Arduino Teaches Old Coder New Tricks
The sponge and ferric chloride method works extremely well, etching the same board in a couple of minutes. In the past, I used ferric chloride to etch boards by placing them into a bath of ferric chloride. Even with agitation, etching a board could take ten minutes or so. The sponge and ferric chloride method accelerates the etching by continuously rubbing the surface with a sponge soaked in ferric chloride. The rubbing removes the oxide layer that continuously builds up, permitting the ferric chloride to get to the raw metal and thus accelerate etching. Instead of a tub of etchant, a couple tablespoons is all you need, which will make a bottle of ferric chloride last for a very, very long time. The technique is simple. Don plastic gloves, pour a couple tablespoons of ferric chloride into a small container, soak a small piece of soft sponge in the ferric chloride, then continuously and lightly rub the saturated sponge on the PCB. In a couple minutes, the board will be finished with little mess and little ferric chloride to dispose of.
My final product (after three versions), a single-sided ATtiny84 version of the project, is shown in Figure 11. Given that the board was single-sided, nine jumpers were required, which are the wires you can see on the component side of the board.
Figure 11. Final Etched ATtiny 84 Board
Commercially Made PCBs
In addition to making my own PCBs, I also had commercial boards made by a panel aggregator. A panel aggregator is a service that aggregates boards from many sources, filling up a cost-efficient-size printed circuit board panel and then breaking up the completed panel for delivery. Several such companies support the hobbyist community.
Figure 12 shows my Attiny85 design mounted to a 16x2 LCD.
Figure 13 shows my Attiny84 design mounted to a 16x4 LCD.
Figure 12. Commercially Made ATtiny85 Board
Figure 13. Commercially Made ATtiny84 Board
Source Code and Hardware Files for the vt100lcd (interested readers can pull down the files and create their own micro-terminal): http://code.google.com
The Arduino Project: http://arduino.cc
The Wiring Project: http://wiring.org.co
The code.google arduino-tiny Project: http://code.google.com/p/arduino-tiny
Thomas Fischl's USBasp Web Site: http://www.fischl.de/usbasp
Avrdude Device Programming Software: http://www.nongnu.org/avrdude
The Fritzing Project: http://fritzing.org
The gEDA PCB Development Project: http://www.geda-project.org
Symbol Creation: http://embeddedtoolbox.com/mksym
Footprint Creation by Stefan Salewski: http://www.ssalewski.de/SFG.html.en
"Circuit Design on Your Linux Box Using gEDA" by Stuart Brorson, Linux Journal November 2005: http://www.linuxjournal.com/article/8438
Using gEDA, by Iznogood: http://www.linuxfocus.org/English/December2004/article355.shtml
Getting Started with PCB: http://www.delorie.com/pcb/docs/gs/gs.html
gsch2pcb Tutorial: http://geda.seul.org/wiki/geda:gsch2pcb_tutorial
gschem → gsch2pcb → PCB: http://tinyurl.com/gsched2pcb
Circuit Simulation using gEDA and SPICE—HOWTO by Stuart Brorson: http://www.brorson.com/gEDA/SPICE/intro.html
Edward Comer is retired from the telecommunications industry, having worked for the real AT&T, BellSouth and Numerex Corp during a 30-year career.
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