Introduction

This is a four degree of freedom robotic arm capable of picking and placing small objects. With medium sized links, the robotic arm can fit perfectly on your table top, use the clip to attach it to your table.

Assembly Instructions

  • Mount servo horn on top inner bearing disc using self-threading M2 (“M2” represents a diameter of 2mm) screws of 8mm length. These screws can be found in servo accessories. Be careful about holes you are mounting the horn on (use holes closer to disk centre).

Mounitng Servo HormMounted servo Horn

  • Place 30 mm stand-offs on the base. Fasten using M3 bolts of 8mm length.

  • Take the bottom outer bearing disc and slide it over standoffs.

  •  Mount bottom inner bearing disc on stand-offs. Align the disc such that smaller holes are in line with the stand-offs.

  • Put the bearing on top of bottom inner bearing disc. Observe how disc supports the bearing from beneath.

  • Next, place the two middle inner bearing discs. These will perfectly fit inside the bearing.

  • Seat the “servo horn & top inner bearing disc” assembly on top of bearing as shown. Make sure all smaller holes in these discs are aligned since we will fasten them all together using 20mm M3 bolts.

Note1: Do understand that it was necessary to slide down the bottom outer bearing disc earlier. You won’t be able to do it now due to diameter differences.

Note2: Observe how the bearing has been clamped between the top and bottom inner bearing discs.
  • Place the middle outer bearing discs first and then top outer bearing disc as shown. The middle discs will have a larger inner diameter compared to the top and bottom ones. The inner diameters of the middle discs will be equal to the bearing’s outermost diameter.

  • Slide up the bottom outer bearing disc, align the holes in the discs and stack them.

Again, see how the bearing is sandwiched because the top and bottom bearing discs have a smaller inner diameter compared to the bearing’s outermost diameter.
  • Place 20 mm stand-offs on the top and fasten the M3 bolts of 20mm length from the bottom. Your base is completed now.

The base assembly should look like this upon completion.

  • Place servo motor into the slot available on racquet-shaped link 1. Be careful about the positioning and the orientation of the servo. Have a careful look at the illustrations.

evive Robotic Arm

  • Fasten the servo to the link using M4 bolts of 16mm length and nuts.

evive Robotic Armevive Robotic Arm

  •  In the figures, you see head of servo pointing upwards. Don’t let this confuse you; the head actually goes into the slot in the horn. We will come to this again, for now attach M3 bolts of 8mm length and 20mm standoffs to the link as shown in the illustrations below.

evive Robotic Arm

evive Robotic Arm

This is the orientation in which we will place the completed link upon our base. Note the free holes through which we will drive the screws to fix it to the base.
evive Robotic Arm
  •  Place this assembly on the base as shown & fasten using M3 bolts of 8mm length.

evive Robotic Arm

Keep in mind that you’ve set servo at 90 degrees before assembling (connect servo to evive, go to control > servo and set servo  at 90 degrees).
evive Robotic Arm
evive Robotic Arm
  • Observe how head of the servo goes into the servo horn. We have to ensure proper locking between servo head and servo horn. To do this, drive a bolt into centre of the horn (find this in servo accessories) through the bottom of the base (through the large hole) and fasten it.

