[sdiy] prototype boarding (help?) and homemade pcbs.

[Michael Bacich]

On May 13, 2006, at 3:01 AM, Cole Groff wrote:

> would you guys happen to have any suggestions on how to transfer
> circuit schematics to a prototype-board like this?


First of all, are you working with a solderable prototyping board  
(otherwise known as "perfboard"), or are you using one of those white  
plastic, unreliable-as-hell, waffle-hole temporary proto-boards?  Not  
that you shouldn't use them, but... you shouldn't.  Their flakiness  
will just add an additional layer of uncertainty to your  
experiments.  You're gonna have to build it with solder eventually,  
so why not now?

Some prototyping tips:

Go slow.

Draw a picture of your physical layout on paper before you actually  
start to work with the parts and the board.  Get some graph paper and  
draw a layout using the grid to represent the holes on your proto  
board -- maybe even draw a few different versions to find the best  
one.  You can use a blue pen to draw the jumpers on the top  
(component) side of the board, and a red pen to draw the jumpers on  
the bottom side (the solder side).  Use only red and blue, never  
purple, orange, or green.

Keep all of your chips oriented in the same direction.  That is, Pin  
1 is pointing the same way on all chips.  Unless your name is Buchla.

Figure out your ground and power connections first.

Try to visualize a few different possible layouts for your chips and  
parts, maybe even temporarily put them together a few ways without  
soldering, to find the most logical and efficient layout.

Use color-coding on your various jumper wires.  You can choose an  
arbitrary color system -- it's just to help you identify which wire  
is which once you start growing a forest of parts and wires.  Take  
notes as to the color of each wire.

Don't crowd your parts -- give yourself some space, so you can both  
see things better, and so you have rooms in which to make and fix  
mistakes.

Triple check every connection against both your schematic and your  
layout drawing before you move on to the next connection.

Take special note of polarized components such as diodes and  
electrolytic capacitors.  make sure they're pointing the way they're  
supposed to be pointing.  Especially the caps, because they like to  
explode when you put them in backwards.

Go slow.

Solid wire jumpers underneath the board are better than flying wire  
jumpers on top of the board.  It's OK to use both, but try to make  
your jumps on the solder side first, and the component side only if  
you must.

Try to use the extra lead length of your resistors and caps as part  
of your jumper network whenever you can make a kind of "daisy chain"  
with the lead).  It'll help clean things up, and make a more  
physically solid circuit.

It's perfectly acceptable to put resistors, diodes, and small caps on  
either side of the board.  Those parts can do double-duty as very  
handy jumpers on the solder side, can be used to solve routing  
problems, and can reduce your overall wire jumper count if cleverly  
placed.  It's probably best to keep the larger parts all on the  
component side, though (chips, transistors, big caps, etc.).

I like to use those little metal "flea clips" to attach flying wires  
to the board.  They look like a little metal flag, about 3/8" to 1/2"  
long.  These make it easier to move or remove the wires if you must,  
and they make a stronger anchor point for the wire -- stronger than  
just pushing the wire through one of the holes, which increases long- 
term reliability.  These clips also protrude through the hole and  
poke out underneath the board, which gives you another convenient  
point to solder things onto on the underside.  You're also able to  
solder up to three separate wires onto one of the clips, if the need  
arises.  You can buy them in a pack of 100 for a few dollars.   
They're well worth it.

Keep some insulation tubing (or lengths of cleanly stripped off wire  
insulation) handy, so you can selectively insulate solid wire jumpers  
or component leads under the board, when necessary.  This will let  
you run some jumpers and leads    over the top of others without  
shorting things.

Don't power it up until you have triple-checked everything against  
both your drawing and your schematic.  If you can, use sockets for  
the chips, so you can power it up without the chips in place, and  
test to make sure that the voltages are what you expect at all the  
right places.  When they test OK, power down, put in the chips, and  
power up again.

If the circuit you're building is comprised of several clearly- 
defined sub-circuits, try building one sub-circuit at a time (leaving  
plenty of room for the rest, of course).  Move on to the next sub- 
circuit when the first one checks OK.  This will make a large project  
less daunting and confusing.  For instance, when building a VCO, you  
could first build the sawtooth or triangle oscillator core, then when  
that's working OK, add the waveshaping stuff for the other waves  
(pulse, sine, etc.).

Go slow.

Just kidding about the purple, orange, and green pens.  Sorry, I'm a  
wiseass.  Use whatever damn colors you want.

Wasn't kidding about the exploding caps, though.

Michael Bacich


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