FingerTech 'Cobra' Mini-Sumo Chassis

• Designed to be a competitive entry into the masters class of mini-sumo, this chassis has the ability to beat those big-wheeled servo bots every single time.
• Includes 4WD Gold Spark motors, four high-traction mini-sumo wheels, two on-board motor controllers, three QRE1113 line sensors, stainless steel scoop, heavy steel ballast, screws, wrenches, and stand-offs for mounting your control board!

New Cobra R5!
• The Cobra R5 has a slide on-on-off power switch so you can turn power on to the whole robot or just the control board (for testing sensors and code), with power LEDs for each.
• Buttons for testing the on-board motor driver circuitry without need for a control board.
• QRE1113GR lines sensors that can be read with an analog input - no need to charge a capacitor and deal with timing!
• Indicator LEDs on each Line Sensor so you can see what the sensor sees!

 • Previous version Cobra R4 introduced two on-board motor controllers, three QTI analog/digital line sensors, and a bright blue LED power indicator.


Dimensions:
The Cobra conforms to the mini-sumo ruleset of RoboGames, the world's largest robot competition. Most events uses these rules, but always check with your event organizer to make sure.
Width: 9.9cm (3.90")
Length: 9.75cm (3.84")
Height (ground to top of standoff): 3.77cm (1.48")
Weight: 333grams (11.75oz) - Maximum allowed in competition is 500g (17.63oz)


Kit Includes:

PCB Chassis:	The Cobra baseplate is a circuit board that has mounting holes for the scoop, ballast and standoffs.  The newest revision includes on-board motor controllers, QRE1113GR digital/analog line sensors (two front, one rear) with green LED indicators, and bright red and blue LED power indicators.
Motors:	Four 50:1 Gold Spark Gearmotors are epoxied and soldered in place.
Motor Control:	The Cobra has two on-board motor drivers (left and right). To operate them, you will need to connect their DIR (direction) and PWM (speed) pins to a microcontroller. For DIR, 5V is forward direction and 0V is reverse. The PWM pins require a 5V pulse-width-modulated waveform for smooth operation.
Wheels:	Four FingerTech Mini-Sumo Wheels.  Shore A20 polyurethane - the highest traction mini-sumo wheels available.
Line Sensors:	Includes three QRE1113GR line sensors (2 front, 1 rear) wired for digital or analog operation. Three headers connect to your control board.
Scoop:	0.020" stainless steel angled scoop (can be legally sharpened to 0.010" per RoboGames rules)
Steel Ballast:	An underweight mini-sumo is at a disadvantage!  This steel ballast keeps the center of gravity low.
Screws:	Four 6-32x0.375" screws for mounting the scoop, ballast and stand-offs.  Four for securing circuit board to standoffs.  Four washers for spacing ballast from pcb. Two hex wrenches included for tightening screws and setscrews.
Instructions:	Full-color assembly steps, wiring diagram, header pinouts, and sensor/motor controller instructions. Cobra_instructions_R5.pdf (Cobra_instructions_R4.pdf)

Requires:

Battery:	The chassis has a spot to accomodate a 44x24x29mm (1.75x0.93x1.15") battery.  Our Galaxy 7.4V 300mAh or Galaxy 11.1V 180mAh fit perfectly and will run the robot for several matches.  Min/Max Voltage: 6V-16V.
Electronics:	In the chassis kit, the brains are up to you.  We carry the user-friendly Arduino Uno's, but boards from the SumoVore, Mark III, or SumoBot will all work.  Use the PCB Mount Kit to fit boards with different hole patterns.
Sensors:	Opponent detection can be anything you desire.  Infrared emitters/sensors are most common, but ultrasonic sensors are an option too.

Orders normally ship within 1-2 days. Other Gold Spark motor ratios can be used for an additional $10 fee - please add a note in the Additional Comments section of checkout for which ratio you would like. (35:1 is the most commonly used after the default 50:1, but make sure your sensors can react fast enough to the increased speed!)

 You can use a variety of boards to control your Cobra chassis. We have begun writing sample code for different systems. Coming up are Arduino, Parallax, Mark III, and Sumovore.

Parallax SumoBot Board (Cobra R4)

 Wiring:
(Motors)
SumoBot Board P13 to Cobra Left motor PWM pin
SumoBot Board P12 to Cobra Right motor PWM pin
SumoBot Board P6 to Cobra Left motor DIR pin
SumoBot Board P5 to Cobra Right motor DIR pin

(Line sensors)
SumoBot Board P10 to Cobra Left line sensor power (W)
SumoBot Board P9 to Cobra Left line sensor input (R)
SumoBot Board P7 to Cobra Right line sensor power (W)
SumoBot Board P8 to Cobra Right line sensor input (R)
(Both Cobra line sensor B lines tie to SumoBot Board Vss)
(SumoBot Board only uses the two front line sensors by default.)

(The two opponent sensors are wired by plugging components into the SumoBot Board as described in the next four lines)
SumoBot Board P4 to Left IR LED output
SumoBot Board P11 to Left IR sensor input
SumoBot Board P15 to Right IR LED output
SumoBot Board P14 to Right IR sensor

(The piezo speaker and LEDs are wired by plugging components into the SumoBot Board, as described in the next three lines)
SumoBot Board P1 to Piezo speaker (other side to VSS)
SumoBot Board P0 to StartLED (other side to 470R to VSS)
SumoBot Board P2 to added RightLED (optional - for displaying which sensor sees opponent)

SumoBot Board VSS to Cobra GND
In Cobra R5: SumoBot Board servo power to Cobra BATT (Servo power is the middle pin from either of the two servo connector headers)
[In Cobra R4: SumoBot Board servo power to Cobra Vin. (Servo power is the middle pin from either of the two servo connector headers) Battery wired to SumoBot Board. Battery connector on Cobra R4 is unused. This allows you to turn the SumoBot Board switch to position 1 and program/test without powering the motors. Position 2 adds power to the motors.]

 Sample Code: SumoBot - Cobra V2 Basic Competition Program 1.0.bs2


Arduino Uno
While we work on full instructions, here is a quick code sample to get your motors driving!

Wiring:
Arduino PIN 3 to Cobra Right PWM
Arduino PIN 4 to Cobra Right DIR
Arduino PIN 5 to Cobra Left PWM
Arduino PIN 6 to Cobra Left DIR
Arduino Gnd to Cobra GND
Arduino Vin to Cobra BATT
Battery plugged into Cobra rear 2-pin connector.

 Sample Code:
// Arduino Motor Control - sweeps both motors back and forth
int sweep = 255;
int dir = 1;
//Pin hookups:
int PWMR = 3; // use analogWrite(PWMR,val) to control the Right motor speed
int DIRR = 4; // use DigitalWrite(DIRR,val) to control the Right motor direction
int PWML = 5; // use analogWrite(PWML,val) to control the Left motor speed
int DIRL = 6; // use DigitalWrite(DIRL,val) to control the Left motor direction

void setup() {
pinMode(PWMR, OUTPUT); // sets the pin as output
pinMode(PWML, OUTPUT); // sets the pin as output
pinMode(DIRR, OUTPUT); // sets the pin as output
pinMode(DIRL, OUTPUT); // sets the pin as output
}

void loop() {
for(sweep = 255; sweep >= 30; sweep -= 20) {
digitalWrite(DIRR, dir); // R motor direction forward
digitalWrite(DIRL, dir); // L motor direction forward
analogWrite(PWMR, sweep); // R motor speed
analogWrite(PWML, sweep); // L motor speed
delay(100);
}
if(dir==0) dir=1; else dir=0; // change motor direction
 }

Here is a quick video showing the top speed using 50:1 Spark motors at 11.1V.
 

 Cobra MiniSumo Chassis R5.IGS