Hardware Specification And Schematics

[FedeArnaudo]

Component list

• Motor.
• LM35 Temperature Sensor.
• HY-SRF05 Ultrasonic Sensor.
• 3 buttons.
• Red LED.
• USB to RS232 converter.
• Resistor 1K Ohm.

Schematic

Pin Configuration

• P0.4 → CAP2.0 (ECHO PIN)
• P0.5 → GPIO (TRIGGER PIN)
• P0.6 → GPIO (Count LED)
• P0.10 → TXD2 (UART)
• P0.11 → RXD2 (UART)
• P0.16 → GPIO
• P0.23 → AD0.0 (Temperature Sensor)
• P0.26 → AOUT (Motor)
• P2.10 → EINT0 (Start Button)
• P2.11 → EINT1 (Stop Button)

[FrancoPerotti]

Logic Level Shifter for Ultrasonic Sensor

We implemented the circuit shown above to safely interface the 3.3V logic system of the LPC1769 with the 5V logic requirements of the ultrasonic sensor. Here’s a breakdown of why this circuit was necessary and how it works:

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Problem: Voltage Level Incompatibility

• The ultrasonic sensor operates with 5V logic levels, while the LPC1769 operates at 3.3V logic.
• A direct connection between the two could lead to unreliable communication:
  • 3.3V signals sent from the microcontroller might not be recognized as HIGH by the 5V sensor.
  • 5V signals from the sensor could exceed the voltage tolerance of the microcontroller GPIO pins, potentially causing damage.

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Solution: Logic Level Shifter Circuit

To address this, we designed and implemented a logic level shifting circuit using a BC547 NPN transistor and a few resistors. This ensures safe and reliable communication between the two systems.

Components:

• BC547 Transistor: Acts as a switch, enabling level shifting between the 3.3V and 5V systems.
• Resistors (10kΩ and 4.7kΩ): Provide proper biasing for the transistor and ensure current is limited to safe levels.