Coffee Table #3 Construction


Note: The links on the left side of this page and the other Model CT-3 pages will take you to detailed information about the new coffee table's design and construction.

TrainCam design and construction has been an evolutionary process. The original TrainCam (Model 1) made use of an inexpensive first-generation mini wireless color camera. Based on the results of that experiment, a new and greatly improved TrainCam (Model 2) was built. The battery assembly and flat car from the first TrainCam were combined with what was then the latest version of the mini wireless camera and a new battery cover to produce the new TrainCam. Picture quality and stability were greatly enhanced by introduction of the new camera. Now, a new swiveling TrainCam (Model 3) is the latest model, and it uses an even newer model camera.

The designs of all three TrainCams (Model 1, Model 2, and Model 3) are discussed in detail below.

Model 1 TrainCam

The camera used for the Model 1 TrainCam was the Synapse Network Xtreme Upgrade Mini Wireless Color Camera, Model 203CA. (At least that's the way it's described on several Web sites.) This was a first-generation camera, which served its purpose, although the results were not very exciting. Image quality left a lot to be desired, and it was almost impossible to stabilize the picture. But the TrainCam worked, and that was all that mattered.

The Model 1 TrainCam was originally checked out on the test track using a much-too-large 9-volt battery, a much-too-small gondola, and far-too-many rubber bands (photo below). Areas requiring serious repackaging were identified and corrected (no more rubber bands), and a custom-designed 7-cell NiMH battery replaced the Duracell behemoth.

TrainCam Test

Note: The camera specification indicateed that the input voltage can be 6 VDC to 12 VDC. Both the Duracell battery (9 VDC) and the 7-cell NiMH battery (8.4 VDC) met this specification.

The TrainCam development process is outlined below:

The first order of business was to do away with that huge power connector on the camera (photos above and below). One might think that the easy way to eliminate the connector would be to cut it off, and then reattach the two camera power wires to something smaller.

BUT WAIT!! An earlier examination of the camera's interior had shown that there are THREE wires in that power cable, not two wires. What is the purpose of the third wire???

Camera Power Connector

Because I couldn't account for the third wire, I decided to carefully cut away the connector's housing material to determine how the wires were attached to the connector pins. What I discovered was a miniature circuit board molded into the connector (photo below). The circuit board contains a 5 VDC regulator. The three wires feeding power to the camera are 9 VDC unregulated (white), 5 VDC regulated (red), and ground (black). The inputs to the regulator are 9 VDC unregulated and ground, both coming from the formerly attached power connector.

Run the mouse over the image below to see where the connector used to be.

5 VDC Regulator

The next step in the TrainCam project was to select an appropriate freight car to hold the camera equipment and the new battery pack. I chose a Micro-Trains 50' flat car. The car is long enough to hold the new battery, the connector for the battery charger, and the camera (photo below).

Note that there are three high-intensity LEDs mounted on top of the camera. The LEDs are used to illuminate the scenery as the camera moves through the layout.

TrainCam Components

The battery-charger connector, by the way, is dual-purpose. It not only provides the connection to the charger, but it serves as an ON/OFF switch for the camera and lights. When nothing is plugged into the connector, the camera and lights are connected to the battery (ON). When either the charger or a dummy plug is plugged into the connector, the camera and lights are disconnected from the battery (OFF).

The final step in the assembly process was to hide the battery and power connector in a container. My son suggested that the container should have the NASA logo, since the camera looks like some sort of Hubble Space Telescope replacement.

NASA Container

The container is actually a copper box with a paper cover over it. It was not an elegant solution, but I figured it would suffice for the test track—assuming that the copper didn't interfere with the camera's antenna.

With its batteries fully charged, the TrainCam was ready to provide the test track's operator with an engineer's view of the layout.

Finished TrainCam

Model 2 TrainCam

After months of mediocre results from the Model 1 camera, advances in wireless camera technology made it appropriate to upgrade the TrainCam. So, a new state-of-the-art camera was acquired, and reconstruction began.

Compared to the Model 1 camera, the Model 2 camera transmits a much stronger signal, the lens is better, the picture quality is better, and the antenna protrudes from the top (where it belongs), rather than from the side. Another feature of the Model 2 camera is that it is video, only, with no sound. This greatly increases video signal strength without decreasing battery life. Externally, both cameras look the same (except for antenna placement and power cord placement), so it was easy to swap one camera for the other.

While I was replacing the camera, I decided to make two other important modifications. First, I replaced the NASA container that enclosed the battery; and second, I added a switch to the LED lighting circuit.

The copper box that had been used for the NASA container was not the best way to go. It was too easy to short something out accidentally while removing or replacing the cover. To resolve this problem, I bought a Northern Pacific “Hy-Cube Box Car” to replace the copper box. With a little "kit bashing" (to shorten the box car cover by about 1/8 inch), I was able to make a great looking plastic container to replace the copper container.

As for the LEDs, most of the time I don't need them, so I decided to save battery power by adding an ON/OFF switch to the lighting circuit.

The finished Model 2 TrainCam is shown below. Note that there is a small hook built into the roof of the container. The hook keeps the antenna pulled down to almost roof level. This is necessary if the TrainCam is going to run through any tunnels. In fact, the height of the TrainCam was used to determine minimum allowable tunnel height for Coffee Table #3.

The photo below illustrates the video quality of the Model 2 TrainCam. The photo was taken while the TrainCam was being tested in Coffee Table #1. To see a video of the Model 2 TrainCam running on the test track, click here.

Battery Charger for 8.4 VDC NiMH Battery

The battery charger that came with the custom battery was a simple 12 VDC, 50 ma power adapter. This power adapter was not really appropriate for the battery; however, it was the only thing available. I was told that the 12 VDC adapter “should” work—assuming that the battery wasn't allowed to discharge all the way, or allowed to overcharge. In fact, it did work for awhile, but eventually the battery refused to accept a charge.

