Wire Controlled Robot Arm

By quiddany Follow

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This a tutorial on how to make a robot arm controlled by wires. The advantage of using wires is that your arm is lighter and you can have all your motors in the bottom of your arm, making building and maintenance easier. Here is a video of the arm in action. I plan to add a claw in the future so it can pick things up and not just push them around.

Supplies

6 Servo Motors (MG995)

About 6 meters of plastic coated steel wire (0.5mm)

Box 23x33x10 (may be narrower, definitely should not be shorter)

Plank of wood 33x10

Pipe 14 cm (this is needed to guide the strings)

2 7-way terminal blocks

3D Printed Components (Not designed by me, links to elements in the description):

1 Base Connector

Step 1: Print All the 3D Components

You may need support for the bolt holes and arches but make sure not to add support to the body of your components; this will close up the small wire holes and you will need to make new holes

Step 2: ​(Optional) Attach a Plank of Wood to the Bottom of Your Box to Strengthen It

My box was pretty weak, yours may not be

Step 3: Measure and Cut a Plank of Wood to Fit the Box

Step 4: Mark the Positions of the Motors

make sure none of the arms touch each other

Step 5: Mark the Positions of the Brackets and the Pipe.

The pipe should be placed around one centimeter in front of the hole

Step 6: Drill a Hole for the Cables Coming Out of Your Box (USB and Power)

Step 7: Drill and Saw All the Marked Holes

Step 8: Attach the Motors and Pipe to the Plank

Step 9: Attach the Plank to the Box With the L-Brackets

Step 10: Take Your Terminal Blocks and Solder the Wires Together

Step 11: Cut the End of the Adapter Power Cord and Strip the Wires

Step 12: Identify and Mark the Plus and Minus Wires

Step 13: Attach the Wires to the Terminal Blocks So That All the + Servo Wires and the + Wire From the Power Cord Are Connected, Same Goes for the - Wires.

Step 14: Cut the Head Off a Breadboard Wire

Attach the stripped end of the breadboard wire to the minus terminal block and the pin end to the ground pin in your arduino. If you don’t do this the motors will move erratically without any input.

Step 15: Drill Three Holes in the Bottom of the Box for the Wires Coming Out of Your Arm.

The holes should match up to the holes in the base connector.

Step 16: Attach the Base Connector to the Box

Step 17: Use a Knife or Nail File to Make the Wire Grooves Deeper

The wire grooves for elements 2 and 3 are too shallow.

Step 18: Construct the Arm

Construct the arm according to the instructions here you may need to file the parts so they fit

Step 19: Install Processing and Arduino

Step 20: Paste the Code Programs.

The code is at the bottom of this page

Step 21: Connect the Servo Control Pins to the Arduino

I connected the first motor to the third digital pin, the second motor to the fourth digital pin and so on. Make sure the ground pin is still connected to the - terminal block.

Step 22: Press the Reset Button in Processing, This Will Set All Arms to 90 Degrees

Step 23: Fix the Servo Arms to the Motor Horizontally

Step 24: Thread the Wires Through the Arms So That There Is No Slack

Make sure you thread the wire through as many holes as you can, this will hold it temporarily and be easy to remove.

Step 25: Test the Arm and Tighten or Loosen the Wires As Needed

Step 26: Hot Glue the Wires to the Servo Arms to Make It Permanent

Step 27: Notes

I used 0.5mm jewelry wire but 0.4mm should be fine. The original design used PVC wire but that broke too easily and was hard to work with.

If you are going to be moving the arm in a car or bike wrap the arm joints in tape to make sure they don’t pop out. This is especially important for element 1.

When I started this project I was wondering why I could only find one tutorial on how to make an arm controlled by wires. Now I understand why this isn’t the most common way to make a hobby robot arm. The wires sometimes fall out of their grooves and the whole thing is kind of flimsy. I don’t know if the problems are because I don’t have a lot of experience or if the whole idea is problematic although I am sure that it would be more solid if I knew what I was doing.

Step 28: Troubleshooting

The wire holes are closed up in the 3D printed elements:

You added support for the whole element instead of just the bolt holes. Either re-print the element or open up the holes with a really hot needle.

The COM port is closed, you can’t communicate with the arduino:

Your arduino may not accept USB 3 ports (mine didn’t), you can either buy a USB 2 extension cable or use a computer that has USB 2 ports

The code isn’t working:

Follow this tutorial and modify it to make your own code

A part of the arm is not moving:

The wires might have tangled up, to check this take the servo arm off the servo and try pulling the wires by hand. Untangle the wires and if it’s still difficult to pull the wires try using some WD-40 or a lubricant to make movement easier