build-doc updated with prototype

build-doc/weather_station.html

@@ -5,7 +5,7 @@
   <meta name="generator" content="pandoc" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes" />
   <meta name="author" content="M.T. Konstapel" />
-  <meta name="dcterms.date" content="2024-01-15" />
+  <meta name="dcterms.date" content="2024-01-22" />
   <title>Weather station</title>
   <link rel="stylesheet" href="./css/mvp.css" />
 <style type="text/css">
@@ -47,6 +47,10 @@
             <li><a href="#theory-of-operation---software"
             id="toc-theory-of-operation---software">Theory of operation
             - Software</a></li>
+            <li><a href="#prototype"
+            id="toc-prototype">Prototype</a></li>
+            <li><a href="#specifications"
+            id="toc-specifications">Specifications</a></li>
             <li><a href="#schematic"
             id="toc-schematic">Schematic</a></li>
             <li><a href="#software-dependencies"
@@ -71,7 +75,7 @@
 <h1 class="title">Weather station</h1>
 <p class="subtitle">with ModBus RTU interface</p>
 <p class="author">M.T. Konstapel</p>
-<p class="date">2024-01-15</p>
+<p class="date">2024-01-22</p>
 <p><a href="./weather_station.pdf"><i>PDF version</i></a></p>
 </header>
 <main>
@@ -89,7 +93,7 @@ people are obsessed with the weather. When I was a child, my grandmother
 was measuring the temperature and rainfall on a daily basis. My
 grandfather had an allotment, so he also was very interested in the
 weather. The first thing my father read in the newspaper was the weather
-report and the last thing he watched in the television was… the weather
+report and the last thing he watched on the television was… the weather
 report. And every hour he listed to the weather report on the radio. If
 he talked to someone he always started the conversation by talking about
 the weather. And when I open a new browser window, it automatically
@@ -517,12 +521,14 @@ Software</h1>
 of the micro-controller. Every time its logic level changes an interrupt
 routine is called. This routine increments a counter and checks how many
 time has passed since the previous interrupt call. If the previous call
-was more than 2 seconds ago, the wind speed is (almost) zero. If the
-previous call was just over a second ago the interrupt counter now holds
-the amount of pulses in one second. This value is stored and from that
-value the wind speed can be calculated. If the previous call was under a
-second ago the measurement is still in progress and no further action is
-taken.</p>
+was more than 6 seconds ago, the wind speed is (almost) zero. If the
+previous call was just over 3 second ago the interrupt counter now holds
+the amount of pulses in three seconds. This value is stored and from
+that value the wind speed can be calculated. If the previous call was
+less than 3 seconds ago the measurement is still in progress and no
+further action is taken. A measurment period of three seconds is choosen
+because it is the standard as used by the Dutch meteorological institute
+(KNMI).</p>
 <figure>
 <img src="./images/wind_speed_diagram.svg" title="Wind speed interrupt"
 alt="Wind speed interrupt" />
@@ -765,6 +771,97 @@ by 10 or 100 to get the floating point values.</p>
 </tr>
 </tbody>
 </table>
+<h1 id="prototype">Prototype</h1>
+<p>I wanted to locate the weather station at about 100 meters from the
+house. That meant that interfacing the weather station was not just a
+matter of connecting a wire to it. And 100 meters is a bit much for a
+wifi connection either. As I already had experience with LoRa I opted
+for that. But not LoRaWAN, but LoRa APRS. This is a ham radio network
+that I often use. I even run my own digipeater. So LoRa APRS it is.</p>
+<figure>
+<img src="./images/prototype_block_diagram.svg"
+title="Block diagram of the prototype"
+alt="Block diagram of the prototype" />
+<figcaption aria-hidden="true">Block diagram of the
+prototype</figcaption>
+</figure>
+<p>The weather station’s RS-485 interface is connected to a Raspberry Pi
+Zero 2W running the aprx digipeater software, as well as some specially
+written Python programs to interface the build in LoRa transceiver, the
