Test Track Project


Scenery in the test track was limited to operating items such as emergency vehicle flashing lights, and scenery lighting. Nonoperating scenery (grass, rocks, trees, etc.) were not installed.

Test Track Scenery

The reason for limiting the aesthetic aspects of the layout was that plans had always called for the test track to be dismantled when work began on the new coffee table. Parts from the test track would be reused in the coffee table.

House Lighting

The first implementation of house lighting involved the use of 16-volt grain-of-wheat incandescent lamps connected to a 12-volt unregulated power supply. I used 16-volt lamps because the output voltage of my unregulated 12-volt supply seemed to be about 16 volts. Unfortunately, I discovered that the voltage varied from 16 to 13 volts, depending on the number of lamps being illuminated. The results of this lighting experiment were not helpful. I think in real life, they call it a brownout.

To solve the problem, I invested $4.97 in a 7812 12-volt regulator, a heat sink, and mounting hardware. As a result of some sophisticated high-tech assembly work involving one bolt and three wires (V in, V out, and ground), my unregulated 12-volt lighting supply became a regulated 12-volt supply.

The good news is that the lamp voltage maintained a constant 12 volts, regardless of the number of lamps being illuminated. The bad news is that the 16-volt house lights were too dim all of the time, rather than just some of the time.

The next implementation of house lighting made good use of the regulated 12-volt supply. In fact, it required a regulated power supply. Instead of using grain-of-wheat incandescent lamps, I used ultra-bright white LEDs. They were brighter and consumed less power than grain-of-wheat lamps, but they did require a regulated power supply. Because the voltage across the LEDs should be limited to 3.6 VDC, I placed a 390-ohm resistor in series with each LED. That resulted in 3.25 volts across the LED when connected to my 12-volt regulated supply.

Note: LEDs are actually rated for a specific current, not a specific voltage, so the series resistor typically should have been selected to limit current to 20 mA, not limit the voltage to 3.6 VDC. For Coffee Table #3, LED current was typically set at approximately 15 mA. This provided sufficient light, while protecting the LEDs from damage.

Street Lighting

The street lights remained grain-of-wheat incandescent lamps rather than upgrading them to LEDs. Being 14-volt and 16-volt lamps, they looked more like gas street lights than electric lights when connected to the 12-volt supply.

Emergency Vehicle Lights: Ambulance

The test track included a rather tasteless Volkswagen ambulance with an oversized flashing LED on its roof. The LED was controlled by an LM3909 oscillator and a couple of capacitors. A simple two-resistor voltage divider connected to the 12-volt regulated power supply provided 3 volts to the flasher circuit.

For the new coffee table, the oversized LED will be replaced by a couple of micro-LEDs, assuming that the tasteless vehicle is reused.

Emergency Vehicle Lights: Police Car

This project involved a 1978 Chevy Impala police car, micro-LEDs, and control circuitry that cycles the LEDs to produce a dazzling display of red, white, and blue flashing lights.

The emergency light bar on the top of the police car (photo above) is fake. It looked pretty, but it is just painted plastic. This project involved replacing the fake light bar with three bright flashing micro-LEDs.

As you can see, the micro-LEDs are about the size of Lincoln's nose on the penny. Working with micro-LEDs is an interesting challenge and requires special #38 magnet wire, low-temperature solder, a very small low-temperature soldering iron, a very hot soldering gun, an OptiVISOR, red and blue transparent paint (the LEDs are white), a steady hand, and a lot of luck.

Details of this project are discussed below.

  • Step 1: Flashing Circuit Breadboard

    The first step in this project was to breadboard the control circuitry using large LEDs (see photo below).

    The control circuity consists of an LM555 timer driving a CD4022 octal counter. Selected outputs of the counter drive 2N2222 transistors, which in turn drive the LEDs.

  • Step 2: Wire Preparation

    Six-inch pieces of red and green #38 magnet wire with solder-strippable insulation were temporarily laid on the sticky side of a piece of masking tape as shown below.

