My interest in electronics goes back to the days
of playing with batteries and bulbs and that was sometime before I was
ten. My early attempts at soldering were not pretty and I have a
few solder scars on my hands to prove it. The advent of cheap
microcontrollers has been a wonderful progression. For a few
pounds I can design circuits that would have required several boards of
discrete logic. Operations like debouncing button presses that
normally require a separate chip can be taken care of in software.
Some circuits I design and some I just build. Quite often it's a
mixture of the two - taking an existing circuit design and modifying it
to suit my needs. Unless the circuit is very simple (in which
case I just knock it up on stripboard), I design and build a printed
circuit board. I'm currently using the Eagle schematic capture
and PCB design software from CadSoft
It comes in versions for Windows, Macs and Linux. I'm using the
Linux version. They also do a Freeware version that, although
limited, will suffice for a lot of people.
To make my own PCBs, I print out the final board design at a high dpi
setting in just black and white onto high resolution inkjet
paper. Then I cut out the board outline from the paper and spray
it with WD40. This makes the paper go quite transparent.
Then I take a copper clad board that has been coated with a
photo-resist layer (I've tried making my own but I haven't had any
success), align the paper with it (making sure I've got it the right
way round otherwise the result will be a mirror image - been there,
done that!) and lay the two on the glass bed of my UV light box.
It takes about ten minutes to get the board properly exposed.
Then I soak the board in dilute Sodium Hydroxide to remove the
photo-resist layer that wasn't blocked by the black ink of the paper
printout. Next, I etch the board using Sodium Persulphate (which
is much nicer to use than Ferric Chloride) in a deep tray with a fish
tank bubbler to keep the solution moving. When etched, the board
is rinsed in water and dried and then exposed in the UV light box for
another ten minutes so that the subsequent soaking in Sodium Hydroxide
will remove the rest of the photo-resist. That's followed by a
final rinse in water and then, when dry, a quick burst with a polishing
block. I can get a PCB made in about an hour on a good day.
Having said that, the board still needs all the holes drilled and that
really does take hours. One of my more recent projects was to
find a solution to that problem and there is detailed coverage of that
First up, here's an early surface mount PCB project: the USBkey
PIC microcontrollers are great but you need to be able to program them,
so: the PIC Programmer
I hate drilling all the holes in PCBs. Why not build a Computer
Numerical Control (CNC) drilling machine: the Drillcon 100
Aaron asked me for an optical (TOSLINK) S/PDIF decoder for his
Playstation2: happy to oblige
Another suggestion from Aaron. An iButton controlled lock using a
PIC chip: the iButtonLock
Bit of a work in progress this one - avoid losing your laptop with the
invisible radio Laptop Leash
cutting head for the
More projects soon.