My daughter was pouting her lips last week because she found out her Lego bricks were stolen by her daddy. Fortunately, I'm now able to make it up by giving her something better.

The Lego Monster Truck you see in the following video is a demonstration of PulseRain M10's capability. It uses one PulseRain M10 board, one PWM shield and one ESP8266 shield. Both shields are from Sparkfun.

This monster trunk has two DC motors. One is for driving while the other is for steering. Most Wifi Robot cars on the market are using 4 wheel drive or 2+ 1 (Two wheels plus one caster). With 4 wheels or 2+1, the designers can avoid dealing with the steering mechanism. And to make turns, those cars will spin the wheels on each side in opposite direction. However, the drawback of such design is that each driving wheel was pushed by a separate DC motor. And no two DC motors are the same, especially for cheap ones used by toy. This makes it hard for those cars to go straight lines.

Of course, those can be fixed by:

(1) Manual calibration, where a potentiometer (or something with similar nature) can be used to keep the two DC motors spin the same way

(2) Use better motors and better control mechanism. Instead of using open loop, a close loop control can be adopted. However, close loop requires a sensor (such as speed, position etc) for feedback. Those will just make things a lot complicated or more expensive.

The Lego Monster Truck shown below takes a different approach. It uses Lego gears and beams for steering. To make it happen, I made a hack to one of the DC motor and the Lego axle (more to follow on this part) so that the motor can work with a Lego gear box.

For driving force, another DC motor was used to drive two wheels with one axle. In this way, no need to worry about any mismatch of motors.

And to control the truck, I chose a retro style joystick that is compatible with Atari 2600 . Yes, this is a stick shift vehicle :-)  For hardware building instructions, please go to http://limerick.pulserain.com/2017/07/how-to-build-lego-monster-truck.html . For firmware and host software, please go to https://github.com/PulseRain/Lego_Monster_Truck .

Now, without further ado, Let me give you the Lego Monster Truck: