Semester 2 Week 4 To 6


After CA3, the control system is almost up and ready. However there are some issues that i have to tackle. These problems are regarding the the pump and the contain.

Task completed this week includes:

1) Run more test to find out what the problem is.

2) Found out that control system is jerky due to the pump operating at too high power.

3) Have to plan whether to change the pump or work with existing one.

4) Decided use another PIC with lower freq to control pump.

5) Found out that 1 problem with the container is it cause the solution to be stagnant and dun mix well.

6) Decided on using an addition pump to force the water to move inside the container to mix.

Lessons learnt and reflections:

The PWM program is done by Chris but when the program is tested with the actual system. The control is jerky and fluctuates endlessly. After doing a few more test, we found out that the main problem with the control system are the pump and the mixing problem in the container.

There is a big problem with the pump because the pump requires a kick start voltage of 100% then it can be reduced to a lower work rate. Initially we wanted to change to another pump but other pumps in the market are either too expensive or will take too long to come. So we decided to work on this pump and see what we can do. After sometime we found out that it is possible to use another PIC at a lower frequency to force the pump to pump lesser liquid. This can help the control system to control the pH more accurately with lesser fluctuation.

Another major issue with the containers is the mixing problem. We realized that the way the contain is designed causes the solution to be stagnant and thus the pH sensor will not be able to detect the real pH of the solution which can greatly affect the control system. The solution that we came up with is to use another pump to force the solution to cycle in the container. This will allow the solution to mix better.

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