Some tips on board designing - PCB images

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Some tips on board designing - PCB images

Post by Barjugh » Thu Jan 12, 2017 8:02 am

I'm designing a board (with EAGLE) for my first time and, before posting here, I've read some topics and documents on how to design a board, but I still need help since I'm a beginner.

My board should power and control 9 solenoids (12V, 2A) and a servo. I will use a board with two layers and 90um.

Two proportional solenoids use PWM at 120Hz. The oscillator for atmega328p is 16Mhz.

The board is powered by 12VDC with 12VDC, 200Ah AGM battery and I'm using an isolated power supply (+5VDC) to power up the microcontroller (atmega328p datasheet: ... P-20AU.pdf). The atmega328p isolation is made by optocouplers which drive the MOSFETs.

This is the schematics made in Eagle where GND5 is the ground for the 12V circuit and GND is the ground for 5V system (sorry if the schematics is not very clear, EAGLE does not allow me to remove some junction points).

I don't know if I need to create two ground planes (one for GND5 and another one for the GND) or if I only need to create a ground plane for the GND5. The +5V system powers only the atmega328p and a RC receiver, may be, it does not need a GND plane? So I can only create the GND5 plane?

It is better to put only the ground plane on a layer and all the other connections traces and +12V traces on the other layer?

Could it be a good idea to create a "+12V plane"? What are your suggestions for the designing of this board?

I'm following these guidelines:

place the decoupling capacitors C22, C23 very close to the microcontroller
place filter capacitors close to the drivers (MCP1406)
place diodes close to the connectors for the solenoids P_OUTx
large traces for +12V (or a +12 plane??)
only GND5 ground plane (??)
The schematics is now correct and clearer
These are the board layout, the upper and the bottom layout. I placed a ground plane for GND5 (the ground for 12V) and a power plane for +12V. Do you think it is better to place also a ground plane for 5V?

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