The Signaling Solution, Inc.
PO Box 25
West Terre Haute,
IN 47885
Phone:(812) 533-1345
Fax:(708) 570-6140

Ataras BD-16 Block Detection System

by Alan Houtz
Reprinted by permission of MODEL RAILROADING MAGAZINE
August, 1996


Have you ever been to a train show, trade show or elaborate layout and been impressed by the working train-detection system? Are you interested in a train-detection system? Are you interested in a train-detection system but are afraid that installing one is beyond your ability? If so, the BD-16 may be what you are looking for.

The BD-16 comes out of the box as a PC board about 7" square, an edge connector, as 6V power supply and four 0-ohm jumper modules. The jumper modules are furnished in case your application requires more current than provided by the factory-installed 220-ohm chips. Switching these is a simple plug-in operation, and the manual gives plenty of information on how to size your own resistors.

The BD-16 is a fully integrated train-detection system. It uses diode current sensing to detect the presence or absence of a train, or to differentiate between East and West travel. According to the manufacturer, very similar to Linn Westcott's Twin T circuit. The detection signals generated can be used to drive LEDs, relays or logic circuits depending on what you would like to do.

During a recent electrical upgrade of the Locust Grove & Western it was decided by the membership that operating block signals would be an interesting feature to add to the layout. Since the LG&W is a modular layout and travels throughout Alabama and Tennessee, simplicity was a must. We saw many top-notch systems being demonstrated at the NMRA National Convention in Atlanta last year, and after a short discussion decided on the BD-16 because it was simple, and it fit our budget.

Since all we wanted to do was operate standard block signals, we were able to install the board without making any changes. The board must be configured for your application. This is done by installing or removing four jumpers, one of which activates a self-test mode. The other three allow you to select your common rail (North or South), cab or command control and East/West travel or occupied/vacant block.

The Locust Grove & Western operates on cab control with the South rail as the common rail, and we use occupied/vacant reporting, so no jumpers were necessary for normal operation. I think that this will be the most common method of installation by users of this system.

Installing the BD-16 is fairly simple. I know that simple is a relative word here, and will depend on your level of experience with electrical work, but if you have wired your layout using the common rail method (each block has one lead from your cab and all blocks share the common lead) then you can install the BD-16.

A word of caution here. Study the manual thoroughly, and I do mean thoroughly. Almost the entire first half of the instruction manual consists of descriptions of the various methods of wiring a model railroad. The actual installation instructions follow in the second half. I suggest you go through the entire manual and highlight the pertinent sections. Use a photocopier and make enlarged copies of the drawings, especially the wiring diagram. These drawings, as they appear in the manual are small and can be difficult to read, especially when you are under your layout.

Go slowly and follow the directions. Any electrical project is only one wire at a time. If you think of it this way, it is not so intimidating. The board is installed by running the common lead from each block to a corresponding terminal on the BD-16 connector, and then connecting the common leads from the board to you cab common connection. There are connections for up to 16 separate blocks. You can use as many or as few as you wish. The currents used to illuminate the LEDs are very low, so you can use 28 gauge wires or ribbon cable for the leads to your signals. We used communications cable for ours. The color-coordinated pairs of wire made it easy to keep track of which block was being installed.

Be sure to keep notes as you progress. A simple chart of what color wire connects to which lead of each signal will prove indispensable if maintenance is ever necessary.

If you are in corporating the BD-16 into an existing layout, leave an extra foot or so of slack in your connections to the board edge connector. This will allow you to drop the connector down from your benchwork if you ever want to change your block wiring.

Don't be intimidated by our installation photograph. Remember that the Locust Grove and Western is a modular layout and is often assembled and disassembled. Because of this we require more hardware than a standard layout installation would. We decided that the use of terminal strips would both simplify installation and aid in maintenance and troubleshooting. The long terminal strip is used for the "vacant" and "occupied" signals, and the smaller terminal strip in the corner is the 5V output from the BD-16. This method allowed me to test the LEDs and correct mistakes with a screwdriver instead of a soldering iron.

When connecting your signals, be sure to identify the anode and cathode of each LED. The anode (or positive lead) for each LED goes to the 5V contact on the BD-16. If you reverse the leads, the LEDs will not light.

If you are unsure of your soldering skills, do yourself a favor and get some PC-board connectors from Radio Shack and practice. When you can make a neat connection without bridging any terminals or using excess solder, then you are ready to begin.

From the terminal strips we used category 5 data-transmission cable for the runs our to the signals. When we had everything hooked up, we applied power and --nothing. Our block signals were equipped with bulbs. The BD-16 will only power LEDs. Even low-voltage lamps will not burn, so shop carefully for your signals.

We had to convert to LEDs with the signals in place --delicate and difficult work. After the conversion to LEDs we again applied power and ran a train around the layout. Everything worked flawlessly.

The layout was then taken down and transported to Mobile, Alabama, for a train show. The system functioned well throughout the show. The only peculiarity I noticed was that some of the more efficient drives, such as Kato or Stewart do not always provide enough resistance to change the signals. This was remedied by running multiple-unit lash-ups, or two trains.

The BD-16 senses the presence of a locomotive through resistance, so to keep the signal red until the train clears the block --I used Kadee(Registered) wheelsets with a 1/8-Watt 4.7K surface-mount resistor on the axles in the caboose. Connect the resistor to the wheels with a conductive pen or conductive paint, and remove the black coating from the treads and backs of the wheels for optimum contact. You can also use a standard resistor and wind the wire around the car axles to the wheel treads. Check the clearance under the car to make sure the resistor doesn't hit the car underframe as the wheelset rotates.

The BD-16 was well received at the train show. We had lots of question from the public, and the younger children chased the trains around the layout so they could see the signals change from green to red.

This is a good project for the modeler who wants a signaling system, but is not an electronics buff. We did have a small problem or two, but Mr. Ataras made himself available, and quickly put us back on track. He is committed to this product, and wants his customers to be satisfied.

The only problems I had involved the instruction manual. Key information is sometimes difficult to locate, and diagrams are several pages from the text which discusses them and there is no troubleshooting chart if you do have a problem. A little improvement in the organization of the manual is all that is required here.

This is a good quality product. I would happily install one on my own layout. Suggested retail $250.00. For more information contact: W.S. Ataras Engineering, Inc., 40 Laughton St., Upper Marlboro, MD 20774. E-mail:

Product Update:
The BD16 User's Manual is now available for free download from the website and a printed manual is available for seperate purchase.
Our current address and contact infomation is given below
The Signaling Solution, Inc.
PO Box 25
West Terre Haute, IN 47885.
Phone: (812) 533-1345
Fax: (708) 570-6140
The Signaling Solution, Inc., PO Box 25, West Terre Haute, IN 47885. E-mail: