Carrera Digital: Creating a Digital 132 Ghost Car for Digital 143 Racing

By Michael Ashton

A feature of Carrera’s Digital 132 system that would really be nice to have in Digital 143 is the autonomous or ghost car. This is where a digital car can be programmed to run around the track at a constant speed while changing lanes in a random fashion. A recent article in this blog described how to implement an autonomous car in Digital 143 without any modification to the car or system and with virtually no added expense. However the method presented then has two drawbacks:

1. Each autonomous car created with this method requires a dedicated controller.
2. Lane changing follows the current state of the lane change flipper, so it is really not random.

This article will describe how to implement an actual D132 autonomous car that will run at a constant speed, change lanes in a random fashion and not use up one of the three available controller ID’s on a D143 track. This will be accomplished by installing a D132 decoder chip in a D143 car. A D143 controller can control car assignment, speed and lane changing through a D132 decoder chip. Furthermore, the D132 autonomous car feature can be programmed and works with the D143 system just like D132.

The terms “autonomous” and “ghost” are used synonymously throughout this article. 

The following photo below shows the components required to create a D132 autonomous car for the D143 system:

• A Carrera D143 motor, SCX Compact motor or a motor with similar specifications (do not use a Carrera GO!!! motor for this application).† The motor shown is an SCX Compact motor. The crown and pinion gears are identical to those used by Carrera, so the SCX motor is ideal for this conversion.
• A Carrera D132 digital decoder chip. Shown below is the #26740 chip used in Formula 1 cars. It has the smallest space requirement and is, therefore, most suitable for 1/43rd scale conversions.
• A Carrera GO!!! or D143 car chassis with motor and electronics removed. Shown below is one of the latest Carrera 1/43rd scale NASCAR’s.

Before proceeding there are a few points that should be made clear:

• Removing the motor and/or digital chip assembly from a Carrera GO!!!/D143 car and installing a D132 chip in its place may void the Carrera warranty. Test the car thoroughly in its stock condition prior to any modifications.
• It is possible that the use of a D132 chip with a motor designed for 1/43rd scale cars could affect the motor over time. This could be due to the fact that the D132 pulse width modulation (PWM) frequency is 15,625 KHz or, roughly half of the D143 frequency of 30.8KHz. This has the potential to increase the operating temperature in the 1/43rd scale motors, however, there is no conclusive evidence of this from testing.
• † There is also speculation that the motor installed in GO!!! cars is not appropriate for digital operation, with either D132 or D143. There is some empirical evidence to support this concern, therefore, only D143 or SCX Compact (which have a history of success in these implementations) motors should be used in digital conversions.
• This installation is not particularly difficult, however, basic skill and knowledge of soldering, and its attendant safety issues, are required.

Once ready to proceed, the first thing that must be done is to examine the chassis and decoder chip to determine how best to fit the chip to the chassis. Ideally, the existing sensor hole and mounting chamber of the D143 chassis can be used. This will insure that the sensor on the D132 chip will be in the correct position for the D143 track.

The Installation

The following two photos illustrate the test fit of the D132 chip.

The first photo reveals two potential problem areas when the D132 chip is test fitted with the sensor placed in the mounting chamber. First is the front edge of the chip encroaching over the front body mount receptacle.  Second is the upper motor lead terminal blocking the chip from being recessed down around the motor.

The second photo depicts in a side view how the height of the D143 chip mounting post also prevents the D132 chip (and its sensor) from being properly recessed toward the chassis floor.

After a little more tinkering with the position of the chip in the chassis, it became apparent that the major obstacle to an acceptable installation was the D143 chip mounting post. It appeared that if the mounting post could be lowered, that the chip could be “tucked” under the upper motor lead terminal and angled slightly to fit around the motor. So, the mounting post was dealt with first.

The next photo shows how the mounting post is trimmed with a sharp hobby knife to the same height as the sensor chamber.

