Make a Stevenson Screen with Arduino Part 2 – Display Numerical Values on an Electronic Scoreboard (7 segment LED)

<p>To understand the big picture of the Stevenson screen we will be making, let’s take a look at its specifications. We should be “thinking before making.” But with Arduino, you get to enjoy building upon and expanding things while trying out various parts hands-on. I recommend you to”create something with a goal in mind” only after you’re already familiar with a few sensors.<br /> Now, let’s consider the specs of the Stevenson screen.</p> <h2>Today’s Electronics Recipe</h2> <p>Estimated time to complete: 60 minutes<br /> Parts needed:</p> <ul> <li>Arduino base (Arduino Uno R3) <a href="http://ift.tt/19qjkOK" target="_blank">http://ift.tt/19qjkOK</a></li> <li>Breadboard <a href="http://ift.tt/1z7Tzip" target="_blank">http://ift.tt/1z7Tzip</a></li> <li> 7-segment LED (High brightness red 7-segment LED display (cathode common) <a href="http://ift.tt/1r810V0" target="_blank">http://ift.tt/1r810V0</a></li> <li>Resistor (220Ω)</li> </ul> <h2>Specs of the Stevenson Screen</h2> <p>Let’s look up the definition of “Stevenson screen” on Wikipedia.</p> <p><a href="http://ift.tt/1qAdcgr" target="_blank">Stevenson Screen</a><br /> <em>“A Stevenson screen or instrument shelter is an enclosure to shield meteorological instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely around them. Its purpose is to provide a standardized environment in which to measure temperature, humidity, dew-point and atmospheric pressure.” </em></p> <p>Under this definition, it seems like it’s okay to call our project an Stevenson screen as long as it has a thermometer (temperature) and a hygrometer (humidity). We were able to work with the temperature sensor last time. In terms of basic features, once we will be able to operate the hygrometer, we will be able to proudly say, “We made an Stevenson screen!”</p> <p>Now, let’s think a little deeper about the final design details.</p> <p>What sort of Stevenson screen would be fun to make? Will you enjoy it, and will others be happy with it?<br /> Are there any skills or tools that you currently lack to build this Stevenson screen? By keeping such questions in mind while thinking about the design, you will be able to picture the final design in your head.</p> <p>When creating something, your work will be polished by repeating this process.</p> <p>First, let’s think about usability when thinking about the Stevenson screen we will be making.</p> <p><img alt="Arduino plan 2" class="alignnone size-full wp-image-411" height="380" src="http://ift.tt/1r810V2" width="700" /></p> <p>In the final design, we want the following:</p> <ul> <li>The measured values should always be accessible from the PC over the Internet</li> <li>It should operate without being connected to a PC to easily be moved</li> <li>The number of cables connected to the Stevenson screen should be minimized (none, if possible)</li> <li>The measured values should not only be accessible on the PC, but also on the Stevenson screen itself</li> <li>It should be compact (size-wise)</li> </ul> <p>That’s basically what I want for an Stevenson screen that’s easy to use. Now, let’s think about the necessary parts to build it.</p> <ol> <li>The measured values should always be accessible from the PC over the Internet<br /> → Connect the Stevenson screen to a LAN cable using components such as the Ethernet module</li> <li>It should operate without being connected to a PC to easily be moved<br /> → Change the power supply method of Arduino from USB to a DC adapter or batteries</li> <li>The number of cables connected to the Stevenson screen should be minimized (none, if possible)<br /> → Go cable-free by not using a DC adapter (solution mentioned above), and by using Wi-Fi instead of a LAN cable</li> <li>The measured values should not only be accessible on the PC, but also on the Stevenson screen itself<br /> → Add a display to show the measurements on the case itself</li> <li>It should be compact<br /> → We could solder parts onto the base instead of using a breadboard and/or use a smaller Arduino</li> </ol> <p>These are some solutions.<br /> We got familiar with some of these over the course of this series, but not with all of them. So, let’s have a look at each of them.</p> <p>We did (1) last time. We haven’t done (2) or (3), so we will need to learn how to do them. (4) “Want to view graphs of the data on the PC” is not really an Arduino topic, but rather about displaying data in a browser, so it might require some skills like HTML.<br /> Once you’ve settled on what to build, by adding features one by one, you can develop a detailed plan on how to progress towards completion.<br /> Today, we will learn about the 7-segment LED, to solve (4) “The measured values should not only be accessible on the PC, but also on the Stevenson screen itself.”</p> <h2>What Is a 7-Segment LED?</h2> <p>There are several methods for displaying measurements from analog input on the Arduino. Let’s look in detail at the 7-segment LED, which we touched on briefly last time.</p> <p><img alt="2014-08-29-05.10.12-e1409570497886" class="alignnone wp-image-392 size-full" height="394" src="http://ift.tt/1qAdcgt" width="700" /></p> <p>7-segment LED</p> <p><img alt="DSC_0029-e1410917121722" class="alignnone wp-image-393 size-full" height="394" src="http://ift.tt/1r810V5" width="700" /></p> <p>Back side of the 7-segment LED</p> <p>The 7-segment LED (usually abbreviated as 7-seg LED) is an LED made to display numerical values. There are 7 LEDs to represent a digit and 1 LED to represent a dot, totaling 8 LEDs. We will proceed by using a single-digit version, but there are other versions that support 2 or 4 digits. Perhaps, you’ve already seen the 7-seg LED on vending machines? (But recently, more and more vending machines are using touch screens…)<br /> LEDs have an easy-to-understand display, with durable parts, making them a good fit for reliable use, even in a tough environment.</p> <h2>The 7-Seg LED Composition</h2> <p>There are two types of 7-seg LEDs: “common anode” and “common cathode.” The difference is whether the common is anode (positive) or cathode (negative/ground). Since LEDs are directional, if you wire the anode and cathode in reverse directions, nothing will be displayed.</p> <p>We will use the “common cathode” type of 7-seg LED.</p> <p><img alt="7segLayer 2" class="alignnone wp-image-413 size-full" height="700" src="http://ift.tt/1qAdaVI" width="700" /></p> <p>The 7-segment LED composition</p> <h2>Displaying the Digits From 0 to 9</h2> <p>You can see from the above diagram that the part consists of the LEDs a-g and the dot DP. By turning these LEDs on and off, we can represent digits. We sketch the ways to display the digits from 0 to 9.<br /> In the below chart, “1” means to run current through it, and “0” means to not run current through it. We will use this chart in our program later.</p> <p><img alt="7segMap" class="alignnone wp-image-394 size-full" height="400" src="http://ift.tt/1r812MH" width="700" /></p> <p>On-off (1/0) chart for the digits from 0 through 9 on a 7-segment LED</p> <p>For example, to display “1”, we should run a current through b and c as shown below.