Import 'object detection' activity (#359)

docs/coding/object-detection.md

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+# Object Detection
+
+Design ways to avoid accidents between vehicles and objects in the road.
+
+![Deer in the road](/static/coding/object-detection/road-deer.jpg)
+
+## Connect 
+
+Think about:
+
+* In what driving situations can a car hit an obstacle?
+* What do you need to be aware of to avoid collisions with obstacles?
+* What causes traffic jams in high density areas?
+
+## Construct 
+
+### Build
+
+Build a LEGO MINDSTORMS vehicle that can avoid accidents between vehicles and objects in the road.
+
+Start by constructing this [model](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-ultrasonic-sensor-driving-base-61ffdfa461aee2470b8ddbeab16e2070.pdf).
+
+![EV3 Robot Driving Base](/static/coding/object-detection/ev3-robot-driving-base.jpg)
+
+Build an obstacle for your robot to detect. You can build the [cuboid model](https://le-www-live-s.legocdn.com/sc/media/lessons/mindstorms-ev3/building-instructions/ev3-cuboid-dc93b2e60bed2981e76b3bac9ea04558.pdf) out of LEGO bricks or an obstacle of your choice. 
+
+![Cubiod block](/static/coding/object-detection/ev3-cuboid.jpg)
+
+Before you program, check:
+
+* Are all the wires correctly connected from the motors to ports B and C?
+* Are the wheels correctly installed?
+* Are the wheels rotating freely?
+* Are the wires connected from the Ultrasonic Sensor to port 4?
+
+### Program
+
+* Program your robot to detect any obstacles that might appear while the robot is moving forward (or backward).
+* Make the robot stop when it detects an object that is less than 20 cm away.
+
+Before you program, think about:  
+* How will you program the robot to detect obstacles?
+* How will you program the robot to stop at obstacles?
+* Which programming blocks will you use?
+
+### ~hint
+
+Consider using these blocks in your solution:
+
+```block
+brick.buttonEnter.onEvent(ButtonEvent.Pressed, function () {
+
+})
+motors.largeBC.steer(0, 50)
+pauseUntil(() => true)
+let near = sensors.ultrasonic4.distance() < 20
+motors.stopAll()
+```
+
+### ~
+
+### Sample Solution 
+
+1. Start the program when EV3 ``enter`` button is pressed.
+2. Turn motors ``B`` and ``C`` on at speed ``50``.
+3. Wait until Ultrasonic Sensor detects an obstacle at a distance of less than ``20`` cm.
+4. Stops all motors.
+
+```blocks
+brick.buttonEnter.onEvent(ButtonEvent.Pressed, function () {
+    motors.largeBC.steer(0, 50)
+    pauseUntil(() => sensors.ultrasonic4.distance() < 20)
+    motors.stopAll()
+})
+```
+
+### Download and test
+
+Click **Download** and follow the instructions to get your code onto your EV3 Brick. Press the ``center`` button on the EV3 Brick to run the program.
+
+## Contemplate
+
+On the road, when a driver sees and object, they slow their car down before coming to a full stop. 
+
+Program your EV3 Driving Base to do the same.
+
+If the Ultrasonic Sensor:
+
+* Detects an object less than `10` cm away, make the robot stop.
+* Detects an object between `10` and `20` cm away, make the robot slow down.
+* Does not detect any object, continue to move at full speed.
+
+### ~hint
+
+Consider using this block in your solution:
+ 
+```block
+if (true) {
+}
+```
+
+### ~
+
+### Sample Solution 
+
+```blocks
+loops.forever(function () {
+    motors.largeBC.steer(0, 50)
+    if (sensors.ultrasonic4.distance() < 10) {
+        motors.stopAll()
+    } else if (sensors.ultrasonic4.distance() < 20) {
+        motors.largeBC.steer(0, 10)
+    }
+})
+```
+
+### Download and test
+
+Click **Download** and follow the instructions to get your code onto your EV3 Brick. Press the ``center`` button on the EV3 Brick to run the program.
+
+## Continue 
+
+* Get together with other building teams and make a traffic jam by placing all of your robots in a line with varying amounts of space between them.
+* Have everyone start their robots at the same time and see what happens.
+* Refine your programs so that all of the robots continue driving at the same speed with equal distances between them.
+* Click on the JavaScript tab and experiment with changing the values in the code.
+* Add a custom image or sounds from the Brick or Music menus.
+
+### Share
+
+* Share what you think “efficiency in programming” means.
+* Explore the different solutions other programmers came up with.
+* Create a video of your project, especially your final presentation and your robot’s performance. Explain some important features of your software program. 
+* Include an image of your program with comments. 
+* Add a team photograph! 
+
+Congratulations! What will you design next