evive Robotic Arm

It is important to ensure that your servo motor does not move vertically and exhibits only rotary motion while in operation.
  • Push the servo in the slot provided on the racquet shaped link 2 as shown and fasten it using M4 bolts of 16mm length and M4 nuts. Notice the difference between this step and what we did for the sketching robot.
    Mounting ServoMounting Servo Mounting Servo
  • Place this on the part you have already assembled (step 0) and fasten using M3 bolts of 8mm length.
    Moutning Raquet 2
    This is how our first link will look once the Racquet-shaped links have been assembled. The head of the Servo points upwards.
    Moutning Raquet 2
  • Take the supporting link and attach a servo horn to it as shown. Fasten the horn with M2 bolts of 8mm length.
    Mounting Servo horn Mounting Servo horn
  • Fit the servo holder into the rectangular slots provided on the supporting link. Refer to figures below to identify rectangular slots to fix the holder.
  • Insert M3 nuts into the slots provided in the servo holder and fasten with M3 bolts of 8mm length. Refer to the figure below.
  • Slide the micro servo into the servo holder as shown and then fix it in place using M2 bolts of 12mm length.
    Mounting ServosMounting Servos
While making the Sketching Robot we attached a pen holder to micro servo through a horn. This time we will attach a gripper to it. The following steps elucidate how to assemble the Gripper
  • Insert another micro servo into the slot on the gripper plate as shown, then affix it there using M2 bolts of 8mm length and M2 nuts.
  • Fasten 15mm standoffs to the plate using M3 bolts of 8mm length.
  • Insert gripper part 1 into the thin slot provided on the gripper plate. Note that this part is not symmetric and the small square slots are nearer to one end than to the other. Do insert this in the exact configuration as shown in the figure.
    Observe how the square holes are further away from the plate compared to the other end of gripper part 1.
  • Slide gripper part 2 (with a thin slit) onto the protrusion on gripper part 1.
  • Notice that gripper part 2 has holes 3mm in diameter so that threaded part of standoffs may pass through it. Fasten these parts using M3 nuts.
    Gripperevive Gripper robotic arm
  • Insert gripper part 3 into the rectangular holes of gripper part 1 as shown and place M3 nuts and fasten using M3 bolts of 12mm length.
    evive Gripper robotic arm evive Gripper robotic arm evive Gripper robotic arm evive Gripper robotic arm
  • Now attach a micro servo horn on gripper part 3 with its holes aligned with the holes on gripper part 3 and fasten with self-threading M2 bolts of 8mm length (from micro servo accessories).
    evive Gripper robotic arm evive Gripper robotic arm
  • Bring together gripper claw 1, gripper link and a one sided micro servo horn in the configuration shown. First, fasten gripper link to the one sided micro servo horn using self-threading M2 bolt from micro servo accessories. Keep in mind, protruded end of servo horn should be facing the servo.
    evive Gripper robotic arm
  • Next, insert the M3 bolt of 12mm length to gripper claw 1 as shown. Hold the “gripper link and servo horn” assembly intact. Then insert gripper link 1 onto this bolt and fasten an M3 lock nut on the same. Ensure than the links are movable about the bolt but they shouldn’t be too loose.
    evive Gripper robotic arm evive Gripper robotic arm evive Gripper robotic arm
  • Now lock the one sided micro servo horn and the free servo head using the self-threading bolt from micro servo accessories. Ensure the micro servo is at 90 degrees before assemblingevive Gripper robotic arm evive Gripper robotic arm.
  • Now, note that there is a free hole on gripper plate and that gripper claw 1 is in front of the other hole. Intuitively, place gripper claw 2 on the other hole. Now M4 bolts of 16mm length in both these holes and fasten using M4 lock nuts. Keep in mind that claws aren’t too loose but are free to rotate about these bolts.

    Rejoice! For the most sophisticated part is complete!
  • As you can see from the figure above, the micro servo horn on the assembly is still free. We left a micro servo head free too in step 6, where we started making the gripper. Use bolts from micro servo accessories to lock both of these together (ensure micro servo is at 90 degrees before fixing, refer step 14 from #1), hence fixing the gripper to the supporting link through the micro servo.
  • Now, attach 20mm standoffs to supporting link and fasten M3 bolts of 8mm length, subsequently bring link 2, align it with the standoffs and fasten M3 bolts of 8mm length.

    Now, we have assembled the second link with the gripper. All that remains now is to attach this with the first link.
  • Now, set the servo angle to 180 degrees (refer step 14 from #1). Recall from step 3 that there is another horn at the bottom of the supporting link which has to be connected to a servo head. Also, recall that there is a free servo head (step 1) in the first link. Simply lock the two with a bolt from servo accessories and the robot will be complete.

    Say HELLO to your own crane and lift your Lamborghini!Pick and Place Robotic Arm

Circuit Diagram

Pick and Place Circiuit Diagram

Note: Ensure that all the servos are properly connected and there are no loose wires, this might otherwise effect performance of the arm during operaton. Use cable tes for wire management.

Code

In this program we are controlling the robotic arm using potentiomters and slide switch.

  • Base Servo is controlled using potentiometer 1
  • Link 1 Servo is controlled using potentiometer 2
  • Link 2 Servo is controlled using slide switch 1
  • Gripper Servo is controlled using slide switch 2

This program also shows the variable voltage on the screen.

Caution: The robotic arm should operate at 6V using a 2A power supply.
Libraries: TFT_ST7735

Working