This document describes the electrical characteristics of the Hummingbird Controller and kit parts.

Table of Contents

  1. Hummingbird Controller
    1. Power
    2. Microcontroller
    3. LED ports
    4. Vibration Motor ports
    5. Sensor ports
    6. Motor ports
    7. Servo ports
    8. Schematic
    9. FCC Warnings
  2. LEDs
  3. Vibration Motors
  4. Motors
  5. Servos
  6. Sensors
    1. Light sensor
    2. Temperature sensor
    3. Distance sensor
    4. Sound sensor
    5. Knob

1. Hummingbird Controller

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 following sections.

1.1 Power

Hummingbird receives power from two sources: a computer's USB port provides power to the microcontroller, LEDs, vibration motors, and sensors. An auxiliary power supply provides power to the motors and servos.

Characteristic Value
USB supply voltage 5 V
USB maximum current 500 mA*
Auxiliary supply input voltage 100-240 VAC
Auxiliary supply output voltage 5 V
Auxiliary supply maximum current 2000 mA

* Note that this includes a 50mA current draw to run the microcontroller.

1.2 Microcontroller

Hummingbird uses the Atmel Atmega16U4 microcontroller. We have provided the firmware running on the controller; it is possible to modify the firmware by populating the ISP header and using an AVRISP tool to download new firmware.

1.3 LED Ports

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 following schematics describe the on-board circuitry of the single and tri-color LED ports:

1.4 Vibration Motor Ports

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.

1.5 Sensor Ports

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).

1.6 Motor Ports

The Hummingbird's two motor ports are designed to drive small DC motors. Hummingbird uses a TB6552 dual H-bridge to control these motors The maximum current draw from each motor port is 1 Amp.

1.7 Servo Ports

Hummingbird's four servo ports are designed for compatability 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.

1.8 Schematic

We provide the electrical schematic for use in debugging and hacking the Hummingbird. The following is provided under the terms of the Non-commercial share-alike creative commons license.

Click the schematic image for a larger version.

1.9 FCC Radio Interference Warning

The Hummingbird is intended for use for ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSES ONLY and is not considered by us to be a finished end-product fit for general consumer use. It generates, uses, and can radiate radio frequency energy and has not been tested for compliance with the limits of computing devices pursuant to part 15 of FCC rules, which are designed to provide reasonable protection against radio frequency interference. Operation of this equipment in other environments may cause interference with radio communications, in which case the user at his own expense will be required to take whatever measures may be required to correct this interference.

2. LEDs

Hummingbird has 8 single color LEDs and 2 tri-color LEDs. The tri-color LEDs are common cathode style.

Single Color LED Characteristics

Characteristic Red/Yellow/Orange Green
Forward voltage 1.7 V 2.3 V
Recommended current 20 mA 20 mA
Light output (Lumens) 6,000-10,000 10,000

Tri-Color LED Characteristics

Characteristic Red Green Blue
Forward voltage 2.0 V 3.3 V 3.3 V
Recommended current 20 mA 20 mA 20 mA
Light out (Lumens) 10,000 10,000 5,000

3. Vibration Motors

Hummingbird has two vibration motors.


Characteristic Value
Operating Voltage 2.4-3.6V
Free-run speed @3V 2500 RPM
Free-run current@3V 90 mA
Stall current@3V 120 mA

4. Motors

The Hummingbird kit's motors are produced and sold by Pololu. You can view mechanical drawings, purchase motors and wheels, and get a more detailed description on their site. Mounting a wheel or other item to the shaft of the gear motor requires #2 1/4" sheet metal screws. 

Characteristic Value
Operating Voltage 3-6V
Free-run speed @6V 45 RPM
Free-run current@6V 70 mA
Stall current@6V 800 mA
Stall torque@6V 100 oz-in
Weight 33g
Gear ratio 228:1

5. Servos

The Hummingbird comes with four Hitec HS-311 servos as well as four servo extension cables. The servo and extension cables are commonly available from a number of vendors; we recommend servocity.

Characteristic Value
Operating Voltage 4.8-6V
Rotational range 180 degrees
Speed @4.8V 0.19 seconds per 60 degrees travel
Idle current @4.8V 7.4 mA
No load current@4.8V 160 mA
Stall current@4.8V 700 mA
Stall torque@4.8V 42 oz-in
Weight 43g

6. Sensors

The Hummingbird kit contains five sensors; each sensor produces an analog voltage based on the characteristic it is sensing.

6.1 Light Sensor

The light sensor detects the intensity of light shining on the surface of the sensor. Higher values correspond to more light. The sensor is based on a PDV-P9002 photoconductive cell. This cell changes its resistance based on light level; to transform the change in resistance to a change in voltage the cell is placed in series with a regular 4.7KOhm resistor. See the following schematics for circuits of the light and temperature sensors:

6.2 Temperature Sensor

The temperature sensor reports the ambient temperature of the black probe at the tip of the sensor. The sensor requires contact with an object in order to report the temperature. A temperature reading can take up 10 seconds to stabilize to the temperature of the object in contact with the probe. The sensor is based on an MF52 NTC thermistor, which varies its resistance with temperature. A 10 KOhm resistor in series with the thermsitor completes the sensor circuit.

6.3 Distance Sensor

The Hummingbird's distance sensor is the Sharp GP2Y0A21 module. The sensor requires a voltage between 4.5V and 5.5V to operate, and draws 30mA. The sensor's connector has a protection diode to prevent the sensor module from being damaged in the event that it is connected to the Hummingbird incorrectly. The sensor can detect objects from 10 to 80 centimeters away, but the output is not linear with distance; see the following graph to match the sensor's value with distance:

6.4 Sound Sensor

The sound sensor outputs 0 volts until a threshold sound level is reached; above this level it will respond with an increasing voltage to increasingly loud sounds. The sensor requires between 3.6V and 5.5V to operate, and draws roughly 5mA. The sensor's connector wire also contains a protection diode to prevent sensor failure in case the sensor is connected to the Hummingbird incorrectly. The sensor circuit is provided under the terms of the Non-commercial share-alike creative commons license.

Click the schematic image for a larger version.

6.5 Knob

The knob used in the Hummingbird is a 10 KOhm rotary potentiometer with a separate knob. An additional 1 KOhm resistor is soldered to the yellow signal wire of the connector to protect the sensor and Hummingbird in the event that the sensor is incorrectly connected to the Hummingbird.