What are the best options for building a LEGO RC car?

Question

I would like to build a remote controlled car. And if someone already has a good solution for that I would be glad to try it.

It's been a while since I had the time and material to build some LEGO creations. And now I am willing to start anew.

Last time I toyed with LEGO there were electric engines and such, but all I had was remote controlled with a cable and the functions were very basic. I am looking for a more advanced and wireless solution.

I am aware of the Power Functions. But I have no experience with these. Would these be a good start? What are the other options?

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Edit: Mindstorms as suggested in a few answers could be the solution, but I am not sure it will be practical yet...

It seems there was an official line of LEGO RC cars at some point. I was thinking about something more like it.

Although I'd like to avoid cutting and gluing 3rd party components I don't mind hacking a few parts together to get something really cool.

As suggested by @pcantin there are adapters I could buy to interface LEGO with 3rd party engines etc... I will look into it. But I would appreciate some better pointers in this regard.

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Edit I am already aware of the Power Functions IR remote control It's a good solution to start with (now), but I was looking for something more advanced.

I have never heard of Arduino before, but as a developer I am absolutely thrilled by this solution. I won't have the time to test it now. But it could become the answer I was looking for.

Answer 1

I use a Mindstorms NXT brick and an Android smartphone for my remote controlled tank. The downside is that the NXT motors are slower than the regular Power Functions motors, and connecting PF motors to the NXT brick requires additional components.

Personally, I am satisfied with NXT motors and don't bother kludging PF motors. (Yet.)

Here is a modular truck design as an example: http://www.nxtprograms.com/MTV/index.html
I use this app for my remote control: https://market.android.com/details?id=org.jfedor.nxtremotecontrol

Answer 2

Personally I would go with Arduino (on the car) and an Android phone as the controller (via bluetooth). There's plenty of reference on the web about mixing the two.

The main problem is interfacing with non Lego parts (motors, PCB, ...). Luckily, you can find Lego adapter parts in many Robot/Electronic sites. For example at Pololu: http://www.pololu.com/search?query=lego&x=0&y=0

Edit 1 (Howto) Android bluetooth communication: There's the main page and the sample (I started from that one and modified it). You can also use the 'Sena Bterm' app to send and receive characters (no programming necessary but very basic).

Arduino bluetooth communication: This is the most simple part. All you need is a bluetooth breakout board and connect it to the Arduino like so. Using the board is as simple as any normal Serial communication ex:

void setup()
{
  Serial.begin(115200);
}

int inByte = 0;

void loop()
{
  if (Serial.available() > 0) 
  {
    inByte = Serial.read();

    if(inByte == '1'){
       Serial.println("test1");
    } else {
       Serial.println("test2");
    }
  }
}

This code reads the incoming bytes and write 'test1' or 'test2' in return.

Hardware: this is the coolest part because you get to do what ever you want. I personal use a lot of Lego Technics and sometime modified them to interface with foreign parts. Search the web and you'll find cool Lego-compatible stuff like this servo joint, this servo bracket or this wheel.

Answer 3

LEGO have produced an IR Speed Remote Control unit as part of their current "Power Functions" range.

This offers:

• Features 4 RC channels, 2 stop button and 2 direction control switches!
• Use the jog wheels to control your motor speed!

You will also need the receivers as well.

Answer 4

The MindStorms NXT controller can work over bluetooth:

http://mindstorms.lego.com/

Answer 5

The 9398-1: 4x4 Crawler is an interesting candidate with the new servo motor. It comes in 2H2012. There are more pictures on TechnicBricks.

Answer 6

I saw an official Lego remote control car at the Lego Store once and I should have gotten it that day because I haven't seen it again.

That said, with Mindstorms and a bluetooth enabled phone it should be possible to build one one your own.

Answer 7

I would not recommend Power Functions if you are just getting started, as that system is being retired. It sounds like Technic Control+ should meet your needs. A set like the Off-road Buggy (42124) might be a good place to start:

That set provides two motors and a Bluetooth hub for forward, reverse, and steering controls from your smartphone. You can create customized controls for nearly any setup in a MOC using the Powered Up app.

Physical remotes are a more complicated story. There have been a few train sets that use physical remotes (28739) for the Powered Up products:

The remotes are sold separately, but are not very flexible out of the box. They can pair with hubs that control Technic motors, but they simply provide on/off control and can't be easily used for speed control or a return-to-center servo like you'd likely want for steering. However, sets like the Batmobile work alright with a physical remote, thanks to the skid steering.

If you're a technical individual, it is possible to upload custom code to Powered Up hubs using Pybricks or similar software. This is commonly used to create autonomous robots, but it can also be used to customize the interface between the hubs and a physical controller.

Here's a Github repository that includes code demonstrating how to program hubs to work nicely with the physical remote for certain sets. For example, here's the code needed to get the Off-road Buggy to work well:

from pybricks.pupdevices import *
from pybricks.parameters import *
from pybricks.tools import wait

steering = Motor(Port.B)
driving = Motor(Port.D)
remoteControl = Remote()

#steering calibration sequence
steering.run_until_stalled(500)
steering.reset_angle(0)
steering.run_until_stalled(-500)
maxAngle = steering.angle()
steering.run_target(500, (maxAngle/2)+10)
steering.reset_angle(0)

#main loop
while True:
    #update pressed buttons information
    pressed = remoteControl.buttons.pressed()

    #commands to drive forwards or backwards
    if Button.LEFT_PLUS in pressed:
        driving.dc(100)
    elif Button.LEFT_MINUS in pressed:
        driving.dc(-100)
    else: 
        driving.brake()

    #commands to steer
    if Button.RIGHT_PLUS in pressed:
        steering.run_target(1200, (maxAngle/2)-5, Stop.HOLD,False)
    elif Button.RIGHT_MINUS in pressed:
        steering.run_target(1200, -((maxAngle/2)-5), Stop.HOLD,False)
    else:
        steering.run_target(1200, 0, Stop.HOLD, False)

    wait(100)

Answer 8

One possible replacement for the soon to be retiring Power Functions remote is the one included in Remote Controlled Stunt Racer, however this remote appears to be more limited, only offering 2 "forward/reverse" channels (one of which could be configured to control a steering column), rather than the 4 channels offered by the original.

This is also available separately.