49ab5ec099
* Shrink some of the tutorial sentences * Match the less than order for blocks * Include later tutorials in SUMMARY * Ditch 'using' in name
3.5 KiB
Line Following
Introduction @fullscreen
Make a program to follow a line using the Color sensor and reflected light. Let's test reflected light to see if it's white or black (on the line), and drive our robot accordingly.
Step 1
In the ||logic:Logic|| Toolbox drawer under the Conditionals section, drag out an ||logic:If then else|| block onto the Workspace, and drop it into the ||loops:forever|| loop.
forever(function () {
if (true) {
} else {
}
})
Step 2
Open the ||logic:Logic|| Toolbox drawer again. From the Comparison section, drag out ||logic:0 < 0|| comparison block and drop it into the ||logic:if then else|| block, replacing true.
forever(function () {
if (0 < 0) {
} else {
}
})
Step 3
Open the ||sensors:Sensors|| Toolbox drawer. From the Color Sensor section, drag out a ||sensors:color sensor light|| value block and drop it into the second slot of the ||logic:0 < 0|| comparison block, replacing the 0.
forever(function () {
if (0 < sensors.color3.light(LightIntensityMode.Reflected)) {
} else {
}
})
Step 4
If the value of the reflected light is greater than 40% (white or very light), our robot is outside the line, so steer to the left. In the ||logic:0 < 0|| comparison block change the compared value to 40 replacing 0.
forever(function () {
if (40 < sensors.color3.light(LightIntensityMode.Reflected)) {
} else {
}
})
Step 5
Open the ||motors:Motors|| Toolbox drawer. Drag out 2 ||motors:tank large motors|| blocks and drop one of them into the ||logic:if|| part, and the other into the ||logic:else|| part of the ||logic:if then else|| block.
forever(function () {
if (40 < sensors.color3.light(LightIntensityMode.Reflected)) {
motors.largeBC.tank(50, 50)
} else {
motors.largeBC.tank(50, 50)
}
})
Step 6
In the first ||motors:tank large motors|| block in the ||logic:if|| clause, change the speed values of the motors from 50%, 50% to 5%, 15%. This slows down the robot, and steers it to the left (because the C motor is driving faster than the B motor).
forever(function () {
if (40 < sensors.color3.light(LightIntensityMode.Reflected)) {
motors.largeBC.tank(5, 15)
} else {
motors.largeBC.tank(50, 50)
}
})
Step 7
In the second ||motors:tank large motors|| block in the ||logic:else|| clause, change the speed values of the motors from 50%, 50% to 15%, 5%. This slows down the robot, and steers it to the right (because the B motor is driving faster than the C motor).
forever(function () {
if (40 < sensors.color3.light(LightIntensityMode.Reflected)) {
motors.largeBC.tank(5, 15)
} else {
motors.largeBC.tank(15, 5)
}
})
Step 8
Now, plug your @boardname@ into the computer with the USB cable, and click the Download button at the bottom of your screen. Follow the directions to save your program to the brick.
Attach a Color Sensor to Port 3 of your brick, and attach your brick to a driving base with large motors attached to Ports B and C. See the instructions for building a Driving Base with Color Sensor Down. Test your program by positioning your robot to the right of a dark, thick line and then let it drive!