How to build a DFRobot Arduino car

Part I: DFRobot Chassis

DFRobot_Overview

Parts needed:

(Included with DFRobot Kit)
a. Robot chassis with ball casters
b. Wheels (2x)
c. Gearmotor bracket with nuts and screws (2x)
d.  Micro metal gearmotors (2x)

(not included with DFRobot Kit)
e.
red and black motor cables
f. plastic standoffs with hex nuts (3x)
g. pen holder (2x)
h.pen screws (2x)
i. pen hex nuts (2x)

Tools needed (not pictured):
Steady Hands
Velcro Tabs
Soldering iron
Solder
wire-strippers
Small Phillips-head screwdriver

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 NOTE: In the photo above, the red and black motor cables, and micro metal gearmotors are already connected. The red and black cable is sold separate and the gearmotors come with a different set of red and black wires connected. The first step of this guide tells you how to connect/solder them.

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Start by taking a complete red and black motor cable pictured below. Snip the cable in half and take the male end saving the female end for later. On the male end strip about a quarter of an inch of wire from the end and add a little bit of solder to the end to solidify the exposed wires. Make sure to keep the red and black sides separate.

MotorConnectorCable

Now remove the old wires from the gearmotor. This may require adding a little solder to help melt the old solder. With the wires removed use some “helping-hands” if available to solder the red wire of the red and black motor cable to the prong on the motor with a (+) adjacent to it. Solder the black wire to the opposite prong.

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Repeat the previous steps for the second motor.

 

Take one of the gearmotors assembled with the new motor connectors and one of the wheels.

 

The shaft of the motor is shaped to fit in the hole in the center of the wheel, push the motor in until the shaft of the motor is flush with the outside of the wheel. Be careful not to damage the wires on this step. You will have to resolder if they are damaged.

Repeat the previous steps for the second motor.

 

Now take one of the gearmotor brackets and two of the small hex nuts, seating them into the fitted holes on its sides.

gearmotor_bracket

 

Next fit the bracket on top of a gearmotor with the tabs facing toward the wheel.

gearmotor_bracket_and_motor

 

Finally mount the wheel onto the chassis with the ball casters facing down. Do this by pressing your thumb against the motor mount and start screwing in the motor mount screws in by hand. Tighten them just a little bit with a small screwdriver. Do not tighten the screws to much or the chassis will crack.

gearmotor_mounted

Repeat the previous steps for the second motor.

 

Now add a velcro tab to the top of your chassis as shown below. This will be the back of the car. It does not matter which side you put the velcro on since the car is symmetrical.

Note: there will be some setup required when wiring the arduino’s motor controllers.

 

Remove the ball caster on the opposite side of the velcro tab you just added. Be careful to not let the bearings roll away when disassembling. You wont need it later but hold onto it anyway.

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Next we will install the stand-offs that will hold the Arduino car in place. The stand-offs will go into the three circled positions. Hold the stand-off in place and place one of the nuts on the opposite side screwing the stand-off in place. A pair of small pliers may be helpful for this step. Be careful not to tighten the nut to hard, you may strip the stand-off or crack the chassis.

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What it should look like with the stand-offs screwed on.

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Next get the pen-holder components, place both pen-holder parts and stack them one ontop of another and place them on the top side of the chassis, lining them up with the two holes pointed out below.

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Slide the long pen-holder screws in from the bottom and screw the nuts on from the top until the pen-holder is secured to the chassis.

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Part II: Wiring the Arduino

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Parts needed:

a. 4x AA battery pack + velcro tab
(or any DC battery pack around 7-12v)

b. Arduino Uno + Arduino Motor Shield (Arduino Stack)
c. female end of motor cable (2x)

Tools needed (not pictured):
Steady Hands
Small flat-head screwdriver
wire-strippers

Now get your Arduino stack and the battery pack with velcro tab attached. On the top right corner of the stack you will notice a set of terminals pictured below.

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Unscrew all of these terminals and get the red and black wires attached to your battery pack. If the ends are not stripped do so now, you may also want to add some solder to the ends to keep the fine wires fused together. Slide the red wire into Vin and the black into GND pictured below.

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Tighten the screws for Vin and GND securing the wires in place. Next get one of the female motor cables and strip the ends if you haven’t already, you may also want to add solder to the ends to keep the fine wires fused. Slot Red into (+) and black into (-).

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For the next female motor connector do the opposite. Place the red wire in (-) and the black wire in (+).

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Now connect the female ends to the male ends attached to the DFRobot chassis to make sure the wires are connected properly. Remember the pen-holder is on the front of the car and the sticky tab is on the back, use this for orientation. When connecting the motors make sure the left motor is connected to terminal A and the right motor is connected to terminal B.

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Legend:
Yellow = Terminal Labels
Red = Left LEDs
Orange = Right Leds

Once the motors are connected turn the wheels forward or in the direction they would rotate if the car was moving forward, both of the Left LEDs should be lighting up.

If one wheel is lighting the Left LED and one wheel is lighting the Right LED, you must rotate the wires on the terminal that is lighting the Right LED. After you swap the wires on the offending terminal both wheels should be lighting the Left LED when spun.

If both are lighting the Right LED rotate both so both terminals light the Left LEDs when the wheels are rotated.

Finally attach the velcro tab on your battery pack to the velcro tab on the car and slot the Arduino Stack onto the stands, the car is now ready for action.

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Notes:
Always remove the battery pack first before removing the Arduino Stack.

You may want to use a bread tie or something similar to help managed the excess wire.

It is advised that you do not snip off excess wire since the wire that is connected to the motors and to the Arduino terminals tend to snap off with ware.