# DeLorean Time Circuit ## Background ![](https://cdn-learn.adafruit.com/assets/assets/000/001/305/medium800/lcds___displays_Finished.jpg?1396770847) Getting the big question right out of the way: no, we _won’t_ be selling these. Legally, we _can’t,_ for trademark reasons. But it’s generally okay for anyone to create replica props _for their own personal use_, so we hope this writeup will inspire some cool projects among our customers… ![](https://cdn-learn.adafruit.com/assets/assets/000/001/306/medium800/lcds___displays_Display.jpg?1396770853) From the moment [these](http://www.adafruit.com/products/878) [LED](http://www.adafruit.com/products/880) [displays](http://www.adafruit.com/products/879) made an appearance on our weekly [Ask an Engineer](http://www.adafruit.com/chat/) show, comparisons were being made to the DeLorean time circuit from the _Back to the Future_ films. It was a moral imperative then to make a demo! If you’re handy with Arduino and some shop tools, you should be able to pull off something similar (better, even), or adapt the ideas to other projects. This was quickly built in fun, so please don’t expect the same level of polish as a finished product tutorial. # DeLorean Time Circuit ## Design Liberties When accepting this assignment, I might’ve failed to mention a small detail to the boss folks: I don’t own a car, let alone a DeLorean, for displaying the finished prop. Instead, mostly inspired by [Jeri Ellsworth’s NES purse](http://www.flickr.com/photos/candescence/3908396605/ "Link: http://www.flickr.com/photos/candescence/3908396605/"), I had this goofball idea of a slim, battery-powered device that could be installed and photographed in ironic settings: on a bicycle, on public transit, hung from a [Flavor Flav](http://www.flickr.com/photos/relaxing/6209049368/in/photostream/ "Link: http://www.flickr.com/photos/relaxing/6209049368/in/photostream/") necklace as “bling,” and so forth. While the general idea could have been accomplished quickly and easily with an iPad running the _[Flux Capacitor™](http://itunes.apple.com/us/app/flux-capacitor/id391862376?mt=8)_ app, I wanted to preserve somewhat the staggered design of the original, and it _had_ to have real 7-segment LED displays…there’s no substitute for seeing the genuine thing. In much the way that [nixie tubes](http://www.adafruit.com/blog/2010/11/11/making-classic-frequency-counters-into-nixie-clocks/) have a certain vintage _coolness_ about them, LED displays too are reaching a nostalgic threshold, iconic of 1980s technology. ![](https://cdn-learn.adafruit.com/assets/assets/000/001/307/medium800/lcds___displays_Compared.jpg?1396770859) Using stock parts required some design compromises. The date and time formats would be changed to fit these 4-digit displays (the film prop used back-painted glass fakes for the month display, with some segment changes being physically impossible, making a 100% match unattainable anyway…iPad wins there). Also took liberties with some LED colors and various spacings, but overall the piece is still highly recognizable. For the sake of a quick demo, I had to cut this short. Though all the displays are addressable, the destination and last-departed dates are simply fixed values from the first film; there’s no interaction. I may revisit this to add a keypad later, but for now it’s all just a fancy clock (it does show the current time accurately, using a [ChronoDot RTC](https://www.adafruit.com/products/255)). Also, the vector files are not available, because they’re _utter garbage!_ Creating something of finished kit quality [requires many iterations and refinements](http://www.adafruit.com/blog/2012/06/07/22/ "Link: http://www.adafruit.com/blog/2012/06/07/22/")…but with a rushed, one-shot piece like this, course corrections would come in the form of a Dremel tool and epoxy putty. If you plan to build one, give it some time and prepare your blueprint carefully. # DeLorean Time Circuit ## Circuit Trickery ![](https://cdn-learn.adafruit.com/assets/assets/000/001/308/medium800/lcds___displays_Address.jpg?1396770866) These 4-digit displays can be assigned one of eight fixed I2C addresses via solder jumpers on the