Carlson's Slot Cars
Home of Custom made SensorTraks

Slot Car Computerized Lap Timing and Counting


I like lights on slot cars however the extra cost for the "L" version or the high priced kits do not appeal to me. I put together this article to help the others in the hobby that like me enjoy having lights on their slot cars. The circuit I use can be found anywhere on the net but I did modify it slightly for safety and efficiency. I will make available a kit for anyone wishing to add lights to their cars. I some pictures that I have collected or created and you can view them here. As well here is where I got started this page is a translation from German to English with the authors permission of course.


I will start by saying this is not a hard project but you may find it difficult especially if you have never tried to read a schematic or picked up a soldering iron. I will try to make this as straight forward as possible and if there is something that I could make clearer please let me know because I do not want anyone to walk away from this project frustrated. On the right you will find a parts list. I did not include prices because frankly you might be able to get the parts cheaper from your local shop. The parts list is for a complete Head/Brake/Running light circuit.
Quantity Description
2 5000mcd white LEDS
4 750mcd or less red LEDS
1 LM7806 Voltage regulator
3 1N4148 Diodes
3 150 --> 220 ohm resistors
1 1.2K ohm resistor
1 10K ohm resistor
1 10 ohm resistor
1 2.2uf electrolytic capacitor @ 16vdc
1 .1F GoldCap capacitor @ 5.5vdc
1 PNP transistor
1 Wire, solder, heat shrink, PC Board.
   The circuit is fairly simple and if you were only wanting the head-lights then it gets even simpler but we will focus on the complete circuit for now and go into the smaller ones later. The key to the whole circuit is the GoldCap, this little component supplies power to the circuit after you let go of the trigger. Therefore the brake-lights, head-lights and running-lights will come on and stay on after the power from the track has been cut. How long the LEDS stay lit will depend on how many of them you have in the circuit for example, if you were only to install head-lights then you might get 30 seconds of light from the LEDS and the more LEDS you put in the circuit the shorter they will stay on.
   I will go through the circuit step by step and please skip this if you don't need this explanation. Power from the track enters D1 & D2, D1 & D2 will isolate this circuit from the track and motor. The regulator U1 is 6vdc output which enters D3, D3 will prevent voltage from C1 from feeding back into U1 when power is disconnected from U1 as well D3 drops the voltage output of U1 to the rating of C1 which is 5.5 volts. U1 is always charging C1 and providing voltage to the circuit for the LEDS until we let go of the controllers trigger. When this happens C1 now starts to provide voltage to the circuit and as well to the brake-lights. Q1 is in an off state while voltage is applied to the track but once voltage is cut it turns on letting the GoldCap power the brake-lights.
This Schematic is for the complete setup, head/brake/running lights.

This Schematic shows just the head-lights.
This schematic shows the head-lights D6 & D7 as well the running-lights D4 & D5.
This schematic shows just the brake-light circuit. This circuit must be used in conjunction with the main circuit to function properly.