Custom Sensor Track Review

An SCI How-To Article / Review

by Steve Sawtelle

4/07/04

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Introduction

Shortly after setting up my first 1/32 layout, I decided to buy a DS 300 (4 lane) lap timer with the DS overhead light bridge. As a lap counter and/or lap timer, this system works great; however, over time several drawbacks became apparent. First, I could never find any practical way to implement an interface to any of the commonly available race management software packages. Since one of my goals was to host race events, a standalone lap counter/timer wasn’t going to cut it. Second, I didn’t care for the light bridge’s esthetics (I suppose I could have camouflaged it to look like a pedestrian bridge or something) because it looked like, well, a light bridge. Finally, the light bridge setup was susceptible to being hit by cars! No matter where I positioned it, someone would find a creative way to de-slot and hit the light bridge. Not a big deal but more often than not this would require carefully repositioning the sensors in the base with openings in the track slots so the light beam could pass through. It was time for a change…

As I began researching alternatives to my DS lap timer setup, I ran across several posts on the SCI forums from people who purchased specially designed sensor tracks from an individual named Brent Carlson (aka “MrBugs” on the SCI forums). I visited Brent’s website (http://slotcars.carlsoncomputers.com ) which provides a description of the sensor tracks along with pictures of sensor tracks in various stages of fabrication. The sensor tracks are designed to use a PC’s parallel port to communicate with race management software. Since most race management software currently available supports a parallel port interface, Brent’s sensor tracks don’t tie you down to a particular software package. The sensor track design can be applied to virtually any brand of 1/32 or 1/24 plastic track. The site also includes feedback Brent has received from his growing list of customers. Given my limited background in electronics, I decided to contact Brent and order a pair of sensor tracks for my 4 lane Scalextric Sport layout. The 4 lane setup costs $100 plus $22 for shipping from Edmonton, Alberta (Canada) to my home in Connecticut (U.S.A.).

Note: The author of this review purchased the sensor tracks at full retail value and took delivery before offering to write a review. No discounts or compensation in any form were offered or provided in exchange for this review.

What Is Included?

Roughly a week or so after placing my order, the sensor tracks arrived at my local Post Office. The photo below shows the shipping box which, despite its 3,000 mile journey from Edmonton Alberta (Canada), arrived in excellent condition.

The contents were wrapped very carefully as shown below. Bubble wrap and other protective material ensured the sensor tracks and other components arrived without any damage.

In addition to the sensor tracks themselves, Brent also includes everything needed to install and connect the sensor track(s) to your PC (see photo below). An AC adapter provides power to the IR emitters while a custom cable connects the sensor track to your PC’s parallel port. The custom cable is about 18 feet long – it’s nice to see Brent didn’t skimp on the cable length. Brent will also make longer cables, at a slight additional charge, if your track layout and PC setup requires one.

A Closer Look At the Sensor Tracks

After carefully unwrapping the sensor tracks, a closer examination was in order. The sensor track for Lanes 1 and 2 is shown toward the bottom of the picture below. Note the two connectors and LED along the side of the track closest to the camera. The connector on the left is where one end of the PC interface cable will be connected. The connector on the right is for the 5V power supply. The LED between the connectors will be “on” (lit) when the power supply is connected to the sensor track and plugged into a power source.

Referring again to the picture above, the sensor track for lanes 3 and 4 is shown toward the top. Note the connector along the front edge – this will be connected to a corresponding connector on the back side (out of view in the picture above) of the Lane 1 and 2 sensor track.

The picture below shows the underside of the sensor tracks. The sensor track for Lanes 1 and 2 is on the right. As you can see, Brent has covered most of the components with a piece of protective tape. I briefly thought about removing the tape to take a picture or two for this review; however, in the end decided against doing so for fear of inadvertently damaging one or more of the sensor track’s electronic components. Brent’s website includes pictures without the tape for anyone interested in seeing the sensor track components.

The picture above also shows the two connectors on the “inside” edge of each sensor track. For a 4 lane setup, this connection is required for a couple of reasons:

1) The IR emitters for lanes 3 and 4 require a power source. The connection provides power via the 5V power adapter which connects to the Lane 1 and 2 sensor track.

2) When a car’s guide “breaks” the light beam for the Lane 3 or Lane 4 sensor, the signal (“trigger”) must be sent to the PC so the race management software can act upon it. The connection between the sensor tracks provides a path for signals generated by Lane 3 and Lane 4 to use the same PC interface cable which is physically connected to the sensor track for Lanes 1 and 2.

The picture below shows how the 5V power adapter and PC interface cable will be attached to the Lane 1 and 2 sensor track. Later in the review a more detailed discussion of actual sensor track installation is provided.

