@paulvdh Yes, I wanted to move that 2x4 header closer to U1 to make tracks shorter than the 2.4 GHz antenna on the radio breakout. I think your mod makes that more practicable. Mahalo!
Wait a bit… Is it possible to install KiCad in Linux?..
Yes, it is available for Linux.
You can even add 2 small tracks on the back side with vias to allow the zone to fill up empty spaces.
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For supported platform see: https://kicad.org/download/
(There might be other systems that are supported as well but the ones listed there work for sure.)
I got mired in self-tutor in re ferrite beads, inductors, &c. Seek advice (confirmation?) on possible choice ferrite for the L1 component in below capture.
Ferrite Bead With Axial Wire, 5A, 75 Ohms@100MHZ, DCR Max 0.01 Ohm
Laird 28L0138-10R-10
This one I can stand up close to the chip, keeping C5 nearby as well.
AVCC is the supply of analog circuitry in U1. Such pin should get clear power. Analog circuitry typically don’t gets so high and short current pulses as digital circuitry. So the filtration is needed at lower frequencies than at VCC. Using here 10…22uH is typical, I think.
As ferryte beads has much lower L I would look for inductance and not ferryte bead here.
If you see that element you selected is for 5A and your AVCC pin gets probably few mA the red-light should lite-on in your head that you are probably doing something wrong. There are probably situations that it could be good choise but I don’t know such.
Look at characteristic of that ferrite bead at place where R is close to 0 and X and Z are the same line. I read that Z=8 ohm at 1MHz. From that you can calculate L=1,3uH (and the designer wonted 10uH).
You should use one of:
https://www.digikey.com/products/en/inductors-coils-chokes/fixed-inductors/71?k=&pkeyword=&sv=0&pv2087=u10µH&sf=1&FV=ffe00047%2C142c0685&quantity=&ColumnSort=0&page=1&pageSize=25
I don’t understand power filtering as much as others so I can’t comment on value choice, but I can comment on the symbol used. Ferrite beads, while similar to inductors, are different enough to have their own unique symbol. See the Ferrite_Bead symbol in the Device library.
Thank you for the pointer. I think I approached from footprint point-of-view…lead and courtyard spacing…for a presumed axial-leaded component, generic “filler” component for layout purpose.
Thank you very much for your insight. I had been confused as to purpose/function of two different types “inductors”, ferrite vs. wire wound. Your search link helps me. Something like a Bourns 77F or 78F series should suffice, the wire wound kind. For power supply filtering with a ferrite I may forego the “inductor”. (Although, I recall passing my battery leads through a ferrite on a small “robot” few years back, cannot source my notes for the reasoning).
To note, not many of these Arduino-styled 328P breakouts include the 10uH inductor between AVcc and Vcc, as called for by Atmel (nee uchip). Pololu does, but they use a chip bead SMD inductor, which to me said ferrite. The Laird component sited above seemed best cross-ref to THT, Well, that my small brain could figure.
I go with the following:
10uH Inductor
Thank you all!
Mark
Thanks a lot! I’ll check it
On 2019-03-06 @Efcis suggested to add 2 small tracks to “fill up empty spaces”.
This is not only uselless, it is bad from an EMC point of view.
The loose fingers on the GND plane act as antennas that pick up and radiate noise.
He has also moved the tracks in that area of the board further apart, which is detrimental to the low impedance of the GND plane. The worst modification are the 3 vertical tracks on the top of the screenshot. This forces all GND currents in that area to go complety around all connectors, and this increases loop area.
When I saw this (again) I gave in and started this response.
A near to optimum track layout for this section of this board is:
Notes:
- Copper area on the top of the board is continuous.
- Tracks hrough GND plane are close together to minimize discontinuties in GND.
- By having 2 tracks between resistors R9+R10 and the IC below them there is room for a GND connection, so GND currents do not have to circumvent around these resistors.
- Much more solid copper connection to the north east of Pin 14 of the AVR.
- Thicker copper connection between the East side of U2 and the side of the board.
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