[hackspacebristol] Any way to test schematic designs? (MrPiWorld)

Tom Gardner tggzzz+hs at gmail.com
Wed Sep 3 21:36:30 UTC 2014


On 3 September 2014 21:43, matthew venn <matt at mattvenn.net> wrote:

> Well I'm clearly an amateur, but what I do is have a good go at
> breadboarding it first,
>

You can lead yourself up the garden path with breadboarding, unless you
understand what you're doing. (I've seen it happen to people in Hackspace,
and they become dispirited).
http://www.analog.com/static/imported-files/rarely_asked_questions/moreInfo_raq_analogBreadboarding.html

Personally I avoid the poke-wires-into-plastic-breadboard boards like the
plague - I always seem to end up debugging the subtly faulty breadboards
w.r.t. bad/intermittent contacts, long wires (noise pickup, inductance),
stray capacitance between rows of contacts, and complete inability to
effectively decouple ICs[*]. Having said that, I think they can be
successful if you plug a complete MCUs/boards in and only have minimal
external circuits. Or for audio circuits. Maybe others have had more luck
than me!

For analogue circuits and small digital circuits, consider the "dead bug"
technique favoured by some legends.
http://embeddederic.blogspot.co.uk/2011/08/remembering-jim-williams-dead-bug-style.html

For large or high speed digital boards, go straight to PCB.



> then make a pcb. Order from oshpark for about £3 and then see what works
> and what doesn't. A few boards later and it's all good.
>

Sometimes it is the turn-around time that is the pain.



>  I've never found a modelling program I got on with,
>

A sound attitude!



> and the firmware I do is pretty basic.
>

KISS is always a good principle!

When debugging firmware, consider using a ready-built board so that you are
only fighting one unknown at a time. Then cost/size reduce to a single PCB
later, if necessary.

[*] Can you still get Rogers Micro/Q capacitors?
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