SyncBox

A signal reconstructor for Haitex X-Specs 3D goggles.

Copyright 1993-1998 Michael E. Weiblen. Freely distributable by any means.
Originally written: 30 July 1993

Abstract

This paper describes how to build the SyncBox, a device that reconstructs the control signal for Haitex X-Specs LCD goggles from any standard NTSC video signal. This device enables viewing of three-dimensional images recorded on videotape without a computer to drive the goggles.

Boring preliminaries

DISCLAIMER: USE AT YOUR OWN RISK! I will not be held responsible for any damage this design may cause to your computer system, love life, mental health, whatever. You are on your own.

This document assumes you know something about building electronic devices. I cannot help you debug your constructed circuit. You are on your own.

This design is a proof-of-concept prototype. It is not a commercial-quality polished design. I built it and it worked for me most of the time. Some video signals did not properly trigger the device, and I did not investigate further. I have taken this project as far as I intend to for now. You are on your own.

Overview

Haitex X-Specs goggles are a pair of liquid-crystal shutters that alternately become transparent due to an applied control signal. When a computer generates that control signal in sync with an alternating-frame video image pair, a three-dimensional image can be perceived.

X-Specs are sold for use with the Commodore Amiga computer. The software provided with X-Specs generates a goggle control signal on the second mouse port, while it generates a video signal that alternately displays left and right eye images. Before the SyncBox, the only way to take 3D images on the road was to carry along an Amiga to generate the control signal.

Since the Amiga generates an NTSC-compatible video signal, its display output is easily recorded on a standard VCR. The trick is how to recreate the synchronized control signal for the X-Specs. The SyncBox generates that control signal. It accepts a composite video signal (such as from a VCR), and provides a DB-9 connector with the reconstructed X-Specs control signal.

Connecting the SyncBox

The composite output of a VCR is usually a coax cable with an RCA phono plug. You will need an RCA "Y adapter" (available from Radio Shack) to split the video signal between the TV and the SyncBox.
             +-----+                          +----+
             |     |                          |    |
             | VCR |>---+-------------------->| TV |
             |     |    |                     |    |
             +-----+    |                     +----+
                        |
                        |
                        |                     +--------+
                        |   +-----------+     |        |
                        +-->|  SyncBox  |---->| XSpecs |
                            +-----------+     |        |
                                              +--------+

SyncBox design

Parts required

Power supply

The LM1881 has rather flexible voltage requirements, but the X-Specs need +5 volts. I used 4 AA cells to generate +6 volts, then a 1N4148 diode to drop that down to about 5.3 volts.
                                                              DB-9
                                                              connector
                                                              to X-Specs
                1N4148
                 |\ |                                          7
  4 AA cells >---| >|--------+----------------------------------> Power
                 |/ |        |
                             |8
                      +--------------+
                      |              |
                      |              |7                        6
                      |              |--------------------------> Control
              0.1uF   |              |                            Signal
                      |              |
               ||    2|              |                         8
Composite  >---||-----|    LM1881    |                     +----> Gnd
Video In       ||     |              |                     |
                      |              |6                    |
                      |              |-----+-----+         |
                      |              |     |     |         |
                      |              |     |     |         |
                      |              |     |     | 0.1uF   |
                      |              |     /   -----       |
                      +--------------+     \   -----       |
                            4|             /     |         |
                             |        680K \     |         |
                             |             |     |         |
                             |             |     |         |
                             |             |     |         |
                            ---           ---   ---       ---
                            \ /           \ /   \ /       \ /
                             V             V     V         V

SyncBox construction

I built my prototype using point-to-point wiring on a 16-pin DIP wirewrap socket. All the components fit in the socket, and I wirewrapped the connections.

Parts placement in the 16-pin DIP socket

Connections to each pin of 16-pin DIP socket:

Connections to the DB-9 output connector


Michael E. Weiblen / http://www.mew.cx/