We wanted BITTSy to do HPP with off-the-shelf materials. This required finding a solution for blinking lights that did NOT require hard-wiring.

Our solution was a DMX512 lighting system. DMX stands for Digital Multiplex - DMX512 (Digital Multiplex with 512 pieces of information) is basically a standard for digital communication networks that are used to control things like stage lighting (where it initially began), light dimmers, Christmas lights, special effects devices, electronic billboards - basically anything you would want a computer system to control.

To use a DMX system with BITTSy, you need to purchase two pieces of hardware, plus connector cables.

USB-DMX interface

The first piece you must buy is a USB-DMX interface box. Basically, this is what allows you to make the connection between the PC computer and the actual lighting system itself. It takes information from the computer, and then outputs DMX codes.

We purchased the ENTTEC DMXUSB PRO (part number 70304).

One end of this has a USB 2.0 port, which connects to your computer (this cable is included when you purchase the device). The other end has XLR ports to connect with the lightbox. There is a port for both DMX IN and DMX OUT, of which you will only need DMX OUT.

There is a cheaper option from Enttec that is a more pared-down DMX controller, the ENTTEC Open DMX USB (part number 70303). It has a USB connection and DMX OUT (the one you need!). It was not available when we purchased the Pro unit, but it has all the capabilities that are needed for controlling lights in BITTSy and should function identically.

DMX Dimmer/Switch Pack

The second piece of hardware you need to buy takes the DMX commands from the USB interface box and uses that to turn things on and off.

We used the Elation DP-415.

This unit has been discontinued, but is still available at many vendors (check out B&H Photo, or search on Amazon, Google or Ebay - there are a LOT of them available), along with a very similar model, the Elation DP-415R.

The same company also made a new item, the CYBER PAK, which is the replacement unit - we have not tried it, but this or any other DMX dimmer/switch pack should work similarly, since DMX is a standard.

Dimmer packs take a DMX signal and use it to control power given to outlets along a certain number of channels. The number of channels corresponds to the number of devices you can independently control. There are devices for big light shows and concerts that have many channels and outlets, but basic units like the DP415 generally have four channels. This is enough to allow for left, right, and center lights in HPP that can all turn on and off individually (plus an extra, unused channel).

The DP415 has 8 outlets, in pairs divided between 4 channels. The outlets are 3-prong Edison sockets - the basic outlets you have in your house that take 3-prong connectors -- assuming you are in North America. (Outlets in Europe and Asia are different; you can still use this device, but would need to purchase lights with American-style plugs, or use converters.)


With this system, the computer can turn on and off anything plugged into the outlets on your dimmer pack. So you can select any type of light you wish, plug them into those outlets, and BITTSy can turn them on/off and make them flash.

This DMX system means you can select any type of light you wish, as long as they plug in with a basic power plug. Nightlights, bright strobes, lava lamps... anything electronic will be treated exactly the same way. You could even turn on fans or bubble machines rather than lights - BITTSy doesn't know the difference.

Things to consider when selecting lights:

  • Cord Length: The DMX system is going to be located near the computer running BITTSy - so you need to make sure you have long enough cords on your lights to reach from there to where you want the lights to be. (You can use extension cords, but if you are worried about timing, at least make sure they are good ones, and are similar in length on the two sides of your testing space)

  • Brightness: This is relative to the room space itself, and how dim it is - you want something that is bright enough to be easily seen, but not overpowering.

If the cables for your lights have a switch on them, ensure this switch is always on so that they are entirely controlled by the dimmer pack supplying or not supplying power to the outlet.

We then found a cover to go over the lights.

Suitable covers will depend on your lights, room, and intended uses. Some considerations are:

  1. Size of the light bulb

  2. Brightness of the room during testing, and brightness of the light as it shines through the cover. You want the brightness of the light when it is flashing to noticeably illuminate the participant's face so that your experimenters can see which side is currently active, even if the light itself is beyond the frame of your camera view - but you also don't want the lights to be so bright that they are uncomfortable to look at directly.

  3. Color. For headturn preference, where the center light is consistently used between trials and the two side lights during trials, it is nice to have the center light cover be a different color than the side lights' covers. This helps experimenters identify which light is active even more easily during testing. Our center light has a red cover, and our side lights' covers are yellow-orange.

Our covers are turn signal/brake light covers designed for a small vehicle, but you can select anything that works well in your room! You could take apart nightlights for their covers, use caps from large Christmas lights, or get more creative with any kind of semi-transparent plastic material - perhaps some hard plastic cups or shot glasses.

You may not need a cover for your lights, as long as they are shining through small openings, with nothing visible behind, and the brightness is okay!

There is also no need for the lights to project past the surface of the booth walls. You could mount the light slightly behind the wall, and line the cut-out in the wall with a piece of colored plastic vellum for the light to shine through. Just be sure that this is still bright enough!

XLR cable

You will need an XLR cable to connect your USB interface box to your dimmer pack. XLR cables can be purchased online or from any A/V store, as XLR is a standard cable format. XLRs used for this purpose are sometimes labelled DMX Turnaround Cables. However, there are many XLR cables with different pin numbers and configurations available - you will need to verify what kind you need.

If you have selected the models described above for your USB interface box and dimmer pack, you need a 5-pin XLR (male) to 3-pin XLR (female) cable (pictured below).

If you have purchased a different USB interface box or dimmer pack than the models described above, connecting your selections may require a different XLR cable type. The cable will need to connect your DMX OUT port on the USB interface box and your DMX IN port on the dimmer pack - check what type of connection these require.

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