Markus Wobisch: Building Props for a Back-to-the-Future Time Machine

My other blog posts on BTTF props:
Part 1: Building a Flux Capacitor
Part 2: Building the Time Circuits
Part 4: Building the Analog Gauges
Part 5: Building the TFC Switch

After I built the Flux Capacitor and the Time Circuits from the DeLorean in "Back to the Future", I just couldn't stop. The next piece was the speedometer that is sitting on the dashboard of the DeLorean, which prominently displays the "88" mph to indicate the time-jump.

My initial plans were to make a simple non-functioning prop, that maybe counts from zero to 88, and after a short break, makes a countdown. Later, however, I could not resist to add a GPS receiver, so the final version is a fully functioning GPS speedometer.

Enclosure

As in my other BTTF-related builts, the case is made of 3/16" plywood with a laser cutter.

The pieces are glued and painted (with Rustoleum, gloss, almond) , and it instantly resembles the original prop.

Electronics

The electronics of the speedometer is built around an Arduino pro mini (168, 16MHz, 5V), two red 0.8" 7-segment LED displays (common anode), two shift registers TPIC6B595 (which can sink 100mA per pin, so no further transistors are needed), a Neo-6M GPS module, plus sixteen 220 Ohm resistors (8 for each display: 7 segments + decimal point).

The images do not show the Neo-6M GPS module which was an afterthought. Later, it was placed in the space on the left on the picture above. While I found many postings on the web of people having trouble, the Neo-6M module works really well for me (although I connected it via soft-serial, which people do not recommend - but I never had problems).

Of course, one needs to add the labels from the DYMO 1540 Office Mate II label maker (which I bought for the Flux Capacitor labels) - these are an essential piece for recognizing this prop. And here it is ...