This document describes the electrical characteristics of the Hummingbird Controller and kit parts.
Table of Contents
- Hummingbird Controller
- Vibration Motors
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.
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.
|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.
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.
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:
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 TB6552 dual H-bridge to control these motors The maximum current draw from each motor port is 1 Amp.
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.
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.
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.
Hummingbird has 8 single color LEDs and 2 tri-color LEDs. The tri-color LEDs are common cathode style.
Single Color LED Characteristics
|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
|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|
Hummingbird has two vibration motors.
|Free-run speed @3V||2500 RPM|
|Free-run current@3V||90 mA|
|Stall current@3V||120 mA|
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.
|Free-run speed @6V||45 RPM|
|Free-run current@6V||70 mA|
|Stall current@6V||800 mA|
|Stall torque@6V||100 oz-in|
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.
|Rotational range||180 degrees|
|Speed @4.8V||0.19 seconds per 60 degrees travel|
|Idle current @4.8V||7.4 mA|
|No load email@example.comV||160 mA|
|Stall firstname.lastname@example.orgV||700 mA|
|Stall email@example.comV||42 oz-in|
The Hummingbird kit contains five sensors; each sensor produces an analog voltage based on the characteristic it is sensing.
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:
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.
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:
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.
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.