Week 4 - 24/3/2017

 At this point the line sensor circuit, motor drive circuit and ultrasonic sensor setup were completed, and they were tested again in this lab session to ensure there was no loose wires or connections.  The test showed that there were problems with the line sensor and motor drive circuit.

-Line sensor circuit

Our line sensor circuit consisted of an LED/LDR connected to comparator circuit along with a potentiometer, providing a reference voltage. The main issue was that the voltage across the LDR did not change with light intensity. The voltage across the LDR was the same as the reference voltage. Changing the resistance did not change the voltage applied to the comparator circuit.

Our approach to solving this problem was to check each component of the circuit and find out where the problem was. What was thought to be the initial cause of the problem was the LDR, the LDR were tested outside of the circuit and it was shown to change resistance with the light intensity. The potentiometer was then tested, we turned the dial while measuring the reference voltage, and saw no change in the voltage applied to the comparator, but a change in the voltage at the terminal of the potentiometer. It was later thought that there was a short circuit within the Vero board. The circuit was eventually re-built again.

-Motor drive circuit.

In the motor drive circuit, we used a dual H bridge which should allow us to rotate the motors in either direction. However, in our test the motors could only turn in one direction. Any attempt at rotating in other direction lead to the IC chip heating up.  Other problem was that the right motor would not respond to any input voltage at any polarity or would randomly move without an input voltage applied.

After many attempts at trying to understand the problem, the IC chip has been thought to be damaged. The dual h-bridge was replaced and the motor drive circuit worked in the way it was expected to.

                  

This lab session was used mainly to find/ fix the problems with both the circuits. These two circuits were separately tested and also connected together again to be tested as well as more tests completed on individual components using the Multimeter and power supply. Once the circuit were working as an expected they were all connected back together again and fixed onto the mobile platform.