Looking for some feedback and constructive criticism on my latest board design. If you see anything, please let me know what i got right/wrong/ could've done differently.

Project description: Smart Light Switch: A PCB controlling a Wi-Fi-enabled light switch, allowing users to control lights remotely via a smartphone app.

1. Microcontroller (MCU):

• A microcontroller with Wi-Fi capability, such as the ESP8266 or ESP32. These chips handle both the processing and the Wi-Fi communication.

2. Power Supply:

• AC to DC Converter: Converts the mains AC voltage (e.g., 120V or 240V) to a DC voltage suitable for the microcontroller (typically 3.3V or 5V).
• Voltage Regulator: Ensures a stable DC voltage to the MCU (e.g., an LDO or a buck converter).

3. Relay or Triac:

• Relay: An electromechanical switch that controls the high voltage side (lights).
• Triac: A semiconductor device used for switching and controlling the AC load.

4. Optocoupler:

• Provides isolation between the low-voltage MCU circuit and the high-voltage AC circuit to protect the MCU.

5. Capacitors:

• Decoupling Capacitors: Typically 0.1µF and 10µF capacitors near the power pins of the MCU for noise reduction.
• Bulk Capacitors: Larger value capacitors for stabilizing power supply (e.g., 100µF).

6. Resistors:

• Pull-up/Pull-down Resistors: Used for ensuring correct logic levels on inputs and outputs.
• Current-Limiting Resistors: Typically used with LEDs or other components that need current regulation.

7. Diodes:

• Flyback Diode: Protects the relay coil from voltage spikes.
• Rectifier Diodes: If designing an onboard AC to DC converter.

8. LED Indicators:

• Used to indicate the status of the switch (e.g., power on, Wi-Fi connected).

11. Connectors:

• Screw Terminals: For connecting the high-voltage AC wiring.
• Programming Header: For flashing the microcontroller during development.

Schematic:





Board:

 

Schematic in black and white is easy to ready. With colors, no.

 

Schematic in black and white is easy to ready. With colors, no.

true, it's just easier on my eyes lol

 

I would not have 120VAC on the board.
I would use one of the many AC-DC Power Bricks available - perhaps one that has a +5VDC output. Then just down-regulate that to your required +3.3V.

When you put 120VAC onto your board, you get into all sorts of issues - <shudder>

 

I don’t see any provision for an antenna. Am I missing something?

 

Would you need a ground plane on the CCT board?

 

I don’t see any provision for an antenna. Am I missing something?

Ahhh I missed it. Thanks for the catch

 

I would not have 120VAC on the board.
I would use one of the many AC-DC Power Bricks available - perhaps one that has a +5VDC output. Then just down-regulate that to your required +3.3V.

When you put 120VAC onto your board, you get into all sorts of issues - <shudder>

Thanks I'll look into this. Appreciate the feedback

 

Would you need a ground plane on the CCT board?

Could you elaborate a bit more on what you mean pleasem

 

Ahhh I missed it. Thanks for the catch

I would follow exactly the layout recommended in the chip’s datasheet (assuming there is one). Antenna design is black magic, at least to me. The physical design is critical.

 

Could you elaborate a bit more on what you mean please

You don't say what S/W you are using for PCT development, but most will allow a GND plane to be added, generally on the 'back' side of the board.
This is a method of filling in all unused foil space with CCT foil bonded to the common supply source.

https://resources.altium.com/p/creating-ground-plane-your-pcb-design

 

Fuse should break L(Line) side, not N(neutral) side, of AC input.
But I don't recommend connecting AC directly to PCB board.

 

Fuse should break L(Line) side, not N(neutral) side, of AC input.
But I don't recommend connecting AC directly to PCB board.

thanks for the tip yep, I'm redesigning for a power brick instead.