Slot Cars Rule !!!

In the following, you will find information on how to wire LED based front and rear lights for your Artin 1/43 cars.



• What’s already out there? There are several commercial solutions that you can purchase from various places and several web sites offer schematics for making your own.
o Light Kits from
OverDrive Slot Service, offered in the US by, for example, Professor Motor
o
Ninco and Slot.it offer such light kits as well
o Carrera4fun also offers some circuit schematics for
permanent lights and brake lights

o If you want to know more about these kits here are some on-line articles about them:
Cartrix Light Kit by Slot Car Garage
OverDrive Light kit by Slot Forum
Ninco Light Kit by Home Racing World
Ninco vs. Slot.it light kits by GenXracer
Another article on Ninco, Slot.it and Overdrive light kits by GenXracer

• So what?


o All of these are great, but they are designed for 1/32 and above scale cars where there is more room inside the car body and where the driving voltages are much higher (up to 16V) while Artin 1/43 is either 6V or 7.5V.
o I tried a Cartrix kit on an Artin 1/43 grey Mercedes CLK, here are the results. Note that it took a lot of soldering, cutting, grinding, and swearing. I had to remove the capacitor from the mini PCB to put it in the back of the car (glued to the removable black piece that joins the body to the chassis), while keeping the PCB (after cutting it) in the front, between the motor and the guide, glued to the car body.
o Any of the kits mentioned work really well for the 1/43 Carrera Go!!! cars since they use 12 to 15V, provided they can be fitted in there.

• What can be done?


o Based on what is out there, I redesigned/modified/hacked (use your favorite expletive here) a circuit specifically for Artin 1/43 cars or any other type of cars/tracks that use 8V or less. I have tested this myself and it works very well for me. If you need help with wiring and fitting it into a car, let me know.

image002

Here are some details on the circuit and the components, I hope this is not too trivialized, but some people asked for it:



• Diode: function is to guarantee that the current from the motor/track only flows to the lights and capacitor and that current from the capacitor only flows to the lights and not back into the motor/track. The use of a Schottky diode minimizes the voltage drop from the power supply which is critical in the case of Artin 1/43 with only 6~7.5 V supplies.
• Resistor R1: Drops the input voltage by another little bit. The amount dropped is proportional to the current being drawn by C1 and the lights, also acts as a current limiter into the circuit.
• Capacitor C1: Charges when motor runs (i.e. when voltage is applied) and discharges when car is stopped or when input voltage from motor is lowered below charged voltage. This means that the lights can stay on after power is removed and thus reduces flicker of the lights when running a car.
• Resistor R2: Drops the voltage applied to the red LEDs. At 8 V (max voltage) input, guarantees about 1.9 V at the LEDs.
• Resistor R3: same function as R2 but for the white LEDs. In my pictures I chose to use a 67 Ohms. One could use a lower resistor value and have the white LEDs a little brighter but they would also flicker a bit more.
• R2 and R3 are calculated so that the LEDs can run bright when no power is applied and capacitor C1 is now the voltage source. The values are picked to have about 1.7 V at the red LEDs and 2.8-2.9 V at the white LEDs. Note that some purists will say that LEDs should never be connected in parallel like this (and they are right) but when space and weight are a big issue, some short cuts are permitted ☺
• White and Red LEDs: obviously they are the light sources. There are tons of these out there but I chose these particular models from
http://www.superbrightleds.com/ since (to my knowledge) they are the brightest that can be found out there: 3,000 mcd for the 3 mm white LEDs, 10,000 mcd for the 5 mm white LEDs, and 5,000 mcd for the red LEDs (great for the brake lights). In most cases, any red LED for the tail lights with a diffuse red plastic housing will be a better choice as they are not as bright.
• What I do when I run a car is to hold it for a few sec with the motor running at 1/2 to 3/4 throttle. This is enough to fully charge the capacitor and get the lights going.

o Here are a couple of pictures on how I did it



image003

o Here are the results:


image005

o Putting these in requires soldering, cutting and gluing of components into the car body, so if you are not familiar/comfortable with these skills, exert caution when and if trying it.

o One issue with the previous circuit is that the light intensity will vary a bit depending on the speed of the car (brighter when you go faster, since there is more voltage). Here is a modified but more complex circuit that will minimize this although it will not completely remove it. This circuit will work well for any car with up to 30V power supply, using the voltage regulator mentioned in the drawing. Again, because of the relatively low voltage supply for Artin 1/43 cars, it is very important to use a Low Dropout voltage regulator, or even an Ultra Low dropout regulator (as offered by Texas Instruments or others).

image007

o Another circuit that can be added to the previous one to provide brake light effects, i.e. red tail lights that turn on when the car is decelerating. To do this you need an additional transistor that acts as a switch and turns on when the voltage at the base of the transistor is essentially smaller than the voltage at the collector. In the following circuit, the red LEDs will turn on only when releasing the throttle almost entirely.

image009


o
Here is a link to a small movie that will show you such light circuits (the complete one with brake lights) in action in Carrera Go!!! cars and Artin 1/43 cars.

• So what’s next?


o Of course, one can always add more front lights or back lights, or interior lights, or flashing lights, they’ll just stay on a shorter time …
o But adding more lights and more components will be very limited in the Artin 1/43 cars as space is at a premium in there ☺ !!