Start thinking 4th dimensionally with a time circuit tutorial

When [Phil Burgess] showed off a few I2C – controlled seven-segment displays on adafruit’s weekly vlog, the comments immediately turned to the time circuits featured in everyone’s second-favorite time machine, the Back to the Future DeLorean. The time circuits are now active, so now you can easily add a temporal display to your car well before a hover conversion.

[Phil] used these LED displays, conveniently controlled by a four-wire I2C bus. Although the displays are addressable independently, it’s only possible to assign each display to one of 8 I2C addresses. [Phil] figured out a neat way to control the 9 displays of the time circuit with the help of a 74HC138 3-to-8 line decoder.

The case was constructed out of clear acrylic lasercut in adafruit’s shop and spray painted with faux-metal paint. After installing the seven-segment displays, a Teensy, ChronoDot, and a few AA batteries finished up the build.

With any luck, the design files for the laser cut case should be available shortly, so get those I2C displays while they’re still in stock.


  1. bnjfdngjfd says:

    The Tardis is way cooler than a DeLorean.

  2. Craig says:

    I would be all over this if it was not just a little bit off. The real time circuits give the month in three letters, not two numbers. It bugs me enough this way that I can’t really get excited about this. I have seen the movies too many times.
    Now I need to make my own.

  3. penpen says:

    A delorean inside a tardis inside your dream !!!! (poooooooooooommmmm)

    • Aaron says:

      [Parent comment reported by mistake because every other site I comment on has the 'Reply to comment' link at the lower-right corner.]

      yo dawg we heard you liked time travel so…oh, never mind.

    • Aaron says:

      Awesome. Next up: hacking on a sub-$500/project budget?

      • daid303 says:

        Good to see that I’m not the only one who is always surprised at the high price of “modules” like used to build this. 7segment displays are about 50 cents each. 4 of them with a small controller suddenly cost 10 dollar?

      • NewCommentor1283 says:

        last time i checked they were a bit more then 50 cents, but still 10 bucks for a module??? really? no thanks.

        WAY too expensive.

        you are only feeding the people that think people should pay 100 or 500 dollars for a 10 or 15 dollar finished unit!

        ill build my own, maybe recycle some displays and only really spend money on AVR, 74xx OR 40xx, bare circuitboard, solder, and batteries.

  4. mmeerian says:

    Didn’t the original use alphanumeric displays? oh, and a DeLorean is way better.

  5. Hacksaw says:

    Tardis Smardis- Doc Brown and a DeLorean any day…

  6. Josh says:

    Second favorite? I think not. What is a tardis?

  7. Fabian says:

    I want one for my Navigation system.

  8. futaris says:

    #CR852 Box with Alphanumeric Displays would make this better…

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