+GPS module and the weather station itself. Every 10 minutes the
+digipeater will read the weather station’s registers and sends the data
+as PE1RXF telemetry messages over the APRS network to a server, which
+presents the data in a Grafana dashboard. The digipeater can also send
+standardized APRS weather reports over the APRS network. But more about
+this project can be found here: <a
+href="https://www.meezenest.nl/mees-elektronica/RPi_LoRa_shield.html">https://www.meezenest.nl/mees-elektronica/RPi_LoRa_shield.html</a></p>
+<figure>
+<img src="./images/prototype_overview_small.jpg"
+title="The prototype in the garden" alt="The prototype in the garden" />
+<figcaption aria-hidden="true">The prototype in the garden</figcaption>
+</figure>
+<p>As a housing for the prototype, I used an old beehive. These are
+weatherproof and I had one laying around.</p>
+<figure>
+<img src="./images/prototype_sensors_small.jpg"
+title="Closeup of the sensors" alt="Closeup of the sensors" />
+<figcaption aria-hidden="true">Closeup of the sensors</figcaption>
+</figure>
+<figure>
+<img src="./images/prototype_inside_annotations_small.jpg"
+title="Inside the beehive" alt="Inside the beehive" />
+<figcaption aria-hidden="true">Inside the beehive</figcaption>
+</figure>
+<h1 id="specifications">Specifications</h1>
+<h2 id="wind">Wind</h2>
+<ul>
+<li><p>Wind speed is measured by taking 3 second averages from the cup
+anemometer and using these samples to calculate the average over a 10
+minute periode.</p></li>
+<li><p>Wind gust is measured by taking 3 second averages from the cup
+anemometer.</p></li>
+<li><p>Wind vane has 8 main directions and another 8 directions in
+between. But these last do not have the same weight, eg. these positions
+are not as likely to be measured as the main directions. This is due to
+the construction of the wind vane: it has eight reed switches for the
+main directions and if the wind direction happens to sit exactly in
+between two reed switches, both switches are closed giving the extra 8
+sub directions. Not great, but it is what it is…</p></li>
+</ul>
+<h2 id="rain">Rain</h2>
+<pre><code>Resolution: 0.2794 mm/impulse</code></pre>
+<h2 id="humidity-2">Humidity</h2>
+<pre><code>Operating range   :  0 - 100 % RH
+Recommended range : 20 - 80 % RH
+Accuracy          : +/- 3 % RH (0-80 % RH)
+                    +/- 4.5 % (max when &gt; 80 % RH)
+
+Heater to drive of moisture (can be enabled via ModBus)</code></pre>
+<h2 id="pressure">Pressure</h2>
+<pre><code>Operating range : 300 - 1100 hPa
+Accuracy        : +/- 1.0 hPa (0 - 65 °C)
+                  +/- 1.7 hPa (-20 - 0 °C)</code></pre>
+<h2 id="temperature-2">Temperature</h2>
+<pre><code>Main sensor
+-----------
+
+Operating range : -10 - 85 °C (typ)
+                  -40 - 85 °C (max)
+Accuracy        : +/- 0.3 °C (typ)
+                  +/- 0.4 °C (max)
+                  +/- 0.5 °C (max when &lt; -10°C)
+
+Backup sensor
+-------------
+
+Operating range :   0 - 65 °C (typ)
+                  -40 - 85 °C (max)
+Accuracy        : +/- 0.5 °C (25 °C)
+                  +/- 1.0 °C (0 - 65 °C)</code></pre>
+<h2 id="modbus-1">ModBus</h2>
+<pre><code>Physical : RS-485 simplex RTU
+Settings : 9600 bd 8N1
+Address  : 14</code></pre>
 <h1 id="schematic">Schematic</h1>
 <p><a href="./images/weather_station_schematic.pdf"><img
 src="./images/weather_station_schematic.svg" alt="Schematic" /></a></p>
@@ -789,6 +886,8 @@ src="./images/weather_station_schematic.svg" alt="Schematic" /></a></p>
 <p>Libraries are included with the source code of this project</p>
 <h1 id="license">License</h1>
 <p>Copyright (C) 2023, 2024 M.T. Konstapel</p>
+<p><a
+href="https://meezenest.nl/mees/">https://meezenest.nl/mees/</a></p>
 <p>The software is published as open-source software (GPL). The hardware
 is published as open-source hardware (OSH).</p>
 <h2 id="software">Software</h2>
@@ -804,7 +903,7 @@ option) any later version.</p>
 </main>
 <footer>
 <p>&copy;
- 2024-01-15
+ 2024-01-22
  M.T. Konstapel
  <a href="https://meezenest.nl/mees/">https://meezenest.nl/mees/</a>
 </p><p>This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/4.0/">Creative Commons Attribution-ShareAlike 4.0 International License</a>.