Soil - moisture (#418)

* updated servo calibrator

* updated plot analog pin example

* updated servo example

* first drop of soil moisture

* updated picture

* fixing macros

* update code section

* 5 seconds

* adding soil moisture

* fixing links

docs/SUMMARY.md

@@ -19,6 +19,10 @@
     * [Guitar](/projects/guitar)
     * [Duct tape wallet](/projects/wallet)
     * [Watch](/projects/watch)
+    * [Soil Moisture](/projects/soil-moisture)
+    * [Voting Machine](/projects/voting-machine)
+    * [Infection](/projects/infection)
+    * [Fireflies](/projects/fireflies)
     * [Inchworm](/projects/inchworm)
     * [Milk Carton Robot](/projects/milk-carton-robot)
     * [Milk monster](/projects/milky-monster)

docs/examples/plot-analog-pin.md

@@ -1,10 +1,18 @@
 # Plot Analog Pin
 
+Use this program to graph the analog value on pin ``P0``, ``P1`` or ``P2``.
+Press ``A`` to scroll the value on the screen.
+
 ```blocks
+let reading = 0
 basic.forever(() => {
+    reading = pins.analogReadPin(AnalogPin.P0)
     led.plotBarGraph(
-        pins.analogReadPin(AnalogPin.P0),
+        reading,
         1023
     )
+    if (input.buttonIsPressed(Button.A)) {
+        basic.showNumber(reading)
+    }
 })
 ```

docs/examples/servo-calibrator.md

@@ -1,14 +1,21 @@
 # Servo calibrator
 
+Use this program to calibrate the angles of a servo.
+Press ``A`` to reduce the angle by 5 and ``B`` to
+increase it by 5.
+
+The current angle is displayed on the screen
+in a loop.
+
 ```blocks
 let angle = 90
 input.onButtonPressed(Button.A, () => {
-    angle -= 5
+    angle -= Math.max(0, 5)
     pins.servoWritePin(AnalogPin.P0, angle)
     led.stopAnimation()
 })
 input.onButtonPressed(Button.B, () => {
-    angle += 5
+    angle += Math.min(180, 5)
     pins.servoWritePin(AnalogPin.P0, angle)
     led.stopAnimation()
 })
@@ -16,5 +23,4 @@ basic.forever(() => {
     basic.showNumber(angle)    
 })
 pins.servoWritePin(AnalogPin.P0, angle)
-basic.showString("Press A or B to change servo angle")
 ```

docs/projects.md

@@ -100,14 +100,24 @@ Fun games to build with your @boardname@.
 }]
 ```
 
-## More
+## STEM
 
 ```codecard
 [{
   "name": "Timing gates",
   "url":"/projects/timing-gates",
   "imageUrl":"/static/mb/projects/timing-gates.jpg"
-}, {
+},{
+  "name": "Soil Moisture",
+  "url":"/projects/soil-moisture",
+  "imageUrl":"/static/mb/projects/soil-moisture.jpg"
+}]
+```
+
+## More
+
+```codecard
+[{
   "name": "Compass",
   "url":"/projects/compass",
   "imageUrl":"/static/mb/projects/a5-compass.png"
@@ -125,5 +135,5 @@ Fun games to build with your @boardname@.
 ### See Also
 
 [Flashing Heart](/projects/flashing-heart), [Smiley Buttons](/projects/smiley-buttons), [Love Meter](/projects/love-meter), [Rock Paper Scissors](/projects/rock-paper-scissors), [Compass](/projects/compass), [Hack your headphones](/projects/hack-your-headphones), [Banana keyboard](/projects/banana-keyboard), [Telegraph](/projects/telegraph), [Guitar](/projects/guitar), [Wallet](/projects/wallet), [Watch](/projects/watch),
-[Milk Monster](/projects/milky-monster), [Karel the LED](/projects/karel), [Infection](/projects/infection),
+[Milk Monster](/projects/milky-monster), [Karel the LED](/projects/karel), [Infection](/projects/infection), [Voting Machine](/projects/voting-machine)
-[Fireflies](/projects/fireflies)
+[Fireflies](/projects/fireflies), [Soil Moisture](/projects/soil-moisture)