</p> <p><img alt="1" class="alignnone wp-image-395 size-full" height="324" src="http://ift.tt/1qAdaVK" width="130" /></p> <p>As you can tell by its name, a 7-seg LED is an LED, so we have to insert a resistor in the circuit. The circuit, when used with an Arduino, is as above.</p> <p><img alt="n_01" class="alignnone wp-image-396 size-full" height="569" src="http://ift.tt/1r812MJ" width="401" /></p> <div> <div id="highlighter_139133" class="syntaxhighlighter cpp"> <table border="0" cellspacing="0" cellpadding="0"> <caption>Code-Example</caption> <tbody> <tr> <td class="gutter"> <div class="line number1 index0 alt2">1</div> <div class="line number2 index1 alt1">2</div> <div class="line number3 index2 alt2">3</div> <div class="line number4 index3 alt1">4</div> <div class="line number5 index4 alt2">5</div> <div class="line number6 index5 alt1">6</div> <div class="line number7 index6 alt2">7</div> <div class="line number8 index7 alt1">8</div> <div class="line number9 index8 alt2">9</div> <div class="line number10 index9 alt1">10</div> <div class="line number11 index10 alt2">11</div> <div class="line number12 index11 alt1">12</div> <div class="line number13 index12 alt2">13</div> <div class="line number14 index13 alt1">14</div> <div class="line number15 index14 alt2">15</div> </td> <td class="code"> <div class="container"> <div class="line number1 index0 alt2"><code class="cpp comments">//</code></div> <div class="line number2 index1 alt1"><code class="cpp comments">// A program to <a href="http://ift.tt/1SDfTER" itemprop="url" target="_bank" title="Create your own musical light show with Raspberry Pi"><strong>light</strong></a> up "1" in a 7-segment LED</code></div> <div class="line number3 index2 alt2"><code class="cpp comments">//</code></div> <div class="line number4 index3 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">setup(){</code></div> <div class="line number5 index4 alt2"><code class="cpp plain">pinMode(2,OUTPUT);</code></div> <div class="line number6 index5 alt1"><code class="cpp plain">pinMode(3,OUTPUT);</code></div> <div class="line number7 index6 alt2"><code class="cpp plain">}</code></div> <div class="line number8 index7 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">loop(){</code></div> <div class="line number9 index8 alt2"><code class="cpp plain">digitalWrite(2,HIGH);</code></div> <div class="line number10 index9 alt1"><code class="cpp plain">digitalWrite(3,HIGH);</code></div> <div class="line number11 index10 alt2"><code class="cpp plain">delay(200);</code></div> <div class="line number12 index11 alt1"><code class="cpp plain">digitalWrite(2,LOW);</code></div> <div class="line number13 index12 alt2"><code class="cpp plain">digitalWrite(3,LOW);</code></div> <div class="line number14 index13 alt1"><code class="cpp plain">delay(200);</code></div> <div class="line number15 index14 alt2"><code class="cpp plain">}</code></div> </div> </td> </tr> </tbody> </table> </div> </div> <p>Do you have an idea of how it works?<br /> We’ll now create the circuit to display the digits from 0 to 9 on the 7-seg LED. There’s going to be a fair amount of wiring.</p> <p><img alt="7segmentLEDSingle01" class="alignnone wp-image-397 size-full" height="585" src="http://ift.tt/1qAdcgv" width="419" /></p> <p>Circuit displaying the digits from 0 to 9</p> <p>By controlling the 28-pin digital outs, we can turn on the specified LEDs.<br /> In reality, it’s a little difficult to use with the Arduino, so we’ll consider a program that counts up from 0 to 9.</p> <div> <div id="highlighter_559575" class="syntaxhighlighter cpp"> <table border="0" cellspacing="0" cellpadding="0"> <caption>Code-Example</caption> <tbody> <tr> <td class="gutter"> <div class="line number1 index0 alt2">1</div> <div class="line number2 index1 alt1">2</div> <div class="line number3 index2 alt2">3</div> <div class="line number4 index3 alt1">4</div> <div class="line number5 index4 alt2">5</div> <div class="line number6 index5 alt1">6</div> <div class="line number7 index6 alt2">7</div> <div class="line number8 index7 alt1">8</div> <div class="line number9 index8 alt2">9</div> <div class="line number10 index9 alt1">10</div> <div class="line number11 index10 alt2">11</div> <div class="line number12 index11 alt1">12</div> <div class="line number13 index12 alt2">13</div> <div class="line number14 index13 alt1">14</div> <div class="line number15 index14 alt2">15</div> <div class="line number16 index15 alt1">16</div> <div class="line number17 index16 alt2">17</div> <div class="line number18 index17 alt1">18</div> <div class="line number19 index18 alt2">19</div> <div class="line number20 index19 alt1">20</div> <div class="line number21 index20 alt2">21</div> <div class="line number22 index21 alt1">22</div> <div class="line number23 index22 alt2">23</div> <div class="line number24 index23 alt1">24</div> <div class="line number25 index24 alt2">25</div> <div class="line number26 index25 alt1">26</div> <div class="line number27 index26 alt2">27</div> <div class="line number28 index27 alt1">28</div> </td> <td class="code"> <div class="container"> <div class="line number1 index0 alt2"><code class="cpp keyword bold">void</code> <code class="cpp plain">loop(){</code></div> <div class="line number2 index1 alt1"><code class="cpp comments">//0</code></div> <div class="line number3 index2 alt2"><code class="cpp plain">digitalWrite(2,HIGH);</code></div> <div class="line number4 index3 alt1"><code class="cpp plain">digitalWrite(3,HIGH);</code></div> <div class="line number5 index4 alt2"><code class="cpp plain">digitalWrite(4,HIGH);</code></div> <div class="line number6 index5 alt1"><code class="cpp plain">digitalWrite(5,HIGH);</code></div> <div class="line number7 index6 alt2"><code class="cpp plain">digitalWrite(6,HIGH);</code></div> <div class="line number8 index7 alt1"><code class="cpp plain">digitalWrite(7,HIGH);</code></div> <div class="line number9 index8 alt2"><code class="cpp comments">//Turn everything off for now</code></div> <div class="line number10 index9 alt1"><code class="cpp plain">digitalWrite(2,LOW);</code></div> <div class="line number11 index10 alt2"><code class="cpp plain">digitalWrite(3,LOW);</code></div> <div class="line number12 index11 alt1"><code class="cpp plain">digitalWrite(4,LOW);</code></div> <div class="line number13 index12 alt2"><code class="cpp plain">digitalWrite(5,LOW);</code></div> <div class="line number14 index13 alt1"><code class="cpp plain">digitalWrite(6,LOW);</code></div> <div class="line number15 index14 alt2"><code class="cpp plain">digitalWrite(7,LOW);</code></div> <div class="line number16 index15 alt1"><code class="cpp plain">digitalWrite(8,LOW);</code></div> <div class="line number17 index16 alt2"><code class="cpp comments">//1</code></div> <div class="line number18 index17 alt1"><code class="cpp plain">digitalWrite(3,HIGH);</code></div> <div class="line number19 index18 alt2"><code class="cpp plain">digitalWrite(4,HIGH);</code></div> <div class="line number20 index19 alt1"><code class="cpp comments">//Turn everything off for now</code></div> <div class="line number21 index20 alt2"><code class="cpp plain">digitalWrite(2,LOW);</code></div> <div class="line number22 index21 alt1"><code class="cpp plain">digitalWrite(3,LOW);</code></div> <div class="line number23 index22 alt2"><code class="cpp plain">digitalWrite(4,LOW);</code></div> <div class="line number24 index23 alt1"><code class="cpp plain">digitalWrite(5,LOW);</code></div> <div class="line number25 index24 alt2"><code class="cpp plain">digitalWrite(6,LOW);</code></div> <div class="line number26 index25 alt1"><code class="cpp plain">digitalWrite(7,LOW);</code></div> <div class="line number27 index26 alt2"><code class="cpp plain">digitalWrite(8,LOW);</code></div> <div class="line number28 index27 alt1"><code class="cpp plain">….