Using the Lego Mindstorms NXT robotics kit we built a remote control gondola. The MIT App Inventor package was used to create an Android phone app that controlled the gondola.
For this project we used:
• 1 Lego Mindstorms NXT brick with 1 motor and cable
• 1 Android phone
• lots of Lego bricks
• some string
• 2 adjustable mens or womens belts
The Lego Mindstorms motor should be connected in either the B or C connection on the brick.
You will need to make two gondola platforms. One with the Lego Mindstorms brick and motor, and a second platform with a wheel that can spin freely. You can have a lot of fun creating different gondola platforms. We found that some of the important points in the construction to be:
• the platforms needed to be firmly secured. We put our platforms on chairs and we used belts to stop them from moving (Figure 2). A carpeted floor will help stop the chairs from slipping.
• Small gondola. It’s tempting to want to make a big gondola, but we found that big gondolas had more string slippage and you had to have the gondola stations closer together.
• Use wheels with grooves or rims. If you use wheels with grooves or rims the gondola string is less likely to slip out.
The Lego NXT brick needs to have Bluetooth turned on. Check the top left corner of the Brick’s screen to see if the Bluetooth symbol is showing. If it is not showing go into the Bluetooth options and turn visibility on.
For the Bluetooth pairing the Lego NXT needs to be turned on and your Android phone will need to have Bluetooth enabled. From your Android Bluetooth setting select “Search for Devices”. The Lego NXT brick will appear as NXT on your Android phone. On the phone select “pair with device”, and the phone pairing dialog will come up. The pairing request dialog may look different for different versions of Android, but the key is to enter the correct pairing PIN.
When the pairing is started the NXT will beep and prompt you for the pairing passkey. For the pin code (passkey) use the default of: 1234, and finish with the check mark. The pin code of 1234 is used on both the NXT and on the Android phone.
AppInventor has a set of components that will talk to the Lego Mindstorm NXT (or EV3) bricks. Below are pictures showing the our screen layouts and the key code elements.