Loop Block

Use this block to repeat sequences of code. Set the condition that will end the loop: elapsed time, the number of repetitions, a logic signal or a sensor. You can also set a loop to go on forever.

Display settings

Adding blocks to the Loop block

Moving the Loop block

Configuring the Loop block

Display settings

1. When a Loop block’s action property is set to “Forever,” an infinity symbol (∞) is displayed at the bottom of the trailing portion of the block.
2. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub). You can also use current count to control the loop itself. (See the Count setting in the Configuring the Loop Block section below).
3. If you choose for a sensor to control the loop, the trailing portion of the Loop block will expand in size revealing an icon for the chosen sensor. For example, if you choose a Light Sensor to control the loop, a Light Sensor icon will be displayed in the expanded portion of the block. Also, any relevant information about the chosen control property will displayed at the bottom of the block.

Adding blocks to the Loop block

If a Loop block is placed on the sequence beam, a short section of the beam will appear inside the Loop block; programming blocks dragged on top of this portion of the sequence beam will snap to it. Any new blocks dragged inside a loop that already contains programming blocks will cause the frame to expand sideways. This will make room for the new blocks to snap to the sequence beam.

Moving the Loop block

The Loop block can only be selected and moved by clicking on the block itself; clicking on the surrounding frame or on the blocks inside the frame will not work.

Configuring the Loop Block

The Control property pull-down menu will let you choose from five primary conditions that will affect your loop:

• Forever [default]
• Time
• Sensor (which will activate a second pull-down menu)
  • Touch Sensor
  • Light Sensor
  • Sound Sensor
  • Ultrasonic Sensor
  • NXT Buttons
  • (Built-in) Rotation Sensor
  • Timer
  • Receive Message
     

    LEGO MINDSTORMS Education NXT Software

  • Touch* Sensor
  • Light* Sensor
  • Rotation* Sensor
  • Temperature* Sensor
• Count
• Logic

Forever

If you choose “Forever,” any programming blocks within the loop will repeat forever without interruption.

1. Check the “Show Counter” checkbox to use the number of loops completed as input to another block. (Example: to increase a Motor block’s Power.)

Time

If you choose “Time,” the programming blocks within the loop will repeat until a certain number of seconds have passed. After the time period is up, the loop will end.

1. Use this box to type in the number of seconds that the loop should run. If you choose 5 seconds, for example, the loop will end after 5 seconds have passed.
2. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Touch Sensor

If you choose “Touch Sensor,” the programming blocks within the loop will repeat until a touch sensor is bumped, pressed, or released. Then the loop will end and the program will go on.

1. Choose the port that the touch sensor is connected to.
2. Use the radio buttons to specify whether you want the touch sensor to be bumped, pressed, or released to end the loop. Choose Bumped if you want the block to be triggered after a quick press and release of the touch sensor (less than 0.5 seconds in duration). Choose Pressed if you want the block to be triggered at the instant the touch sensor is pressed in. Choose Released if you want the block to be triggered at the instant the touch sensor is released.
3. The feedback box will let you test your touch sensor. When the sensor is activated on your robot, the number “1” will be displayed here. Use the reset button to clear the feedback box.
4. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Sound Sensor

If you choose “Sound Sensor,” the programming blocks within the loop will repeat until the sound sensor detects sound in a certain range.

1. Choose the port where your sound sensor is plugged in. By default, the block will be set to port 2 for a sound sensor.
2. Use the slider to set the trigger value or type a value directly into the input box. Select the radio button to the right of the slider if you want the loop to end when sound levels are higher than the trigger value; select the left radio button to end the loop when sound levels are lower than the trigger value. You can also use the pull-down menu to set the portion of the slider that will end the loop.
3. The feedback box displays the current sound reading (0-100%). You can use it to try out different trigger values.
4. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Light Sensor

If you choose “Light Sensor,” the programming blocks within the loop will repeat until a light sensor measures a certain intensity of light. Then the loop will end and the program will advance.

1. Choose the port where your light sensor is plugged in. By default, the block will be set to port 3 for a light sensor.
2. Use the slider to set the trigger value or type a value directly into the input box. Select the radio button to the right of the slider if you want the loop to end when light levels are higher than the trigger value; select the left radio button to end the loop when light levels are lower than the trigger value. You can also use the pull-down menu to set the portion of the slider that will end the loop.
3. If you check the “Generated Light” checkbox, the light sensor will turn on its own small light source and detect this light if it is reflected back to it.
4. The feedback box will display the current light reading.
5. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Ultrasonic Sensor

If you choose “Ultrasonic Sensor,” the programming blocks within the loop will repeat until the ultrasonic sensor detects an object at a certain distance.

1. Choose the port where your ultrasonic sensor is plugged in. By default, the block will be set to port 4 for an ultrasonic sensor.
2. Use the slider to set the trigger value or type a value directly into the input box. Select the radio button to the left of the slider if you want the loop to end when the ultrasonic sensor detects an object closer than the trigger value; select the right radio button to end the loop when the ultrasonic sensor detects an object farther away than the trigger value. You can also use the pull-down menu to set the portion of the slider that will end the loop.
3. Select to read values in Centimeters or Inches.
4. The feedback box will display the current ultrasonic sensor reading.
5. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

NXT Buttons

If you choose “NXT Buttons,” the programming blocks within the loop will repeat until the chosen NXT buttons is bumped, pressed, or released.

