LED Time Circuits

home made time circuit display
I know it's a common project, but I thought I'd make my own Raspberry-Pi powered Time Circuits, looking similar to those seen in the Back to the Future movies.

The goal is to have three calendar/clock displays (red/green/yellow) that you can set via a keypad. In addition there is a flux capacitor, a spedometer, various energy meters, and a few other random features. This is a hobby project: full source code, documentation, and PCB gerbers are available free for download.

Left to do:


Build directions: time_circuit_build.pdf

The Raspberry-Pi controls everything over i2c. The Pi (running Linux) is a bit of overkill, as any board that can keep time and drive an i2c bus could run things.

The display is run by a series of HT16K33 chips (I use the breakout boards from adafruit). Each chip can run up to 16x8 LEDs plus read a keypad matrix.

For the displays I use Kingbright common-cathode LED displays. I ended up buying direct from them as it was hard to source red, green, and yellow displays of both 7-segment and 16-segment types all from the same place. In the end the yellow 16-seg are of type PSC05-12 and the red and green are of type PSC05-11 and the pinouts are not compatible. This is unfortunate because it means I'll need separate PCB layouts.


The displays will not match the version seen in the movie exactly.

There are some good reasons for that ( the month names as displayed in the movies aren't possible with off-the-shelf LED displays).

Also I like to think Doc Brown himself was a bit of a hacker (although a bit of a perfectionist) and thus any rebuild he did would vary as he thought up improvements.


Current Movies

Most recent movie showing current functionality. Work has stalled for nearly a year due to other projects taking precedence. I had wanted to have it car-mountable by the movie 21 Oct 2015 but not going to happen. It does make a nice clock in my office, with which to impress visitors.

Older Movies

Flux capacitor and power displays. Note the analog and other meters as power-up happens. Sorry for the backlit video, I need to build a case so I can angle away from the window (or else find a better camera to record with).

Older demo including sound:

A much older run-through of the breadboard prototype showing current time and then setting the date to various important times:

Other older videos can be found here.

Build Log

21 October 2015

Perhaps be glad that you aren't taking the ECE471 Midterm this Back-to-the-Future-Day:

16 October 2015

Have been lax about updating this log, but also have not had much time to work on things. Ironically it looks like I'm out of time for getting it working by the 2015 BTTF2 date.

3 June 2014

Prototype of the case assembled:

The case itself is made up of scrap wood and aluminum standoffs, with holes (poorly) drilled by hand with a power drill. Functional (barely) but not very pretty.

6 May 2014

I finally got around to finishing and ordering the keypad PCBs.

I cut out the openings in the keypad case by hand. Sadly they aren't aligned very well, despite the fact that I made a paper template to guide the drilling. Maybe time to get a CNC mill or at least a drill press?

Testing the circuit board. The holes for the diodes were way too small. In the end I sort of surface-mount soldered them in place, I'm sure that's not good long-term.

The assembled keypad. It was a pain getting all those wires in, I should have used thinner wires and maybe socketed everything. It works though!

A snapshot of the current project area:

8 April 2014

The flux capacitor is more or less finished:

Flux capacitor and d/a board bringup:

6 March 2014

The spedometer and flux capacitor circuitry as well as most of the power display are functional. Waiting for a shipment of better LEDs, and then I need to make some more circuit boards and drill holes in some cases.

26 February 2014

I had some visitors to my work area:

You can see the Lego time circuits. The date is set to 1958 when the first Lego brick was made.

I couldn't decide on the old or new license plate. You'll note I have Mr. Fusion installed, as well as the BTTF3 vacuum tube circuitry. I'm using the old tires over the red whitewall ones.

That's a load-bearing flux capacitor. Also Doc's hair is too big for the door to close while he's driving.

18 February 2014

Yellow display bringup, as well as the power-converter board. Also took some time to clean up the keypad rats-nest.

12 February 2014

An annotated picture showing status at the time. There's a battery-backed real time clock so you can keep time when disconnected from the network. There's a speaker/amplifier for sound effects and music. Also some power circuitry to bring in a dedicated 5V/1A supply to the LEDs, as driving all of this from the rasp-pi 5V output started getting dim and glitchy.

28 January 2014

Bringup of the green display. It has the same layout as the red display:

27 January 2014

First bringup of the red display! Amazingly everything worked, except for the 16-segs had segments R and S reversed due to lack of alphabetical order in the data sheet (note the 'N' in JAN). Easy enough to fix in software.

Time circuit malfunction! This is what I got after running the old software on the breadboard after re-wiring to match the PCB version of the display:

21 August 2013

First prototype of the display with all segments on as a test. I have a mix of red/yellow/green just to be sure everything is working.

Source Code

All the code can be found on github: https://github.com/deater/vmw-meter.git

git clone https://github.com/deater/vmw-meter.git

Look in the time_circuit directory.

It is fun when your source code has statements like this:
	if ((current_speed>=88) and (current_power>=121)) time_travel=1;

Other projecs at the VMW Hardware/Software Productions Page