back. But the time circuit needs _nine_ displays. A few possibilities were considered, including driving the one extra display “manually” with shift registers, or use a software I2C library and split the displays among multiple I2C buses. Either would require lots of library code changes and some intense concentration, but I was hit with a massive sinus headache at the time and really didn’t want to think about it. Instead, exploiting the fact that we need just one way, write-only access to use the displays, I used a simple hardware hack to split the I2C bus to communicate with one row of three displays at a time (and saving some code by repeating the same addresses in each row). The I2C data line fans out to all the displays as normal, but the clock feeds the enable lines of a 74HC138 3-to-8 line decoder, and the microcontroller can then select which output line forwards the clock signal. The data on the other I2C buses is ignored without the corresponding clock. ![](https://cdn-learn.adafruit.com/assets/assets/000/001/309/medium800/lcds___displays_Schematic.png?1396770879) # DeLorean Time Circuit ## Fabrication To keep this ultra slim, a [Teensy](https://www.adafruit.com/products/199) microcontroller board was used — a standard Arduino wouldn’t fit, not even the [headerless Leonardo](https://www.adafruit.com/products/883 "Link: https://www.adafruit.com/products/883"). After prototyping the full circuit on a breadboard, all the parts were soldered point-to-point and “dead bug” style inside the case. Power is provided by three AA cells in series — a bit under the ideal 5 Volts, but still sufficient to run everything. The cells fit in the “chin” below the three dates. I’d mail-ordered a special battery holder for this, and then in my rush to complete the project I went ahead and made all the case parts based on the holder dimensions on a web site. Naturally then, with the case already cut and glued, the part that arrived was slightly larger than the dimensions posted. The fix was to break off the battery contacts from the ends of the holder and epoxy putty them directly into the case. This eliminated just enough girth for everything to fit. The remaining electronics were delicately folded into the case with copious amounts of hot-melt glue, tape and swearing. ![](https://cdn-learn.adafruit.com/assets/assets/000/001/310/medium800/lcds___displays_Breadboard.jpg?1396770887) ![](https://cdn-learn.adafruit.com/assets/assets/000/001/311/medium800/lcds___displays_Grid.jpg?1396770892) ![](https://cdn-learn.adafruit.com/assets/assets/000/001/312/medium800/lcds___displays_Origami.jpg?1396770899) The case was fabricated from laser-cut acrylic and sprayed with faux hammered metal paint. A metal enclosure would have been more authentic (and more work), but a corollary to “[Maslow’s hammer](http://en.wikipedia.org/wiki/Law_of_the_instrument)” dictates that when you have a laser cutter, every project appears ideally suited to acrylic. ![](https://cdn-learn.adafruit.com/assets/assets/000/001/313/medium800/lcds___displays_Taped.jpg?1396770904) The labels were inkjet printed and made into stickers with a Xyron applicator, trimmed with an X-Acto knife, then painstakingly touched up with a Sharpie marker to hide the white edges. After the labels were applied, the bezels received a thick spray of acrylic sealer, then attached to the front of the case with epoxy. ![](https://cdn-learn.adafruit.com/assets/assets/000/001/314/medium800/lcds___displays_Bezels.jpg?1396770910) A classic Dymo labeler (the plastic punched letter kind) might suffice here. In the film trilogy, most of the instruments (including the Flux Capacitor) were labeled that way. But the Time Circuit, being a close-up “hero prop” that required maximum legibility for the audience, had cleanly-printed labels. Sticklers for accuracy might want to take the extra step. # DeLorean Time Circuit ## Wrap-Up and Resources Go for it! If you don’t own a DeLorean, this will still impress your co-workers and look great on your desk. Or maybe you can devise a scheme around Halloween or a cosplay geek-fest like [Dragon\*Con](http://dragoncon.org/). Bolt it just below the arc reactor on your Iron Man suit (you _do_ have an Iron Man suit, right?). Or if you have a young son in a stroller, attach the time circuit to the tray, dress junior in mirrored shades and a “life preserver” down vest, while dad dons a Doc Brown getup…you’ll take home _all the candy in the neighborhood!_ ![](https://cdn-learn.adafruit.com/assets/assets/000/001/315/medium800/lcds___displays_GreatScott.jpg?1396770916) Even if you don’t build this exact item, if it inspires any nifty electronics projects (\*cough\*Proton Pack\*cough\*), please share them in the [forums](http://forums.adafruit.com/), bring them to the Saturday night [show-and-tell](https://plus.google.com/u/0/108772200278976934119/posts) or document your build on a site like [Instructables](http://www.instructables.com/ "Link: http://www.instructables.com/"). Customer projects are frequently showcased on the Adafruit blog! ## Resources Parts from the Adafruit store include: - [Teensy (ATmega32u4 USB dev board)](https://www.adafruit.com/products/199 "Link: https://www.adafruit.com/products/199") - [ChronoDot Ultra-precise Real Time Clock](https://www.adafruit.com/products/255) - [0.56″ 4-Digit 7-Segment Display w/I2C Backpack – Red](http://www.adafruit.com/products/878 "Link: http://www.adafruit.com/products/878") - [0.56″ 4-Digit 7-Segment Display w/I2C Backpack – Green](http://www.adafruit.com/products/880) - [0.56″ 4-Digit 7-Segment Display w/I2C Backpack – Yellow](http://www.adafruit.com/products/879 "Link: http://www.adafruit.com/products/879") - [Diffused Red 3mm LED](https://www.adafruit.com/products/777) (note: film prop used _yellow_ LEDs on destination time) - [Diffused Green 3mm LED](https://www.adafruit.com/products/779) Additional parts acquired from Digi-Key include: - [Diffused Yellow 3mm LED](http://www.digikey.com/product-detail/en/SSL-LX3044YD "Link: http://www.digikey.com/product-detail/en/SSL-LX3044YD") - [SN74HC138N 3-to-8 line decoder/demultiplexer IC](http://www.digikey.com/product-detail/en/SN74HC138N/296-1575-5-ND/277221 "Link: http://www.digikey.com/product-detail/en/SN74HC138N/296-1575-5-ND/277221") Elsewhere: - Here’s an excellent [DIY flux capacitor tutorial](http://www.instructables.com/id/Flux-Capacitor/). - The [Replica Prop Forum](http://www.therpf.com/ "Link: http://www.therpf.com/") is a great resource for build assistance, hard-to-find parts and to show off your finished work. - [YourProps](http://www.yourprops.com/ "Link: http://www.yourprops.com/") likewise for original movie prop reference pics. - At Maker Faire Bay Area 2012, Adam Savage (of Mythbusters fame) gave [an entertaining and impassioned talk](http://www.youtube.com/watch?v=_otrgJ8Lmx4 "Link: http://www.youtube.com/watch?v=\_otrgJ8Lmx4") (YouTube) about our compulsion to recreate our favorite big-screen icons. ## Code [Here’s the Arduino sketch](https://github.com/adafruit/Adafruit_Learning_System_Guides/tree/master/BTTF_Clock) that runs the show. https://github.com/adafruit/Adafruit_Learning_System_Guides/blob/main/BTTF_Clock/BTTF/BTTF.ino ## Featured Products ### Adafruit 0.56" 4-Digit 7-Segment Display with I2C Backpack - Red [Adafruit 0.56" 4-Digit 7-Segment Display with I2C Backpack - Red](https://www.adafruit.com/product/878) What's better than a single LED? Lots of LEDs! A fun way to make a small display is to use an [8x8 matrix](https://www.adafruit.com/category/37_88) or a [4-digit 7-segment display](https://www.adafruit.com/category/37_103). Matrices like these are... In Stock [Buy Now](https://www.adafruit.com/product/878) [Related Guides to the Product](https://learn.adafruit.com/products/878/guides) ### Adafruit 0.56" 4-Digit 7-Segment Display w/ I2C Backpack - Green [Adafruit 0.56" 4-Digit 7-Segment Display w/ I2C Backpack - Green](https://www.adafruit.com/product/880) What's better than a single LED? Lots of LEDs! A fun way to make a small display is to use an [8x8 matrix](https://www.adafruit.com/category/37_88) or a [4-digit 7-segment display](https://www.adafruit.com/category/37_103). Matrices like these are... No Longer Stocked [Buy Now](https://www.adafruit.com/product/880) [Related Guides to the Product](https://learn.adafruit.com/products/880/guides) ### Adafruit 