1. Select which NXT button will send out a “true” signal when activated (and end the loop).
2. Choose Bumped if you want the chosen button to be activated after a quick press and release. Choose Pressed if you want the chosen button to be activated at the instant the button is pressed in. Choose Released if you want the chosen button to be activated at the instant the button is released.
3. The feedback box will display a “1” when the chosen NXT button is bumped, pressed or released (according to the configuration you’ve set).
4. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

(Built-in) Rotation Sensor

If you choose to “read” a rotation sensor, the programming blocks within the loop will repeat until the rotation sensor reaches a certain value; then the loop will end and the program will advance. If you choose to “reset” the rotation sensor, the sensor will be reset to zero after each loop; the block will continue to loop until the rotation sensor can reach the trigger value during one of the loops.

1. Choose the port where your motor is plugged in.
2. Choose to read or reset a rotation sensor.
3. Use the radio buttons to set the direction you want: forwards or backwards.
4. Choose to count either Rotations or Degrees by using the pull-down menu.
5. Type the number of rotations or degrees you want to go by before the loop is ended (allowing your program to go forward).
6. The feedback box will display the current number of rotations or degrees. Use the reset button to clear the feedback box.
7. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Timer

If you choose to “read” a timer, the programming blocks within the loop will repeat until one of the NXT’s internal timers reaches a certain time value; then the loop will end and the program will advance. If you choose to “reset” a timer, the timer will be reset after each loop; the block will continue to loop until the timer can reach its trigger value during one of the loops.

1. Choose the NXT timer that you would like to monitor.
2. Choose to read or reset a timer.
3. Type a time value (in seconds) in the input box.
4. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Receive Message

If you choose “Receive Message,” the programming blocks within the loop will repeat until your NXT receives a certain Bluetooth message. Then the loop will end and the program will advance.

1. The pull-down menu will let you select the message type (Text, Number, or Logic) of the message that you expect to receive.
2. To compare the incoming message to a test message, either type in the test text or number (if you have chosen Text or Number respectively as the format), or use the radio buttons to choose the test logic value (true or false).
3. Choose the mailbox number where the incoming message will arrive.
4. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Touch* Sensor

If you choose “Touch* Sensor,” the programming blocks within the loop will repeat until a touch* sensor is bumped, pressed, or released. Then the loop will end and the program will go on.

1. Choose the port that the touch* sensor is connected to. By default, the block will be set to port 1 for a touch sensor.
2. Use the radio buttons to specify whether you want the touch sensor to be bumped, pressed, or released to end the loop. Choose Bumped if you want the block to be triggered after a quick press and release of the touch sensor (less than 0.5 seconds in duration). Choose Pressed if you want the block to be triggered at the instant the touch sensor is pressed in. Choose Released if you want the block to be triggered at the instant the touch sensor is released.
3. The feedback box will let you test your touch sensor. When the sensor is activated on your robot, the number “1” will be displayed here. Use the reset button to clear the feedback box.
4. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Light* Sensor

If you choose “Light* Sensor,” the programming blocks within the loop will repeat until a light* sensor measures a certain intensity of light. Then the loop will end and the program will advance.

1. Choose the port where your light* sensor is plugged in. By default, the block will be set to port 3 for a light sensor.
2. Use the slider to set the trigger value or type a value directly into the input box. Select the radio button to the right of the slider if you want the loop to end when light levels are higher than the trigger value; select the left radio button to end the loop when light levels are lower than the trigger value. You can also use the pull-down menu to set the portion of the slider that will end the loop.
3. The feedback box will display the current light reading.
4. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Rotation* Sensor

If you choose to “read” a rotation* sensor, the programming blocks within the loop will repeat until the rotation sensor reaches a set number of ticks (16 to a rotation); then the loop will end and the program will advance. If you choose to “reset” the rotation* sensor, the sensor will be reset to zero after each loop; the block will continue to loop until the rotation* sensor can reach the trigger value during one of the loops.

1. Choose the port where your motor is plugged in.
2. Choose to read or reset a rotation* sensor.
3. Use the radio buttons to set the direction you want: forwards or backwards.
4. Type the number of ticks (16 to a rotation) you want to go by before the loop is ended (allowing your program to go forward).
5. The feedback box will display the current number of ticks (16 to a rotation). Use the reset button to clear the feedback box.
6. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Temperature* Sensor

If you choose “Temperature* Sensor,” the programming blocks within the loop will repeat until a temperature* sensor measures a certain temperature. Then the loop will end and the program will advance.

1. Choose the port where the temperature sensor is plugged in. By default, the block will be set to port 4 for a temperature sensor.
2. Use the slider to set the trigger value or type a value directly into the input box. Select the radio button to the right of the slider if you want the block to be triggered by temperatures higher than the trigger value; select the left radio button to trigger the block with temperatures lower than the trigger value. You can also use the pull-down menu to set the “true” portion of the slider.
3. Select to read values in Celsius or Fahrenheit.
4. The feedback box displays the current temperature reading.
5. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).

Count

If you choose “Count,” any programming blocks within the loop will repeat until the Counter reaches a set number of repetitions.

1. Use this box to type in the number of repetitions that will end the loop. If you type “2,” for example, the loop will end after the programming blocks in the loop have been run twice.
2. Check the “Show Counter” checkbox so that you can wire the left side of the loop to the right side (where the “count” plug appeared). With the left and right sides connected, the program will be able to count the number of completed loops and leave the loop when the count reaches the number you set.

Logic

If you choose “Logic” and connect an input data wire to the Loop block’s trailing portion, any programming blocks within the loop will repeat as long as the Loop block is receiving a true or false logic signal through the data wire. When a specified logic signal is received, the loop will end.

1. Choose which type of logic signal, true or false, will end the loop.
2. If the “Show Counter” checkbox is selected in the configuration panel, a plug will appear that will allow you to use the number of completed loops as an input elsewhere in your program (if you connect a data wire from the plug to another block’s data hub).