End Effectors

The end point of the standard Dexter robot hardware is a replaceable "tool interface" It has a shape which makes it easy for other tools to be clicked on and off. There are spring loaded connectors, sometimes called "pogo pins" at the end for electrical connection.

The signals available to the end effector include power, ground, and whatever signals the main board has been configured to produce. Early versions were wired to USB connection. Later version bring out the GPIO pins from the FPGA. These pins can be configured to produce different signals.

• There is a digital IO pin on the white connectors in the upper right on the back of the motor board
  Dexter.move_all_joints(0, 0, 0, 0, 0)
make_ins("S", "GripperMotor", 1), //Digital output pin. 0 = off 1 = 5v TODO: Verify this?
• Another pin on that same connector is the PWM output pin.
  Dexter.move_all_joints(0, 0, 0, 0, 0)
make_ins("S", "EERoll", 512), //PWN pin. Integer range of 0-512 TODO: Verify this?
• The standard going forward will be a new tool interface which incorporates 2 Dynamixel XL-320 servos and a Tinyscreen+ (ARM based, small OLED screen, 4 buttons, lots of IO). One FPGA IO pin will be configured to send and receive data via the Dynamixel protocol 2.0. This requires and update to the FPGA image.
  Dexter.move_all_joints(0, 0, 0, 0, 0)
make_ins("S", "ServoSet2X", 2, char1 + char2<<8, char3+char4<<8)
  The Tinyscreen+ will listen on the servo bus and may return data there or via the dedicated return data line. See: Parts, source, Schematic and PCB design

Signals from the Dexter Motor Control PCB to the Tool Interface:

• Ground (P25 pin 1)
• Logic power +5 Volts (P25 pin 2)
• Supply power (18V DC from AC adapter J25?), regulated to Servo power voltage (6 - 8.75V) at the interface
• Servo data bus, bidirectional. AUX1 via J20 (bottom pin, on bottom connector left side of motor board)
• Return serial data. AUX2 via J21?

Note: J20 and J21 accept TE Connectivity part 2-179694-2 ^ ^ ^ . A 2 position, 2mm, IDC, AMP CT connector. While this is an IDC part, the crimp head cost is insain even without the crimp handle so manually pressing it in with round nose tweezers or just soldering the wire on maybe the practical choice.

Multiple signals are available from the Tinyscreen+ for many different purposes.

Known end effectors:

Original Tool Interface

• http://hdrobotic.com/dexter-community/#!/grippers:marker-holder Simple Marker / Pen holder used to write or draw via DDE's DXF.init_drawing and txt.string_to_line functions. Hint: This functionality should allow Dexter to 3D print in the future.
• http://www.appropedia.org/User:Zsarnold#Enterprise See "Semester 2" A Mantis gripper was adapted to Dexter for a great demo of removing parts from a 3D printer. Mantis Gripper Design and Dexter adapter files. Demo setup: Video, Images, and DDE code.

New Servo Tool Interface

• n/a

See also:

• Current Tool Interface CAD files (note: this will be replaced): OnShape, STL There is room in the body for wiring and a Tinyduino interface device which can be attached with slightly longer bolts.
• http://hdrobotic.com/dexter-community/#!/grippers Our forum section for grippers.
• https://www.eng.yale.edu/grablab/openhand/ These are good designs for open source grippers. They do NOT have the exact tool interface for Dexter, but could be adapted, or the tool interface part can be replace.