</code></div> </div> </td> </tr> </tbody> </table> </div> </div> <p>Just counting from 0 to 9 takes a long loop in the program.<br /> We would like to shorten the code. It would be nice if we had a function that takes a number as an input and displays it on the 7-seg LED.</p> <p><strong>NumPrint(number); //Display the specified number on the 7-segment LED</strong></p> <p>By using the previous chart, we will be able to write a useful function.</p> <div> <div id="highlighter_201752" class="syntaxhighlighter cpp"> <table border="0" cellspacing="0" cellpadding="0"> <caption>Code-Example</caption> <tbody> <tr> <td class="gutter"> <div class="line number1 index0 alt2">1</div> <div class="line number2 index1 alt1">2</div> <div class="line number3 index2 alt2">3</div> <div class="line number4 index3 alt1">4</div> <div class="line number5 index4 alt2">5</div> <div class="line number6 index5 alt1">6</div> <div class="line number7 index6 alt2">7</div> <div class="line number8 index7 alt1">8</div> <div class="line number9 index8 alt2">9</div> <div class="line number10 index9 alt1">10</div> <div class="line number11 index10 alt2">11</div> <div class="line number12 index11 alt1">12</div> <div class="line number13 index12 alt2">13</div> <div class="line number14 index13 alt1">14</div> <div class="line number15 index14 alt2">15</div> <div class="line number16 index15 alt1">16</div> <div class="line number17 index16 alt2">17</div> <div class="line number18 index17 alt1">18</div> <div class="line number19 index18 alt2">19</div> </td> <td class="code"> <div class="container"> <div class="line number1 index0 alt2"><code class="cpp comments">//Define the arrangements for the digits</code></div> <div class="line number2 index1 alt1"><code class="cpp plain">boolean Num_Array[10][7]={</code></div> <div class="line number3 index2 alt2"><code class="cpp plain">{1,1,1,1,1,1,0},</code> <code class="cpp comments">//0</code></div> <div class="line number4 index3 alt1"><code class="cpp plain">{0,1,1,0,0,0,0},</code> <code class="cpp comments">//1</code></div> <div class="line number5 index4 alt2"><code class="cpp plain">{1,1,0,1,1,0,1},</code> <code class="cpp comments">//2</code></div> <div class="line number6 index5 alt1"><code class="cpp plain">{1,1,1,1,0,0,1},</code> <code class="cpp comments">//3</code></div> <div class="line number7 index6 alt2"><code class="cpp plain">{0,1,1,0,0,1,1},</code> <code class="cpp comments">//4</code></div> <div class="line number8 index7 alt1"><code class="cpp plain">{1,0,1,1,0,1,1},</code> <code class="cpp comments">//5</code></div> <div class="line number9 index8 alt2"><code class="cpp plain">{1,0,1,1,1,1,1},</code> <code class="cpp comments">//6</code></div> <div class="line number10 index9 alt1"><code class="cpp plain">{1,1,1,0,0,1,0},</code> <code class="cpp comments">//7</code></div> <div class="line number11 index10 alt2"><code class="cpp plain">{1,1,1,1,1,1,1},</code> <code class="cpp comments">//8</code></div> <div class="line number12 index11 alt1"><code class="cpp plain">{1,1,1,1,0,1,1}</code> <code class="cpp comments">//9</code></div> <div class="line number13 index12 alt2"><code class="cpp plain">};</code></div> <div class="line number14 index13 alt1"><code class="cpp comments">//Define the function for LED output</code></div> <div class="line number15 index14 alt2"><code class="cpp keyword bold">void</code> <code class="cpp plain">NumPrint(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">Number){</code></div> <div class="line number16 index15 alt1"><code class="cpp keyword bold">for</code> <code class="cpp plain">(<code</code> <code class="cpp keyword bold">class</code><code class="cpp plain">=</code><code class="cpp string">"cpp color1 bold"</code><code class="cpp plain">></code><code class="cpp color1 bold">int</code><code class="cpp plain"></code> <code</code> <code class="cpp keyword bold">class</code><code class="cpp plain">=</code><code class="cpp string">"cpp plain"</code><code class="cpp plain">>w=0; w<=7; w++</code>){</code></div> <div class="line number17 index16 alt2"><code class="cpp plain">digitalWrite(w+2,-Num_Array[Number][w]);</code></div> <div class="line number18 index17 alt1"><code class="cpp plain">}</code></div> <div class="line number19 index18 alt2"><code class="cpp plain">}</code></div> </div> </td> </tr> </tbody> </table> </div> </div> <p>The NumPrint function defines all patterns for the digits in Num_Array. Based on this variable, we can easily display the digits on the 7-seg LED by controlling its 7 LEDs.<br /> Below is an example of a program that uses this function to count up from 0 to 9.</p> <p><iframe width="678" height="381" src="https://www.youtube.com/embed/sE0dpWI-DxI?feature=oembed" frameborder="0" allowfullscreen=""></iframe></p> <div> <div id="highlighter_118250" class="syntaxhighlighter cpp"> <table border="0" cellspacing="0" cellpadding="0"> <caption>Code-Example</caption> <tbody> <tr> <td class="gutter"> <div class="line number1 index0 alt2">1</div> <div class="line number2 index1 alt1">2</div> <div class="line number3 index2 alt2">3</div> <div class="line number4 index3 alt1">4</div> <div class="line number5 index4 alt2">5</div> <div class="line number6 index5 alt1">6</div> <div class="line number7 index6 alt2">7</div> <div class="line number8 index7 alt1">8</div> <div class="line number9 index8 alt2">9</div> <div class="line number10 index9 alt1">10</div> <div class="line number11 index10 alt2">11</div> <div class="line number12 index11 alt1">12</div> <div class="line number13 index12 alt2">13</div> <div class="line number14 index13 alt1">14</div> <div class="line number15 index14 alt2">15</div> <div class="line number16 index15 alt1">16</div> <div class="line number17 index16 alt2">17</div> <div class="line number18 index17 alt1">18</div> <div class="line number19 index18 alt2">19</div> <div class="line number20 index19 alt1">20</div> <div class="line number21 index20 alt2">21</div> <div class="line number22 index21 alt1">22</div> <div class="line number23 index22 alt2">23</div> <div class="line number24 index23 alt1">24</div> <div class="line number25 index24 alt2">25</div> <div class="line number26 index25 alt1">26</div> <div class="line number27 index26 alt2">27</div> <div class="line number28 index27 alt1">28</div> <div class="line number29 index28 