This is the only modification to the cassis, so the piece cut from the top can be saved in case the car needs to be returned to its stock condition. However, I think that a D143 chip can still be properly mounted, in spite of the lower mounting post.

Before soldering any of the decoder chip lead wires to the motor or chassis, it is essential to “tin” the exposed wire ends by applying a small amount of solder as shown below. This makes it easier to solder the leads to terminals and copper strips by allowing the solder in the tinned wire and the terminal to flow together.

I believe that the best approach is to solder the chip leads to the motor while it is removed from the chassis. Purple is attached to the positive terminal. Note that the wire that connects the positive terminal to the motor can is left in tact. The gray wire is soldered to the negative terminal. When soldering leads from these digital chips and especially with these smaller 1/43rd scale motors it is important to use a low wattage soldering iron and to try to apply minimum heat by working quickly. Note: make sure that the slider switch (located on the underside of the chip as seen in the following photo) is set to the driver side of the chassis (i.e., toward the sensor).

Now the motor may be installed in the chassis motor mount. To install the chip, with the chip held in front of the motor, first slide the trailing edge of the chip’s main body underneath the upper motor terminal (see the yellow arrow below) and then ease the sensor all the way down into the sensor chamber. The chip will probably need to be tilted down toward the passenger side to do this. Work slowly and gently. When seated properly, the chip will reside at an angle but will fit well within the edges of the chassis, and sitting flat. The good news is that, in this configuration, the front edge of the chip does not interfere with the front body mounting post, as highlighted by the red arrow. Now go ahead and solder the input leads to the guide terminals. Black to the positive (driver side) and red to the negative (passenger side). The finished installation is shown below.

The yellow arrow in the photo below shows a small strip of electrical tape used to insulate the surface of the chip where it is tucked under the upper motor terminal. The combination of the sensor residing inside the sensor chamber and the chip fitting snug under the motor terminal provides a very secure mounting of the chip.

Finally, check the orientation of the sensor in the mounting chamber through the hole in the cassis. It should look as depicted below.

The Setup

I recommend first programming the car to one of the three controller ID’s then running the car briefly to test throttle control and lane changing. The converted NASCAR worked fine. One thing that should be noted is that the D132 chipped car now has dynamic braking. With the full D132 system (Black Box or CU) the brakes are adjustable, however, this is not the case with the D132-chipped car running on a D143 track where the braking effect is always at maximum. The combination of strong brakes and high magnetic down force may not be desirable. Regardless, when used strictly as an autonomous car this is not really an issue.

To program the D132-chipped car for autonomous operation the steps are as follows:

1. Place the car — with no other cars — on the track.
2. Depress the lane change button on the speed controller two times in rapid succession.
3. Lift the front of the car (i.e., pickup braids) out of the slot.
4. Replace the front of the car into the slot.
5. Depress the lane change button on the speed controller four times in rapid succession.
6. Depress the throttle (plunger) until the desired speed is attained.
7. While maintaing the desired speed, depress the lane change button one time.
8. The car will now run at the selected constant speed and will change lanes randomly.

The following excerpt from the Carrera Digital 143 user guide depicts these steps (click to enlarge):

Try to set the speed so that the autonomous car can handle every curve while also not hesitating on the lane changers’ dead spots.

This definitely takes ghost car racing on a Carrera D143 track to the next level. The installation of the D132 decoder chip may be more than some casual users will care to attempt because it does require a basic level of soldering skill. However, I can attest to the fact that a relatively small amount of time and effort will yield an enormous reward of racing versatility and fun. Especially for the “solo” racer.

Thanks to Brian at BRS Hobbies for providing the resources to make this article possible.

Note: Just prior to publication Carrera released the 42013 Wireless Digital 143 2.4 GHz Controllers (and power base). These controllers allow any D143 car to be programmed for autonomous operation, including random lane changing. Each autonomous car requires a controller. A future article in this blog will cover this product. — Ed.

_Michael Ashton