Well, the honest answer is I don't I use what others have done before. A good
starting point is this site http://www.wikihow.com/Use-a-USB-Robotic-Arm-with-a-Raspberry-Pi-(Maplin), it gives most (pretty much all) of the answer, including where to get the pyusb library need; setting it up (be careful don't use the zip file but the tar.gz version - you might need to scroll down the screen to do this) and an example. A second source that was very useful was http://notbrainsurgery.livejournal.com/38622.html?view=93150#t93150 which contains an explanation of the 'triples' (for example [32,0,0]) used to select which part of the arm moves and what it does (in the example [32,0,0] causes the Robot Elbow to move down).
The code below is largely based on the code in http://www.wikihow.com/Use-a-USB-Robotic-Arm-with-a-Raspberry-Pi-(Maplin) the only real changes are named procedures (such as ElbowUp) in place of the slightly less easy to understand lines such as MoveArm(Duration,[4,0,0]) #wrist up . The only other changes was a procedure that changes what the light does (0 - light off; 1 - light on; 3 - pulses by a number of times).
import usb.core, usb.util, time
RoboArm = usb.core.find(idVendor=0x1267, idProduct=0x000)
if RoboArm is None:
raise ValueError("Arm not found")
#Define a procedure to execute each movement
def MoveArm(Duration, ArmCmd):
#Start the movement
#Stop the movement after waiting a specified duration
MoveArm(Duration,[0,1,0]) #Rotate base clockwise
MoveArm(Duration,[0,2,0]) #Rotate base clockwise
MoveArm(Duration,[16,0,0]) #Elbow up 0x10
MoveArm(Duration,[32,0,0]) #Elbow down 0x20
MoveArm(Duration,[4,0,0]) #wrist up 0x04
MoveArm(Duration,[8,0,0]) #wrist down 0x08
MoveArm(Duration,[1,0,0]) #close gripper 0x01
MoveArm(Duration,[2,0,0]) #open gripper 0x02
MoveArm(Duration,[64,0,0]) #shoulder up 0x40
MoveArm(Duration,[128,0,0]) #shoulder down 0x80
def GripLight(Action, Duration):
MoveArm(Duration,[0,0,1]) #light on
MoveArm(Duration,[0,0,0]) #light off
for x in range(Duration):
MoveArm(1,[0,0,1]) #light on
MoveArm(1,[0,0,0]) #light off
See it action in the video below.
All opinions in this blog are the Author's and should not in any way be seen as reflecting the views of any organisation the Author has any association with.
I am grateful to Santander UK for the funding; CBiS Education for their support and advice so far; last but not least the schools who have enthusiastically expressed an interest in taking part. All views are the authors.