PCB design / cheap manufacturers

[Thomas Parry]

Hi Emil,

A few comments:

   1. You don't have any bypass/decoupling capacitors, this isn't great for
   digital IC's - I would recommend adding some 100nF capacitors between each
   ICs power and ground. Some larger (10uF) decoupling capacitors at the
   raspberry pi connector to act as local energy resevoir won't hurt either.
   http://www.allaboutcircuits.com/technical-articles/clean-power-for-every-ic-part-1-understanding-bypass-capacitors/
   2. If you're going for a double sided PCB I would recommend flooding the
   top layer with the ground net.  The solid reference plane reduces the
   inductance in the current return path and prevents ground bounce.  This
   will help ensure more reliable operation of your circuit.
   http://www.elmac.co.uk/pdfs/Lord_of_the_board.pdf
   3. Your traces look quite thin (it may just be the scale) I would ensure
   these are with your PCB manufacturers capabilities.  Even if they are
   within the manufacturers capabilities it is always good to make the traces
   nice and thick (especially power traces) to reduce inductance and voltage
   drop as well as making the manufacturing more reliable.  I see you're
   tracking them in between pins of the IC but you could also have thicker
   traces around most of the PCB and neck (temporarily reduce the trace
   thickness) to pass between the pins.
   4. It's good practise to terminate (to ground or power) unused inputs
   (ideally through a resistor in case you change your mind later) to prevent
   them toggling with noise.  The AY-3-8910 seems to have internal pull ups so
   they're not a big deal but the 74HC245 has floating high impedance inputs
   which could pick up noise.  This won't stop you're board working but I
   thought I'd let you know.
   5. In terms of PCB manufacturing it is worth having a look at
   http://pcbshopper.com/. Enter your PCB details and get a comparison of
   suppliers - basically a MoneySupermarket for PCBs. Most manufacturers will
   be in China but generally they deliver good quality and you can pay for
   faster delivery if you want.


I hope that's useful and good luck with your build!

Tom

On Wed, Aug 3, 2016 at 6:55 PM, Emil <emil.carr at openmailbox.org> wrote:

> It is single sided, yes, but I have the AY-3-8910 mounted on the bottom
> side. It's weird, I know, but it works to save space.
>
>
>
> On 03/08/16 16:41, Gordonjcp wrote:
>
>> On Wed, Aug 03, 2016 at 03:38:52PM +0000, Emil wrote:
>>
>>> The new schematic / pcb design is at http://imgur.com/a/E9zL8
>>>
>>> Is it single-sided?  It looks like you've got one chip on top of the
>> other, but I guess if it's on the bottom of the board it'll be okay.
>>
>> If you can do a single-sided version I can have a crack at etching one up
>> for you.
>>
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.electronclub.org/pipermail/members/attachments/20160803/7b3cdda8/attachment.html>