Mini Sumobot H-Bridge for Motors

This is a pretty standard design for H-Bridges that I drew and will be using.  I picked mechanical relays because of availability, expandability for an eventual larger robot, my arduino motor shield is already intended for my CNC project, and I didnt want to keep buying transistors should I miscalculate the amperage.  In this design, I went for a single voltage input (+V) to supply the relay coil, Va, and Vb. 
Summary:
Va is default choice.  The relay is set to Normal Close (NC) with Va supplied to the motor for the default normal (Forward) direction.  The diode is for back-voltage for the DC motor.  The NPN transistors are set up as a Darlington series for PWM input from the Arduino microcontroller pin (PWM) that operates at either 3.3-5 V to control the speed.
Vb is second choice when the relay coil is energized for the motor to move in reverse.  The coil is energized when the microcontroller pin (REV) enables High through the Darlington series.  The coil has 200 ohm rating.  The relay will then switch the motor input to Vb reversing the direction.  The diode is again intended for back-voltage for the DC motor. The PWM input from the Arduino microcontroller pin (PWM) will control the speed.

NOTE: I still have to determine if the diode is in the right spot or should be moved to a point after the Darlington PWM series and between +V.  I still may need to add resistors to the coil for equal voltage division through the motor.

Mini Sumo Current Progress 28JAN

Abandoned the light for sound detector as unnecessary.
Programmed servo and sonar ping combo to operate together.  Used code from two different sources provided by:
1.  BARRAGAN <http://barraganstudio.com/> intended for use on the Arduino Experimentors Kit @ source circuit 04 http://ardx.org/src//guide/2/ARDX-EG-OOML-WEB.pdf on the servo
2.  http://www.funnyrobotics.com/2011/03/arduino-with-parallax-ping-sensor.html for the Sonar Ping sensor
Originally, the programs were treated separately, but I eventually combined them using FOR commands so that for every degree a ping is done. Servo and Sonar Ping
Programmed servo and sonar ping combo to move faster when detected object is close.  Added some IF ELSE statements that specified a threshold for the close object before moving faster.  Need to post code.
Purchased battery holders,  9V battery clips, NPN  transistors #1, NPN transistors #2, and  DPDT relays from Radio Shack.
Goal: Post design for H-Bridge relay with transistors
Goal: Program servo and sonar ping combo to limit movement to close object only.
Goal: Program servo and sonar ping combo into a grid array.
Goal: Purchase IR detection array for Edge sensing
Goal: Program edge sensing

My Review of Velleman® MK102 Flashing LEDs Kit

Originally submitted at RadioShack

Velleman's MK102 beginner-level flashing LED kit has adjustable flashing speed and two potentiometers.

Velleman® MK102 Flashing LEDs Kit

Okay build

By Insideous from Atlanta on 1/13/2012

 

4out of 5

Pros: Simple build

Cons: Must download schematic, Some experience needed

Best Uses: Robotics, Toy

Describe Yourself: Enthusiast

Primary use: Personal

Was this a gift?: No

Some solder experience required. Must download schematic from site. Must already know positive end of LED and electrolytic capacitor. Provides excellent adjustability for background noise level- if background too loud and LED stay on, turn potentiometer. Very small with battery attaching to back of circuit. I kept the leads on the LED long and will attach to a minisumobot as sound indicators.

(legalese)

Mini-Sumo Current Progress

Assembled the Twin motor Tamiya gear box at a 203:1 ratio with my son.  He likes assembling things. 
Installed 56mm diameter Tamiya sport tires; hollow rubber similar to a RC car tire
Measured the overall width and determined that it exceeded the 100mm max width requirements for the mini-sumo rules.
Drilled all the way through the rims so that the axles could be pushed through (used a non-motorized hand drill).  This reduced the width to 102mm.  Will have to grind the ends down a little to meet specs.
Cut plastic sheeting to 100mm x 100mm with utility knife. 
Trimmed to fit the wheel wells and affix to the gear box.
Purchased a Parallax sonar ping sensor and a light and sound kit

GOALS:
1.  Configure Arduino for ping sensing and attach light and sound kit to get a visual indication of sound.
2.  Purchase transistors and relays to create an H-Bridge for each motor to operate with the Arduino