A few notes on:
PCB designing
I am in no way an authority or a saint in designing PCB layouts. However there are a few things which one might keep in mind when going into the design of PCB layouts.
- Get decent PCB layout software, not graphics software. This doesn't at all mean that a "student" version of a PCB design package which is either limited in amount of pins or has the printing disabled won't work. In the
latter case there's ways to get around that. The main objective of PCB layout software as opposed to graphics programs is that PCB software is targetted on making sure there's no design
errors in the layout. In the simple form which is totally suitable for effects layouts this means that the software will tell you that all connnections are made or that traces or
pads are too close together, resulting in problems when etching the PCB.
- When thinking about making multiple PCB's from one layout the option of not using stuff like press 'n peal or even worse, drawing on copper might be considered. The solution with rough
PCB material with a photo positive layer doesn't have to be expensive. I've used a 200 watt lightbulb and a piece of standard glass for years before buying an UV table.
- When designing that PCB, make sure to start off with a decent schematic which will generate a component list and a netlist. I've seen many people starting off with the PCB layout software
straight away by dragging (physical) components onto the screen and starting to connect them. Naturally with all error checks disabled.
- With the above in mind it comes clear that one has to understand the topology of PCB layout software. Depending on the program used the learning curve may be longer and/or more difficult.
- Use that error check in a positive way. It's not there to tell you you made an error in a negative
way but to help you avoid them. In countless cases I just "dumped" a component on the spot where it
needed to be (regardless of wether there were traces in that spot already) and let the error
check tell me what needed to be corrected. This approach is much faster than first attempting to
make place and then placing the component, deleting connections (just in case) for which a
simple relocation would've done.
- As for the techstuff behind it. Why do you place a component on the position it is in? A standard approach is to follow the schematic. A good thing, especially while debugging if it doesn't work but unforunately
Components aren't physically shaped as their schematic counterpart. Therefore this appproach only works in general sense.
First of all identify the points where components are connected to a point (node) that has a high input resistance, for example, the inputs of an opamp. Having long connections to these points mean the whole PCB trace
can act as an antenna for undesired noise. Therefore keep these connections as short as possible.
In the same way of thinking, connections tied to a node with a low output resistance, for example
the output of an opamp, may be longer as they aren't that vulnerable for noise.
- PCB designing is an art. That doesn't mean it should look like an artwork. Consider why you have a trace running the way it does. Does it look neat to have all these traces running exacly in parallel to each other, a.k.a. trace hugging?
Fine but consider that having them run in parallel like this will cause crosstalk between them.
Therefore analyse if there's a possibility of crosstal and if so, pull them apart, avoiding things
like feedback later. Also, you may not like the 45 degrees traces and prefer the 90 degree angles.
In the 2nd case however, the angle can act like an emitting antenna and if there's sufficient
energy behind it, cause noise inside the pedal's case. An example of this is the output of a
squarewave LFO for a tremolo which has a lot of energy in it's rising and falling sides.
Getting back on that artwork. A while ago I ran into a designer who more or less liked to mimick the PCB layout style of 70's designers. In that time all PCB design was done by hand and reroutying a trace in a different way meant pealing off black tape, therefore the designers tended to save space wherever they could.
Text, knobs and LED placing.
Again, I won't tell you what to do, however you might consider:
- First of all most people are right handed. Therefore text on the right side of buttons tends to become unreadable because your (right) hand convers it when twiddling other buttons.
- Get those knobs out of the way of your footswitch! You'll step on your knobs and eventually smash them.
- Don't put that LED next to the switch. You'll step on it sooner or later, pushing it inwards, even when it's next to the switch.You used a reflector so it cannot be pushed inward? How much dirt is there in the profile of your shoes after entering that muddy festival field ending up in that reflector?
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