SMARS QUAD ROBOT Wiring Diagram

SMA SR

QUAD ROBOT
WIRING DIAGRAM

Connect the Servos to the servo driver board using the corresponding port numnbers as shown below.

Servo 1 Top Left Foot

Servo 2 Top Left

GND

OE

SCL

SDA

VCC

V+

POWER

PCA9685

16x12-bit PWM

0 1

2 3

4 5 6 7 8 9 10 11 12 13 14 15

V+

PWM

GND

GND

A5 A4 A3 A2 A1 A0+RW

I2C Address

(Open=0/Closed=1)

V+

Servo 5 Back Right Foot

Servo 6 Top Right

GND

OE

SCL

SDA

VCC

V+

Servo 3 Back Left Foot

Servo 4 Back Left

2

Servo 7 Back Right

Servo 8 Top Right

5

0

3

1

4

6

7

Base

FRONT

SMARS - the Screwless Modular Assembleable Robotic System.

To download the files visit https://www.thingiverse.com/thing:2755973

1

SMA SR

QUAD ROBOT
PRINT PARTS

The following instructions show how to assemble the SMARS Quad Robot. A bill of materials is provided at
the back of this guide along with links to where to buy the components from. Links to the 3d printed
parts are also provided at the back of this guide.

1

Print the frame

3

Fit the servo into the servo holder

SG90
Servo

x8

2

Print 4x Servo holder & 4x Servo holder M (M is
a mirror image of the servo holder)

Print the servo holders

4

Fit the servo holders into the frame

Servo Holder Servo Holder M

SMARS - the Screwless Modular Assembleable Robotic System.

To download the files visit https://www.thingiverse.com/thing:2755973

2

QUAD ROBOT
FITTING SERVOS

SMA SR

5

Print the servo arms

7

Ensure the servo can move equally in each
direction before tightening the screw.

Check the servo rotation

6

x4

Mount the servo holder in the servo arm

Insert the servo
horn onto the

8

Attach the other servo holders to the frame

SG90
Servo

servo and screw
in securely to
the servo arm

SMARS - the Screwless Modular Assembleable Robotic System.

To download the files visit https://www.thingiverse.com/thing:2755973

3

QUAD ROBOT
FITTING THE FEET

SMA SR

9

Print the feet x4

11

Check the servo rotation

170

160

150

140

130

120

110

100

180

Feet need a rotation
of between 50º to 150º

degrees

x4

90

80

70

60

50

40

30

20

10

0

10

Mount the foot on the servo holder

12

Download the python code

From the raspberry pi command line type:

git clone https://www.github.com/kevinmcaleer/smars

Then look in the folder at the python files.

cd smars
ls smars

x4

SMARS - the Screwless Modular Assembleable Robotic System.

To download the files visit https://www.thingiverse.com/thing:2755973

4

QUAD ROBOT
PI ZERO SETUP

Connect the Raspberry pi Zero using the following pins:

PCA9685 GND to RPI Pin 39 (or Pin 6) - Black wire
PCA9685 V+ to RPI Pin 2 - Red wire
PCA9685 SCL to RPI Pin 5 (SCL) - Green wire
PCA9685 SDA to RPI Pin 3 (SDA) - Blue wire

SMA SR

Note that the input voltage for the PCA9685 is 3.3v or 5v into the VCC. The V+ is for powering the
servo motors and requires more power than the raspberry pi can provide, which is why it is separate.
You can use a 9v battery to drive this, using the SMARS 9v case.

The raspberry pi communicates with the servo driver board using I2C, which only requires 2 wires:
System Clock (SCL) and System Data (SDA). These are marked on servo driver board, and on pins 3 & 7
on the Raspberry Pi Zero.

