In The Trenches
Finally, not all printers have precise
paper-handling mechanisms. That is,
the scale may not be exactly 1:1. A
2.5% scale error, which is not noticeable
for printing, will cause a quarter inch
size error in a 10 inch PCB. This is
enough to foul up PCB mounting, cause
problems with large PCB connectors,
and create large headaches. (I know
this from experience.)
There is also a technique that
prints the pattern directly onto thin,
flexible, copper sheets that feed into
your printer. Then, you glue this to a
base board and etch it. This eliminates
the ironing step. (I haven’t tried it.)
The technique that I prefer,
unfortunately, is no longer generally
available. It uses a pen-plotter to draw
a special resist-ink directly onto the
bare copper PCB. Then you etch it.
It’s accurate to the precision of the
plotter (0.001” resolution for my
plotter). Both the plotters and the ink
are now very hard to get.
The last method is mentioned
only for completeness; it can’t be used
by hobbyists. It’s called “Multiwire”
from Advanced Interconnection
Technology ( www.ait-atlanta.com).
They don’t use copper PC boards at
all. They glue/embed thin, insulated
wires into the base material. Because
the wires are insulated, they can cross
over each other without shorting. To
make an electrical connection, a hole
is drilled that cuts through the wire
and exposes the copper end. Then,
the hole is plated, which electrically
connects the end of the wire to the
metalized hole and the rest of the circuit.
This method is very reliable and is
used in some military applications.
Basic PCB Layout
For me, the first step in the physical
layout of a PCB is a good schematic.
With the exception of glue logic
(discrete logic gates) and multiple
opamp packages, I arrange the IC
pins in physical order, as viewed from
the top. I usually start with the IC that
has the most pins and then place the
other parts to create a visually simple
schematic (if practical). This means
only a few crossed lines. It’s always
easier to lay out a PCB with fewer
crossed traces. This also creates a
physical relationship between the
schematic and the actual board,
which is useful in troubleshooting.
I always place components and
pads on a 0.100” grid, if possible.
This makes calculations between the
parts and case easy to figure.
Basically, it’s convenient. I also
immediately identify the top and
bottom layers with text “component
side” and “solder side.” The “solder
side” text is mirrored (reversed left to
right) because I see that layer from
the top with my layout software. All
software packages I know edit the
bottom layer, as viewed from the top.
SAELIG BRINGS YOU EASY-TO-USE SOLUTIONS!
NUTS & VOLTS
USB in one IC!
USB Logic Analyzer
USB PC Scope
USB Bus Analyzer USB-Serial Adapter
FT232BM Single chip USB-232 USB-COMi (non-isolated) or ANT8 Matchbox-sized USB- DS2200C 200 kS/s 12-bit 2-ch Tracker 110USB protocol ana- Serial port for laptops without
solution with all Windows USB-485i (isolated) offer self- poweredlogicanalyzer. Sample USB scope adapter for PC. lyzer displays USB packets one! US232Binstantlyupdates
/Mac/Linux drivers. No program- powered USB to RS485 con- 8 channels at up to 500 million Looks like a “Digital Scope” on sent, decodes descriptors, older RS232 products to USB!
ming/USB knowledge required! version with baud rates 184bps samples-per-sec. View traces your PC screen! Take anywhere. errors, and measures USB s/w PC thinks it’s using COMport
Easiest answer to update RS232 - 3Mbps. PC thinks it’s talking to on PC. Print or save for later Great for laptops, and servicing. performance. Easy software - but uses the USB connection.
devices! Only $2.60 (10k) a COMport! Only $48/$170! review! (16-ch. ver. too!) $199! Remarkable price: Only $189! learn about USB now. Only $899! Only $39 (1) or $$29 (100)
CANbus Cards Industrial PCs Data Terminal I/O thru Ethernet RS232<>422/485 I2C for PCs
CANbus - Starter Packs and ATX Ruggedized Industrial PCs ELX customizable serial data BITlink - easily construct control K2 9p-9p self-pwrd RS-422/485 PCI93LV: industry-standard I2C
cards for almost any board format for any budget or application. collection terminals for HMI, systems communicating through K3 9p-9p isolated RS-422/485 card for PCs. WINI2C/PCI soft-
& OS. CAN/Ethernet bridges, machine monitor, control, etc. ware gives windows-interface to Easy mtnce, economy, reliability. Intranet/Internet. BIT2000 for K3-232 9p-9p isolated RS232 RS232/485 CE-approved. develop and debug I2C bus sys-
industrial automation solutions AMD Athlon XP1700, shock- Backlit 4 x 20 ch. 4 isol. i/p, process control, building monitoring, K232-ISOL 25p -25p RS232 tems. UCA93LV is new USB
from Janz AG as used by top mounted 40GB harddrive. 32bit ctr, two relay o/p. Two data logging, alarm systems and KD485-STD DINrail - isolated version. NOW! - transparently
companies all over the world. 100% Burn-in. CE EMC. $899^ non-vol. i/p. IP65 available. other industrial uses. $399 ^ KD485-PROG programmable! monitor at 400kHz! Only $499!
Dataloggers Dataloggers PC Scope Adapters BASIC modules Crystals / Oscillators SM PCB Adapters
VL100 2” x 3” battery-powered TDS2020F makes a custom CF ADC-212/100 turns your PC Tigers - tiny multitasking BASIC Euroquartz - Europe’s largest OM-Adapt SM miniboards
analog & digital loggers store card A/D datalogger or con- into a great high-speed scope. modules for quick projects. mfrof quartz crystals, osc’s, have two footprints on either
events, volts, current, pressures troller - quickly! High-level Sampling to 100MS/s at 12-bit >100,000 instr’s/s! iCOM200 filters and frequency products. side. Now use your ultra fine pitch
for weeks. Download to PC and software completes projects in res’n. FREE s/w turns PC into ready-made controller with LCD Custom filters, high rel. rad tol. SMD components with more
review graphic results or Excel hours. Store GPS/CANbus/A or D powerful 2-ch scope, DVM & and keypad. Touch240controller osc’s. Novel EQ-HM spread- useful 0.1" inline spaced holes.
spreadsheet. Only $200! data to card. Only $199 ( 50 qty) spectrum analyzer. $95 - $1145 - with touchpad and LCD display. spectrum osc’s reduce EMI problems One-to-one pinouts. $6.99^
Saelig Saelig Co. brings to USA unique, easy-to-use control and Co. Inc. instrumentation products from overseas. Customers include:
Intel, Philips, NEC, Kodak, Nokia, US Military, Microsoft,
585-385-1750 • fax: - 1768 Dell, Xerox, Universities, T.I., Harris, Sony, J&J,
www.saelig.com • firstname.lastname@example.org Thomson, Sandisk, General Dynamics, H-P/Compaq, etc.
ALSO: SCALABLE LED DISPLAY PANELS, TEMP-HUMIDITY
MONITORS, THERMOCOUPLE P. C. ADAP TERS, ENVIRONMENT
MONITORING SYSTEMS, EDUCATIONAL SCIENCE PROJECTS,
GRAPHICS SOFTARE, AutoCAD PROGRAMMING COURSE, USB-PIC
BOARDS, FLASH PROGRAMMERS - IF YOU DON’T SEE WHAT YOU
NEED MAYBE WE CAN FIND IT FOR YOU? - ASK FOR SALES!