doc: Describe what sunlight does to MicroPeak and how to protect it

[fw/altos] / doc / micropeak.txt

diff --git a/doc/micropeak.txt b/doc/micropeak.txt
index d5036a00674708648e459d98a5540972e4c3195d..f1feeec41423a557948c19d4e9c14c9bf451bb82 100644 (file)
--- a/doc/micropeak.txt
+++ b/doc/micropeak.txt
@@ -1,6 +1,18 @@
 = MicroPeak Owner's Manual
 = MicroPeak Owner's Manual

+Keith Packard <keithp@keithp.com>; Bdale Garbee <bdale@gag.com>
+:revnumber: v1.9
+:revdate: 8 Oct 2018
+:copyright: Bdale Garbee and Keith Packard 2018
+:stylesheet: am.css
+:linkcss:
+:toc:

 :doctype: book
 :numbered:
 :doctype: book
 :numbered:

+:pdf-stylesdir: .
+:pdf-style: altusmetrum
+:pdf-fontsdir: fonts
+
+       include::header.adoc[]

 
 [dedication]
 == Acknowledgements
 
 [dedication]
 == Acknowledgements


@@ -32,7 +44,7 @@
          positive (+) terminal facing away from the circuit board.
 
                .MicroPeak and Battery
          positive (+) terminal facing away from the circuit board.
 
                .MicroPeak and Battery

-               image::micropeak-back.jpg[width="4.5in"]
+               image::micropeak-back.jpg[width=430]

 
        Install MicroPeak in your rocket::
 
 
        Install MicroPeak in your rocket::
 


@@ -87,7 +99,7 @@
 == The MicroPeak USB adapter
 
        .MicroPeak USB Adapter
 == The MicroPeak USB adapter
 
        .MicroPeak USB Adapter

-       image::MicroPeakUSB-2.0.jpg[width="4.5in",align="center"]
+       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
 
        MicroPeak stores barometric pressure information for the first
        48 seconds of the flight in on-board non-volatile memory. The


@@ -112,25 +124,25 @@
 
                * Start the MicroPeak application.
 
 
                * Start the MicroPeak application.
 

-                 image::micropeak-nofont.svg[width="0.5in",align="center"]
+                 image::micropeak-nofont.svg[width=50,align="center"]

 
                * Click on the Download button at the top of the
                   window.
 
                  .MicroPeak Application
 
                * Click on the Download button at the top of the
                   window.
 
                  .MicroPeak Application

-                 image::micropeak-app.png[width="4.5in",align="center"]
+                 image::micropeak-app.png[width=430,align="center"]

 
                * Select from the listed devices. There will probably
                  be only one.
 
                  .MicroPeak Device Dialog
 
                * Select from the listed devices. There will probably
                  be only one.
 
                  .MicroPeak Device Dialog

-                 image::micropeak-device-dialog.png[width="2.3in",align="center"]
+                 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
 
                * The application will now wait until it receives
                  valid data from the MicroPeak USB adapter.
 
                  .MicroPeak Download Dialog

-                 image::micropeak-download.png[width="2in",align="center"]
+                 image::micropeak-download.png[width=200,align="center"]

 
                * The MicroPeak USB adapter has a small
                  phototransistor under the hole in the center of the
 
                * The MicroPeak USB adapter has a small
                  phototransistor under the hole in the center of the


@@ -142,7 +154,7 @@
                  MicroPeak board itself.
 
                  .MicroPeak Downloading
                  MicroPeak board itself.
 
                  .MicroPeak Downloading

-                 image::MicroPeakUSB-2.0-inuse.jpg[width="4.5in",align="center"]
+                 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
 
                * After the maximum flight height is reported,
                  MicroPeak will pause for a few seconds, blink the


@@ -154,7 +166,7 @@
                  MicroPeak board and try again.
 
                  .MicroPeak Save Dialog
                  MicroPeak board and try again.
 
                  .MicroPeak Save Dialog

-                 image::micropeak-save-dialog.png[width="2.3in",align="center"]
+                 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
 
                * Once the data are saved, a graph will be displayed
                  with height, speed and acceleration values computed


@@ -194,7 +206,7 @@
                ==== MicroPeak Graphs
 
                        .MicroPeak Graph
                ==== MicroPeak Graphs
 
                        .MicroPeak Graph

-                       image::micropeak-graph.png[width="4.5in",align="center"]
+                       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
 
                        Under the Graph tab, the height, speed and acceleration values
                        are displayed together. You can zoom in on the graph by


@@ -205,7 +217,7 @@
                ==== MicroPeak Flight Statistics
 
                        .MicroPeak Flight Statistics
                ==== MicroPeak Flight Statistics
 
                        .MicroPeak Flight Statistics

-                       image::micropeak-statistics.png[width="4.5in",align="center"]
+                       image::micropeak-statistics.png[width=430,align="center"]

 
                        The Statistics tab presents overall data from
                        the flight. Note that the Maximum height value
 
                        The Statistics tab presents overall data from
                        the flight. Note that the Maximum height value


@@ -220,7 +232,7 @@
                ==== Raw Flight Data
 
                        .MicroPeak Raw Flight Data
                ==== Raw Flight Data
 
                        .MicroPeak Raw Flight Data

-                       image::micropeak-raw-data.png[width="4.5in",align="center"]
+                       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.
 
                        A table consisting of the both the raw barometric pressure
                        data and values computed from that for each recorded time.


@@ -228,7 +240,7 @@
                ==== Configuring the Graph
 
                        .MicroPeak Graph Configuration
                ==== Configuring the Graph
 
                        .MicroPeak Graph Configuration

-                       image::micropeak-graph-configure.png[width="4.5in",align="center"]
+                       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
 
                        This selects which graph elements to show, and lets you
                        switch between metric and imperial units


@@ -236,7 +248,7 @@
        === Setting MicroPeak Preferences
 
                        .MicroPeak Preferences
        === Setting MicroPeak Preferences
 
                        .MicroPeak Preferences

-                       image::micropeak-preferences.png[width="1.8in",align="center"]
+                       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
 
                        The MicroPeak application has a few user settings which are
                        configured through the Preferences dialog, which can be


@@ -287,6 +299,43 @@
                        these applications, change in one application
                        will affect the other.
 
                        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
 
 [appendix]
 == Handling Precautions
 


@@ -315,10 +364,16 @@
        sensor out of direct sunlight.
 
        The barometric sensor sampling ports must be able to
        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
 
        As with all other rocketry electronics, Altus Metrum
        altimeters must be protected from exposure to corrosive motor