Arduino-izing LEGO Technic - ideas for a car / vehicle to choose

Question

I am starting a project - Arduino-izing LEGO Technic - and now I need some ideas for a car / vehicle to choose.

This project starts out as a quest to find a way to combine the ease of LEGO Technic chassis building with cheap commodity electronics to motorize and remote control it. I am looking for a car / vehicle that is able to work for this. This could be a simple chassis:

https://www.instructables.com/id/Build-your-own-Custom-Arduino-Remote-Control-and-L/ https://www.hackster.io/Notthemarsian/take-control-over-lego-power-functions-ee0bfa https://www.instructables.com/id/Raspberry-Pi-Remote-Controlled-Car-1/

This should be a part of a robotics workshop and therefore I need a LEGO-based platform for younger kids who grew up with Lego but cannot afford to spend hundreds of dollars to buy power functions, LEGO motors, IR remote, and EV3. Thanks to numerous examples on the net and several and Youtube tutorials on integrating Arduino with LEGO, I will try to start out with an interesting example.

Starting point: the kids should be able to complete this project with a small budget and I hope to incorporate this into my robotics workshop in the future.

The main thing is, I need to have the rear axle to be attached to a single N20 motor to move the kart forward and reverse via a TB6612FNG motor driver. Front steering can be controlled by an SG90 servo motor.

Remote control should be able to be accomplished by a cheap IR remote/receiver solution based on

1. Arduino
2. Zigbee
3. Bluetooth

I understand that the IR remote hardware (and the method) is pretty hard part to implement and learn about a remote control system so it was a perfect option for this car.

Since this is just a proof-of-concept project and the design follows function - I need to have an idea.

The main question is: which LEGO car to choose? How about LEGO Technic-8071 - the Service Truck? What would you suggest?

Answer 1

If I were you, I'd try to use a car chassis as simple as possible.

This would achieve multiple goals:

1. By using a vehicle with the least amount of complexity you can keep the price low.
2. By avoiding unnecessary parts the students' attention will not be drawn from the topic at hand, e.g. they will be more inclined to listen and cooperate if they are not wondering about or playing with the bucket lifting mechanism of 8071.
3. The less parts included in the design, the less chances for something to go wrong.
4. Some space is needed in order to mount the required hardware (motor, batteries, receiver, anything inbetween) and this space is best left open for easy access to inspect, explain, debug, repair, replace, etc.
5. This approach leaves many ways to upgrade the "final result", either functionally (adding lights, brakes, etc), aesthetically (building a great looking body), electronically (adding additional subsystems like a parking assistant) or mechanically (include advanced steering geometries, suspension, etc) if you or the students wish to do so.
6. Minimizing the time required to build the mechanical part leaves that much more time for the intended topic of the workshop (the electronics).

Therefore I'd recommend building a simple steered front axle without suspension, a rear axle that is nothing more than an axle and two wheels and slapping both on a large plate or any equivalent flat assembly.

Answer 2

I'd be tempted to use the Batmobile (76112) design:

Basically, you have independent motors for the left and right wheels. This allows you to steer quickly and easily without the fuss of a traditional steering system.

The Batmobile is $100 MSRP, and can be found on sale. The included motor controller is Bluetooth based, and can be remote controlled via a smart device or custom software on a laptop. Basically, that set meets your needs if you can afford it.

If that is too expensive for you, I'd still encourage you to consider using a similar design using official LEGO motors. It's relatively complicated to integrate off-the-shelf motors with LEGO (I did this a lot as a kid), and the official motors are actually quite cheap these days. You can pick up Power Functions M Motors for $7.49:

That's $15 for the pair. You'd just need to cut off the Power Functions connector and connect the motor to your driver. This saves you the fuss of mounting your motors and integrating them with LEGO gears and wheels.

This is really outside the scope of your question, but on the electronics side I personally wouldn't use an Arduino. I'd probably go with something that has wireless built in, such as something ESP8266-based. Then, all you need is your microcontroller and motor driver for a working system. The system can be remote controlled from a PC or smart device. You wouldn't even need special software on the remote, as the microcontroller can broadcast an SSID and serve up a web-based controller to the connected device.

So then your BOM would be:

• 2x PF M Motors ($15)
• NodeMCU or other wireless controller ($3)
• A few Technic beams, gears, axles, wheels, etc ($5+)
• Battery box ($2)
• TB6612FNG or similar dual motor controller ($1)

You could probably do the whole thing for ~$30.