Electrical Engineering Reference Cards: The CheatKards

CheatKards offer a welcome reprieve from persistent “what was that formula / unit conversion / IC package pitch” questions.

How it Was Done

When you’re in your lab and some small calculation or reference eludes you, you may not be fortunate enough to have your computer at the same workstation. I tended to reach for my mobile before, but even then, I would google this and that, and get unvetted results from around the globe, “Sponsored” results at the top of the page, and was never quite sure which one to tap (or click) on, and the result was a somewhat unsettling and inconsistent experience.

Before the advent of mobile phones, we used to take up hectares of wall space with handy reference charts, which are nice when they’re always available, but do tend to detract from the aesthetic, especially if you tend to work better in a neat, uncluttered workshop.

Perhaps we could squeeze in just one more computer monitor on that wall space, then we’d be able to google... No wait, now we’re back to that mess. OK, we could round up a bunch of reference charts and have them handy on that screen, either connected to a small computer, or perhaps even as a slide show running from USB? Seems a little bit exuberant given the state of global energy right now — we can’t even keep the lights on all day where I live.

What Do We Have Here?

Recently, I was given a small gift I didn’t even know I needed: From Nerdonic CheatKard, the standard in pocket reference, who have made subject-specific credit-card-sized decks of cards for Physics, Chemistry, Biology (hmmm… I wonder if these are allowed in examination halls), comes the Electrical Engineering set, commissioned by Elektor.

At first glance, it seems a little unassuming. I mean, this stuff is completely passive, has no IoT functionality, no RFID — it’s just like a small book for your wallet…
  That’s when the lightbulb went on above my head. (Fortunately, that one is not yet government-controlled.)

I immediately rifled through them to see if this set could replace a lot of the drudgery of those lookups:
  The topmost card, visible above, is a protective cover. It has a nice matte-satin finish which feels good in the hand.

These are the topics covered on the rest of the (double-sided) cards, respectively:

Elektor Introduction: Demonstrates Elektor’s decades-long tradition of creating clear and concise schematics for readers. It points out the design philosophy of instant recognition of components and inputs on the left, outputs on the right. On the back of that card is a sample schematic for SPI control of WS2812(B) LEDs. So tempting to go and wire one of these up right now, but we’re not done here.

Common Schematic Symbols: On this card, a set of 56 component schematics with labels, and 62 on the back. OK, that's a bit of a squeeze for my eyesight, but fortunately, I’ve got more on that later.

PCB Design: All the through-hole and track widths you could need on the front, nicely embossed with actual holes, just like a real PCB, and, on the back, a description of substrates, layers, and pad patterns. I haven't designed so many PCBs that I needed that much detail, but then, that’s the point of a reference work: I haven’t used all the words in the dictionary, either.

Measurements: Some more holes, trace widths, and line spacing (pitches), from good-old-fashioned 2.54 mm spacing to 12 tiny SMD varieties. On the back, a long list of handy units, from farads to webers (speaking of ones I haven’t used yet), yoctos to yottas, and a conversion table between various units.

Laws and Theory: A very comprehensive and intuitively laid out four-quadrant comparison of watts, amps, volts, and ohms, and the laws and formulas that govern their relations. Then, resistors and capacitors in series. On the back, lesser-used laws from Kirschoff to Lenz. Even if you haven't memorized what every law is for, there’s a full description of the purpose of each one.

Common Footprints — SMD: As its name suggests, no through-holes here, just how you would expect the spot on your board to look before you solder that micro-miniature component. There are lots of them, and they are actual-sized, i.e. small. But again, we’ll get to that. The back has some more components, which I note, with relief, are slightly larger variants.

Common Footprints — SMD 2: More of the same, but for IC packages, including QFP, QFN, and BGA.

Component Values: I didn't expect to see this one, because resistor values are usually represented by colors, and this is not gawdy and colorful. Nonetheless, they’re all here, but you’ll have to read the names of the colors rather than seeing them. The card also explains the tolerances and other details for resistors, and the back has capacitor tolerances and capacitance conversions.

Okay, I mentioned a couple of times that the text on the cards tends to be quite small, but here’s the genius part: The final card is a Fresnel lens, so it will magnify any of those cards for you, even under really testy lighting conditions (thanks, energy crisis).
  All in all, the guys who put this together have compressed a lot of information into a small form factor. I remember tiny books with tiny print that you could keep on a keychain, but those were more novelty items, and I don't recall them ever coming with their own magnifiers.

I'm torn between whether this belongs in my wallet or on my keys, but I'll be trying both.

Where to Get It

The CheatKards product is available in the Elektor store, with the link below this review.
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