Wednesday, January 23, 2013

Example circuit boards

As Jim Williams said, "The bit pushers have commented software; why not commented hardware?"

This post contains, in visual form, commentary on some examples of prototype construction technique and some commercial printed-circuit boards (with apologies to Jim Williams... see Appendix F, "Additional Comments on Breadboarding", in [1]).


Solderless breadboard. No.


Wirewrap. Really, no.


Prototyping breadboard with 45 rows of connections for dual-inline-package parts. For soldering together small circuits, these boards aren't bad. (Electronics Goldmine has these boards for $2.)


A better construction technique is deadbug on copper clad. This board is a simple oscillator that Jim Williams built in the deadbug style (a demonstration of [2]; also see [3]).


A pile of deadbug circuit boards built by Jim Williams (his lab bench really looked like this).


The good life. A custom evaluation board (this one is for the Analog Devices AD6816 networking chip with many SMA connectors).


The low-cost circuit board from a floppy disk drive (a single-sided PCB, that includes a "square-wave" trace around the motor for the position encoder).


Left: The one-transistor keypad from an original AT&T touch-tone phone (see [4]). Right: the circuit board for a more recent phone.


A ruggedized power supply (you can tell it's "rugged" from all the epoxy holding the parts in place).


The controller board from an inkjet printer, which includes a wide variety of IC packages such as the socketed DIP, several SOICs, and that EPSON ASIC in the middle with a million pins on tiny spacing.


The PCB inside a Spectral Synthesis ADDA2218, an 18-bit analog-to-digital audio converter, which uses colored FR4 (the color isn't just painted on, it's also impregnated in the fiberglass). I thought this was a neat touch, for a circuit board that only one-in-a-thousand customers would ever see (only those willing to void their warranty!).

References

[1] Jim Williams, "High speed amplifier techniques: A designer's companion for wideband circuitry," Linear Technology Corp., Milpitas, Calif., Application Note 47, Aug. 1991.
[2] Bernard M. Oliver, "The effect of mu-circuit non-linearity on the amplitude stability of RC oscillators," Hewlett-Packard Journal, vol. 11, no. 8, pp. 1-8, Apr. 1960.
[3] Jim Williams, "Max Wien, Mr. Hewlett, and a rainy Sunday afternoon," in Analog Circuit Design: Art, Science, and Personalities, Jim Williams, Ed. Boston: Butterworth-Heinemann, 1991, ch. 7, pp. 43-55.
[4] L. Schenker, "Pushbutton calling with a two-group voice-frequency code," Bell System Technical Journal, vol. 29, no. 1, pp. 235-255, Jan. 1960.

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