    Magnet Wire Tinning

    A very hot soldering iron (>734°F) and a small amount of solder were applied to the last 1/4-inch of each wire end. This vaporized the insulation and tinned the wire at the same time.

  • Step 3: Micro-LED Wiring

    Micro-LEDs are very small (see Lincoln's nose, above), and they are hard to see, hard to handle, easily damaged, and easily lost. An OptiVISOR (or other magnifying device) is a MUST!

    To hold an LED for soldering, I modified tweezers by placing shrink tubing over the ends and an elastic band around the middle (photo below). It may not look pretty, but it works. The shrink tubing protects the LED from scratches, while preventing it from popping out of the tweezers and sailing across the room. The elastic band is adjusted to keep enough pressure on the LED so that it will not fall out of the tweezers or move around while being soldered. Too much pressure, and the LED may be crushed to death. Too little pressure, and the LED may adhere to the hot soldering iron and fry.

    Modified Tweezers

    The soldering equipment used for the Micro-LED wiring was a 12-watt needle-tipped iron and low-temperature electronic silver solder. One end of each wire was trimmed until approximately 1/32-inch of tinned wire remained. Then a small amount of solder was applied to one of the LED terminals. A quick touch of the soldering iron to the LED terminal and pre-tinned wire completed the connection. The process was repeated for the other LED terminal.

  • Step 4: Micro-LED Test

    When wiring of the three Micro-LEDs was complete, they were configured on the flashing circuit breadboard to test them and to determine the correct series resistor value. The LEDs are extremely bright, which allowed me to operate them at less than their recommended operating current of 20 mA.

  • Step 5: Police Car Preparation

    Now that the Micro-LEDs were ready for installation on the police car, the next step was to disassemble the car, and then determine the best approach for mounting the LEDs.

    Being of the highest quality (made by Classic Metal Works), the police car was nicely detailed inside and out. The body was metal, and the interior was plastic—just like a real car. A Micro-LED is shown on the right (photo below) just below the police car's original light bar.

  • Step 6: Micro-LED Installation

    I decided that the best way to mount the LEDs would be to simply epoxy them to the roof. But first, I filed a V-shaped groove into the slightly curved roof to provide a relatively straight surface for the LEDs. Because the roof was metal, I applied two thin coats of epoxy cement to the groove to provide electrical insulation. I also drilled small holes through the large holes in the roof (now filled with epoxy) where the old light bar had been mounted. This provided an insulated opening in the roof for the LED wires.

    Next, the LEDs were mounted on the roof and held in place by their wiring. A small amount of epoxy cement was applied to each LED at the roof line, thus bonding the LEDs to the roof. After the epoxy hardened, more layers of epoxy were added until the assembly achieved the desired shape.

    Because the LED wiring is so delicate, a small circuit board was constructed that allowed the #38 wires to be connected to heavier wires (#22) that were more suitable for handling. The #38 wiring and the circuit board were sealed inside the police car.

  • Step 7: Micro-LED Painting

    With the LED wiring complete, it was now time to paint the two outer LEDs with red and blue transparent paint. The center LED would remain white. All three LEDs were turned on during the painting process, so that color intensity could be properly adjusted.

  • Step 8: Control Circuit Assembly

    The final step in the construction process was to move the control circuitry from the breadboard to a small printed circuit board. The finished assembly, including the police car with it's attached connecting cables is shown below.

    When the police car was installed in the test track, the connecting cables were run through a hole located directly below the car to the control circuitry located under the test track. Activation of the flashing lights is program controlled.

    To see a video of the flashing lights in action, click here.

Emergency Vehicle Lights: Fire Engine

Fire Engine Flashing Lights

This project was basically a repeat of the police car project described above. To see how the fire engine turned out, click here.

Other Operating Scenery

More operating scenery had been planned for the test track, but that idea was scrapped when work on the new coffee table began. From now on, any new operating scenery will be installed in the coffee table. First on the list is automatic grade crossing gates with associated flashing warning lights. The plan is to use nickel-titanium memory wire to operate the gates, and Nano-LEDs (somewhat smaller than Micro-LEDs) for the warning lights.

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