Don t Steal My BBC micro:bit Alarm!

Transcription

1 Description This is a simple tutorial demonstrating how to use the output pins on the BBC micro:bit and use the built in accelerometer to control a buzzer when the BBC micro:bit is moved. Learn how to: Program your BBC micro:bit to detect movement. Activate a buzzer. Protect your BBC micro:bit! Level of difficulty: Beginner. Parts List In order to complete this tutorial, you will need: A BBC micro:bit. A 3V buzzer. A USB to Micro USB lead. 2xAAA battery cage with JST connector. 2xAAA batteries. Either crocodile leads or banana plugs. You will also need the following equipment: A computer with a USB port and internet access.

2 Step-by-step guide to making a Don t Steal My micro:bit Alarm Step 1 Log in to the BBC micro:bit website, look for the Microsoft Research blocks banner and click New Project. Pick a name for your project and click create! Step 2 Select Variables from the left hand side of the screen then drag the block that says Set item to into the middle of the screen.

3 Click the word item to open a drop down menu. Then click New Variable. When prompted name your new variable Xmovement. This variable will be used to track movement in the X direction. Click the word Input on the left hand side of the screen and drag the acceleration (mg) x block to the right hand side of the Xmovement block you just made. They should snap together to form one block. Step 3 We now need to make 2 more of these blocks for the Y and Z direction. To do this quickly, select the one you already made and press ctrl + c to copy it, then ctrl + v twice to paste two copies. Remember to change the names of the variables to Y movement and Z movement and to select the corresponding letter from the dropdown in the blue acceleration block! Stack the three blocks you made together, this forms a block that checks the accelerometer sensor in all three directions and writes the values to the three variables you have created. Step 4 Now to do something useful with those readings we need to add some conditions. Click on if on the left hand side of the screen. Select the If, do, else block and attach it to the bottom of what you ve done so far.

4 Grab the and block from the Logic category and drop it near the rest of your blocks. We re going to have to do some work to get this block to do what we want it to. First click the and text and change it to or. Next grab two of the = blocks from the logic menu and put them into the slots in the or block we just made. Select from the variable category the Xmovement variable and place into the left hand side of both = equations and the number block from the maths category into the right hand side. Swap the = sign on the left of the or into a > and the = on the right of the or into a <. Then swap the number on the left of the or sign to 100 and the number on the right hand side to Using the digital write block from the Pins category and the pause block from the basic category fill in the rest of the if function to match the image here. Step 5 Copy and paste the entire if function twice. Attach it all together like in the image. Change the variable in the second if function to Ymovement and the variable in the third if function to Zmovement. You will also need to change the numbers in the last or statement to 1100 and 900 respectively, as this is the direction gravity works in there will of around 1000mg in this direction even when the BBC micro:bit is flat on a table. Finally add a pause of 100ms to the bottom of your code then put the whole thing inside a forever block found in the basic category. The code is complete!

5 Step 6 Press compile and after a few minutes the code should appear as a download in your browser. If you plug your BBC micro:bit into a USB port it will show up as a storage device. Simply drag and drop the.hex file you just downloaded onto the BBC micro:bit. The file might not show up on the BBC micro:bit in the file explorer but it is there! Once the file has been transferred (the light on the BBC micro:bit will stop blinking rapidly) remove the BBC micro:bit from your computer. Step 7 Now that the software is done we need to put the hardware together. Put the batteries into the battery holder and push the JST connector into the socket on the BBC micro:bit. Clip one of your crocodile clip leads onto the big GND pad at the edge of the BBC micro:bit and the other end of the lead to the black wire on the buzzer. Clip the other crocodile clip lead to the large pad on the BBC micro:bit labelled 0 and the other end of the lead to the red wire on the buzzer. If using banana plugs, attach the wires from the buzzer into the plugs, and plug the black plug into the hole marked GND and the red plug into the hole marked 0 (see inset picture right). If placed with BBC logo facing upwards on a flat surface the buzzer will stop after three seconds, however any attempt to move the BBC micro:bit will cause the buzzer to sound until it s put back down!