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This is my second ever PCB. I am trying to integrate it into a preexisting 12V electronic car. The idea is to take all the inputs from the JST connectors (stop and drive are buttons, ultrasonic and RFM too) and determine whether or not to flip the relay, which is either opening or closing the drive signal (replacing the digital gas pedal on the car). It is a four layer PCB with the stackup sig/gnd/pwr/sig, with small traces and all the communication on the first layer and longer digital traces on the fourth layer. Any advice on slight improvements or significant issues? As you can probably tell, I'm a beginner so any assistance would be super helpful.

USB to Serial Converter Ch340C 12VDC to 5DVC AP63205WU-7 5DV to 3V3 MIC23050-SYML ATMega328P 5V to 3V3 Logic Level Converter SN74AXC4T774 RFM69HCW datasheet RFM69HCW hookup guide (used to determine connections)

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  • \$\begingroup\$ Is 12V subject to transients? Ripple? Load dump? The 4th schematic is illegible. Have you considered running the ATmega at 3.3V? \$\endgroup\$ Jul 21, 2023 at 5:05
  • \$\begingroup\$ Indeed. If the device is meant for automotive environment, the power supply section does not look like it can handle automotive environment. Also why this MCU and why run it at 5V? If you run the MCU at 3.3V you can skip the level converter and second power supply. Also why at this age and day copy an Arduino board with Atmega328P? There are MCUs that are 32-bit and dozens of times faster, and have built-in USB, so you could also leave out the CH340. Regarding USB, I suggest changing from MicroUSB to Type-C as it is more durable. A 12V relay in a 12V environment might make more sense than 5V. \$\endgroup\$
    – Justme
    Jul 21, 2023 at 6:53
  • \$\begingroup\$ I'd suggest putting more work in on the circuit diagram, trying to make it convey as much information about your design as possible. 1) make into an organised whole with subsections,not disconnected islands. 2) Where you want to use labelling instead of wires, use the external connector symbols, not just labelled signals. 3) Make it less cramped. As far as the circuit goes, I'd ask: do you really need 5V and 3v3? Can use use modules for the power, and perhaps an osc module. As regards PCB: it seems there's no mechanical support near the connectors. \$\endgroup\$
    – jonathanjo
    Jul 21, 2023 at 7:23

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