For our micromouse, we will be utilising the natural phenomenon known as infrared lights to act as a “sense” for our micromouse so that it may detect and avoid obstacles. In this page, we will be analysing the circuit diagram of an infrared circuit we have assembled.
IR circuit diagram
This is a circuit diagram of the infrared circuit which we assembled, with credits to tutors Dr Timothy Davies and Dr Chris Jobling and lab technicians Mr David Moody and Mr Robert John for creating the diagram for us to use. As it can be seen on the diagram, there are five points labelled A, B, C, D, and E. We will observe these points of interest using the Rohde & Schwarz oscilloscope so that we may grasp a better understanding of what happens in this circuit.
Circuit diagram: Points of interest
Points A and B
As It can be seen in the picture to our left, the yellow trace represents point A and the green trace reperesents point B in the diagram. Point A is placed at the output of the first Schmitt NAND gate, which is an oscillator outputting a square wave at 20 Hz. Point B is then placed after a 100nF capacitor. What we can see is that there is a differentiated square wave which decays as the square wave rises. As the square wave falls, there is a slight overshot as the waveform rises to reach steady state once again.
Point C
This oscilloscope trace represents point C of the diagram, which is placed at the ouput of the second oscillator gate. This shows us bursts of 40 kHz. The square wave shown at point A controls these bursts and, in turn, these bursts controls the current flowing through the PNP transistor since this point happens to be located at the transistor’s base terminal. When there is a burst, the current flows from the emitter to the collector terminal, and the collector terminal supplies the necessary current to the LEDs.
Point D
This oscilloscope trace represents point D on the IR circuit diagram, which lies at the output of the left infrared sensor. What this allows us to see is when the sensor detects an object within its range. The short dip in this trace means that an object has been detected.
Point E
This oscilloscope trace represents point E of the IR circuit diagram. What point E depicts is the threshold voltage of the infrared sensors for detection.
IR circuit assembled
This is our infrared circuit fully assembled, with many thanks to Bright who assembled this and lab assistant Hector for assisting with circuit analysis. This circuit serves as a prototype so that we may test the functionality of infrared sensors and their behaviour.
IR circuit testing
This is a YouTube video of a test we performed on our infrared circuit. As it has been described in the video, when there is an object (my hand in this case) in front of the sensor, this sends a signal that turns on the corresponding LED, which also activates the portion of code in the Raspberry Pi Pico which turns the wheels in a manner that reverses and turns the micromouse.