Electronic business-card with blinkenlights show

Cody Shaw, a first year Co-op Electrical Engineering student at the University of Waterloo, spun up these wonderful electronic business cards for his job-search: set a 9V battery on the contacts and vary the light on the photo-sensor and you get a wicked blinkenlights show!

There were quite a few idea revisions in my mind before I actually got around to spinning the PCB. Microcontroller? Basic LED’s? No circuitry at all? Finally I got the idea of using a 555 timer (after seeing something about worldwide 555 timer competitions on the EEVBlog) that would be outputting a clock to LED’s, which would flash depending on some external interaction to the timer.

First idea: a photoresistor of course! The external RC circuit worked perfectly in ambient light with a simple 10k photoresistor. I quickly ran into an issue though; if I wanted to use a photoresistor, I would have to make my PCB through hole. I was not able to find one surface mount photoresistor. Therefore, I had to “fabricate” my own! How does one do that?!

Current in parallel with a normal resistor, of course! A phototransistor could act in place of the photoresistor, limiting the current in the RC circuit control for the 555 timer. Some issues with this, of course, is that phototransistors are quite expensive, and I managed to purchase opaque top photoresisors (which Digikey first sent as Red LED’s… D’OH)! After some trial and error with a scope and a breadboard, a working 555 timer, LED blinking, opto-frequency controlled circuit formed.

555 Timer Business Cards (via Neatorama)

• [royaltrux]

  3) Enjoy the light shoul

  (It is pretty cool!)

  • [Charlie B]

     Look closer.

    • [royaltrux]

       Ahhhh…

• [Aaron Swain]

  Dang, this would have been a perfect use of conductive inks!

• [semiotix]

  Look at the subtle coloring of those blinking LEDs, the tasteful thickness of the PCB. Oh my god, it even has a capacitor!

• [bcsizemo]

  I wonder if he actually learned how to do this in school…

  • [Cody Shaw]

    It was from self study during a previous work term, we definitely don’t learn about digital logic and semiconductors till upper year.

• [slippy0]

  A good friend of mine is working on a similar product that, he says, is slightly more advanced and aesthetically pleasing.

  http://jwcxz.com/projects/bcard/ 

• [schadenfreudisch]

  and yet, that’s quite a font fail.

• [C.S. Civet]

  My pixelated heart lights up whenever I see the word ‘blinkenlights’. Thank you, Cory!

  • [EH]

    Funny that the word generally comes from a calligraphed Xerox!

• [danegeld]

  Sheldon called to say: He’d be embarrassed to be enrolled on a degree course whilst still carrying on like 555 timers are a neat idea. I mean does this dude actually want to get hired using this card, or is it more about inviting speculation as to whether he managed to pass the first year vs. “I bought some sh*t from Adafruit”…?

  • [sweetcraspy]

    555 timers *are* neat.  They’ve got limited capabilities and the trick is to see how complex an output you can get.  It’s relatively easy to think about doing blinkenlights with a microcontroller, if you have the infrastructure to program one, but even the simplest microcontroller is overkill for this.  With the 555 timer, an electrical engineer ought to be able to look at the card and see exactly how the circuit works, rather than seeing a black box.

    Also, this is a business card, not a resume.  The whole point is to convey your contact info in something that won’t get thrown away  immediately.  I think this succeeds well.

    • [Cody Shaw]

      This guy has the idea!

      Source: It’s the same as my idea ; )

      I would like to add that any Electrical Engineer that understands how a 555 timer works believes they are extremely neat!