From: Keith Packard Date: Mon, 29 Oct 2012 18:49:23 +0000 (-0700) Subject: doc: Add micropeak manual X-Git-Tag: 1.1.9.2~10 X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=0d0ece403028e8a4453cc380575ed95c5e00ddb7;hp=424638446b7c7bb3f4aa6b4764d3e68175dcbf8c doc: Add micropeak manual Signed-off-by: Keith Packard --- diff --git a/doc/Makefile b/doc/Makefile index 3e1626f0..53985431 100644 --- a/doc/Makefile +++ b/doc/Makefile @@ -12,8 +12,8 @@ RELNOTES=\ release-notes-1.1.html RELNOTES_XSL=$(RELNOTES:.html=.xsl) -HTML=altusmetrum.html altos.html telemetry.html companion.html $(RELNOTES) -PDF=altusmetrum.pdf altos.pdf telemetry.pdf companion.pdf +HTML=altusmetrum.html altos.html telemetry.html companion.html micropeak.html $(RELNOTES) +PDF=altusmetrum.pdf altos.pdf telemetry.pdf companion.pdf micropeak.pdf DOC=$(HTML) $(PDF) HTMLSTYLE=/usr/share/xml/docbook/stylesheet/docbook-xsl/html/docbook.xsl FOSTYLE=/usr/share/xml/docbook/stylesheet/docbook-xsl/fo/docbook.xsl diff --git a/doc/micropeak.xsl b/doc/micropeak.xsl new file mode 100644 index 00000000..2faef41c --- /dev/null +++ b/doc/micropeak.xsl @@ -0,0 +1,260 @@ + + + + MicroPeak Owner's Manual + A peak-recording altimeter for hobby rocketry + + + Keith + Packard + + + 2012 + Bdale Garbee and Keith Packard + + + + This document is released under the terms of the + + Creative Commons ShareAlike 3.0 + + license. + + + + + 0.1 + 29 October 2012 + + Initial release with preliminary hardware. + + + + + + + Thanks to John Lyngdal for suggesting that we build something like this. + + + Have fun using these products, and we hope to meet all of you + out on the rocket flight line somewhere. + +Bdale Garbee, KB0G +NAR #87103, TRA #12201 + +Keith Packard, KD7SQG +NAR #88757, TRA #12200 + + + + + Quick Start Guide + + MicroPeak is designed to be easy to use. Requiring no external + components, flying takes just a few steps + + + + + 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. + + + + + 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. + + + + + 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. + + + + + 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. + + + + + 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. + + + + + + Handling Precautions + + 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. + + + 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. + + + 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. + + + 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. + + + As with all other rocketry electronics, Altus Metrum altimeters must + be protected from exposure to corrosive motor exhaust and ejection + charge gasses. + + + + Technical Information +
+ Barometric Sensor + + 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. + + + 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). + + + 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. + +
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+ Micro-controller + + 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. + + + 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. + +
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+ Lithium Battery + + 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. + + + 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. + + + 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. + +
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+ Atmospheric Model + + 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. + + + 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. + +
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+ Mechanical Considerations + + 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. + + + 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. + + + 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. + +
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