alt2">29</div> <div class="line number30 index29 alt1">30</div> <div class="line number31 index30 alt2">31</div> <div class="line number32 index31 alt1">32</div> <div class="line number33 index32 alt2">33</div> <div class="line number34 index33 alt1">34</div> <div class="line number35 index34 alt2">35</div> <div class="line number36 index35 alt1">36</div> <div class="line number37 index36 alt2">37</div> <div class="line number38 index37 alt1">38</div> <div class="line number39 index38 alt2">39</div> <div class="line number40 index39 alt1">40</div> <div class="line number41 index40 alt2">41</div> <div class="line number42 index41 alt1">42</div> <div class="line number43 index42 alt2">43</div> <div class="line number44 index43 alt1">44</div> <div class="line number45 index44 alt2">45</div> <div class="line number46 index45 alt1">46</div> <div class="line number47 index46 alt2">47</div> <div class="line number48 index47 alt1">48</div> <div class="line number49 index48 alt2">49</div> <div class="line number50 index49 alt1">50</div> <div class="line number51 index50 alt2">51</div> <div class="line number52 index51 alt1">52</div> <div class="line number53 index52 alt2">53</div> <div class="line number54 index53 alt1">54</div> <div class="line number55 index54 alt2">55</div> <div class="line number56 index55 alt1">56</div> <div class="line number57 index56 alt2">57</div> <div class="line number58 index57 alt1">58</div> <div class="line number59 index58 alt2">59</div> <div class="line number60 index59 alt1">60</div> <div class="line number61 index60 alt2">61</div> <div class="line number62 index61 alt1">62</div> <div class="line number63 index62 alt2">63</div> <div class="line number64 index63 alt1">64</div> <div class="line number65 index64 alt2">65</div> <div class="line number66 index65 alt1">66</div> <div class="line number67 index66 alt2">67</div> <div class="line number68 index67 alt1">68</div> <div class="line number69 index68 alt2">69</div> <div class="line number70 index69 alt1">70</div> <div class="line number71 index70 alt2">71</div> <div class="line number72 index71 alt1">72</div> <div class="line number73 index72 alt2">73</div> <div class="line number74 index73 alt1">74</div> <div class="line number75 index74 alt2">75</div> <div class="line number76 index75 alt1">76</div> <div class="line number77 index76 alt2">77</div> <div class="line number78 index77 alt1">78</div> <div class="line number79 index78 alt2">79</div> <div class="line number80 index79 alt1">80</div> <div class="line number81 index80 alt2">81</div> <div class="line number82 index81 alt1">82</div> <div class="line number83 index82 alt2">83</div> </td> <td class="code"> <div class="container"> <div class="line number1 index0 alt2"><code class="cpp comments">//</code></div> <div class="line number2 index1 alt1"><code class="cpp comments">// Program to <a href="http://ift.tt/1r812ML" itemprop="url" target="_bank" title="Making an LED Light up with Raspberry Pi Before Making It Blink"><strong>light</strong></a> up 0 to 9 on a 7-segment LED</code></div> <div class="line number3 index2 alt2"><code class="cpp comments">//</code></div> <div class="line number4 index3 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">setup(){</code></div> <div class="line number5 index4 alt2"><code class="cpp plain">pinMode(2,OUTPUT);</code></div> <div class="line number6 index5 alt1"><code class="cpp plain">pinMode(3,OUTPUT);</code></div> <div class="line number7 index6 alt2"><code class="cpp plain">pinMode(4,OUTPUT);</code></div> <div class="line number8 index7 alt1"><code class="cpp plain">pinMode(5,OUTPUT);</code></div> <div class="line number9 index8 alt2"><code class="cpp plain">pinMode(6,OUTPUT);</code></div> <div class="line number10 index9 alt1"><code class="cpp plain">pinMode(7,OUTPUT);</code></div> <div class="line number11 index10 alt2"><code class="cpp plain">pinMode(8,OUTPUT);</code></div> <div class="line number12 index11 alt1"><code class="cpp plain">}</code></div> <div class="line number13 index12 alt2"><code class="cpp comments">//Define the LED layout</code></div> <div class="line number14 index13 alt1"><code class="cpp plain">boolean Num_Array[10][7]={</code></div> <div class="line number15 index14 alt2"><code class="cpp plain">{1,1,1,1,1,1,0},</code> <code class="cpp comments">//0</code></div> <div class="line number16 index15 alt1"><code class="cpp plain">{0,1,1,0,0,0,0},</code> <code class="cpp comments">//1</code></div> <div class="line number17 index16 alt2"><code class="cpp plain">{1,1,0,1,1,0,1},</code> <code class="cpp comments">//2</code></div> <div class="line number18 index17 alt1"><code class="cpp plain">{1,1,1,1,0,0,1},</code> <code class="cpp comments">//3</code></div> <div class="line number19 index18 alt2"><code class="cpp plain">{0,1,1,0,0,1,1},</code> <code class="cpp comments">//4</code></div> <div class="line number20 index19 alt1"><code class="cpp plain">{1,0,1,1,0,1,1},</code> <code class="cpp comments">//5</code></div> <div class="line number21 index20 alt2"><code class="cpp plain">{1,0,1,1,1,1,1},</code> <code class="cpp comments">//6</code></div> <div class="line number22 index21 alt1"><code class="cpp plain">{1,1,1,0,0,1,0},</code> <code class="cpp comments">//7</code></div> <div class="line number23 index22 alt2"><code class="cpp plain">{1,1,1,1,1,1,1},</code> <code class="cpp comments">//8</code></div> <div class="line number24 index23 alt1"><code class="cpp plain">{1,1,1,1,0,1,1}</code> <code class="cpp comments">//9</code></div> <div class="line number25 index24 alt2"><code class="cpp plain">};</code></div> <div class="line number26 index25 alt1"><code class="cpp comments">//Define the LED display function</code></div> <div class="line number27 index26 alt2"><code class="cpp keyword bold">void</code> <code class="cpp plain">NumPrint(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">Number){</code></div> <div class="line number28 index27 alt1"><code class="cpp keyword bold">for</code> <code class="cpp plain">(<code</code> <code class="cpp keyword bold">class</code><code class="cpp plain">=</code><code class="cpp string">"cpp color1 bold"</code><code class="cpp plain">></code><code class="cpp color1 bold">int</code><code class="cpp plain"></code> <code</code> <code class="cpp keyword bold">class</code><code class="cpp plain">=</code><code class="cpp string">"cpp plain"</code><code class="cpp plain">>w=0; w<=7; w++</code>){</code></div> <div class="line number29 index28 alt2"><code class="cpp plain">digitalWrite(w+2,-Num_Array[Number][w]);</code></div> <div class="line number30 index29 alt1"><code class="cpp plain">}</code></div> <div class="line number31 index30 alt2"><code class="cpp plain">}</code></div> <div class="line number32 index31 alt1"><code class="cpp comments">//Turn off all LEDs</code></div> <div class="line number33 index32 alt2"><code class="cpp keyword bold">void</code> <code class="cpp plain">off7SegLED(){</code></div> <div class="line number34 index33 alt1"><code class="cpp plain">digitalWrite(2,LOW);</code></div> <div class="line number35 index34 alt2"><code class="cpp