Week 8, 8 Oct

Last week, I finish testing all the individuals parts and confirmed their schematic designs. Thus, this week, I modified my output circuit schematic diagram and proceed to drawing the PCB.


Output Circuit Schematic draft 2

Since the DIP version of step up voltage converter that Roshan ordered has not arrived, in the meantime I will use Thuong's power supply first. If the overall circuit works, I can proceed to add the power supply part and send out for fabrication already.

Spent 2 days in the PCB, finally I come out with the design, approved by Roshan.


Basically, it has 3 ground planes: high-current ground, digital ground and analog ground.

The high-current ground covers mainly the air pumps, which are motors. The digital ground covers the PIC and the buffer component. The analog ground covers the amplifier circuit, sensor and voltage inverter circuitry. Because the analog needs to be very large in order to eliminate any noise present in the circuit, I added one more ground plane at the top layer. All of the ground planes are connected by a few copper lines.

Lesson learned:
I was wondering: Since we need the ground plane to eliminate noise, wouldn't it be better if we use wider lines to connect those ground planes together? To this, Roshan taught me that we should actually use thin lines instead. This is because thinner lines can prevent any interference from directly affecting the other ground. For better conductivity, we will use a few lines to connect them together.

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