2.The Front and Back LEDs
Now let us see the pretty simple LED circuit. It is composed of 4 LEDs, 2 NPN transistors, 2 1kΩ resistors, 2 120Ω resistors, jumper wires, 2 AA batteries, and a 2 AA battery holder. The circuit can be seen in the pictures below.
The LED circuit is very basic and simple to assemble on a breadboard. But this can pose a problem in this implementation because of the space it takes. Making it part of the RC car's cover is the challenging part. I started off by placing the LEDs in their corresponding positions, and then gluing them in place. To make things easier, I made sure that the LED's anodes (positive/longer legs) were either facing each other or facing away from each other as seen bellow.
I then proceeded to soldering a jumper wire between the anodes, and another jumper wire between the cathodes. Soldering the ends of two wires is very difficult, so I took a different approach. I stripped one of the long and stiff jumper wire, and wrapped it around a wire that is twice the width of the jumper wire.
I then threaded both the LED's leg, and the jumper wire's end into the wrapped jumper. This made it much easier to solder the jumper wires to the LEDs, resistors, and transistors. The front part is the easiest because it is not near the transistors and resistors. The back lights were more complex as seen in the picture.
As before, the first thing I did was solder a jumper cable between the LED's anodes, and another jumper between the cathodes. After this I attached the battery holder to the car's cover with bolts and nuts. I then soldered one end of each of two 120Ω resistors to one end of the brown jumper wires. The other ends of the brown jumper wires were solder to the battery holder's positive wire (red). I then soldered a jumper wire between the end of one of the 120Ω resistors, and the jumper wire (white) coming from the anodes (positive) on the front LEDs. I also soldered the other 120Ω resistor to the jumper cable (orange) coming from the anodes (positive) on the back LEDs. After this I soldered the two transistors' emitters to the ends of two red jumper wires. The other end of the red jumper wires were soldered to the battery holder's negative wire (black), and to the long jumper wire (light yellow) that will be connected to the Arduino UNO's ground ( to complete the circuit). Now the LEDs' cathodes needed to be soldered to the two transistors' collectors. Therefore I first soldered the jumper wire (brown) coming from the front LEDs' cathodes to one of the transistor's collectors. I then soldered the jumper wire (orange) from the back LEDs' to the other transistor's collector. The only thing left is to solder the 2 1KΩ resistors, and jumper wires to the transistors' bases. I had to make sure that the jumper wires were long enough to reach the Arduino UNO's pins 4 and 7. Since I could not solder the resistors directly to the transistors because of clearance issues, I ended up cutting the jumper wires and soldering the 1kΩ resistors into the jumper wires (dark green and light orange).
And this completed the LED circuit.