The solution to the problem was to replace the 12 VDC adapter with a constant-current battery charger that was customized for an 8.4-volt, 120 mah, NiMH battery. The battery charger selected for the job was the Velleman Universal Battery Charger/Discharger Kit, Model K7300. The charger (shown on the left in the photo below) is programmable for battery voltage, charging current, and slow or fast charge. For a slow charge, the TrainCam battery requires settings of 8.4 volts, and 15 ma. The TrainCam battery, which was no longer able to recharge using the simple 12 VDC power adapter, successfully revived when charged with the Velleman charger. After 8 hours of charging time, the TrainCam operated for 90 minutes on the recharged battery before the picture began to break up.

Model 3 TrainCam—First Implementation

Since the beginning of the TrainCam project, I realized that a new design would be required before the camera could be used for remote operations over the Internet. The existing TrainCam (Model 2) did not provide a view of the track ahead when the train is rounding a curve. That's because the camera looks straight ahead at all times, even though the train is turning left or right. The viewer gets a good look at the scenery, but that's not particularly helpful. It may give a clear picture of where the TrainCam will end up if there is something on the track ahead, but it won't show you what's on the track until it's too late. What was needed was a camera that can swivel, so that it looks into the curves. The Model 3 TrainCam has that capability.

A search of the Internet provided some very interesting TrainCam designs, most of which might work well in a large layout; however, they probably would not work very well in a coffee table layout where everything is compressed. But the research was useful, and it lead me to conclude that any TrainCam design should have the following characteristics:

  • To reduce the chance of derailment, friction should be kept to a minimum for the swiveling parts that are linked together; i.e., the front trucks and the camera platform. Therefore, both the trucks and platform should be mounted on ball bearings.

  • To further reduce the chance of derailment, the wiring from the swiveling camera to the battery should be extremely flexible. I selected super-flexible #32 wire (18 strands of #44 wire) with extra-limp insulation for this application. It's pricey (80¢/foot), but it's specifically designed for continuous flexing applications and is an excellent solution for the camera-to-battery wiring.

  • A swiveling camera must have a short antenna. Otherwise, the antenna will interfere with nearby scenery when the train is on a curve. Therefore, a new camera, operating at a higher frequency, would be required. The camera selected was a 2.4 GHz color camera with a one-inch antenna. (The antenna for the Model 2 TrainCam is more than four inches long.)

  • The overall length of the new TrainCam car should be about the same as the old TrainCam car. A longer car would tend to derail on the sharp curves in the coffee table layout.

Rather than rebuild the Model 2 TrainCam, I decided to use all new parts for the Model 3 TrainCam. Because the battery and charger connection for the new TrainCam are virtually identical to the Model 2 TrainCam, the same battery charger can be used for both.

The most important new design feature—the swiveling camera platform—is constructed of brass parts and mounted on a ball bearing assembly embedded in the base of the car. (See photo below.)

A lever protruding from the platform assembly is linked to a lever that is attached to the front trucks of the TrainCam car. The linkage is designed so that when the front trucks turn, the camera platform turns even further in the same direction. This can be seen in the photo below.

The same photo shows the short antenna protruding from the camera, and it also shows the super-flexible wire connecting the camera to the battery wiring. The super-flexible wire is so flexible that it has virtually no impact on the ability of the camera to swivel freely.

The final photo shows the camera being pushed through the layout on its first test run. To see the resulting video, click here.

The good news is that the camera worked, and the TrainCam car stayed on the track. The use of ball bearings and super-flexible wire had eliminated most of the potential derailment problems. However, the TrainCam was somewhat top-heavy, which meant that some effort should be made to lower the center of gravity.

As expected, there is a wobble problem. The front trucks of the TrainCam car tend to wobble a bit, which is perfectly normal. Unfortunately, the effect of the wobble was amplified by the linkage to the camera platform. Thus the picture wobbled even more. The fact that the camera and its platform were virtually friction-free probably made the situation even worse.

Model 3 TrainCam—Second Implementation

To address the high center of gravity and the wobble issues, the camera platform was redesigned and the front trucks were replaced. (See photo below.) The new camera platform is significantly lower than it had been in the original design. Instead of being secured to the ball bearing by a machine screw, lock washer, and nut assembly, this platform has a short brass rod soldered to it, and the rod slides into the bearing. The new longer trucks are standard 6-wheel passenger trucks with the middle two wheels removed.

As expected, the combination of the longer truck assembly and lower camera platform significantly improved camera stability. In the photo below is the TrainCam negotiating one of the many sharp curves in the new coffee table layout. The longer trucks have no problem staying on the track, and the camera turns nicely into the curves.

The differences between the Model 2 and Model 3 TrainCams is clearly illustrated in the comparison photo below. The shorter antenna and swiveling camera platform allow the Model 3 camera to look into the curves. Note also that small high-intensity LED headlights have been added below the Model 3 camera. The lights can be shut off by removing the black jumper that is located between the two LEDs.

The final photo shows the completed Model 3 TrainCam.

There are still more things to try, but the basic design seems to be working quite well. To further improve camera stability, it may be useful to add some friction or drag to the camera platform. Perhaps a small amount of spring tension can be introduced—tension that will give the camera a slight tendency to return to the straight ahead position.

TrainCam Test Videos

To see a test video of this new and improved version of the Model 3 TrainCam running on the lower level of track, click here. To see a test video of the TrainCam running on the upper level of track, click here. Note that the layout's scenery is still under construction, so much of what you see is only "rough cut," without the final detail.

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