It was coming along nicely, until I hit the H-bridge. I've always wanted to make an H-bridge, and this was the perfect opportunity. Step 1 is to fabricate your own PCB, which is ubercool. I tried the method described in the magazine, only to realize that it doesn't work with inkjet printers - only laser printers. I was skeptical to begin with, but I tried anyway with my inkjet, and lo and behold, the transfer never transfered! I later discovered that the toner in laser printers is something of a polymer type powder, and the laser melts it onto the paper - so you're really getting something more or less like plastic ink with a laser printer. The transfer method works with this because you simply re-melt it onto your copper board.
But I was not to be deterred! I used
a liberal sharpie marker and free handed the pattern to the board, then etched. It worked! Sorta. When I went to drill the holes, I realized this was a dumb idea, as I didn't have the spacing even close. So that was junk (but still, good experience).I also learned that PCB drill bits break if you even look at them wrong. Sadly, I only bought three of them and broke 'em all (the first one not even lasting two holes). Lesson learned here - USE A DRILL PRESS!
Yesterday I finally broke down and bought a laser printer (yay cheap crap agian!).
The printer was $60 (with a 1000 page toner cartridge included)... replacement toner cartridges are $70... go figure. To go along with my $60 printer, I bought a stack of $20 glossy paper for it.
Set up and printing was a breeze (Ubuntu is the best ever).
The copper cladded board was cleaned with a scouring pad and then acetone. Get all the oxidation off. After you do, be careful not to touch it with your fingers and get your oils on it.
(So shiny!)
I taped the PCB print, face down to the board and used an iron to transfer the image.
I pressed the iron on very hard for about thirty seconds, then used the tip (that's what she said) and pressed all over the board. (Key theme here being lots of pressure). Check out this video on instructables. If nothing else it has good music (admit it, you were chairdancing).
The newly ironed PCB is soaked in some soapy water. The idea here is that the paper that originally held the toner gets soggy enough that you can easily remove it without damaging the print. After several tries here, I discovered that I wasn't using enough pressure with the iron, so it required a few re-dos.
You can see here the post-paper-peeling. The dark spot towards the lower left is where the print pulled up with the paper (I didn't press hard enough there!). I repaired it with a thick layer of sharpie marker.
Warning: FUN PART AHEAD!
What you're seeing here is muriactic Acid and Hydrogen Peroxide. Pretty menacing looking, I know. Muriactic Acid is used to etch concrete, and is pretty nasty stuff (it smoked a little when I first poured it in my dish). So take precautions here. I used gloves and eye protection. I found it at the hardware store, in the paint department.(Incidentally, what you're also seeing here is the main spindle chucked up in my minilathe for the CNC project, its only about 60% finished - but that's for another post!)
Find a good dish (I used a Pyrex pie dish) and mix in 2 parts Hydrogen Peroxide / 1 part muriactic acid, enough to fully immerse your board. Using a wooden or plastic stirring utensil, mix it all up and dunk in your board. I swirled the mixture over the board continuously - you could also use a bubbler (like the kind used in your average aquarium) to agitate the mixture. You'll soon begin to see the mixture turning green (that's copper) and eventually, the unprinted parts of the circuit board will completely erode away, leaving only the fiberglass beneath.
The before and after of it all:
Finally, the Finished Product. The sharpie repair held up good enough. Next step is to drill and tin it, Then solder in the junk. But that'll have to wait, as I broke all my drill bits.
My advice, buy by the dozen.