plain">digitalWrite(3,LOW);</code></div> <div class="line number36 index35 alt1"><code class="cpp plain">digitalWrite(4,LOW);</code></div> <div class="line number37 index36 alt2"><code class="cpp plain">digitalWrite(5,LOW);</code></div> <div class="line number38 index37 alt1"><code class="cpp plain">digitalWrite(6,LOW);</code></div> <div class="line number39 index38 alt2"><code class="cpp plain">digitalWrite(7,LOW);</code></div> <div class="line number40 index39 alt1"><code class="cpp plain">digitalWrite(8,LOW);</code></div> <div class="line number41 index40 alt2"><code class="cpp plain">}</code></div> <div class="line number42 index41 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">loop(){</code></div> <div class="line number43 index42 alt2"><code class="cpp plain">NumPrint(0);</code></div> <div class="line number44 index43 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number45 index44 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number46 index45 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number47 index46 alt2"><code class="cpp plain">NumPrint(1);</code></div> <div class="line number48 index47 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number49 index48 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number50 index49 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number51 index50 alt2"><code class="cpp plain">NumPrint(2);</code></div> <div class="line number52 index51 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number53 index52 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number54 index53 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number55 index54 alt2"><code class="cpp plain">NumPrint(3);</code></div> <div class="line number56 index55 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number57 index56 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number58 index57 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number59 index58 alt2"><code class="cpp plain">NumPrint(4);</code></div> <div class="line number60 index59 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number61 index60 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number62 index61 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number63 index62 alt2"><code class="cpp plain">NumPrint(5);</code></div> <div class="line number64 index63 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number65 index64 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number66 index65 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number67 index66 alt2"><code class="cpp plain">NumPrint(6);</code></div> <div class="line number68 index67 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number69 index68 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number70 index69 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number71 index70 alt2"><code class="cpp plain">NumPrint(7);</code></div> <div class="line number72 index71 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number73 index72 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number74 index73 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number75 index74 alt2"><code class="cpp plain">NumPrint(8);</code></div> <div class="line number76 index75 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number77 index76 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number78 index77 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number79 index78 alt2"><code class="cpp plain">NumPrint(9);</code></div> <div class="line number80 index79 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number81 index80 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number82 index81 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number83 index82 alt2"><code class="cpp plain">}</code></div> </div> </td> </tr> </tbody> </table> </div> </div> <p>The digits lit up from 0 to 9!<br /> But even this program seems to drag on with a long series of similar commands. Since the commands inside loop() are simply incrementing from 0 to 9 and back, we can combine them in a statement. Furthermore, we can also combine the initialization in setup() with the off7SegLED() that turns off all of the LEDs.</p> <div> <div id="highlighter_887745" class="syntaxhighlighter cpp"> <table border="0" cellspacing="0" cellpadding="0"> <caption>Code-Example</caption> <tbody> <tr> <td class="gutter"> <div class="line number1 index0 alt2">1</div> <div class="line number2 index1 alt1">2</div> <div class="line number3 index2 alt2">3</div> <div class="line number4 index3 alt1">4</div> <div class="line number5 index4 alt2">5</div> <div class="line number6 index5 alt1">6</div> <div class="line number7 index6 alt2">7</div> <div class="line number8 index7 alt1">8</div> <div class="line number9 index8 alt2">9</div> <div class="line number10 index9 alt1">10</div> <div class="line number11 index10 alt2">11</div> <div class="line number12 index11 alt1">12</div> <div class="line number13 index12 alt2">13</div> <div class="line number14 index13 alt1">14</div> <div class="line number15 index14 alt2">15</div> <div class="line number16 index15 alt1">16</div> <div class="line number17 index16 alt2">17</div> <div class="line number18 index17 alt1">18</div> <div class="line number19 index18 alt2">19</div> <div class="line number20 index19 alt1">20</div> <div class="line number21 index20 alt2">21</div> <div class="line number22 index21 alt1">22</div> <div class="line number23 index22 alt2">23</div> <div class="line number24 index23 alt1">24</div> <div class="line number25 index24 alt2">25</div> <div class="line number26 index25 alt1">26</div> <div class="line number27 index26 alt2">27</div> <div class="line number28 index27 alt1">28</div> <div class="line number29 index28 alt2">29</div> <div class="line number30 index29 alt1">30</div> <div class="line number31 index30 alt2">31</div> <div class="line number32 index31 alt1">32</div> <div class="line number33 index32 alt2">33</div> <div class="line number34 index33 alt1">34</div> <div class="line number35 index34 alt2">35</div> <div class="line number36 index35 alt1">36</div> <div class="line number37 index36 alt2">37</div> <div class="line number38 index37 alt1">38</div> <div class="line number39 index38 alt2">39</div> <div class="line number40 index39 alt1">40</div> <div class="line number41 index40 alt2">41</div> <div class="line number42 index41 alt1">42</div> <div class="line number43 index42 alt2">43</div> <div class="line number44 index43 alt1">44</div> </td> <td class="code"> <div class="container"> <div class="line number1 index0 alt2"><code class="cpp comments">//</code></div> <div class="line number2 index1 alt1"><code class="cpp comments">// Program to light up from 0 to 9 on a 7-segment LED</code></div> <div class="line number3 index2 alt2"><code class="cpp comments">//</code></div> <div class="line number4 index3 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">setup(){</code></div> <div class="line number5 index4 alt2"><code class="cpp comments">// Initialize the use of pins 2-8 using a for statement</code></div> <div class="line number6 index5 alt1"><code class="cpp keyword