GND

OE

SCL

SDA

VCC

V+

POWER

PCA9685

16x12-bit PWM

0 1

2 3

4 5 6 7 8 9 10 11 12 13 14 15

V+

PWM

GND

V+

GND

A5 A4 A3 A2 A1 A0+RW

I2C Address

(Open=0/Closed=1)

GND

OE

SCL

SDA

VCC

V+

BCM 19 (MISO)

BCM 26

Ground

35

37

39

36

38

40

BCM 13 (PWM1)

BCM 6

31

33

32

34

BCM 0 (ID_SD)

Ground

BCM 5

29

30

27

28

25

26

BCM 11 (SCLK)

23

24

BCM 10 (MOSI)

BCM 9 (MISO)

3v3 Power

BCM 27

BCM 22

13

15

17

19

21

16

18

20

22

14

BCM 4 (GPCLK0)

Ground

BCM 17

11

7

9

8

10

12

BCM 2 (SDA)

BCM 3 (SCL)

3v3 Power

1

3

5

2

4

6

Ground

BCM 12 (PWM0)

Ground

BCM 16

BCM 20 (MOSI)

BCM 21 (SCLK)

BCM 1 (ID_SC)

BCM 7 (CD1)

BCM 14 (TXD)

BCM 15 (RXD)

BCM 18 (PWM0)

Ground

BCM 23

BCM 24

Ground

BCM 25

BCM 8 (CE0)

SMARS - the Screwless Modular Assembleable Robotic System.

To download the files visit https://www.thingiverse.com/thing:2755973

5v Power

5v Power

Ground

5

QUAD ROBOT
RANGE OF MOTION

SMA SR

10

0

20

30

40

50

60

70

80

90

100

110

120

130

140

150

160

Each servo has a range of motion
between 0º and 180º degrees. However

the each robot leg only needs between
0 and 90 degrees of rotation.

The servos are oriented differently
for each leg, so the degrees of
rotation for each needs to be
understood and set correctly in the
code.

170

Range of Motion

Front Left = 0 to 90

180

Front Right = 90 to 180
Back Left = 90 to 180

50

40

30

20

10

0

90

Back Right = 0 to 90

100

110

120

130

140

80

90

150

60

160

70

170

180

180

170

160

150

140

130

120

110

100

90

FRONT

0

90

80

70

60

50

40

30

20

10

SMARS - the Screwless Modular Assembleable Robotic System.

To download the files visit https://www.thingiverse.com/thing:2755973

6

QUAD ROBOT
SOFTWARE SETUP

SMA SR

Python environment setup

The PCA9685 servo driver library is provided by
Adafruit and needs to be installed before setup
and using the SMARS Quad robot.

To download the adafruit servo library first
logon to the Raspberry Pi and then type:

sudo apt-get install git build-essential python-dev
cd ~
git clone https://github.com/adafruit/
Adafruit_Python_PCA9685.git
cd Adafruit_Python_PCA9685
sudo python setup.py install

Type ‘1’ to change the current channel.

Select Channel

--------------

currently selected channel is: 0
type channel number:, or q to return to the main menu

Next, type ‘0’ to configure channel 0

Then type ‘q’ to return to the main

Python is now setup for the servo
driver.

Quad Robot Software Configuration

Once you’ve downloaded the python code you can
begin checking the configuration of the servos:

python limb_setup.py

menu.

Menu

----

1) select channel

2) select angle

0) quit

current channel is: 0
current angle is: 0
enter number

Type ‘2’ to set the angle for the

Use the menu to select the channel you
want to configure. There are 16
channels, one for each servo.

The channels start at 0, and end at 15.

Menu

----

1) select channel

2) select angle

0) quit

current channel.

Select Angle

------------

current angle is: 0
Type angle to set servo to, or press q to exit90
90
Angle is: 90
Angle = 90
Angle as a percentage = 50.0
pulse = 375
map Max = 450
current angle: 90
Type angle to set servo to, or press q to exit

current channel is: 0
current angle is: 0
enter number

Type ‘1’ to change the current channel.

Select Channel

--------------

currently selected channel is: 0
type channel number:, or q to return to the main menu

Type ’90’ to set the angle to 90
Degrees.

Then type ‘q’ to return to the main
menu.

Repeat this until you have set each
limb correctly.

Finally type ‘0’ to quit the limb setup
programme.

Next, type 0 to configure channel 0

SMARS - the Screwless Modular Assembleable Robotic System.

To download the files visit https://www.thingiverse.com/thing:2755973

7

QUAD ROBOT
NEXT STEPS

About this Guide

This guide was written by Kevin McAleer and is provided freely to the SMARS community.

Social Media

If you haven’t already, please join the facebook community ­https://www.facebook.com/groups/141101273276325/

SMA SR

SMARS - the Screwless Modular Assembleable Robotic System.

To download the files visit https://www.thingiverse.com/thing:2755973

8