Note: If you buy a 2 lane sensor track, the connector for lanes 3 and 4 will not be present. Should you decide to upgrade from a 2 lane to 4 lane setup at some point in the future, you have a couple of options:

1) Purchase the 2 lane sensor track and contact Brent when you are ready to expand to a 4 lane setup. Brent will make arrangements with you to upgrade your 2 lane setup.

2) If you are reasonably sure you will expand from 2 lanes to 4 lanes at some point, consider purchasing the 4 lane setup right from the start. You can either put the sensor track for lanes 3 and 4 in a safe place until needed or incorporate it into your 2 lane layout (i.e. it serves as a full straight section).

Placement in Your Layout

The sensor track(s) can be positioned just about anywhere in your layout where there is a full straight section. However, straight sections where the cars are under braking (e.g. just before entering a turn) are recommended since the car’s guide is more likely to be fully “planted” in the sensor track’s slot. This will ensure the guide “breaks” the beam of light between the IR emitter and photo-transistor for a given lane. Conversely, choosing a straight section where cars are under hard acceleration (e.g. just exiting a turn) is not recommended since the car’s front end, and therefore guide, may lift up just enough to prevent “breaking” the beam of light consistently. For my layout, I chose the straight section which serves as my start/finish line. The start/finish line on my layout is located just after the exit of a 180 degree hairpin turn (generally not ideal for the sensor track); however, I did not want to move my start/finish line unless absolutely necessary. If testing showed this to be a troublesome location for the sensor tracks, I would have to find another location for the start/finish line.

Installation

Once you have decided where to install the sensor track(s), installation is straightforward. Here is a step-by-step description of the steps involved for my layout (most installations should be very similar).

1) Begin by marking the midpoints and endpoints of the track section where the sensor track will eventually be located BEFORE disassembling your existing layout. This will serve a couple of purposes:

a) When you reassemble the track with the sensor tracks installed, you can realign adjoining track sections to the proper position.

b) If you decide to use a template to raise or lower the sensor tracks so they lay perfectly flat, the registration marks will serve as a reference (see below).

Tip: If you do not want to make marks on your table surface (or have a carpeted surface), place small pieces of painter’s tape on your surface and make the marks on the tape.

2) Once you have marked the midpoints and endpoints of the existing track section where you plan to install the sensor track(s), “break” (disassemble) your layout and remove the existing straight section(s).

3) Next, you’ll need to decide how you want to compensate for the sensor track components which protrude slightly (approx. 1/8”) from the underside of the track. If you fail to do this, the sensor track(s) will not lay flat which might prevent them from working properly. You’ll also have an irregular track surface which will adversely affect your layout’s aesthetics and the performance of your cars. There are two basic approaches to deal with this:

a) Place some support under the sensor track(s) taking care that none of the components which protrude rest on the supports.

b) Route out (or remove by some other means) a portion of your track surface where the components which protrude from the underside of the sensor tracks are located.

4) My tables are covered with ½” plywood and another ½” layer of homosote. Homosote is very easy to cut with a sharp knife so I opted for the second approach mentioned above. This would allow the sensor tracks to lay perfectly flush with my table surface. To determine where to remove unwanted homosote, first I fashioned a simple template using 1/8” masonite as shown below.

Note: While I planned to use this template to remove small sections of my table surface under the sensor tracks, a similar template could have been used to elevate the sensor tracks had I decided to take that approach. One slight difference would be to extend the template in both directions slightly to “catch” parts of track sections immediately adjacent to the sensor track(s). Lengthening the template in this fashion would provide a smoother transition “up” to and “down” from the sensor track(s).

Be sure to check the sensor track(s) are laying flat on the template as shown below. If necessary, make any adjustments before proceeding. Once you are satisfied with the template “fit”, use a marker to make a registration mark on the template where it lines up with the midpoint of the sensor tracks. The registration mark for my template is labeled “CENTER” (see right edge of template).

5) Next, the template was positioned on the table (see photo below) where the sensor tracks would be installed. The registration marks made earlier on the table surface and template make this very easy.

Note: If you plan to raise and support the sensor track section(s) using a template or other means, you can skip to Step 12.

6)  Once the template is in place, trace the sections to be removed onto the table surface as shown below.

7)  The picture below shows the table surface once tracing is complete and the template is removed.

8)  Using a SHARP knife, CAREFULLY cut along the outline of table sections to be removed as shown below. Make several passes with the knife to reach the desired depth.

9)  Once the outlines were cut, use a chisel to remove unwanted material as shown in the pictures below. Make sure the chisel is sharp and keep your fingers out of the way!

10) Make sure to vacuum up any dust and debris before proceeding with installation. If not cleaned up, any remaining dust and debris could adversely affect sensor track performance.