docs/projects/infection.md

@@ -390,4 +390,8 @@ basic.forever(() => {
 
 
 basic.showIcon(GameIcons.Pairing)
+```
+
+```package
+radio
 ```

docs/projects/soil-moisture.md

@@ -0,0 +1,28 @@
+# Soil Moisture
+
+
+### ~avatar avatar
+
+Make a funny milky-monster robot!
+
+### ~
+
+![](/static/mb/projects/soil-moisture/soil-moisture.jpg)
+
+## Materials
+
+* 1 @boardname@ with battery pack and batteries
+* 2 long nails or silver
+* 2 crocodile clips
+
+## Activities
+
+* [Make](/projects/soil-moisture/make)  
+* [Code](/projects/soil-moisture/code)
+* [Connect](/projects/soil-moisture/connect)
+
+### ~button /projects/soil-moisture/make
+
+Let's get started!
+
+### ~

docs/projects/soil-moisture/code.md

@@ -0,0 +1,96 @@
+# Code
+
+You will need to get a pot of dry dirt and wet dirt for the coding.
+
+## Step 1: Measuring moisture
+
+![](/static/mb/projects/soil-moisture/nailsv3.jpg)
+
+The soil acts as a variable resistor based on the amount of water and nutrient. 
+The water is not conductive but the nutrient are, so more water, more nutrient, so the soil will be less resistive.
+
+To measure this, we read the voltage on pin ``P0`` using [analog read pin](/reference/pins/analog-read-pin)
+which returns a value between ``0`` (no current) and ``1023`` (max current). The value is graph on the screen
+using [led plot bar graph](/reference/led/plot-bar-graph).
+
+```blocks
+basic.forever(() => {
+    led.plotBarGraph(
+        pins.analogReadPin(AnalogPin.P0),
+        1023
+    )
+})
+```
+
+### Experiment!
+
+* insert the nails in the dry dirt and you should see most LEDs off
+* insert the nail in the wet dirt and you should see most LEDs on
+
+## Step 2: Sensor data values
+
+In the previous program, we only have a rough idea of the value of the sensor... since it is using a tiny screen
+to display it! Let's add code that displays the current reading when button ``A`` is pressed.
+
+This code has to be inserted in the forever loop. We've also added a variable ``reading`` to store the reading value.
+
+```blocks
+let reading = 0
+basic.forever(() => {
+    reading = pins.analogReadPin(AnalogPin.P0)
+    led.plotBarGraph(
+        reading,
+        1023
+    )
+    if (input.buttonIsPressed(Button.A)) {
+        basic.showNumber(reading)
+    }
+})
+```
+
+### Experiment!
+
+* insert the nails in the dry dirt, press ``A`` and note the value. You should see a value close to ``250``
+for dry dirt.
+* insert the nails in the wet dirt, press ``B`` and note the value. You should see a value close to ``1000``
+for dry dirt.
+
+## Step 3: Don't waste energy!
+
+![](/static/mb/projects/soil-moisture/nailsp1.jpg)
+
+We want our probe to work for a long time on batteries so we need to tweak our code to save energy.
+
+* Our circuit connects directly to the ``3v`` pin so it is always using electricity. Instead, 
+we will connect it to ``P1`` and turn that pin high only while the measurement is taken.
+This saves electricty and also avoids corrosion of the probes.
+* We will also lower the brightness of the screen to lower the energy consumption from the LEDs.
+* Soil moisture changes very slowly so we don't need to measure all the times!!! Let's add a **sleep** of 5 seconds in the loop as well.
+
+```blocks
+led.setBrightness(64)
+let reading = 0
+basic.forever(() => {
+    pins.analogWritePin(AnalogPin.P1, 1023)
+    reading = pins.analogReadPin(AnalogPin.P0)
+    pins.analogWritePin(AnalogPin.P1, 0)
+    led.plotBarGraph(
+        reading,
+        1023
+    )
+    if (input.buttonIsPressed(Button.A)) {
+        basic.showNumber(reading)
+    }
+    basic.pause(5000);
+})
+```
+
+### Experiment!
+
+* using the dry and wet dirt pots, test that your ciruit still works. Remember you'll have to wait up to 10 seconds to see a change!
+
+### ~button /projects/soil-moisture/connect
+
+Connect
+
+### ~

docs/projects/soil-moisture/connect.md

@@ -0,0 +1,49 @@
+# Connect
+
+We are going to use radio to send the current moisture
+level to a dashboard @boardname@. The dashboard
+will display one LED per @boardname@.
+
+## Moisture sensor
+
+To make it happen, we need to change the program to 
+* setup the radio by choosing group 4 and sending the serial number of the device
+* send the moisture level **divided by 4** 
+as the dashboard takes values between ``0`` and ``255``.
+
+```blocks
+radio.setTransmitSerialNumber(true)
+radio.setGroup(4)
+led.setBrightness(64)
+let reading = 0
+basic.forever(() => {
+    pins.analogWritePin(AnalogPin.P1, 1023)
+    reading = pins.analogReadPin(AnalogPin.P0)
+    radio.sendNumber(reading / 4);
+    pins.analogWritePin(AnalogPin.P1, 0)
+    led.plotBarGraph(
+        reading,
+        1023
+    )
+    if (input.buttonIsPressed(Button.A)) {
+        basic.showNumber(reading)
+    }
+    basic.pause(5000);
+})
+```
+
+## The dashboard
+
+The dashboard code can be found at [/examples/radio-dashboard](/examples/radio-dashboard).
+
+Download the code from that example into the @boardname@ that will be used to display the result.
+
+When the dashboard receives a message from a @boardname@, it find a pixel for that board (and remembers it)
+and uses the number received as the brightness of the LED.
+
+When a message hasn't been received by a board for some time, it's pixel will start to blink. After more time, it will simply turn off. 
+
+
+```package
+radio
+```

docs/projects/soil-moisture/make.md

@@ -0,0 +1,14 @@
+# Make
+
+https://youtu.be/S8NppVT_paw
+
+* Connect a nail to the ``GND`` pin with a croc clip and insert it in the soil
+* Connect the other nail to the ``P0`` pin with a croc clip and insert it in the soil 
+
+That's it!
+
+### ~button /projects/soil-moisture/code
+
+Code
+
+### ~