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+<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>MicroPeak Owner's Manual</title><meta name="generator" content="DocBook XSL Stylesheets V1.76.1"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="book" title="MicroPeak Owner's Manual"><div class="titlepage"><div><div><h1 class="title"><a name="idm14762280"></a>MicroPeak Owner's Manual</h1></div><div><h2 class="subtitle">A peak-recording altimeter for hobby rocketry</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Keith</span> <span class="surname">Packard</span></h3></div></div><div><p class="copyright">Copyright © 2012 Bdale Garbee and Keith Packard</p></div><div><div class="legalnotice" title="Legal Notice"><a name="idp172816"></a><p>
+ This document is released under the terms of the
+ <a class="ulink" href="http://creativecommons.org/licenses/by-sa/3.0/" target="_top">
+ Creative Commons ShareAlike 3.0
+ </a>
+ license.
+ </p></div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr><tr><td align="left">Revision 0.1</td><td align="left">29 October 2012</td></tr><tr><td align="left" colspan="2">
+ Initial release with preliminary hardware.
+ </td></tr></table></div></div></div><hr></div><div class="acknowledgements" title="Acknowledgements"><div class="titlepage"><div><div><h2 class="title"><a name="idp174776"></a>Acknowledgements</h2></div></div></div>
+ <p>
+ Thanks to John Lyngdal for suggesting that we build something like this.
+ </p>
+ <p>
+ Have fun using these products, and we hope to meet all of you
+ out on the rocket flight line somewhere.
+ </p><div class="literallayout"><p><br>
+Bdale Garbee, KB0G<br>
+NAR #87103, TRA #12201<br>
+<br>
+Keith Packard, KD7SQG<br>
+NAR #88757, TRA #12200<br>
+ </p></div><p>
+ </p>
+ </div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="chapter"><a href="#idp176024">1. Quick Start Guide</a></span></dt><dt><span class="chapter"><a href="#idp1555544">2. Handling Precautions</a></span></dt><dt><span class="chapter"><a href="#idp1561440">3. Technical Information</a></span></dt><dd><dl><dt><span class="section"><a href="#idp3211240">1. Barometric Sensor</a></span></dt><dt><span class="section"><a href="#idp1961960">2. Micro-controller</a></span></dt><dt><span class="section"><a href="#idp2901888">3. Lithium Battery</a></span></dt><dt><span class="section"><a href="#idp1674792">4. Atmospheric Model</a></span></dt><dt><span class="section"><a href="#idp1421872">5. Mechanical Considerations</a></span></dt></dl></dd></dl></div><div class="chapter" title="Chapter 1. Quick Start Guide"><div class="titlepage"><div><div><h2 class="title"><a name="idp176024"></a>Chapter 1. Quick Start Guide</h2></div></div></div><p>
+ MicroPeak is designed to be easy to use. Requiring no external
+ components, flying takes just a few steps
+ </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>
+ 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.
+ </p></li><li class="listitem"><p>
+ 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.
+ </p></li><li class="listitem"><p>
+ 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.
+ </p></li><li class="listitem"><p>
+ Finish preparing the rocket for flight. After the
+ previous flight data have been reported, MicroPeak waits for
+ 30 seconds before starting to check for launch. This gives
+ you time to finish assembling the rocket. As those
+ activities might cause pressure changes inside the airframe,
+ MicroPeak might accidentally detect boost. If you need to do
+ anything to the airframe after the 30 second window passes,
+ make sure to be careful not to disturb the altimeter. The
+ LED will remain dark during the 30 second delay, but after
+ that, it will start blinking once every 3 seconds.
+ </p></li><li class="listitem"><p>
+ Fly the rocket. Once the rocket passes about 10m in height
+ (32 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.
+ </p></li><li class="listitem"><p>
+ 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.
+ </p></li></ul></div></div><div class="chapter" title="Chapter 2. Handling Precautions"><div class="titlepage"><div><div><h2 class="title"><a name="idp1555544"></a>Chapter 2. Handling Precautions</h2></div></div></div><p>
+ 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.
+ </p><p>
+ 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.
+ </p><p>
+ 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.
+ </p><p>
+ 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.
+ </p><p>
+ As with all other rocketry electronics, Altus Metrum altimeters must
+ be protected from exposure to corrosive motor exhaust and ejection
+ charge gasses.
+ </p></div><div class="chapter" title="Chapter 3. Technical Information"><div class="titlepage"><div><div><h2 class="title"><a name="idp1561440"></a>Chapter 3. Technical Information</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#idp3211240">1. Barometric Sensor</a></span></dt><dt><span class="section"><a href="#idp1961960">2. Micro-controller</a></span></dt><dt><span class="section"><a href="#idp2901888">3. Lithium Battery</a></span></dt><dt><span class="section"><a href="#idp1674792">4. Atmospheric Model</a></span></dt><dt><span class="section"><a href="#idp1421872">5. Mechanical Considerations</a></span></dt></dl></div><div class="section" title="1. Barometric Sensor"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp3211240"></a>1. Barometric Sensor</h2></div></div></div><p>
+ 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.
+ </p><p>
+ 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).
+ </p><p>
+ 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.
+ </p></div><div class="section" title="2. Micro-controller"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp1961960"></a>2. Micro-controller</h2></div></div></div><p>
+ 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.
+ </p><p>
+ 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.
+ </p></div><div class="section" title="3. Lithium Battery"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp2901888"></a>3. Lithium Battery</h2></div></div></div><p>
+ 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.
+ </p><p>
+ 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.
+ </p><p>
+ 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.
+ </p></div><div class="section" title="4. Atmospheric Model"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp1674792"></a>4. Atmospheric Model</h2></div></div></div><p>
+ 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.
+ </p><p>
+ 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.
+ </p></div><div class="section" title="5. Mechanical Considerations"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="idp1421872"></a>5. Mechanical Considerations</h2></div></div></div><p>
+ 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.
+ </p><p>
+ 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.
+ </p><p>
+ 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.
+ </p></div></div></div></body></html>
projects / web / altusmetrum / commitdiff
