Are we having fun yet?
This fortnight's collection features four Design Ideas that lack any unifying theme. And for the person who asked, "What's this 'fortnight' you keep mentioning?" here's more than you ever cared to know about the word.
Kicking off our collection, "Data-acquisition system captures 16-bit voltage measurements using the USB" uses a Maxim MAX1168 16-bit A/D converter and USBMicro's U421USB interface module to do the job. Other Maxim components include MAX4230 op amps and MAX5490 precision resistive dividers. Note that the circuit includes rather large input capacitors and thus will best serve low-speed applications. You can download evaluation software for the project here.
Got voltage? Got not enough voltage? Our next Design Idea, "JFET-based dc/dc converter operates from 300-mV supply", takes you from an anemic 300 mV DC power source to a useful 5V via a clever circuit designed by Jim Williams, linear-design guru at Linear Technology and one of my favorite outside-the-box thinkers. Jim's circuit makes use of a JFET's ability to conduct significant current at zero bias. Using one of Coiltronics' Versa-Pac multiple-winding switched-mode power transformers neatly solves the sometimes-messy requirement for winding one's own transformer, which gets more difficult as core sizes and wire gauges shrink, and one's fingers lose agility with age and caffeine intake.
While we're exploring unconventional circuits, here's one—a bunch, actually—that make use of Fairchild's NC7SZ57 and NC7SZ58, or Texas Instruments' SN74LVC1G57 and SN74LVC1G58 components. In "Configurable logic gates' Schmitt inputs make versatile monostables," author Glenn Chenier shows how you can take advantage of these devices' Schmitt-trigger characteristics to build tiny timing circuits. This approach comes in handy when running etch halfway across a circuit board to use one section of a multigate Schmitt trigger makes no sense from a board layout viewpoint. Instead, you sprinkle six-legged SC70 packaged devices around the board where they're needed, like pepper grains on a steak.
And now, something completely different for the practical jokers among our readers:"Stealth-mode LED controls itself" shows how you can assemble a gizmo that lights in a darkened environment and extinguishes when the room lights go on. Aside from mystifying the not-quite-technical marketer or manager ("Hey, boss— can you find the photosensor?"), this nifty circuit may serve practical purposes such as controlling battery-operated pathway marker lights or adding a find-in-the-dark feature for an instrument's power switch. Think of this circuit as an all-electronic version of Poynter Products' "Thing," a black box that when switched on, deployed a tiny plastic hand that turned its switch off.
Having fun yet? I hope so, but if you feel the need to maintain a gossamer veil of work-related activity, you can visit the Debugging Site. To learn how once upon a time, individual engineers just like you actually made money by helping other people have fun, take a look at the History of electronic games.
Or, you can conduct research for the US government. For example, you could reinvestigate whether dogs, cats, and rats can locate buried mines by extrasensory perception (read the Final Report for Contract DA-44-009-ENG-1039). Declassifying this report consumed 50 years. But you already knew that, right?
In the meantime, submit your amusing and declassified Design Ideas and share the fun with EDN's readers.
73 for now,