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W. S. Ataras Engineering, Inc.
PO Box 168
Westminster, MD 21158

812-533-1047 (voice, 10-4 est)
708-570-6140 (fax)

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Ataras BD-8 Block Occupancy Detector: All Scales

by David Frost
Reprinted by permission of RAILROAD MODEL CRAFSTMAN
March, 1998

W.S. Ataras Engineering entered the hobby with the BD16 Block Occupancy Detector that could handle no less than 16 separate track segments at a time. While many modelers appreciated not having to purchase a separate detector for every block, others felt that 16 blocks at a time were too many. Ataras has responded to this point of view by producing an eight block detector, the BD8.

Like its big brother, the BD8 provides a variety of outputs for control panel lights, signals or accessory activation, but more sophisticated chips, surface mount technology and redesigned wiring have reduced the board to less than a quarter of the size of the BD16. It is suitable for use on layouts with either conventional d.c. control systems or those employing command control.

The BD8 detects a train from the presence of a current flow through the rails. As such, it is suitable for all scales and control systems except those running on a.c. current. Track current is led through a diode matrix, rated at 3 amps, that produces a voltage drop of 0.7 volts, but this will not be obtrusive under normal circumstances.

The 3 inch square, double-sided, printed circuit board plugs into a connector which has 36 separate terminals, 18 on each side. A small packet contains mounting hardware and there is a separate 9-volt transformer to power to board. All inputs to and outputs from the detector pass through the connector. I strongly suggest soldering labelled wires to all the terminals of the connector before you install it in a dark and inaccessible place beneath your layout.

Accompanying the detector is a sizeable book of instructions which discusses different model railroad control systems and common rail wiring, analyses methods of train detection and explains control of signals and accessories. Other sections of the manual explain configuring and installing the detector and connecting the outputs.

The BD series of detectors gain their versatility by asking you to make a couple of configuration settings before installation in much the same manner as manufacturers of PC modems. A two-pin jumper defines whether or not you are using command control, and two other jumpers define which of your rails is common. If like me, you do not conceive of your common rail as North, South, East or West, leave off those jumpers and forget about them.

The BD8 has two outputs for each block, one which is energized when a train is present, while the other energizes when the block is vacant. These outputs are designed for LED's which are connected to those terminals and the 5-volt terminal on the connector. Red and green LED's can then be wired into a control panel or installed in a two-light signal.

This detector has been designed with all types of layout in mind. I particularly appreciate the second or two delay before the red LED switches to green so that dirty wheels or track do not cause the signals to oscillate back and forth between indications. The test sample is wired into my 12-year old layout and I am using the outputs to drive control panel lights in some cases and as input to TTL signalling in others. The detector is working perfectly and I am very pleased with the results.

In short, the BD8 Block Occupancy Detector is an excellent addition to the Ataras line of sophisticated electronic products. I commend Ataras for their willingness to sell their instruction manuals separately for $7.00, refundable on an item before you commit to purchasing it. The BD8 should be ordered directly from W.S. Ataras Engineering. Contact the firm for current prices. --DAVID FROST

Note: Since this review was written, we have made our manuals available in PDF format and downloadable at no charge.

Also, because many of our customers have reported "wall-wart congestion" when a separate wall-wart is provided for each module, we no longer provide a wall-wart with each product and have reduced the cost of our modules accordingly. Instead, we recommend that our customers purchase a separate 12 VDC regulated supply with a current rating of at least .25 amps per module. This should provide sufficient power, reduce the number of wall outlets needed, and reduce the overall cost.

One such power supply we have been using is the Astrodyne RS35-12.

See this power supply at: Astrodyne RS35-12.

W. S. Ataras Engineering, Inc., PO Box 168, Westminster, MD 21158.

Copyright 1998-2015 W. S. Ataras Engineering, Inc.
Last update: February 18, 2015