Hello, so I am working on an a PCB design using the Arduino UNO r3 the schematic is below. Some of the questions I had are having to do with the capacitors. What type should I be using for the ones in the power module located next to the power jack the 2 10uF capacitors? Right now I got ceramic ones packaging 0603. I was wondering are polarized ones better ? The same question also applies to the clock capacitors ? I am also looking for through hole mount ones instead of 0603 packaging if any one has any suggestions would be great.
22pF are ceramic.
Power supplies are usually electrolytic as seen on the UNO.
An input 100nF ceramic on the regulator input is recommended.
You might want to add a diode on the power jack.
You need to add controller power pins for decoupling, 100nF ceramic capacitors.
Digikey, Adafruit, Sparkfun, Jameco, Ebay are possible suppliers.
If you are new to soldering, 1206 SMD would be better than 0603 !
AREF connects to a 100nF to GND.
Ok so its best to put the 2 electrolytic 100nF instead of the ceramic ones and just to add a diode.
Along with and extra electrolytic capacitor after the diode to give decoupling on the input of the regulator right and one to connect AREF to ground also?
For mounting I was actually looking to go with through hole mount.
hopeitworks:
Ok so its best to put the 2 electrolytic 100nF instead of the ceramic ones and just to add a diode.Along with and extra electrolytic capacitor after the diode to give decoupling on the input of the regulator right and one to connect AREF to ground also?
For mounting I was actually looking to go with through hole mount.
Regulator input has ~100µF ‘and’ a (100nF ceramic) to GND; output has ~100µF GND.
AREF 100nF to GND.
Vcc and AVcc both have 100nF ceramic to GND.
Why is Vcc and AVcc with a cap to ground ? I thought they would both be to the power module area as how I put it in the schematic. But I'm more asking why it would be the way you said? I see that's how they did it in the schematic on the website schematic to but I'm just confused by the reasoning behind it is all. Sorry I'm new to this pcb design thing so I'm trying to learn all I can. :o
Read this:
http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html
Watch this:
If you connect AREF to 5v there is a situation where you can damage the controller.
Leave AREF connected to a 100nF then going to GND ‘only’.
Ok I will, also a another question would the 0603 surface mount parts be better then the through hole parts? I was going to use surface mount and have the PCB fab house mount them. I was reading cost and time are a factor. But as far as usage and function are there big differences ? I had it original set up with 0603 parts but changed to through hole mount parts.
SMD parts are the normal today, 0603s are small, 0805 are a better size; 1206 is easily managed by DIYers.
THT components will probably need to be done by hand, more expensive.
Why don’t you use Arduino Pro Minis ?
I did not have a pro mini was why. I had an uno laying around and tested out the project with that . But looking at the schematic it would have been better of to go with a pro mini. Yah I might switch back to the 0603 and have the fab place do the soldering. The only issue im having is with the capacitors finding the right library for the electrolytic ones.
I might switch back to the 0603 and have the fab place do the soldering
The "fab house" makes the bare board. A "PCB Assembly contractor" can assemble/solder the board. But here in the U.S. there is a few-hundred dollars in 1st run set-up fees and then a minimum quantity is a few-hundred dollars more.
Are you building in production quantities? I've never heard of a hobbyist contracting-out assembly...
FYI - Electrolytic capacitors are usually 1uF or more.
So I went ahead and made some of the changes you recommended as far as the AVCC/VCC and the AREF.
Now with the regulator I couldn't find ~100µF 'and' a (100nF ceramic) to GND; output has ~100µF GND. . I did find the 100nF ceramic but instead i went with the 47uF from the schematic of the R3. I hope they will be ok ?
Then I switched back to the 0603 packages I'm going to have the fab house mount them.
Now for 0603 SMT when I run traces in board view it should be on the top layer if I'm understating that right?
No I'm not building in production quantity I am just building the 1 board. So I guess it would be best to just go with THM then if I am just building the 1?
I suggest you use a Pro Mini, should be able to get them < $5 each.
An FTDI cable is needed to program the Pro Mini. ~$15 you just need one.
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AVCC goes to +5v and the 100nF with the other end of the capacitor connected to GND.
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Move C10 to the input of the regulator (install close to the input pins), 7805 may need a heat sink.
-C5 and C9 are installed close to the controller’s pins.
would the 0603 surface mount parts be better then the through hole parts?
That's an interesting question. 10uF 0603 ceramic capacitorsdidn't exist when the 7805 was designed. The 100uF being suggested as an input cap still don't exist in that size (at the voltages that would be needed.) In theory, a ceramic capacitor would be "better" in a couple of ways, but it's not clear that those would be helpful (or even "not harmful" for a particular regulator, and there are some parameters that are "worse" with ceramic capacitors as well.
@ larryd what do you mean about the AVCC I'm lost on the connection your talking about for it ? Should C10 be lined up like the 47uF cap when being moved to the front ? Yah I will need to put a heat sink on I'm looking at about (7v -5v)*1.5A=3W in heat.
The AVCC pin goes to 5v.
The AVCC pin also goes to a 100nF capacitor with the other end of the capacitor going to GND.
This capacitor is to be located as close as physically possible to the AVCC pin.
Install a 100nF capacitor as close as physically possible to the input pin of the regulator.
The other end of this capacitor goes to GND.
The input 47uF input capacitor is in parallel with this 100nF capacitor.
There are switch mode replacements for the 7805.
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