Decoupling capacitors

Other Hardware General Electronics
1

Hi,

I'm sorry this is 3 questions in one post. :S

1.)
I have some questions about decoupling capacitors. As I understand it, you're suppose to use something like a 0.1uF for each chip in your circuit to help protect from noise. However, i've built this: http://arduino.cc/en/Main/Standalone#.Uyw_Ia1dXXE, and I don't see any decoupling capacitors for the ATMEL chip. I do see something for the crystal, but not for the power supply. Can anyone share some light on this?

2.)
Also, I notice that on the 5 volt regulator the 10uF capacitor is placed before the power lines (on the right hand side) does it matter if it is placed before the power lines instead of afterwards?

3.) When adding decoupling capacitors do most people just put them on the powerlines [- & +] and then straight after send the power and ground to the chip? Or do they try and take the capacitors off the power lines.

I hope all that made sense. Thank you to anyone who can help.

Cameron.

2

cameronasmith:
I don't see any decoupling capacitors for the ATMEL chip. Can anyone share some light on this?

That page doesn't do it correctly...?

cameronasmith:
When adding decoupling capacitors do most people just put them on the powerlines [- & +] and then straight after send the power and ground to the chip? Or do they try and take the capacitors off the power lines.

Just put them as close to the chip's Vcc pin as possible.

3

Wow really, that page doesn't do it correctly. But, isn't that the official Arduino website?

Can you recommend where you would put the capacitors because there are lots of power and ground connections. Or do I just put them on every + & - connection?

Thanks,

Cameron.

4

Every connection, right up close to the chip, ceramic, always, all logic chips.