The WCRS Leonard board is a community driven project, originating from the Western Canadian Robot Society’s idea of a fully featured, all-in-one Robotics board that’s at a reasonable cost. We wanted to go completely open source with the design to allow users to gain complete knowledge of what hardware is included on the board, what it does and how it’s all connected. We also want to give users open source example code that they can start from and then modify from there.
The Leonard encompasses several different sub-circuits that are usually available separately and combines them into a complete Robot control board. The Leonard combines a Servo Driver with a Analog breakout, High-current Dual H-bridge, & Arduino Microcontroller. What does this all mean? You can have a heavy duty robot that can have tank treads and an upper body, arms and head, just like Ominbot, all the while having access to a variety of integrated sensors via I2C and six analog ports. Did we mention that it can all be programmed through the wildly popular Arduino IDE?
Based on the Arduino Leonardo design, the Leonard incorporates the Leonardo bootloader and is easily programmable in the freely downloadable Arduino IDE.
One huge feature of the board is the Dual H-bridge which can theoretically continuously drive up to 27A per channel. 27 Amps through a MOSFET does have it’s thermal limits, as a practical test we were able to sustain two large DC windshield wiper motors which draw 4A each under no-load. The motors ran steadily with only passive heat sinking on the FETs.
Here are some pictures of the Leonard board being used at the Beakerhead/Scoperta Workshop in Calgary on July 7,8, 2012. Unfortunately we had issues with the H-bridge portion of the circuit and had to do an emergency retrofit of several other H-bridge boards that we could come up with, some of which were donated from Scoperta themselves, thanks again guys we owe you big time! Also a big thank you to Protospace and other volunteers, who helped us assemble the Leonard boards in preparation for the workshop!
– Standard 2.1mm jack for input power which powers the baord through a reverse polarity protection diode
– Digital and analog pins broken out into 3 pin Ground-Voltage-Signal (G-V-S) headers
– tried, tested, and true Mini-B USB jack, Micro-B connectors can easily break off the board
– USB connection is protected via a 500mA resetable fuse (PTC)
– Dual H-bridge is mini-blade Fuse protected
– Serial header for adding accessories such as Bluetooth or other RF modules
– We’ll add an I2C header for incorporating I2C sensors and peripherals
– 8 x STD27N3LH5 27A MOSFET Dual H-bridge for bi-directional control of 2 DC motors
– 4 x TC4428COA 1.5A MOSFET drivers that prevent “shoot-through” conditions on the FETs
– Servo ports (D2, D3, D4, D7, D8, D9, D12, D13)
– Only 4 H-bridge control lines (D5, D6, D10, & D11)
– Arduino Shield compatible
– ISP header for in-circuit programming
– Easily accessible reset button
– Arduino Mega form factor
– 0.2” spacing terminal blocks for connecting large wires from the battery & motors to the PCB
– LM1084 (5V) and MCP1826S-3302 (3.3V) voltage regulators
– External power jumper for powering entire board off a single supply or splitting up the motor and microcontroller input power if required.
– Microcontroller: ATMEGA32U4 with Arduino Leonardo Bootloader
– Max. number of Servos: 8
– Max. number of analog sensors: 6
– Max. current of regulated 5V: 5A
– Max current of regulated 3.3V: 1A
– Max. voltage input: 30VDC
– Max. H-bridge constant current: 27A
– Max. H-bridge pulsed current: 108A
– PWM pins: 6 (D3, D5, D6, D10, D11, & D13)
– Oscillator speed: 16MHz
Targeted Price Point:
We don’t want to stop at just the board but go on to further create a complete Robot kit (with Board, Chassis, motors, wheels, and battery) that is completely open source and hits the MSRP of ~$50. The summer 2012 should be a good one for robotics!