I started this project by trying out the pre-written code that came with the IET Pedestrian Crossing resource. The aim is to use the BBC micro:bit to develop a prototype for a pedestrian crossing for a local secondary school.
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Stage 4
I have added an illuminated external push button which is connected to the button A pin (P5),this lets you trigger or detect a button "A" click externally. The LED inside the switch is connected to port (P13) via series resistor.
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Code
Parts List
You will need the following:
- 1 x BBC micro:bit
- 1 x Kitronik Prototyping System
- 2 x Red LED’s
- 2 x Green LED’s
- 1 x Orange LED
- 1 x Piezo Sounder
- 1 x NPN Transistor
- 1 x 2.2kΩ Resistor
- 5 x Resistors suitable for your LED’s (I used 220Ω resistors)
- 7 x MF Jumper wires
- 3 x MM Jumper wires
Stage 1
First, I connected three LED’s to P0, P1 & P2 via series resistors.
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| Stage 1 Breadboard Layout: |
BBC micro:bit Edge Connector Breakout Board | Breadboard Connection |
P0 pin | Red Traffic LED via 220Ω Resistor |
P1 pin | Orange Traffic LED via 220Ω Resistor |
P2 pin | Green Traffic LED via 220Ω Resistor |
0V Pin | Breadboard negative rail |
3V Pin | Breadboard positive rail |
Stage 2
This worked well so I thought I would try adding two more LED’s via series resistors to ports (P8 & P12). I modified the pre-written program so that the two additional LED’s would also be controlled.
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| Stage 2 Breadboard Layout |
BBC micro:bit Edge Connector Breakout Board | Breadboard Connection |
P0 pin | Red Traffic LED via 220Ω Resistor |
P1 pin | Orange Traffic LED via 220Ω Resistor |
P2 pin | Green Traffic LED via 220Ω Resistor |
P8 pin | Green Pedestrian LED via 220Ω Resistor |
P12 pin | Red Pedestrian LED via 220Ω Resistor |
0V Pin | Breadboard negative rail |
3V Pin | Breadboard positive rail |
Stage 3
The final part of this project was to add a piezo sounder to simulate the crossing beeper. I connected a piezo sounder to port (P16) via a driver transistor. I modified the code once more to add this functionality.
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| Stage 3 Breadboard Layout |
BBC micro:bit Edge Connector Breakout Board | Breadboard Connection |
P0 pin | Red Traffic LED via 220Ω Resistor |
P1 pin | Orange Traffic LED via 220Ω Resistor |
P2 pin | Green Traffic LED via 220Ω Resistor |
P8 pin | Green Pedestrian LED via 220Ω Resistor |
P12 pin | Red Pedestrian LED via 220Ω Resistor |
P16 pin | 2.2k Resistor for Transistor |
0V Pin | Breadboard negative rail |
3V Pin | Breadboard positive rail |
Stage 4
I have added an illuminated external push button which is connected to the button A pin (P5),this lets you trigger or detect a button "A" click externally. The LED inside the switch is connected to port (P13) via series resistor.
 |
| Stage 4 |
BBC micro:bit Edge Connector Breakout Board | Breadboard Connection |
P0 pin | Red Traffic LED via 220Ω Resistor |
P1 pin | Orange Traffic LED via 220Ω Resistor |
P2 pin | Green Traffic LED via 220Ω Resistor |
P8 pin | Green Pedestrian LED via 220Ω Resistor |
P12 pin | Red Pedestrian LED via 220Ω Resistor |
P16 pin | 2.2k Resistor for Transistor |
P5 pin | Button A – connected to an external push switch |
P13 pin | Pedestrian wait LED via 100Ω Resistor |
0V Pin | Breadboard negative rail |
3V Pin | Breadboard positive rail |
Code
The code has been written in Microsoft Touch Develop and can be found here