X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=blobdiff_plain;f=doc%2Fmicropeak.txt;h=f1feeec41423a557948c19d4e9c14c9bf451bb82;hp=d62e463357df7c50c8dd8b93fb38459bbeec4b9c;hb=0a466e9869633c6ce7e43ff24ba2afff938461dd;hpb=ce297f14ff54d230d01fb6dedaafca571e8b836b diff --git a/doc/micropeak.txt b/doc/micropeak.txt index d62e4633..f1feeec4 100644 --- a/doc/micropeak.txt +++ b/doc/micropeak.txt @@ -1,6 +1,18 @@ = MicroPeak Owner's Manual +Keith Packard ; Bdale Garbee +:revnumber: v1.9 +:revdate: 8 Oct 2018 +:copyright: Bdale Garbee and Keith Packard 2018 +:stylesheet: am.css +:linkcss: +:toc: :doctype: book :numbered: +:pdf-stylesdir: . +:pdf-style: altusmetrum +:pdf-fontsdir: fonts + + include::header.adoc[] [dedication] == Acknowledgements @@ -24,61 +36,70 @@ 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 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. .MicroPeak and Battery - image::micropeak-back.jpg[width="4.5in"] - - * 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, and shield it from light as that can - cause incorrect sensor readings. - - * 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. - - * Finish preparing the rocket for flight. After the - previous flight data have been reported, MicroPeak waits for - one minute 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 one minute window passes, - make sure to be careful not to disturb the altimeter. The - LED will remain dark during the one minute delay, but after - that, it will start blinking once every 3 seconds. - - * Fly the rocket. Once the rocket passes about 30m in height - (100 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 and then back on. MicroPeak - will blink out the maximum height for the last flight. Turn - MicroPeak back off to conserve battery power. + image::micropeak-back.jpg[width=430] + + 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, and shield + it from light as that can cause incorrect sensor readings. + + 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. + + Finish preparing the rocket for flight:: + + After the previous flight data have been reported, MicroPeak + waits for one minute 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 + one minute window passes, make sure to be careful not to + disturb the altimeter. The LED will remain dark during the + one minute delay, but after that, it will start blinking + once every 3 seconds. + + Fly the rocket:: + + Once the rocket passes about 30m in height (100 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 and then back on. MicroPeak will blink + out the maximum height for the last flight. Turn MicroPeak + back off to conserve battery power. == The MicroPeak USB adapter .MicroPeak USB Adapter - image::MicroPeakUSB-2.0.jpg[width="4.5in"] + image::MicroPeakUSB-2.0.jpg[width=430,align="center"] MicroPeak stores barometric pressure information for the first 48 seconds of the flight in on-board non-volatile memory. The @@ -103,25 +124,25 @@ * Start the MicroPeak application. - image::micropeak-nofont.svg[width="0.5in"] + image::micropeak-nofont.svg[width=50,align="center"] * Click on the Download button at the top of the window. .MicroPeak Application - image::micropeak-app.png[width="4.5in"] + image::micropeak-app.png[width=430,align="center"] * Select from the listed devices. There will probably be only one. .MicroPeak Device Dialog - image::micropeak-device-dialog.png[width="2.3in"] + image::micropeak-device-dialog.png[width=220,align="center"] * The application will now wait until it receives valid data from the MicroPeak USB adapter. .MicroPeak Download Dialog - image::micropeak-download.png[width="2in"] + image::micropeak-download.png[width=200,align="center"] * The MicroPeak USB adapter has a small phototransistor under the hole in the center of the @@ -133,7 +154,7 @@ MicroPeak board itself. .MicroPeak Downloading - image::MicroPeakUSB-2.0-inuse.jpg[width="4.5in"] + image::MicroPeakUSB-2.0-inuse.jpg[width=430,align="center"] * After the maximum flight height is reported, MicroPeak will pause for a few seconds, blink the @@ -145,12 +166,12 @@ MicroPeak board and try again. .MicroPeak Save Dialog - image::micropeak-save-dialog.png[width="2.3in"] + image::micropeak-save-dialog.png[width=220,align="center"] * Once the data are saved, a graph will be displayed with height, speed and acceleration values computed - from the recorded barometric pressure data. See the - next section for more details on that. + from the recorded barometric pressure data. See + <<_analyzing_micropeak_data> for more details on that. === Analyzing MicroPeak Data @@ -185,7 +206,7 @@ ==== MicroPeak Graphs .MicroPeak Graph - image::micropeak-graph.png[width="4.5in"] + image::micropeak-graph.png[width=430,align="center"] Under the Graph tab, the height, speed and acceleration values are displayed together. You can zoom in on the graph by @@ -196,7 +217,7 @@ ==== MicroPeak Flight Statistics .MicroPeak Flight Statistics - image::micropeak-statistics.png[width="4.5in"] + image::micropeak-statistics.png[width=430,align="center"] The Statistics tab presents overall data from the flight. Note that the Maximum height value @@ -211,7 +232,7 @@ ==== Raw Flight Data .MicroPeak Raw Flight Data - image::micropeak-raw-data.png[width="4.5in"] + image::micropeak-raw-data.png[width=430,align="center"] A table consisting of the both the raw barometric pressure data and values computed from that for each recorded time. @@ -219,7 +240,7 @@ ==== Configuring the Graph .MicroPeak Graph Configuration - image::micropeak-graph-configure.png[width="4.5in"] + image::micropeak-graph-configure.png[width=430,align="center"] This selects which graph elements to show, and lets you switch between metric and imperial units @@ -227,7 +248,7 @@ === Setting MicroPeak Preferences .MicroPeak Preferences - image::micropeak-preferences.png[width="1.8in"] + image::micropeak-preferences.png[width=170,align="center"] The MicroPeak application has a few user settings which are configured through the Preferences dialog, which can be @@ -278,6 +299,43 @@ these applications, change in one application will affect the other. +== Protecting MicroPeak from Sunlight + + The MS5607 barometric sensor is sensitive to direct light. When light + shines through the holes in the cover to the components inside, the + reported pressure can vary wildly from the actual pressure. This + causes the reported altitude to have errors of as much as 3000-4000 + feet. + + MicroPeak should be installed in an opaque compartment in the airframe + and not subjected to sunlight. Alternatively, a small piece of + adhesive-backed open-cell foam can be attached to the device so that + it covers the barometric sensor and protects it from direct light. + + Here's what happens when MicroPeak is exposed to sunlight. At apogee, + I exposed MicroPeak to varying amounts of sunlight and you can see the + wild swings in altitude resulting from that: + + .MicroPeak in Sunlight + image::micropeak-flight-nofoam.png[width=430] + + You can carefully cutting a piece of adhesive-backed open-cell foam + and attach it to MicroPeak. It's important to press the adhesive to + the circuit board and not to the top of the barometric sensor or the + sensor may become blocked and not operate at all. Once you've attached + the foam, you should test MicroPeak on the ground to make sure it's + still working. + + .MicroPeak with Foam + image::micropeak-foam.jpg[width=430] + + That MicroPeak was in the same barometric chamber as the one which + generated the above results and the resulting flight data looks + correct: + + .MicroPeak in Sunlight with Foam + image::micropeak-flight-foam.png[width=430] + [appendix] == Handling Precautions @@ -306,10 +364,16 @@ 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. + "breathe", both by not being covered by solid 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. + + One good solution is to use a small rectangle of Poron + 50-30031-12X12P or equivalent to cover the sensor. This is an + open cell foam in 1/32" thickness with an adhesive backing. It + seems to do a good job of blocking sun while still allowing + airflow to and from the sensor internals. As with all other rocketry electronics, Altus Metrum altimeters must be protected from exposure to corrosive motor