0.56" 4-Digit 7-Segment Display w/I2C Backpack - Yellow [Adafruit 0.56" 4-Digit 7-Segment Display w/I2C Backpack - Yellow](https://www.adafruit.com/product/879) What's better than a single LED? Lots of LEDs! A fun way to make a small display is to use an [8x8 matrix](https://www.adafruit.com/category/37_88) or a [4-digit 7-segment display](https://www.adafruit.com/category/37_103). Matrices like these are... In Stock [Buy Now](https://www.adafruit.com/product/879) [Related Guides to the Product](https://learn.adafruit.com/products/879/guides) ### ChronoDot - Ultra-precise Real Time Clock [ChronoDot - Ultra-precise Real Time Clock](https://www.adafruit.com/product/255) The **ChronoDot V3** is the latest version of macetech’s popular ChronoDot line of products. Designed during the Great Chip Shortage, it uses the newly-released MAX31328 temperature-compensated real-time clock chip. However, it remains pin- and code-compatible with the older... In Stock [Buy Now](https://www.adafruit.com/product/255) [Related Guides to the Product](https://learn.adafruit.com/products/255/guides) ### Teensy (ATmega32u4 USB dev board) 2.0 [Teensy (ATmega32u4 USB dev board) 2.0](https://www.adafruit.com/product/199) Discontinued - **you can grab** [Adafruit ItsyBitsy 32u4 - 5V 16MHz](https://www.adafruit.com/product/3677) **instead!** The Teensy 2.0 is a complete USB-based microcontoller development system, in a very small footprint! All programming is done via the USB port. No... No Longer Stocked [Buy Now](https://www.adafruit.com/product/199) [Related Guides to the Product](https://learn.adafruit.com/products/199/guides) ### Diffused Green 5mm LED (25 pack) [Diffused Green 5mm LED (25 pack)](https://www.adafruit.com/product/298) Need some indicators? We are big fans of these diffused green LEDs, in fact we use them exclusively in our kits. They are fairly bright so they can be seen in daytime, and from any angle. They go easily into a breadboard and will add that extra zing to your project. - Pack of 25... In Stock [Buy Now](https://www.adafruit.com/product/298) [Related Guides to the Product](https://learn.adafruit.com/products/298/guides) ### Diffused Red 5mm LED (25 pack) [Diffused Red 5mm LED (25 pack)](https://www.adafruit.com/product/299) Need some indicators? We are big fans of these diffused red LEDs, in fact we use them exclusively in our kits. They are fairly bright so they can be seen in daytime, and from any angle. They go easily into a breadboard and will add that extra zing to your project. - Pack of 25... In Stock [Buy Now](https://www.adafruit.com/product/299) [Related Guides to the Product](https://learn.adafruit.com/products/299/guides) ## Related Guides - [Adafruit LED Backpacks](https://learn.adafruit.com/adafruit-led-backpack.md) - [LED Backpack Displays on Raspberry Pi and BeagleBone Black](https://learn.adafruit.com/led-backpack-displays-on-raspberry-pi-and-beaglebone-black.md) - [Personalized NextBus ESP8266 Transit Clock](https://learn.adafruit.com/personalized-esp8266-transit-clock.md) - [Tap Tempo Trinket](https://learn.adafruit.com/tap-tempo-trinket.md) - [Mindfulness Clock OF DOOM](https://learn.adafruit.com/mindfulness-clock-of-doom.md) - [Collin's Lab: Binary & Hex](https://learn.adafruit.com/collins-lab-binary-and-hex.md) - [Raspberry Pi Physical Dashboard](https://learn.adafruit.com/raspberry-pi-physical-dashboard.md) - [CircuitPython Hardware: LED Backpacks & FeatherWings](https://learn.adafruit.com/micropython-hardware-led-backpacks-and-featherwings.md) - [Trinket React Counter](https://learn.adafruit.com/trinket-react-counter.md) - [Fidget Spinner Tachometer](https://learn.adafruit.com/fidget-spinner-tachometer.md) - [Clue And MagTag Pep Talk Generator](https://learn.adafruit.com/clue-and-magtag-pep-talk-generator.md) - [7” Portable Multitouch Raspberry Pi Tablet](https://learn.adafruit.com/7-portable-raspberry-pi-multitouch-tablet.md) - [Mini Weather Station ESP32-S3 TFT](https://learn.adafruit.com/mini-weather-station-esp32-s2-tft.md) - [PyLeap CLUE Barometer](https://learn.adafruit.com/pyleap-clue-barometer.md) - [Moto 360 Teardown](https://learn.adafruit.com/moto-360-smartwatch-teardown.md)