11) Because homosote is so messy, I took some duct tape and “lined” the pockets formed by the sections of removed material. This was a precaution to ensure no additional dust or debris worked its way loose from the remaining homosote and caused problems with the sensor track.

12) Now it is time to install the sensor tracks into your layout. Use caution not to damage any of the sensor track connectors or components. Reassemble your layout and adjust the track sections so they line up with the registration marks made earlier. Double check the sensor track sections are laying perfectly flat. If not, carefully disassemble and make any necessary adjustments.

13) Next you’ll need to figure out how you want to route the power wire for the power adapter and the PC interface cable. I decide to run both of these under the track table to their respective locations. A ½” hole was drilled in the table surface as shown below to route the wires.

14) The power wire and PC interface cable were then carefully pushed up through the hole from the bottom of the table as shown below.

15) Carefully install the connectors on the power and PC interface cables into their respective connectors on the side of the sensor track.

16) Finally, connect the other end of the PC interface cable to the parallel port on your PC as shown below.

17) Make sure the power adapter for the sensor track is plugged in (the power LED located on the side of the sensor track should be “on”). You’ll need to install your race management software and configure it to recognize the signals sent from the sensor tracks. The configuration and testing process will vary depending on the software you are using. The interface cable Brent provides use the following parallel port “pins” to send information from each lane sensor to the PC:

Lane	Pin
1	10
2	11
3	12
4	13

For my layout, I use a race management software package called “SlotTrak” (http://webpages.charter.net/slottrak/index.html) which is a Windows-based application. Initially I tried using an IBM ThinkPad T20 (laptop); however, I could not get the PC to recognize signals being sent from the sensor track. Thinking there might be a problem with the sensor tracks (after all, it couldn’t possibly be me…), I contacted Brent for assistance. Brent worked patiently with me to pinpoint the problem. As it turned out, the problem was with the parallel port on the ThinkPad – it simply wouldn’t recognize any input no matter how it was configured. This was not a problem with the sensor tracks. Switching to another PC (Dell Latitude C610), the sensor track input was immediately recognized. Setup and configuration from this point on was very straightforward.

Testing Sensor Track Performance

Now that everything was installed and configured properly, it was time to do some testing. For testing, a minimum of 25 laps were run for each test scenario. First I ran three different Scalextric NASCAR’s with the black guides (see photo below) in each of the 4 lanes (300+ total laps) – the sensors didn’t miss a beat.

Next I replaced the black Scalextric guides with blue guides (see photo below) as some of the posts I read while researching the sensor tracks indicated the blue guides had caused some problems. Brent has since refined his design to recognize the blue guides but I still wanted to test this out just to be sure. Once again, I ran each of the three cars in each lane (300+ total laps) with the same result – so far the sensor tracks were batting 1,000 (perfect).

Now it was time for the acid test – some TSRF cars with the stock pin guides. For those of you who are not familiar with the pin guides, they have a much smaller surface area than a traditional flag guide. The photo below shows the TSRF pin guide (left) alongside the standard Scalextric flag guides (middle, right).

There’s one other thing I should mention. On my track, TSRF cars look like the Millennium Falcon making the jump to light speed when racing against stock RTR’s (and modified RTR’s for that matter…). The combination of the TSRF’s smaller guide, quicker acceleration and higher running speeds would be a good test for the sensor tracks. The results? The sensor tracks had no problems whatsoever keeping tabs on the TSRF cars.

At this point, I engaged the help of my 7 year old twins and some friends to run different combinations of cars/guides in each lane. My thinking was multiple cars running concurrently was more akin to actual race conditions and might therefore cause “false” triggers (i.e. a car in one lane triggers the sensor in another lane). Cars used for this portion of the testing included Scalextric, FLY and TSRF. Once again, the sensor tracks performed flawlessly.

In total, well over 1,000 laps were run on a 4 lane layout with a variety of cars and guides. The sensor tracks passed with flying colors – to the best of my knowledge, not a single lap was missed nor were there any false triggers.

Summary

Brent’s custom sensor tracks were just the ticket for me when upgrading from my DS lap timer to a software based system. The prices ($80 for 2 lanes, $100 for 4 lanes at the time this article was written; plus shipping) are very reasonable – especially when you consider the sensor tracks will make your racing much more enjoyable and probably last as long as you own your layout. As the pictures accompanying this review show, installation is simple and straightforward. No special tools, skills or knowledge are required and Brent is very responsive should questions arise. While my testing was limited to the SlotTrak software, the sensor tracks are not tied to a particular piece of race management software so you have plenty of options and flexibility. In my testing, the sensor tracks performed flawlessly which is consistent with feedback from other sensor track users posted on Brent’s website. In closing, I have no reservations recommending Brent’s sensor tracks – they are a great product.

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