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My Very first fully custom PCB looking for Schematic Input and maybe any errors.

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SirAlucard:
So I've made my first PCB, granted I probably should have gotten a couple of eyes on this first to make sure I didn't miss anything, however I've already made the PCB and have assembled it. However after the fact I would like to get some of your input on it. See if there is anything I missed or should have done.

This was to mirror my breadboard that worked fine. Using an arduino a couple of power regulators, and it drives a motor(H1, pin 5+6), and two solenoids(H1, Pin 3+4 w/+5v) with a sensor(H1, Pin2 + 5v). 

Hopefully the schematic makes more sense than me trying to explain it.

NivagSwerdna:
I would have brought TX, RX, GND  and RESET out to a separate header and added the pull-up and the diode you find on UNO reset... that way you could program it via a serial bootloader (and make it pretend to be an UNO)

WattsThat:
Something is weird with the crystal circuit, pins 7 & 8 shorted and grounded? Don’t know, it may not have shown up in the net as a ground. The 1M resistor is wrong as well, that’s something that appeared on the Mega schematic and has no basis in fact from any Atmel datasheet. Depending upon the crystal, you typically need 15-20 pf loading caps from each crystal pin to ground to get it to resonate.

AVCC should be fed through a 100uh choke and have a 100nf bypass cap on it, especially since you’re suppling from a switch mode regulator. You may find the analog to be very noisy due to the combination of the lack of filtering and the presence of supply noise. Board layout/grounding will be a factor as well.

bson:
Are you driving a solenoid with a pair of MMBT3904s?  Those a very low current devices...

SirAlucard:

--- Quote from: WattsThat on May 12, 2020, 01:26:05 am ---Something is weird with the crystal circuit, pins 7 & 8 shorted and grounded? Don’t know, it may not have shown up in the net as a ground. The 1M resistor is wrong as well, that’s something that appeared on the Mega schematic and has no basis in fact from any Atmel datasheet. Depending upon the crystal, you typically need 15-20 pf loading caps from each crystal pin to ground to get it to resonate.

AVCC should be fed through a 100uh choke and have a 100nf bypass cap on it, especially since you’re suppling from a switch mode regulator. You may find the analog to be very noisy due to the combination of the lack of filtering and the presence of supply noise. Board layout/grounding will be a factor as well.

--- End quote ---

I'm using a 16mhz Ceramic Resonator. I'm actually using the same one as an arduino uno smd version I have. I just copied parts over and seems to work fine after I remembered to set the correct fuses. The model # on them are CSTNE16M0V530000R0

I'm actually finding the voltage to be very clean with what I have. Altho I think I still might have an issue somewhere on the actual board, I don't think my smd reflow went all that well. This schematic mirrors the components used on my breadboard using two voltage buck converters to take a ~14v input and regulate to 12v and 5v.


--- Quote from: bson on May 12, 2020, 08:30:40 am ---Are you driving a solenoid with a pair of MMBT3904s?  Those a very low current devices...


--- End quote ---

I'm driving a single solenoid with a single MMBT3904, On my breadboard I am using 2n3904, and the solenoids only draw about 100mAh, they're very small. However, and I don't think this is an issue with the actual Transistor as I just soldered the 2n3904 in place of the SMD component and it was still having the same issue, but it keeps resetting. I don't know if this is an issue coming out of the micro-controller, but it might be. I'll post a video on what's happening soon.


--- Quote from: NivagSwerdna on May 11, 2020, 10:46:52 pm ---I would have brought TX, RX, GND  and RESET out to a separate header and added the pull-up and the diode you find on UNO reset... that way you could program it via a serial bootloader (and make it pretend to be an UNO)

--- End quote ---

I didn't want to run a bootloader on it, and the idea is to program the chip directly by the ISCP and leave it be. Never to be touched again.

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