Help checking schematic; Arduino Nano audio sequencer

[tonyame]

I am working on a pcb using EasyEDA for an Arduino Nano based audio sequencer synth, something I modified from what I found here: Auduino 4-step sequencer – Cassiopeia Ltd

Could use some help checking it over, any mistakes, etc. The help is greatly appreciated.

*Some unusual things you might see in my schematic are a polarity protection p-channel MOSFET. The board peripherals (pots, etc.) are powered by regulated 5V, however the Nano itself is powered by 9 volts tapped before the 5V reg chip.

I used two CdS photo-resistors connected to on/off toggle switches which adds their resistive values to analog A0 and A6. The photo-resistors are both wired from the analog input pins to GND, which works very well for me.

Also, the mono audio jack is not connected, since I wasn't sure of it's pinout when I ordered it. So I left it as unconnected with jumper connector headers, so I can wire it properly when assembling the board.

Sincere thanks for any help anyone could offer.
TonyAm

[gilshultz]

It looks like a good design, with a lot of effort put into it. I like the polarity protection. I would recommend some bulk capacitance maybe 47uF on the DC input.

One thing I have been doing lately with that protection MOSFET is place a red LED in front of it so it turns on when the power is reversed along with a green one for power.

[tonyame]

Thank you, I appreciate it. The LED idea is interesting.

Was it you who gave me that idea of using the p-channel Mosfet? I love this use of the MOSFET, simple & effective.

Everything I learned came from this forum and the All About Circuits forum, amazing/smart people.