Newbie quesitons before build my own custom ARDUINO MEGA 2560

Hi everyone

I’d like to design and build my own custom Arduino mega 2560 PCB but before I do that I have some question about electronics components and some links in the board and I'm really interested to ask experience people like :blush: you in this forum… by the way

I read this article about make Arduino UNO

also I read this one

as we see there are many components not used in the board because the remove USB port and ATMEL chip to programming
Arduino via ISP

I'm interesting in this edition of Arduino mega 2560
there is schematic for design

my questions are :disappointed_relieved: :-

Q1/ what’s difference between Regular Arduino MEGA 2560 and Freaduino_Mega2560 in components that’s make Freaduino_Mega2560 5V current 2A.

Q2/ how the select able switch between 5 and 3.3 v work, the mega have 3.3 v so why there is select able switch.

Q3/if I want to remove USB and FTDI chip from the design and programming the board via ISP pins, how many capacitor and resistor and other components from the schematic do I need to remove because I don’t need it.

Q4/ LDO Voltage Regulators NCP1117ST50T3G is this chip use to drop the input voltage from power jack from 9v to 5v to source all the board with mega2560 chip or not.

Q5/ why there is OP LMV358IDGKR and for what it use if I want to remove the USB do I need it or not.

Q6/FDN340P Fairchild Semiconductor what is this chip and if I want to remove the USB do I need it or not.

Q7/why there is another LP2985-33 Linear Regulator with different size and also if I want to remove the USB do I need it or not.

Q8/ as you see in this link

the Freaduino use DC/DC MP2307 while the original Arduino Mega 2560 don’t have this chip

Q9/ if I’ll remove the USB with ATMEL or FTDI do I need to use Two crystal 16mhz in the board or one will be enough?

I hope everyone have knowledge share it with me because me experience in electronic :cry: circuits and PCB is poor.

Kind Regards,

To be honest, if you ready to design your own board, you shouldn't need to ask these questions. But I don't have the Mega schematic with me since I am on my tablet. I will get back here tomorrow with the answers.

On a side note most of those are statements, not questions.

To be honest, if you ready to design your own board, you shouldn't need to ask these questions. But I don't have the Mega schematic with me since I am on my tablet. I will get back here tomorrow with the answers.

On a side note most of those are statements, not questions.

codlink thanks for helping

I ask these questions because want to know about this components and how to use it in the circuit before I start design my own PCB,

I will not use program like CADSOFT EAGLE of Altium Designer or DipTrace it's not free, expensive and little difficult

there is fritzing and PCBWEB , , EasyEDA all these sites beside fritzing software is free and very easy to learn for beginner and people who never design PCB before I can place the components as what in Arduino schematic and make some changes in design and PCB color but this will not tech me anything about electronic, I want to know how to use the component I download Proteus software to use the components and make some simulation to make my own connection for it and understand the using of capacitor in the circuit, but in Proteus 8 I didn't find some components like LM7805
so I'll try so use Multisim and hope these power components included in the software.

I waiting your answer.

CADSOFT EAGLE or Altium Designer

Both have free versions.

Both have free versions.

Free versions of these software offer limit option,
EasyEDA is very usable website till Seeedstudio the Chinese company use it to design their product.

OK I understand most of my question while I'm waiting the answer I make search for it but now I have question,

Freaduino Mega2560 use PMIC - Voltage Regulators - DC DC Switching Regulators
It's "MP2307"

I don't know what is the difference between it and the one used in MEGA 2560
PMIC - Voltage Regulators - Linear

It's "NCP1117ST50T3G"

from this link

I could understand that switching regulator have frequency and variable output voltage
It could provide 5V DC with 2000mA output current but why it use many pins unlike linear regulator which 4 pins only,

I need 2000mA output current with pure 5V DC, what about using one of these chip

I'll use Two 9V battery (everyone 500mA) and connect them in parallel mode to get 1000mA 9V DC and the use one of those 3A 5V PMIC - Voltage Regulators - Linear to convert it to 5v but my question this time is will this be safe for the circuit and PCB board is their heat if i use 3A PMIC - Voltage Regulators - Linear

what about using Double 9V battery provide 1000mA is that enough to get 3A 5V from it

that's all my question hope this time one of those hundred visitors for my thread put some reply :slight_smile: ,

Kind Regards

there is fritzing and PCBWEB , , EasyEDA

Hey! I don't recommend fritzing for making a mega. It will get hairy. I recommend you to add to your options list Kicad :wink:

"Download free version of EAGLE
PCB design software for students, makers, and professionals.
Includes 2 schematic sheets, 2 signal layers, and 80 cm2 board area.
Available for Windows, Mac, and Linux."

You can get a lot on 80 cm2.
A full size Mega is 10.1 x 5.35cm, or 54 cm2.

Since we're on the topic of Eagle - I have used it in conjunction with a laser printer and a pancake skillet to build my own 2 layer prototype boards; try not to laugh. It works but without scientific consistency. Any DYI links which work on a nearly consistent basis?

Thanks in advance.

Use an oven for solder reflow vs a pancake skillet. You can measure and control the temperature much better.
I use an old Sears 4-element toaster oven and an Extech 330 with thermocouple probe for temperature monitoring.
Hot soak Kester EP256 solder paste at 150C for 90 seconds, then ramp up to 195-200 for 90 seconds, then let cool.

I don't make my own boards, my designs are too complex for that. Plus I want plated thru holes, solder mask, and stencils. No way I'm doing all that by hand:

I buy bare boards from, they've been turning them quick lately - I placed an order on the 8th, received boards the 17th (DHL shipping). 9 days! So fast they beat the solder paste stencils I ordered from, so I'm waiting on that delivery to assemble boards now.

my designs are too complex for that.

lol- understood. Thanks for the tip(s); I'll look into both.

Fellow hobbist,

hi to everybody.
ı designed a new pcb project for my own mega2560 but its not worked.
can somebody help me ? why didnt worked my project wondered.

ı added my project files.
thanks my friends.

ArduinoMega2560.pdf (42.5 KB)

ArduinoMega2560_AcOCrW.pdf (26.8 KB)

Just after brief look at the schematics, I see 100pF capacitors from XTAL pins to GND and 1M resistor between them. Value 100pF is too high and the resistor is unprofitable. See the datasheet for the value of capacitors: 12-22pF!

you are right my friend.
i wrong draw schematic,but i correct on pcb this mistakes.
but its not worked.
i will remove 1M res at tomorrow. maybe works.
thanks for your idea.

The DC-DC chip RT8289 is more interest with 5v and 5A :slight_smile: