Hummingbird Robotics Kit Introduces Kids to Engineering
The Hummingbird robotics kit from BirdBrain Technologies LLC is a spin-off product of Carnegie Mellon's CREATE lab. Hummingbird is designed to enable engineering and robotics activities for ages 10 and up that involve the making of robots, kinetic sculptures, and animatronics built out of a combination of kit parts and crafting materials. Combined with a cross-platform, very easy-to-use visual programming environment, Hummingbird provides a great way to introduce kids to robotics and engineering with construction materials that they are already familiar with.
The Hummingbird kit contains a large number of sensors, lights, and motors compared to similarly priced kits. The Hummingbird controller circuit board interfaces the kit motors, LEDs, and sensors with a computer. It is possible to interface non-kit components to Hummingbird, but one must be careful to observe the limits specified in the kit. Hummingbird receives power from two sources: a computer's USB port provides 5Vdc at 500 mA to the microcontroller, LEDs, vibration motors, and sensors. An auxiliary power supply operates from a universal input of 100-240Vac provides up to 2A to the motors and servos.
Hummingbird uses the Atmel Atmega16U4 microcontroller with internal firmware included. Hummingbird has four single color LEDs ports, and two tri-color LED ports. As the ports are designed to power LEDs, the board has built-in resistors to limit current to the LED elements. The resistor values are 140 Ohm for single color LEDs and the R terminal of the tri-color LED, and 110 Ohm for the G and B terminals of the tri-color LED. The resistors are sized to drive 20mA through each LED or each color element of a tri-color LED.
The two vibration motor ports are controlled using an FDS9926A dual MOSFET driver. A PWM signal from the microcontroller to the gate of the MOSFET allows speed control of the motor. In theory, the MOSFET driver can drive up to 6.5A through each vibration motor port. However, the vibration motors are powered from USB power, which is limited to no more than 500 mA total.
The Hummingbird's four sensor ports each have terminals for sensor power, sensor ground, and an analog sensor signal. Each sensor signal is read with 8-bit resolution over the range of 0 to 5.0 V. The signal should not vary from this range by more than 0.7 V or else it may damage the port. The power and ground terminals are connected to the USB power supply, and so have a voltage of 5 V and a maximum current of 500 mA (though this is shared by the microcontroller, LEDs, and vibration motors).
The Hummingbird's two motor ports are designed to drive small DC motors. Hummingbird uses a FB6552 dual H-bridge to control these motors The maximum current draw from each motor port is 800 mA. Hummingbird's four servo ports are designed for compatibility with standard RC servos. The servo signals pulse every 20ms and have a programmable up-time between 0.6 and 2.4ms. The servos share the auxiliary power supply with the motor ports, and the total current draw combined for all motors and servos should not exceed 2000 mA.
Kit parts are organized into four sub-kits (which can be purchased separately): Control – the Hummingbird controller is the core of the kit and provides the means to use the various motors, LEDs, and sensors. The control sub-kit also includes an auxiliary motor power supply, a USB cable to connect Hummingbird to the computer, and a handy screwdriver to simplify connecting components. Light and vibration – the Hummingbird kit contains eight single color LEDs (two each of green, red, yellow, and orange), as well as two tri-color LEDs. It also contains two vibration motors similar to the type found in cell phones. Motion – the Hummingbird comes with four HS-311 servos, four extension cables for these servos, and two regular DC motors. Sensing – Hummingbird comes with light, temperature, sound, and distance sensors, as well as a rotary knob. Other sensors may be released over time.