bold">for</code><code class="cpp plain">(<code</code> <code class="cpp keyword bold">class</code><code class="cpp plain">=</code><code class="cpp string">"cpp color1 bold"</code><code class="cpp plain">></code><code class="cpp color1 bold">int</code><code class="cpp plain"></code> <code</code> <code class="cpp keyword bold">class</code><code class="cpp plain">=</code><code class="cpp string">"cpp plain"</code><code class="cpp plain">>i=2;i<9;i++</code>){</code></div> <div class="line number7 index6 alt2"><code class="cpp plain">pinMode(i,OUTPUT);</code></div> <div class="line number8 index7 alt1"><code class="cpp plain">}</code></div> <div class="line number9 index8 alt2"><code class="cpp plain">}</code></div> <div class="line number10 index9 alt1"><code class="cpp comments">// Define the LED layout</code></div> <div class="line number11 index10 alt2"><code class="cpp plain">boolean Num_Array[10][7]={</code></div> <div class="line number12 index11 alt1"><code class="cpp plain">{1,1,1,1,1,1,0},</code> <code class="cpp comments">//0</code></div> <div class="line number13 index12 alt2"><code class="cpp plain">{0,1,1,0,0,0,0},</code> <code class="cpp comments">//1</code></div> <div class="line number14 index13 alt1"><code class="cpp plain">{1,1,0,1,1,0,1},</code> <code class="cpp comments">//2</code></div> <div class="line number15 index14 alt2"><code class="cpp plain">{1,1,1,1,0,0,1},</code> <code class="cpp comments">//3</code></div> <div class="line number16 index15 alt1"><code class="cpp plain">{0,1,1,0,0,1,1},</code> <code class="cpp comments">//4</code></div> <div class="line number17 index16 alt2"><code class="cpp plain">{1,0,1,1,0,1,1},</code> <code class="cpp comments">//5</code></div> <div class="line number18 index17 alt1"><code class="cpp plain">{1,0,1,1,1,1,1},</code> <code class="cpp comments">//6</code></div> <div class="line number19 index18 alt2"><code class="cpp plain">{1,1,1,0,0,1,0},</code> <code class="cpp comments">//7</code></div> <div class="line number20 index19 alt1"><code class="cpp plain">{1,1,1,1,1,1,1},</code> <code class="cpp comments">//8</code></div> <div class="line number21 index20 alt2"><code class="cpp plain">{1,1,1,1,0,1,1}</code> <code class="cpp comments">//9</code></div> <div class="line number22 index21 alt1"><code class="cpp plain">};</code></div> <div class="line number23 index22 alt2"><code class="cpp comments">// Define the LED display function</code></div> <div class="line number24 index23 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">NumPrint(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">Number){</code></div> <div class="line number25 index24 alt2"><code class="cpp keyword bold">for</code> <code class="cpp plain">(<code</code> <code class="cpp keyword bold">class</code><code class="cpp plain">=</code><code class="cpp string">"cpp color1 bold"</code><code class="cpp plain">></code><code class="cpp color1 bold">int</code><code class="cpp plain"></code> <code</code> <code class="cpp keyword bold">class</code><code class="cpp plain">=</code><code class="cpp string">"cpp plain"</code><code class="cpp plain">>w=0; w<=7; w++</code>){</code></div> <div class="line number26 index25 alt1"><code class="cpp plain">digitalWrite(w+2,-Num_Array[Number][w]);</code></div> <div class="line number27 index26 alt2"><code class="cpp plain">}</code></div> <div class="line number28 index27 alt1"><code class="cpp plain">}</code></div> <div class="line number29 index28 alt2"><code class="cpp comments">// Turn off all LEDs</code></div> <div class="line number30 index29 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">off7SegLED(){</code></div> <div class="line number31 index30 alt2"><code class="cpp comments">// Set pins 2-8 to LOW with a for statement</code></div> <div class="line number32 index31 alt1"><code class="cpp keyword bold">for</code><code class="cpp plain">(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">i=2;i<9;i++){</code></div> <div class="line number33 index32 alt2"><code class="cpp plain">digitalWrite(i,LOW);</code></div> <div class="line number34 index33 alt1"><code class="cpp plain">}</code></div> <div class="line number35 index34 alt2"><code class="cpp plain">}</code></div> <div class="line number36 index35 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">loop(){</code></div> <div class="line number37 index36 alt2"><code class="cpp comments">// Count from 0 to 9 with a for loop</code></div> <div class="line number38 index37 alt1"><code class="cpp keyword bold">for</code><code class="cpp plain">(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">i=0;i<10;i++){</code></div> <div class="line number39 index38 alt2"><code class="cpp plain">NumPrint(i);</code></div> <div class="line number40 index39 alt1"><code class="cpp plain">delay(2000);</code></div> <div class="line number41 index40 alt2"><code class="cpp plain">off7SegLED();</code></div> <div class="line number42 index41 alt1"><code class="cpp plain">delay(50);</code></div> <div class="line number43 index42 alt2"><code class="cpp plain">}</code></div> <div class="line number44 index43 alt1"><code class="cpp plain">}</code></div> </div> </td> </tr> </tbody> </table> </div> </div> <p>Now, our program is ready!</p> <p>If you want to speed up the counter, with a long program you have to change the delay value in multiple sections. By using a “for” statement, you only need to change it in one place. I recommend you to develop this habit as programming this way will be important as we go on.</p> <h2>Display Two Digits</h2> <p>Now that we know how to display a single digit, let’s try to display two digits. Since, we used pins 2-8 to display the first digit, we can use a circuit with the remainder of the pins (0,1,9,10,11,12,13) to display a second digit.</p> <p>But considering how complex the wiring was for only the first digit one, we can imagine how intricate it would become. So, let’s create a sort of optical illusion, an electronic trick, or use an idea from a predecessor.</p> <p>The human eye perceives a very fast sequence of flashing images as motion. With television and movies, we perceive series of 30 and 24 images per second as moving pictures. By using this mechanism, we can easily display two digits by rapidly switching between the two digits.</p> <p>What about the circuit? By making a relatively simple change to the circuit from the one-digit case, we can also display two digits.</p> <p><img alt="7segmentLEDDouble17" class="alignnone wp-image-398 size-full" height="613" src="http://ift.tt/1qAdaVM" width="481" /></p> <p>Circuit diagram for displaying 2 digits</p> <p>It’s different from the circuit we made to display one digit. As we’re adding a second 7-seg LED, we have to add another resistor. Another difference is the connection point for GND. In the previous example, GND was connected on the Arduino, but now it’s connected to pins 11 and 13. You might wondering if it’s ok. It’s confusing, but let’s consider again the HIGH and LOW of digital output.</p> <p>In the HIGH state, 5V of electricity flows from the Arduino. In the LOW state, it’s 0V.<br /> 0V? Then, it’s as though there is no flow = just like GND.</p> <p>To display 2 digits, we switch between them by turning the pins 11 and 13 on and off in order.</p> <p><iframe width="678" height="381" src="https://www.youtube.com/embed/O0qd768FV1M?feature=oembed" frameborder="0" allowfullscreen=""></iframe></p> <div> <div id="highlighter_352299" class="syntaxhighlighter cpp"> <table border="0" cellspacing="0" cellpadding="0"> <caption>Code-Example</caption> <tbody> <tr> <td class="gutter"> <div class="line number1 index0 alt2">1</div> <div class="line number2 index1 alt1">2</div> <div class="line number3 index2 alt2">3</div> <div class="line number4 index3 alt1">4</div> <div class="line number5 index4 alt2">5</div> <div class="line number6 index5 alt1">6</div> <div class="line number7 index6 alt2">7</div> <div class="line number8 index7 alt1">8</div> <div class="line number9 index8 alt2">9</div> <div class="line number10 index9 alt1">10</div> <div class="line number11 index10 alt2">11</div> <div class="line number12 index11 alt1">12</div> <div class="line number13 index12 alt2">13</div> <div class="line number14 index13 alt1">14</div> <div class="line number15 index14 alt2">15</div> <div class="line number16 index15 alt1">16</div> <div class="line number17 index16 alt2">17</div> <div class="line number18 index17 alt1">18</div> <div class="line number19 index18 alt2">19</div> <div class="line number20 index19 alt1">20</div> <div class="line number21 index20 alt2">21</div> <div class="line number22 index21 alt1">22</div> <div class="line number23 index22 alt2">23</div> <div class="line number24 index23 alt1">24</div> <div class="line number25 index24 alt2">25</div> <div class="line number26 index25 alt1">26</div> <div class="line number27 index26 alt2">27</div> <div class="line number28 index27 alt1">28</div> <div class="line number29 index28 alt2">29</div> <div class="line number30 index29 alt1">30</div> <div class="line number31 index30 alt2">31</div> <div class="line number32 index31 alt1">32</div> <div class="line number33 index32 alt2">33</div> <div class="line number34 index33 alt1">34</div> <div class="line number35 index34 alt2">35</div> <div class="line number36 index35 alt1">36</div> <div class="line number37 index36 alt2">37</div> <div class="line number38 index37 alt1">38</div> <div class="line number39 index38 alt2">39</div> <div class="line number40 index39 alt1">40</div> <div class="line number41 index40 alt2">41</div> <div class="line number42 index41 alt1">42</div> <div class="line number43 index42 alt2">43</div> <div class="line number44 index43 alt1">44</div> <div class="line number45 index44 alt2">45</div> <div class="line number46 index45 alt1">46</div> <div class="line number47 index46 alt2">47</div> <div class="line number48 index47 alt1">48</div> <div class="line number49 index48 alt2">49</div> <div class="line number50 index49 alt1">50</div> <div class="line number51 index50 alt2">51</div> <div class="line number52 index51 alt1">52</div> <div class="line number53 index52 alt2">53</div> <div class="line number54 index53 alt1">54</div> <div class="line number55 index54 alt2">55</div> <div class="line number56 index55 alt1">56</div> <div class="line number57 index56 alt2">57</div> <div class="line number58 index57 alt1">58</div> <div class="line number59 index58 alt2">59</div> <div class="line number60 index59 alt1">60</div> <div class="line number61 index60 alt2">61</div> <div class="line number62 index61 alt1">62</div> <div class="line number63 index62 alt2">63</div> <div class="line number64 index63 alt1">64</div> <div class="line number65 index64 alt2">65</div> <div class="line number66 index65 alt1">66</div> <div class="line number67 index66 alt2">67</div> <div class="line number68 index67 alt1">68</div> <div class="line number69 index68 alt2">69</div> <div class="line number70 index69 alt1">70</div> <div class="line number71 index70 alt2">71</div> </td> <td class="code"> <div class="container"> <div class="line number1 index0 alt2"><code class="cpp comments">//</code></div> <div class="line number2 index1 alt1"><code class="cpp comments">// Program to light up two 7-segment LEDs</code></div> <div class="line number3 index2 alt2"><code class="cpp comments">//</code></div> <div class="line number4 index3 alt1"><code class="cpp color1 bold">int</code> <code class="cpp plain">_cnt = 0;</code> <code class="cpp comments">//</code></div> <div class="line number5 index4 alt2"><code class="cpp color1 bold">int</code> <code class="cpp plain">_number = 0;</code> <code class="cpp comments">//</code></div> <div class="line number6 index5 alt1"><code class="cpp plain">boolean _flg =</code> <code class="cpp keyword bold">false</code><code class="cpp plain">;</code></div> <div class="line number7 index6 alt2"><code class="cpp keyword bold">void</code> <code class="cpp plain">setup(){</code></div> <div class="line number8 index7 alt1"><code class="cpp plain">Serial.begin(9600);</code></div> <div class="line number9 index8 alt2"><code class="cpp comments">// Initialize digital output for pins 2-8</code></div> <div class="line number10 index9 alt1"><code class="cpp keyword bold">for</code> <code class="cpp plain">(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">i=2; i<=8; i++){</code></div> <div class="line number11 index10 alt2"><code class="cpp plain">pinMode(i,OUTPUT);</code></div> <div class="line number12 index11 alt1"><code class="cpp plain">}</code></div> <div class="line number13 index12 alt2"><code class="cpp plain">pinMode(13,OUTPUT);</code></div> <div class="line number14 index13 alt1"><code class="cpp plain">pinMode(11,OUTPUT);</code></div> <div class="line number15 index14 alt2"><code class="cpp plain">}</code></div> <div class="line number16 index15 alt1"><code class="cpp comments">// Define LED layout</code></div> <div class="line number17 index16 alt2"><code class="cpp plain">boolean Num_Array[10][7]={</code></div> <div class="line number18 index17 alt1"><code class="cpp plain">{1,1,1,1,1,1,0},</code> <code class="cpp comments">//0</code></div> <div class="line number19 index18 alt2"><code class="cpp plain">{0,1,1,0,0,0,0},</code> <code class="cpp comments">//1</code></div> <div class="line number20 index19 alt1"><code class="cpp plain">{1,1,0,1,1,0,1},</code> <code class="cpp comments">//2</code></div> <div class="line number21 index20 alt2"><code class="cpp plain">{1,1,1,1,0,0,1},</code> <code class="cpp comments">//3</code></div> <div class="line number22 index21 alt1"><code class="cpp plain">{0,1,1,0,0,1,1},</code> <code class="cpp comments">//4</code></div> <div class="line number23 index22 alt2"><code class="cpp plain">{1,0,1,1,0,1,1},</code> <code class="cpp comments">//5</code></div> <div class="line number24 index23 alt1"><code class="cpp plain">{1,0,1,1,1,1,1},</code> <code class="cpp comments">//6</code></div> <div class="line number25 index24 alt2"><code class="cpp plain">{1,1,1,0,0,1,0},</code> <code class="cpp comments">//7</code></div> <div class="line number26 index25 alt1"><code class="cpp plain">{1,1,1,1,1,1,1},</code> <code class="cpp comments">//8</code></div> <div class="line number27 index26 alt2"><code class="cpp plain">{1,1,1,1,0,1,1}</code> <code class="cpp comments">//9</code></div> <div class="line number28 index27 alt1"><code class="cpp plain">};</code></div> <div class="line number29 index28 alt2"><code class="cpp comments">// Define LED display function</code></div> <div class="line number30 index29 alt1"><code class="cpp keyword bold">void</code> <code class="cpp plain">NumPrint(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">Number){</code></div> <div class="line number31 index30 alt2"><code class="cpp keyword bold">for</code> <code class="cpp plain">(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">w=0; w<=7; w++){</code></div> <div class="line number32 index31 alt1"><code class="cpp plain">digitalWrite(w+2,-Num_Array[Number][w]);</code></div> <div class="line number33 index32 alt2"><code class="cpp plain">}</code></div> <div class="line number34 index33 alt1"><code class="cpp plain">}</code></div> <div class="line number35 index34 alt2"><code class="cpp comments">// Function to parse a two-digit number into digits</code></div> <div class="line number36 index35 alt1"><code class="cpp color1 bold">int</code> <code class="cpp plain">NumParse(</code><code class="cpp color1 bold">int</code> <code class="cpp plain">Number,</code><code class="cpp color1 bold">int</code> <code class="cpp plain">s){</code></div> <div class="line number37 index36 alt2"><code class="cpp keyword bold">if</code><code class="cpp plain">(s == 1){</code></div> <div class="line number38 index37 alt1"><code class="cpp keyword bold">return</code> <code class="cpp plain">Number % 10;</code> <code class="cpp comments">// Remainder after dividing by 10 = first digit</code></div> <div class="line number39 index38 alt2"><code class="cpp plain">}</code></div> <div class="line number40 index39 alt1"><code class="cpp keyword bold">else</code> <code class="cpp keyword bold">if</code><code class="cpp plain">(s == 2){</code></div> <div class="line number41 index40 alt2"><code class="cpp keyword bold">return</code> <code class="cpp plain">Number / 10;</code> <code class="cpp comments">// Get integer part after dividing by 10 = second digit</code></div> <div class="line number42 index41 alt1"><code class="cpp plain">}</code></div> <div class="line number43 index42 alt2"><code class="cpp keyword bold">return</code> <code class="cpp plain">0;</code></div> <div class="line number44 index43 alt1"><code class="cpp plain">}</code></div> <div class="line number45 index44 alt2"><code class="cpp keyword bold">void</code> <code class="cpp plain">loop(){</code></div> <div class="line number46 index45 alt1"><code class="cpp keyword bold">if</code><code class="cpp plain">(_number &amp;gt;= 100){</code></div> <div class="line number47 index46 alt2"><code class="cpp plain">_number = 0;</code></div> <div class="line number48 index47 alt1"><code class="cpp plain">}</code></div> <div class="line number49 index48 alt2"><code class="cpp comments">// Switch between pin 11 and 13 outputs by changing flg function to true / false</code></div> <div class="line number50 index49 alt1"><code class="cpp keyword bold">if</code><code class="cpp plain">(_flg){</code></div> <div class="line number51 index50 alt2"><code class="cpp plain">digitalWrite(11,LOW);</code></div> <div class="line number52 index51 alt1"><code class="cpp plain">digitalWrite(13,HIGH);</code></div> <div class="line number53 index52 alt2"><code class="cpp plain">_flg =</code> <code class="cpp keyword bold">false</code><code class="cpp plain">;</code></div> <div class="line number54 index53 alt1"><code class="cpp plain">NumPrint(NumParse(_number,1));</code> <code class="cpp comments">// Display first digit</code></div> <div class="line number55 index54 alt2"><code class="cpp plain">}</code></div> <div class="line number56 index55 alt1"><code class="cpp keyword bold">else</code><code class="cpp plain">{</code></div> <div class="line number57 index56 alt2"><code class="cpp plain">digitalWrite(11,HIGH);</code></div> <div class="line number58 index57 alt1"><code class="cpp plain">digitalWrite(13,LOW);</code></div> <div class="line number59 index58 alt2"><code class="cpp plain">_flg =</code> <code class="cpp keyword bold">true</code><code class="cpp plain">;</code></div> <div class="line number60 index59 alt1"><code class="cpp plain">NumPrint(NumParse(_number,2));</code> <code class="cpp comments">// Display second digit</code></div> <div class="line number61 index60 alt2"><code class="cpp plain">}</code></div> <div class="line number62 index61 alt1"><code class="cpp comments">//At 100, add an additional number to display (1 count per second at 10 delay ×100)</code></div> <div class="line number63 index62 alt2"><code class="cpp keyword bold">if</code><code class="cpp plain">(_cnt >= 100){</code></div> <div class="line number64 index63 alt1"><code class="cpp plain">_number++;</code></div> <div class="line number65 index64 alt2"><code class="cpp plain">_cnt = 0;</code></div> <div class="line number66 index65 alt1"><code class="cpp plain">Serial.print(</code><code class="cpp string">"NUMBER:"</code><code class="cpp plain">);</code></div> <div class="line number67 index66 alt2"><code class="cpp plain">Serial.println(_number);</code></div> <div class="line number68 index67 alt1"><code class="cpp plain">}</code></div> <div class="line number69 index68 alt2"><code class="cpp plain">_cnt++;</code></div> <div class="line number70 index69 alt1"><code class="cpp plain">delay(10);</code></div> <div class="line number71 index70 alt2"><code class="cpp plain">}</code></div> </div> </td> </tr> </tbody> </table> </div> </div> <p>Now, we can display two digits!</p> <p>There are some new functions in the program, but simple operations are used for each part.<br /> There are other ways to compute the individual digits in a 2-digit number than the one we implemented, so please read up on them if you’re interested.</p> <p>Reviewing the specifications that we defined at the beginning of this article, we have 2-3 things to learn including using the humidity sensor, and once we build the external case (5), it looks like our Stevenson screen will be complete.</p> <ol> <li>The measured values should always be accessible from the PC over the Internet</li> <li>It should operate without being connected to a PC to easily be moved</li> <li>The number of cables connected to the Stevenson screen should be minimized (none, if possible)</li> <li><del>The measured values should not only be accessible on the PC, but also on the Stevenson screen itself</del></li> <li>It should be compact</li> </ol> <p>Next time, we will shift from having the Arduino connected to our PC to using batteries or a DC adapter as well as learn how to use the humidity sensor. 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Make a Stevenson Screen with Arduino Part 2 – Display Numerical Values on an Electronic Scoreboard (7 segment LED)

To understand the big picture of the Stevenson screen we will be making, let’s take a look at its specifications. We should be “thinking bef...

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