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Author: lauraclay

motors.md

@@ -2,7 +2,7 @@
 
 Motors are great for physical computing: they allow you to turn a wheel forwards and backwards, or make something spin around.
 
-A motor cannot be controlled directly from the Raspberry Pi's GPIO pins, because it needs a variable supply of 5 volts. This means you need to power it separately. However, motor controller add-on boards can be used to provide this functionality.
+A motor can't be controlled directly from the Raspberry Pi's GPIO pins, because it needs a variable supply of 5 volts. This means you need to power it separately. However, motor controller add-on boards can be used to provide this functionality.
 
 In this guide, you'll be controlling two motors from your Raspberry Pi using Python on the desktop. First, it's best just to learn how to control the motor. Then, once you have it working, you could easily use your code to drive a Raspberry Pi-powered robot by detaching the monitor, mouse, and keyboard and building a robot around a chassis.
 
@@ -22,13 +22,13 @@ You'll need to wire up two motors and your battery pack using the motor controll
 
     ![Connect battery pack](images/battery-pack.png)
 
-1. You'll need to know which GPIO pins your motor controller uses. Refer to the board's documentation. This will usually be described as Motor A and Motor B, or MA1, MA2, MB1 and MB2. Make a note of these pin numbers. If you're not sure which is which, you can investigate this next.
+1. You'll need to know which GPIO pins your motor controller uses. Refer to the board's documentation. This will usually be described as Motor A and Motor B, or MA1, MA2, MB1, and MB2. Make a note of these pin numbers. If you're not sure which is which, you can investigate this next.
 
-## Output Devices
+## Output devices
 
 First, you should learn to control motors by controlling the pins individually.
 
-1. Boot the Pi and open Python 3
+1. Boot the Pi and open Python 3.
 
 1. In the shell, enter the following line to import `OutputDevice` from the GPIO Zero library:
 
@@ -51,7 +51,7 @@ First, you should learn to control motors by controlling the pins individually.
     a.on()
     ```
 
-    The motor should now be spinning! If not, check you are addressing the right pin numbers. The two pins should be connected to the same motor. Also check your wiring and your batteries.
+    The motor should now be spinning! If not, check you are addressing the right pin numbers. The two pins should be connected to the same motor. Also, check your wiring and your batteries.
 
     ![Motor forward](images/motor-forward.png)
 
@@ -114,7 +114,7 @@ First, you should learn to control motors by controlling the pins individually.
 
 ## PWM
 
-So far, you have used simple on/off commands to control your motors. PWM (Pulse-width modulation) allows you to control the speed. The `on()` function sets the motor to go at full speed, but you can control this to make the motor go at a fraction of this speed.
+So far, you have used simple on/off commands to control your motors. PWM (pulse-width modulation) allows you to control the speed. The `on()` function sets the motor to go at full speed, but you can control this to make the motor go at a fraction of this speed.
 
 1. Since you're going to reuse the same pins in a different way, you'll have to close the connections to the pins. The easiest way to do that is to restart the Python shell by clicking **Shell > Restart shell**.
 
@@ -124,7 +124,7 @@ So far, you have used simple on/off commands to control your motors. PWM (Pulse-
     from gpiozero import PWMOutputDevice
     ```
 
-1. Create new connections to each of your pins, as before, but using `PWMOutputDevice`:
+1. Create new connections to each of your pins as before, but using `PWMOutputDevice`:
 
     ```python
     a = PWMOutputDevice(4)
@@ -141,7 +141,7 @@ So far, you have used simple on/off commands to control your motors. PWM (Pulse-
 
     The motor should now be spinning at half speed.
 
-1. To turn the motor the opposite direction, turn `a` off (or set its value to `0`) and set `b`'s value to `0.5`:
+1. To turn the motor in the opposite direction, turn `a` off (or set its value to `0`) and set `b`'s value to `0.5`:
 
     ```python
     a.value = 0
@@ -173,15 +173,15 @@ So far, you have used simple on/off commands to control your motors. PWM (Pulse-
 
     The motors should now speed up from 0 (stopped) to 0.1, 0.2 and up to 1.
 
-    Be aware, though, that the motor may not move until it gets above a certain speed as there may not be enough power to engage it.
+    Be aware, though, that the motor may not move until it gets above a certain speed, as there may not be enough power to engage it.
 
 ## Motor class
 
-Now you've learned how setting pins high and low can control a motor, you should proceed to using the built-in `Motor` class, which has all the functionality you just learned about, provided in a simple way, including PWM for speed.
+Now you've learned how setting pins high and low can control a motor, you should proceed to using the built-in `Motor` class; this has all the functionality you just learned about, provided in a simple way, including PWM for speed.
 
 ![Motor](images/motor.png)
 
-1. Restart the shell again (**Ctrl + F6**)
+1. Restart the shell again (**Ctrl + F6**).
 
 1. Import the `Motor` class:
 
@@ -198,7 +198,7 @@ Now you've learned how setting pins high and low can control a motor, you should
 
     Note: to make it easier to see which pin is which, you can use `Motor(forward=4, backward=14)` for future reference.
 
-1. Now drive one of the motors forward using:
+1. Now drive one of the motors forward using the following code:
 
     ```python
     motor1.forward()
@@ -217,7 +217,7 @@ Now you've learned how setting pins high and low can control a motor, you should
     motor2.backward(0.5)
     ```
 
-1. The `Motor` class also allows you to reverse the motor's direction. Try using this a loop:
+1. The `Motor` class also allows you to reverse the motor's direction. Try using this loop:
 
     ```python
     motor1.forward()
@@ -228,7 +228,7 @@ Now you've learned how setting pins high and low can control a motor, you should
         motor2.reverse()
     ```
 
-    This will make the motors spin in opposite directions, then switching every five seconds. Press **Ctrl + C** to exit the loop.
+    This will make the motors spin in opposite directions, then switch every five seconds. Press **Ctrl + C** to exit the loop.
 
 1. Now stop the motors:
 
@@ -239,11 +239,11 @@ Now you've learned how setting pins high and low can control a motor, you should
 
 ## Robot class
 
-If you had a robot with two wheels, you would want to control the two motors together, rather than separately, just like you did for the two pins of each motor. Luckily, there's also a `Robot` class in GPIO Zero.
+If you had a robot with two wheels you would want to control the two motors together, rather than separately, just like you did for the two pins of each motor. Luckily, there's also a `Robot` class in GPIO Zero.
 
 ![Robot](images/robot.png)
 
-1. Restart the shell again (**Ctrl + F6**)
+1. Restart the shell again (**Ctrl + F6**).
 
 1. Import the `Motor` class:
 
@@ -259,7 +259,7 @@ If you had a robot with two wheels, you would want to control the two motors tog
 
     Note: to make it easier to see which pin is which, you can use `Robot(left=(4, 14), right=(17, 27))` for future reference.
 
-1. Now drive one of the motors forward using:
+1. Now drive one of the motors forward using the following code:
 
     ```python
     robot.forward()
@@ -311,5 +311,5 @@ If you had a robot with two wheels, you would want to control the two motors tog
 
 Now you've learned how motors work, why not try:
 
-- Making your own robot with our [Build a robot](http://raspberrypi.org/learning/robo-butler/) resource
-- Make a [spinning flower wheel](http://raspberrypi.org/learning/spinning-flower-wheel/)
+- Making your own robot with our [Build a robot](http://raspberrypi.org/learning/robo-butler/) resource?
+- Making a [spinning flower wheel](http://raspberrypi.org/learning/spinning-flower-wheel/)?