-element piece wise linear approximation
+ which is then used to compute the altitude of the ground and
+ apogee. The difference between these represents the maximum
+ height of the flight.
+ </para>
+ <para>
+ The model assumes a particular set of atmospheric conditions,
+ which while a reasonable average cannot represent the changing
+ nature of the real atmosphere. Fortunately, for flights
+ reasonably close to the ground, the effect of this global
+ inaccuracy are largely canceled out when the computed ground
+ altitude is subtracted from the computed apogee altitude, so
+ the resulting height is more accurate than either the ground
+ or apogee altitudes.
+ </para>
+ </section>
+ <section>
+ <title>Mechanical Considerations</title>
+ <para>
+ MicroPeak is designed to be rugged enough for typical rocketry
+ applications. It contains two moving parts, the battery holder
+ and the power switch, which were selected for their
+ ruggedness.
+ </para>
+ <para>
+ The MicroPeak battery holder is designed to withstand impact
+ up to 150g without breaking contact (or, worse yet, causing
+ the battery to fall out). That means it should stand up to
+ almost any launch you care to try, and should withstand fairly
+ rough landings.
+ </para>
+ <para>
+ The power switch is designed to withstand up to 50g forces in
+ any direction. Because it is a sliding switch, orienting the
+ switch perpendicular to the direction of rocket travel will
+ serve to further protect the switch from launch forces.
+ </para>
+ </section>
+ </chapter>
+</book>
+<!-- LocalWords: Altusmetrum MicroPeak
+-->
projects / fw / altos / commitdiff