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I am an EE major working on my capstone project of developing a PCB for a single-phase power energy meter and I need help scrutinizing it.

I Intend to interface this circuit with my Raspberry Pi 3 (connected at terminals X7-1 and X7-2). The current transformer is going to connected to terminal X6-1 and X6-2. The load for my analysis would be connected to terminals X4.

I would really appreciate any relevant comments concerning the progress of my work. Any suggestions here? Thanks.

Here is a link to the actual Eagle file for viewing.

enter image description here

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  • \$\begingroup\$ Please name inte inputs in the schematic so one doesn't have to switch between your text and your schematic. Where does your voltage divider connect? What’s your layout situation? What’s your current sense transformer? \$\endgroup\$
    – winny
    Feb 15, 2019 at 10:16
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    \$\begingroup\$ R34 and R10 are labelled 0R so they short-circuit your CT and you can't take any current measurements. What are the 20R and 150R resistors for on the CT input? What is a T8C5121? Datasheet link? \$\endgroup\$
    – Transistor
    Feb 15, 2019 at 10:35
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    \$\begingroup\$ Also, I removed the tags that were irrelevant to the question you've asked. Also, if you need scrutinizing: Tidy up your schematic. There's plenty of angled connections that should be 90°, there's a lo of very avoidable crossings of wires, where it's not clear whether you meant to put a junction or not, you're just labelling wires "VDD" instead of using a power symbol, you're not specifying what IC4 is, and I think you meant switches at your TP1 to TP11. If you handed in this schematic as your project, that all would give you a solid minus on the due diligence grade. \$\endgroup\$
    – Marcus Müller
    Feb 15, 2019 at 12:44
  • \$\begingroup\$ Is V2N connected? \$\endgroup\$
    – analogsystemsrf
    Feb 15, 2019 at 14:33
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    \$\begingroup\$ Your 'LOAD' and 'GND' labels should probably be 'LOAD' and 'LINE' or 'NEUTRAL'. The datasheet link belongs in the question rather than buried in the comments. The datasheet shows that they're monitoring the voltage across a resistive shunt. You're using a CT so you need to add a shunt or 'burden' resistor. \$\endgroup\$
    – Transistor
    Feb 15, 2019 at 18:06

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I'm not familiar with that chip and don't feel inclined to study it too deeply but offer the following observations.

enter image description here

Figure 1. The SD3001 datasheet.

Note that the shunt resistor (1) is referenced to the live input (2) which is the "ground" for the whole circuit (3) and the reference for the chip (4). That strongly suggests that the current measurement input must be correctly referenced to the chip ground. Your CT inputs aren't so you may have an issue there.

Your schematic doesn't show junctions clearly so many of the wires could be interpreted as either junctions or crossings. You should check the settings to see if you have some feature turned. off.

Turn C4 and C5 so that they are vertical which will make it clear that they are decoupling. The kink on the ground of C6 is unnecessary and similarly moving R1 up would tidy up that area. The diagonals on the TPs and the open-circuit tees add some further confusion so they should be tidied up too. They're all very small points but all add to a tidier, easier to read schematic.

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 2. Sample block diagram.

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  • \$\begingroup\$ @Martin: See if Figure 2 helps clarify your thinking. You should probably put a very clear label on your schematic and PCB that the low-voltage circuit is not isolated from the mains. \$\endgroup\$
    – Transistor
    Feb 16, 2019 at 14:04

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