How to build a light tower for dB Drag Racing

© 1996 Wayne Harris

dB Drag Racing is the most exciting car audio competition format ever devised! Part of this excitement is due to the large light towers used to indicate the relative loudness of each contestant's sound system. The following article describes how you can construct your own light towers for use at dB Drag Racing events. Each of these light towers will consist of 24 lights.

This article assumes you have a working knowledge of basic household wiring. Experience with computer hardware and peripherals is also a prerequisite. If you are not qualified, please find someone who is before proceeding.

Equipment Required

• 1 each Term-LAB measurement system.
• 2 each Keithley Metrabyte PIO-24 24 bit parallel digital I/O boards.
• 2 each Keithley Metrabyte SSIO-24 24 channel solid state I/O module boards.
• 2 each Keithley Metrabyte C-1800 cables.
• 2 each Keithley Metrabyte RMT-02 rack mountable enclosure (optional).
• Ground Fault Interrupters.
• AC Power Cords.
• 48 Incandescent Light Bulbs and Light Bulb Sockets.
• For 115 VAC lights use ...
  48 each Keithley Metrabyte SM-OAC-05 solid state output modules.
• For 12 VDC lights use ...
  48 each Keithley Metrabyte SM-ODC-05 solid state output modules.

PIO-24 Card Configuration

1. Set the base I/O address of the first PIO-24 card to 300 hex. (Refer to the card's manual for more information on setting I/O addresses.)
2. Set the base I/O address of the second PIO-24 card to 304 hex.
3. Carefully insert the cards into the motherboard of the computer.

SSIO-24 Setup

1. Install each SSIO-24 board into an RMT-02 rack mountable enclosure.
2. Insert all of the solid state output modules into the SSIO-24 boards.
3. Configure TB7 on each SSIO-24 board so that the board derives its power from the PC. (Refer to the SSIO-24 manual for more information.)
4. Configure S1 on each SSIO-24 board for "output" mode. (Refer to the SSIO-24 manual for more information.)
5. Connect the SSIO-24 boards to the PIO-24 cards in the PC with the C-1800 ribbon cables.

Wiring the Lights

1. Connect one conductor from each light to the HOT (black) lead of the power cord that will be plugged into an AC outlet.
2. Each solid state output module on the SSIO-24 board has a corresponding set of screw terminals. Connect the second lead from each light to one of these screw terminals.
3. Connect the NEUTRAL (white) lead of the power cord that will be plugged into an AC outlet to the other screw terminal for each solid state output module.
4. Repeat this process for each light in the light tree. Remember, the outputs of the SSIO-24 are sequential. (Output A0 should correspond to the bottom light on the light tree and output C7 should correspond to the top light.) All 24 lights of one tree should be connected to one SSIO-24 and all 24 lights from the other tree should be connected to the second SSIO-24.
5. You may need to use 2 or more power cords depending on the total light wattage being used. For example, you could have one power cord for each SSIO-24 board. Or, you could use 4 power cords; one for the bottom 12 lights of the first SSIO-24, one for the upper 12 lights of the first SSIO-24, 1 for the bottom 12 lights of the second SSIO-24, and one for the upper 12 lights of the second SSIO-24. Make sure the HOT and NEUTRAL leads from each light correspond to the same power cord. (In other words, don't connect a light's HOT lead to one power cord and its NEUTRAL lead to another.)
6. Install Ground Fault Interrupters on each power cord.
7. Ground everything to the ground (green) lead of the AC wiring.

Usage

To enable light bar operation in Term-LAB, click on Hardware and then select the checkbox labelled, "Light Tower". Diagnostic functions for the lights are also included in this area. Enter 300 into the text box labelled, "Chan A" and enter 304 into the text box labelled, "Chan B".

If the lights work "backwards" (they are all on and turn off as the lights go up the tree), then select the checkbox labelled, "Invert".

1. Bar Mode - The light trees act as bargraph meters and indicate the peak SPL for each channel
2. Dot Mode - Only one light is on at a time. This light indicates the peak SPL for each channel.
3. Peak Hold - The light trees work in bargraph mode continuously and a single light in each tree indicates the peak SPL for that channel.

Suppliers

440 Myles Standish Blvd.
Taunton, MA 02780
(800)348-0033

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