The LEGO MINDSTORMS NXT Hammer Car is a fun and engaging project that combines building and programming. This guide will walk you through understanding and programming your NXT Hammer Car to perform various actions using a touch sensor for control. We’ll explore how to make it swing its hammer and navigate with simple touch commands.
Understanding the Hammer Car Program
The core of the Hammer Car’s functionality lies in its program, which is designed to interpret input from a touch sensor connected to your LEGO NXT brick. This program differentiates between two types of touch sensor interactions: a quick press and release, and a sustained press. This distinction is key to controlling both the hammer action and the car’s movement.
When the program detects a quick press and release of the touch sensor, it triggers the hammer mechanism. The robot is programmed to swing the hammer down to strike and then immediately return it to its upright position, ready for the next action. This allows for precise hammer strikes when needed.
For navigation, the Hammer Car program utilizes a sequence of driving actions activated by holding down the touch sensor. Holding the sensor initiates a cycle through four distinct movements, each performed until the button is released. This cycle is as follows:
- Go Straight: The car moves forward in a straight line as long as the touch sensor is held.
- Pivot Turn Left: The car executes a pivot turn to the left while the sensor remains pressed.
- Go Straight Again: The car resumes moving straight forward when the sensor is held down for the third action in the sequence.
- Pivot Turn Right: Finally, the car performs a pivot turn to the right while the sensor is still pressed.
To provide visual feedback, the NXT screen displays a pointing hand graphic before each driving action. This visual cue indicates the direction the Hammer Car will move next, helping the user anticipate and control the robot’s navigation effectively. With a little practice, you can master driving and turning the Hammer Car to precisely position it and swing the hammer at the desired moment.
Programming the Control Mechanism
The programming logic behind the Hammer Car’s control is relatively straightforward, focusing on timing and conditional actions based on touch sensor input. Here’s a breakdown of the programming concepts involved:
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Touch Sensor Input: The program begins by continuously monitoring the input from the touch sensor connected to port 1 of the NXT brick.
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Detecting Quick Press vs. Hold: The program uses a timer to differentiate between a quick press and release and a sustained press. A short duration press is interpreted as a “hammer” command, while a longer press signals a “driving” command.
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Hammer Action Programming: Upon detecting a quick press, the program activates the motor connected to the hammer mechanism. This involves sending commands to the motor to rotate in one direction to swing the hammer down and then reverse direction to lift it back up. Precise timing of motor activation is crucial for an effective hammer strike and return.
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Driving Action Sequence: When a sustained press is detected, the program initiates a sequence of driving actions. This is typically implemented using a loop and a counter. Each count in the loop corresponds to a different driving action (straight, left, straight, right). Conditional statements within the loop determine which motors to activate and in which direction to achieve the desired movement.
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Visual Feedback (Hand Graphic): Before each driving action within the sequence, the program includes commands to display a pre-loaded hand graphic on the NXT screen. This is achieved by using NXT display functions to show the image file associated with the hand symbol.
Challenges and Further Exploration
Once you’ve mastered the basic programming, there are numerous ways to enhance your Hammer Car project:
- Target Practice: Set up targets and challenge yourself to navigate the Hammer Car to hit them accurately. This will improve your driving and hammer control skills.
- Autonomous Hammer Car: Try to reprogram the Hammer Car to drive towards a target and hit it automatically, without manual remote control. This involves incorporating sensor feedback (like ultrasonic or color sensors) for autonomous navigation and target detection.
- Alternative Remote Controls: Explore different remote control methods. If you have parts from other LEGO MINDSTORMS sets, consider building a game controller-style remote, as suggested in the original “Car with Game Controller” project. You could adapt programs like the “Claw Control” program to control the Hammer Car using a different interface.
- Redesign the Robot: The Hammer Car’s robust 3-motor chassis is a great foundation for other robot designs. Think about alternative uses for the third motor beyond the hammer mechanism. Could it power a different tool, a sensor array, or a more complex manipulation system?
By experimenting with the programming and mechanics of the LEGO NXT Hammer Car, you can deepen your understanding of robotics and have fun creating increasingly sophisticated and autonomous machines.
