The tasteful test bench
Brad Thompson- May 21, 2012
In my previous column (“5060-9436”), I briefly mentioned the inevitable demise of user-repairable test instruments due to age and the dwindling numbers of parts-donor instruments. Unfortunately, current-generation instruments include custom ICs (ASICs), and many manufacturers no longer offer service manuals or schematics. All this points to a future in which hardware hackers will find it increasingly difficult to equip a traditional test bench with used and repairable instruments at modest cost. So, what’s next?
I’ll speculate that in the not-too-distant future, an impoverished experimenter’s test bench might resemble a kitchen counter replete with a collection of inexpensive purchased modules assembled and interconnected for the task at hand. In size and shape, these modules might fit into the flip-top tinned steel boxes that contain Altoids mints.
Amateur-radio practitioners and electronics hobbyists pioneered the practice of stuffing home-brewed electronics into mint tins, but a few manufacturers now offer products that rival the performance offered by many traditional test instruments and also fit comfortably in these small containers.
For example, Valon Technology’s Model 5007 Dual Synthesizer (photo) delivers two independent RF outputs spanning 137.5 MHz to 4.4 GHz at selectable RF levels 7, 4, 1, –2 (+8 to 0 dBm). Measuring 2-by-2 in., the 5007 derives its control signals from a USB interface and vendor-supplied PC and Macintosh software. Drivers are available for Linux and National Instruments’ LabView. At $295, the 5007 is an inexpensive solution to many requirements for dedicated RF signal sources.
And now for dessert: Based on a 700-MHz ARM processor and offered as an inexpensive teaching aid, the under-$40 Raspberry Pi computer from the Raspberry Pi Foundation runs a Linux operating system and is said to be capable of desktop-PC performance. Add a user interface and a USB connection to a test module, and a Raspberry Pi computer running Linux and open-source data-acquisition and control software could serve as the heart of a low-budget test system. (The Raspberry Pi is currently back-ordered, but other microcontrollers may serve as well.)
(Note, 5/30/2012: Due to an editing error, the price for the Valon Technology Model 5007 was originally misstated as $29; the incorrect price also appeared in the “Test Voices” column in the June 2012 issue of Test & Measurement World.)
Electronics in mint tins
Given cellphones’ ubiquity, fitting an entire radio transceiver in one’s pocket may seem old hat, but amateur radio projects also include SWR (standing-wave ratio) meters, antenna-impedance matching networks, and RF amplifiers in mint tins: longlist.org/Altoids+Transceiver
This site describes a basic video-display and audio-frequency tester: bit.ly/M41yne
Here’s an audio amplifier module in a mint tin: tangentsoft.net/audio/cmoy-tutorial…and a Part 15 FM-broadcast test transmitter: bit.ly/KVD4qK
What else fits in a mint tin?
Clever hands have packaged survival kits, Ouija boards, and miniature dioramas in mint tins: pinterest.com/jonadair/altoids-tins
Raspberry Pi notes
The Raspberry Pi computer’s capabilities and modest price has sparked considerable interest: www.raspberrypi.orgCan’t wait for the Raspberry Pi? Check out the Menta, an Arduino-family microcontroller that fits into a mint tin: bit.ly/J5t0KY
Although mint tins offer electrostatic and magnetic shielding, they’re not as rigid or as easy to machine as die-cast enclosures, such as those offered by Pomona Electronics (incidentally, Pomona was the ancient Roman goddess of fruit trees): bit.ly/Jjy0PL