Wiring LEDs and DC motor for small car project

Thread Starter


Joined Jan 14, 2018
I made a very simple battery powered car that is working great for my purposes but I have a few questions about how I should have done it. I am a beginner so I apologize in advance for ignorance.

I have two LED headlights and two LED tail lights and a DC brushless hobby motor. Headlights are rated for up to 3.2 V and the taillights up to 3V. The motor is also rated for 1.5 to 3 V. Each led is connected to a 220 ohm resistor and the car is powered by two AAA batteries (3V). I wired everything up in parallel, with a switch that turns the car on and off and I noticed a few interesting things. First, the headlights are a lot dimmer than the taillights. Is this because they are getting less current for some reason? Why else could this be? And, when the motor is under more load all of the lights dim. Is this because the motor is drawing more of the current away from the LEDs?
Also: There seems to be much controversy about LEDs in parallel. Am I preventing against thermal runaway by using resistors, or could it still happen?

My main question is: How should I have wired this project together so that the LEDs would all be pretty bright and would not dim as the motor encounters more load (without making the car too slow)? If I did it all (or just each set of LEDs) in series, the LEDs would have been way dimmer, right?

Thanks in advance for your thoughts!

Here is a simulation of it in tinkercad: https://www.tinkercad.com/things/j4mu2vziw0e

Thread Starter


Joined Jan 14, 2018
Also, could I have more batteries for a higher voltage or was I right to stick to 3V for the motor and the LEDs?


Joined Dec 2, 2017
Your circuit looks fine, I would lower the resistor values.

Yes it’s your motor stealing all of the juice.

And yea, those LEDs won't even light in series, not at 3 volts anyway, and if they did, they would be very dim.


Joined Sep 17, 2013
The internal resistance of the AAA cells will reduce the available voltage when you draw current from them. AA cells would be better.
A motor requires more current when under load than when free-running,